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Title: The First Book of Farming
Author: Goodrich, Charles Landon, 1859-
Language: English
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The First Book of Farming
[Illustration: THE FARM EQUIPMENT--PLANTS, SOILS, ANIMALS, TOOLS,
BUILDINGS.]
The
First Book of Farming
By
CHARLES L. GOODRICH
_Farmer_
Expert in the Bureau of Plant Industry, United States
Department of Agriculture, Washington, D.C.
_Illustrated_
GARDEN CITY NEW YORK
DOUBLEDAY, PAGE & COMPANY
1923
1905, by
DOUBLEDAY, PAGE & COMPANY
PUBLISHED MARCH, 1905
PRINTED IN THE UNITED STATES
AT
THE COUNTRY LIFE PRESS, GARDEN CITY, N.Y.
PREFACE
The most successful farmers of the present day are those who work in
harmony with the forces and laws of nature which control the growth
and development of plants and animals. These men have gained their
knowledge of those laws and forces by careful observation, experiment
and study.
This book is a result of the author's search for these facts and
truths as a student and farmer and his endeavor as a teacher to
present them in a simple manner to others.
The object in presenting the book to the general public is the hope
that it may be of assistance to farmers, students and teachers, in
their search for the fundamental truths and principles of farming.
In the first part of the book an attempt has been made to select the
most important and fundamental truths and principles underlying all
agriculture and to present them in the order of their importance,
beginning with the most important.
An endeavor has been made to present these truths to the reader and
student in a simple and interesting manner. As far as possible each
advance step is based on a previously stated fact or truth. A number
of side truths are introduced at various places.
A number of simple experiments have been introduced into the text in
the belief that they will make the work more interesting to the
general reader, and will aid the student in learning to make simple
investigations for himself.
The author recommends all who use the book to perform the experiments
and to make the observations, and so come actively in touch with the
work.
The observations begin on the farm. The author considers the plant the
central and all-important factor or agent on the farm.
The root is regarded as the most important part of the plant to
itself, and consequently to the plant grower.
The general truths or principles which state the conditions necessary
for the growth and development of plant roots are regarded as the
foundation truths or fundamental principles of all agriculture. These
truths are as follows:
The roots of farm plants need for their best growth and development:
A firm, mellow soil.
A moist soil.
A ventilated soil.
A warm soil.
A soil supplied with plant food.
The first two chapters lead the reader quickly through logical
reasoning to these fundamental truths, on which the remainder of the
work is based.
A study of soils is made in connection with the root studies, as the
two are so closely related.
After the study of roots and soils the other parts of the plant are
considered in the order of their importance to the farmer or plant
grower. The aim is always to get at fundamental facts and principles
underlying all agricultural and horticultural practice.
The author regards the conditions necessary to root growth and
development as the important factor constituting soil fertility, and
in the last ten chapters takes up the discussion of certain farm
operations and practices and their effects on these necessary
conditions, and consequently their effect on the fertility of the
soil.
The author extends gratitude to all who have in any way assisted in
the preparation of this book, whether through advice, preparation of
the text, preparation of the illustrations, or any other way in which
he has received assistance.
C.L. GOODRICH.
GLENNDALE,
Prince George Co., Maryland,
_January_ 21, 1905.
CONTENTS
PART I
GENERAL PRINCIPLES UNDERLYING PLANT CULTURE
Chapter Page
I.--INTRODUCTION TO PLANTS 3
II.--ROOTS 9
Uses of roots to plants 9
Habit of growth of roots 11
Conditions necessary for root growth 20
III.--SOILS 23
Relation of soil to plants 23
Classification of soils 26
How were soils made? 30
Soil texture 37
IV.--RELATION OF SOILS TO WATER 39
Importance of water to plants 39
Sources of soil water 40
Attitude of soils toward water:
Percolation
Absorption from below
Power to hold water 40
The effect of working soils when wet 45
V.--FORMS OF SOIL WATER 48
Free water 48
Capillary water 49
Film water 50
VI.--LOSS OF SOIL WATER
By surface wash
By percolation and leaching
By evaporation
By transpiration
How to check these losses 53
VII.--SOIL TEMPERATURE 57
How soils are warmed 58
How soils lose heat
How to check loss of heat 59
Conditions which influence soil temperature 60
Value of organic matter 61
VIII.--PLANT FOOD IN THE SOIL 63
IX.--SEEDS 70
Conditions necessary for sprouting 70
Seed testing 75
How the seeds come up 77
Use of cotyledons and endosperm 79
X.--SEED PLANTING 81
Depth of planting:
Operation of planting
Planting machines 81
Seed classification 85
Transplanting 87
XI.--SPADING AND PLOWING 90
Spading the soil 90
Plowing 91
Why we spade and plow 91
Parts of a plow 92
Characteristics of a good plow 95
The furrow slice 96
How deep to plow 96
"Breaking out the middles" 97
Ridging the land 98
Time to plow 98
Bare fallow 100
XII.--HARROWING AND ROLLING 101
Harrowing:
Why we harrow
Time to harrow 101
Types of harrows 102
Rolling 106
XIII.--LEAVES 108
Facts about leaves 108
The uses of leaves to plants:
Transpiration
Starch making
Digestion of food
Conditions necessary for leaf work 109
How the work of leaves is interfered with 115
XIV.--STEMS 120
What are stems for? 120
How the work of the stem may be interfered with 126
XV.--FLOWERS 128
Function of flowers 128
Parts of flowers 129
Functions of the parts:
Cross pollination 130
Value of a knowledge of the flowers 134
Fruit 136
PART II
SOIL FERTILITY AS AFFECTED BY FARM OPERATIONS AND
FARM PRACTICES
Chapter Page
XVI.--A FERTILE SOIL 141
Physical properties:
Power to absorb and hold water
Power of ventilation
Power to absorb and hold heat 142
Biological properties 143
Nitrogen-fixing germs 144
Nitrifying germs 145
Denitrifying germs 147
Chemical properties:
Nitrogen in the soil
Phosphoric acid in the soil
Potash in the soil
Lime in the soil
Great importance of physical properties 147
Maintenance of fertility 150
XVII.--SOIL WATER 151
Importance of soil water 151
Necessity of soil water 151
Sources and forms of soil water 153
Too much water 154
Not enough water 154
Loss of soil water 155
How some farm operations influence soil water 156
Hoeing, raking, harrowing and cultivating 158
Manures and soil water 159
Methods of cropping and soil water 159
Selection of crops with reference to soil water 160
XVIII.--THE AFTER-CULTIVATION OF CROPS 164
Loss of water by evaporation 164
Loss of water through weeds 165
Saving the water 165
Time to cultivate 166
Tools for after-cultivation 167
Hilling and ridging 169
XIX.--FARM MANURES 171
The functions of manures and fertilizers 171
Classification 171
Importance of farm manures 172
Barn or stable manure 173
Loss of value 173
Checking the losses 176
Applying the manure to the soil 177
Proper condition of manure when applied 179
Composts 181
XX.--FARM MANURES, CONCLUDED 183
Green-crop manures:
Functions 183
Benefits 185
Character of best plants for green-crop manuring 185
The time for green-manure crops 186
Leguminous green-manure crops 186
Non-leguminous green-manure plants 191
XXI.--COMMERCIAL FERTILIZERS 192
The raw materials 192
Sources of nitrogen 193
Sources of phosphoric acid 195
Sources of potash 199
Sources of lime 200
XXII.--COMMERCIAL FERTILIZERS, CONTINUED 202
Mixed fertilizers:
What they are
Many brands
Safeguard for the farmer
Low grade materials
Inflating the guarantee 202
Valuation 205
Low grade mixtures 207
Buy on the plant food basis 209
XXIII.--COMMERCIAL FERTILIZERS, CONCLUDED 211
Home mixing of fertilizers 211
Kind and amount to buy 212
The crop 213
The soil 215
The system of farming 215
Testing the soil 215
XXIV.--ROTATION OF CROPS 219
Systems of cropping 219
The one crop system 221
Rotation of crops 224
Benefits derived from rotation of crops 230
The typical rotation 231
Conditions which modify the rotation 232
General rules 233
Length of rotation 233
XXV.--FARM DRAINAGE 235
How surplus water affects fertility 235
Indications of a need of drainage 235
Drains:
Surface drains
Open ditch drains
Covered drains or under drains 236
Influence of covered drains on fertility 237
Location of drains:
Grade
Tile drains 238
GLOSSARY 241
LIST OF ILLUSTRATIONS
The farm equipment--plants, soils, animals, tools,
buildings _Frontispiece_
Figure Facing Page
1. Specimen plants for study 6
2. The first effort of a sprouting seed 7
3. Germinating seeds with roots 7
4. To show that plant roots take water from the soil 10
5. To show that plant roots take food from the soil 10
6. A radish root, from which the stored food has been
used to help produce a crop of seeds 11
7. A sweet-potato root producing new plants 11
8. Sweet-potato roots 14
9. Soy-bean roots 15
10. A plow stopped in the furrow, to show what it does to
the roots of plants when used for after-cultivation 18
11. A corn-plant ten days after planting the seed 19
12. To show where growth in length of the root takes place 22
13. Radish seeds sprouted on dark cloth 22
14. To show how water gets into the roots of plants 23
15. To show osmose 23
16. To show that roots need air 26
17. Comparison of fresh and boiled water 26
18. Comparison of moist sand and puddled clay 27
19. Comparing soils 32
20. Water-test of soils 33
21. To show what becomes of the water taken from the soil
by roots 40
22. Percolation experiment. To show the relative powers
of soils to take in water falling on the surface 41
23. Bottles used in place of the lamp chimneys in Figs.
22 and 24 44
24. Capillarity of soils. To show the relative powers of
soils to take water from below 44
25. Water-absorbing and water-holding powers of soils 45
26. Capillary tubes. To show how water rises in small
tubes or is drawn into small spaces 48
27. Capillary plates 48
28. A cone of soil to show capillarity 49
29. To show the relative amounts of film-moisture held
by coarse and fine soils 49
30. To show the effect of a soil mulch 56
31. Soil temperature experiment 57
32. Charts showing average temperature of a set of dry
and wet soils during a period of five days 60
33. To show the value of organic matter 61
34. Soy-bean roots, showing nodules or tubercles 64
35. Garden-pea roots, showing tubercles or nodules 65
36. To show that seeds need water for germination 72
37. To show that seeds need air for germination 72
38. To show that seeds need air for germination 73
39. A seed-tester: two plates and a moist cloth 80
40. A seed-tester: a plaster cast with cavities in the
surface for small seeds 80
41. Germinating corn-kernel and bean 81
42. To show how the bean-plant gets up 82
43. To show how the corn-plant gets out of the soil 82
44. To show the use of cotyledons 83
45. To show the use of the kernel to the young corn-plant 86
46. To show how deeply seeds should be planted 87
47. Operations of seed-planting 88
48. A collection of planting machines 89
49. Spading-fork and spade 92
50. A wood beam-plow 93
51. A slip-nose share and a slip-nose 96
52. A straight knife coulter 96
53. An iron beam-plow with rolling coulter and double
clevis 96
54. A rolling cutter-harrow 97
55. Spring-toothed harrows 97
56. Spike-toothed harrows 104
57. A coulter-toothed harrow 104
58. A plank harrow 105
59. To show transpiration 108
60. Amount of transpiration 109
61. To show that growing leaves contain starch 114
62. To show that starch disappears from the leaf when
the plant is placed in the dark 114
63. To show that sunlight is necessary for starch-making
by leaves 115
64. To show that chlorophyl is necessary for starch
formation in the leaf 115
65. To show the giving off of gas by leaves, and that
sunlight is necessary for it 118
66. Seedling radishes reaching for light 119
67. Elm leaves injured by the "imported elm-tree
leaf-beetle," a chewing insect 119
68. A horse-chestnut stem, showing leaves, buds, and
scars, where last year's leaves dropped off 128
69. An underground stem. Buds show distinctly 129
70. Flower of cherry 130
71. Flower of apple 130
72. Pistil and stamen of flowering raspberry 131
73. Flower of buttercup 131
74. A magnolia flower showing central column of pistils
and stamens 134
75. Flowers of squash 135
76. Flower of a lily 136
77. Bud and flower of jewel-weed or "touch-me-not" 137
78. Pistillate flower and perfect flower of strawberry 137
79. A crop of cowpeas 178
80. Red clover 179
81. Soy-beans in young orchard 182
82. A young alfalfa plant just coming into flower 183
83. Cross-sections of stone-drains 238
84. Cross-section of a pole-drain and of a tile-drain 238
85. A collection of drainage tools 239
86. A poorly laid tile-drain and a properly graded
tile-drain 239
PART I
General Principles Underlying Plant Culture
THE FIRST BOOK OF FARMING
PART I
_General Principles Underlying Plant Culture_
CHAPTER I
INTRODUCTION TO PLANTS
Our object in reading and studying this book is to find out some facts
that will help those of us who are thinking of going into farming and
gardening as a business or recreation to start right, and will also
help those of us that are already in the business to make our farms
and gardens more productive.
In order to make the book of greatest value to you, I would urge you
not only to read and study it, but also to make the excursions
suggested and to perform the experiments. In other words, it will be
of much greater value to you if you will make the observations and
investigations and find out for yourselves the important facts and
principles rather than simply take statements of the book
unquestioned.
A very good time to begin this work is during the latter part of the
summer, when the summer crops are ripening and the fall and winter
crops are starting into growth. So suppose we begin our study with a
visit to some farm in early September, to bring to mind the many
things a farmer works with, the many things he has to think about and
know about.
As we approach the farm we will probably see first the farm-house
surrounded by shade trees, perhaps elms or maples, with the barns and
other buildings grouped nearby. As we pass up the front walk we notice
more or less lawn of neatly clipped grass, with flower beds bordering
the walk, or we may find a number of chickens occupying the front
yard, and the flower beds, placed in red half-barrels, set upon short
posts. In the flower beds we may find petunias, nasturtiums,
geraniums, rose bushes and other flowering plants. Going around the
house, we come upon the dairy, with its rack of cans and pans set out
for the daily sunning and airing. Nearby is a well with its oaken
bucket; at the barn we find the farmer, and he very kindly consents to
go with us to answer questions. In the barn and sheds we find wagons,
plows, harrows, seed drills, hoes, rakes, scythes and many other tools
and machines. Passing on to the fields, we go through the vegetable
garden, where are carrots, parsnips, cabbages, beets, celery, sage and
many other vegetables and herbs.
On the right, we see a field of corn just ready to harvest, and beyond
a field of potatoes. On the left is the orchard, and we are invited to
refresh ourselves with juicy apples. In the field beyond the hired
man is plowing with a fine team of horses. In the South we would find
a field of cotton and one of sweet potatoes, and perhaps sugar cane or
peanuts. We have not failed to notice the pig weeds in the corn field
nor the rag weed in the wheat stubble, and many other weeds and
grasses in the fence corners.
Perhaps we may meet the cows coming from pasture to the stable. All
the way we have been trampling on something very important which we
will notice on our way back. In this field we find a coarse sandy
soil, in the next one a soil that is finer and stiffer. The plow is
turning up a reddish soil. In the garden we find the soil quite dark
in color.
But these are only a few of the things we have found. If you have used
your notebook you will discover that you have long lists of objects
which you have noticed, and these may be grouped under the following
headings: Animals, Plants, Soils, Buildings, Tools, etc.
The farmer, then, in his work on the farm deals with certain agents,
chief among which are Soils, Plants, Animals, Tools and Buildings.
Other agents which assist or retard his work according to
circumstances are the air, sunlight, heat, moisture, plant food,
microscopic organisms called bacteria, etc. These agents are
controlled in their relations to one another by certain forces which
work according to certain laws and principles of nature. To work
intelligently and to obtain the best results the farmer must become
familiar with these agents and must work in harmony with the laws and
principles which control them.
Let us take up the study of some of these groups of agents, beginning
with the most important or central one on the farm.
Which do you think is the most important group? Some will say "tools."
The majority will probably say, study the soil first, "because we must
work the soil before we can grow good crops." Some few will mention
"plants." This last is right. The farm animals are dependent on plants
for food. We till or work the soil to produce plants. Plants are
living, growing things, and certain requirements or conditions are
necessary for their growth and development; we cannot intelligently
prepare the soil for plant growth until we know something about the
work of plants and the conditions they need to do their work well.
For our first study of plants let us get together a number of farm and
garden plants. Say, we have a corn plant, cotton, beet, turnip,
carrot, onion, potato, grass, geranium, marigold, pigweed, thistle, or
other farm or garden plants. In each case get the entire plant, with
as much root as possible. Do these plants in any way resemble one
another? All are green, all have roots, all have stems and leaves,
some of them have flowers, fruit, and seeds, and the others in time
will produce them.
Why does the farmer raise these plants? For food for man and animals;
for clothing; for ornamental purposes; for pleasure, etc.
[Illustration: FIG. 1.--SPECIMEN PLANTS FOR STUDY.]
[Illustration: FIG. 2.
The first effort of a sprouting seed is to send a root down into the
soil.]
[Illustration: FIG. 3.
Germinating seeds produce roots before they send a shoot up into the
air.]
Which part of any or all of these farm plants is of greatest
importance to the plant itself?
I am sure that you will agree that the root is the part most important
to the plant itself, for if any part of a plant be separated from the
root, that part ceases growth and will soon die, unless it is able to
put out new roots. But the root from which the plant was cut will
generally send up new shoots, unless it has nearly completed its life
work. When a slip or cutting is placed in water or in moist sand it
makes a root before it continues much in growth. When a seed is
planted its first effort is to send a rootlet down into the soil.
Experiment to see if this is true by planting slips of willow, or
geranium, or by planting corn or beans in a glass tumbler of soil, or
in a box having a glass side, placing the seeds close to the glass;
then watch and see what the seed does. Figs. 2 and 3.
Which of the parts of the plant is of greatest importance to the
farmer or any plant grower, or to which part of a plant should the
plant grower give his best attention? You will probably mention
different parts of the different plants in answering this question.
For instance, some will say, "The seed is the most important part of
the wheat plant to the farmer, for that is what the wheat is grown
for." "The fruit is the most important part of the apple plant for the
same reason." "The leaves and grain of the corn, the leaves of the
cabbage, are the important parts of these plants and should have the
best attention of the grower, because they are the parts for which he
grows the plants." But you must remember that all of these parts are
dependent on the root for life and growth, as was brought out in the
answer to the last question, and that if the farmer or plant grower
desires a fine crop of leaves, stems, flowers, fruit or seeds, he must
give his very best attention to the root. Judging from the poor way in
which many farmers and plant growers prepare the soil for the plants
they raise, and the poor way they care for the soil during the growth
of the plants, they evidently think least of, and give least attention
to, the roots of the plants.
Then, in studying our plants, which part shall we study first? Why,
the roots, of course: To find out what they do for the plant, how they
do this work, and what conditions are necessary for them to grow and
to do their work well.
CHAPTER II
ROOTS
USES OF ROOTS TO PLANTS
Of what use are roots to plants, or, what work do they perform for the
plants?
If the reader has ever tried to pull up weeds or other plants he will
agree that one function of the roots of plants is to hold them firmly
in place while they are growing.
=Experiment.=--Pull two plants from the soil, shake them free of
earth, and place the roots of one in water and expose the roots of the
other to the air. Notice that the plant whose roots are exposed to the
air soon wilts, while the one whose roots were placed in water keeps
fresh. You have noticed how a potted plant will wilt if the soil in
the pot is allowed to become dry (see Fig. 4), or how the leaves of
corn and other plants curl up and wither during long periods of dry
weather. It is quite evident roots absorb moisture from the soil for
the plant.
=Experiment.=--Plant some seeds in tumblers or in boxes filled with
sand and in others filled with good garden soil. Keep them well
watered and watch their progress for a few weeks (see Fig. 5). The
plants in the garden soil will grow larger than those in the sand. The
roots evidently must get food from the soil and those in the good
garden soil get more than those in the poorer sand. Another important
function of plant roots then is to take food from the soil for the
plant.
You know how thick and fleshy the roots of radishes, beets and turnips
are. Well, go into the garden and see if you can find a spring radish
or an early turnip that has sent up a flower stalk, blossomed and
produced seeds. If you are successful, cut the root in two and notice
that instead of being hard and fleshy like the young radish or turnip,
it has become hollow, or soft and spongy (see Fig. 6). Evidently the
hard, fleshy young root was packed with food, which it afterwards gave
up to produce flower stalk and seeds.
A fourth use of the root, then, is to store food for the future use of
the plant.
=Experiment.=--Plant a sweet potato or place it with the lower end in
a tumbler of water and set it in a warm room. Observe it from day to
day as it puts out new shoots bearing leaves and roots (see Fig. 7).
Break these off and plant them in soil and you have a number of new
plants. If you can get the material, repeat this experiment with roots
of horse-radish, raspberry, blackberry or dahlia. From this we see
that it is the work of some roots to produce new plants. This function
of roots is made use of in propagating or obtaining new plants of the
sweet potato, horse-radish, blackberry, raspberry, dahlia and other
plants.
[Illustration: FIG. 4.
To show that plant-roots take water from the soil, the plants in _A_
are suffering from thirst. _B_ has sufficient water.]
[Illustration: FIG. 5.
To show that plant roots take food from the soil. Both boxes were
planted at the same time.]
[Illustration: FIG. 6.
A radish root, from which the stored food has been used to help
produce a crop of seeds. Notice the spindle shaded seed-vessels.]
[Illustration: FIG. 7.
A sweet-potato root producing new plants.]
We have now learned five important things that roots do for plants,
namely:
Roots hold plants firmly in place.
They absorb water from the soil for the plants.
They absorb food from the soil for the plants.
Some roots store food for the future use of the plant.
Some roots produce new plants.
How do the roots do this work? To answer this question it will be
necessary to study the habit of growth of the roots of our plants.
HABIT OF GROWTH OF ROOTS
The proper place to begin this study is in the field or garden. So we
will make another excursion, and this time we will take with us a
pick-axe or mattock, a shovel or two, a sharp stick, a quart or
half-gallon pitcher, and several buckets of water. Arrived in the
field, we will select a well-developed plant, say, of corn, potato or
cotton. Then we will dig a hole about six feet long, three feet wide,
and five or six feet deep, close to the plant, letting one side come
about four or five inches from the base of the plant. It will be well
to have this hole run across the row rather than lengthwise with it.
Then with the pitcher pour water about the base of the plant and wash
the soil away from the roots. Gently loosening the soil with the
sharpened stick will hasten this work. In this way carefully expose
the roots along the side of the hole, tracing them as far as possible
laterally and as deep as possible, taking care to loosen them as
little as possible from their natural position. (See Figs. 8 and 9.)
Having exposed the roots of one kind of plant to a width and depth of
five or six feet, expose the roots of six or eight plants of different
kinds to a depth of about eighteen inches. As this may require more
time than we can take for it in one day, it will be well to cover the
exposed roots with some old burlaps or other material until we have
them all ready, in order to keep them from drying and from injury.
When all is ready we will study the root system of each plant and
answer these four questions:
In what part of the soil are most of the roots?
How deep do they penetrate the soil?
How near do they come to the surface of the soil?
How far do they reach out sidewise or laterally from the plant?
To the first question, "In what part of the soil are most of the
roots?" you will give the following answers: "In the upper layer." "In
the surface soil." "In the softer soil." "In the darker soil." "In the
plowed soil."
These are all correct, but the last is the important one. Most of the
roots will be formed in that part of the soil that has been plowed or
spaded.
The second question, "How deep do the roots penetrate the soil?" is
easily answered. Roots will be found penetrating the soil to depths of
from two to six feet or more. (See Fig. 8.) The author has traced the
roots of cowpea and soy bean plants to depths of five and six feet,
corn roots four and five feet, parsnips over six feet. The
sweet-potato roots illustrated in Fig. 8 penetrated the soil to a
depth of over five feet. The roots of alfalfa or lucern have been
traced to depths of from thirteen to sixteen feet or more.
How near to the surface of the soil do you find roots? Main side or
lateral roots will be found within two or three inches of the surface,
and little rootlets from these will be found reaching up as near the
surface as there is a supply of moisture. After a continued period of
wet weather, if the soil has not been disturbed, roots will be found
coming to the very surface and even running along the top of the soil.
As to the fourth question, How far do roots reach out sidewise or
laterally from the plant? you will find roots extending three, four,
five and even six or more feet from the plant. They have numerous
branches and rootlets, which fill all parts of the upper soil. Tree
roots have been found thirty or forty feet in length.
We started on this observation lesson to find out something about the
habit of growth of roots, so that we could tell how the roots do their
work for the plant. But before going on with that question, let us
stop right here and see whether we cannot find some very important
lessons for the farmer and plant grower from what we have already
seen. Is a knowledge of these facts we have learned about roots of any
value to the farmer? Let us examine each case and see.
Of what value is it to the farmer to know that the larger part of the
roots of farm plants develop in that part of the soil that has been
plowed or spaded? It tells him that plowing tends to bring about the
soil conditions which are favorable to the growth and development of
roots. Therefore, the deeper he plows, the deeper is the body of the
soil having conditions best suited for root growth, and the larger
will be the crop which grows above the soil.
Of what value is it to the farmer to know that the roots of farm
plants penetrate to depths of five or six feet in the soil? To answer
this question it will be necessary for us to know something of the
conditions necessary for root growth. So we will leave this till
later.
Of what value is it to the farmer to know that many of the roots of
his farm plants come very near the surface of the soil? It tells him
that he should be careful in cultivating his crop to injure as few of
these roots as possible. In some parts of the country, particularly in
the South, the tool commonly used for field cultivation is a small
plow. This is run alongside of the row, throwing the soil from the
crop, and then again throwing the soil to the crop. Suppose we
investigate, and see how this affects the roots of the crop.
[Illustration: FIG. 8.
Sweet potato roots. The great mass of the roots is in the plowed soil.
Many of them reach out 5 to 7 feet from the plant. Some reach a depth
of more than 5 feet, and others come to the very surface of the soil.]
[Illustration: FIG. 9.
Soy-bean roots showing location, extent and depth of root-growth.]
Let us visit a field where some farmer is working a crop with a plow,
or get him to do it, for the sake of the lesson. We will ask him to
stop the plow somewhere opposite a plant, then we will dig a hole a
little to one side of the plow and wash away the soil from over the
plow (see Fig. 10), and see where the roots are. We will find that the
plow-point runs under many strong-feeding lateral roots and tears them
off, thus checking the feeding power of the plant, and consequently
checking its growth. Now, if we can get a cultivator, we will have
that run along the row and then wash away the loosened soil. It will
be found that few, if any, of the main lateral roots have been
injured.
Is it of any value to the farmer to know that roots extend laterally
three to six feet and more on all sides of the plant, and that every
part of the upper soil is filled with their branches and rootlets?
This fact has a bearing on the application of manures and fertilizers.
It tells the farmer that when he applies the manure and fertilizers to
the soil he should mix the most of them thoroughly all through the
soil, placing only a little directly in the row to start the young
plant.
To find out how quickly the roots reach out into the soil, wash the
soil away from some seedlings that have been growing only a few days,
say, seven, ten and fifteen. (See Fig. 11.)
From our observations, then, we have learned the important lessons of
deep, thorough plowing, careful shallow after-cultivation, and that
fertilizers should be well mixed with the soil.
We are now ready to go back to our study of the habit of growth of
roots, and can perhaps tell something of how the root does its work
for the plant.
It is very easy to see how the roots hold the plant firmly in place,
for they penetrate so thoroughly every part of the soil, and to such
distances, that they hold with a grip that makes it impossible to
remove the plant from the soil without tearing it free from the roots.
It is also on account of this very thorough reaching out through the
soil that the roots are able to supply the plant with sufficient
moisture and food.
We have doubtless observed that most of these roots are very slender
and many very delicate. How did they manage to reach out into the soil
so far from the plant? Or where does the root grow in length? To
answer this question I will ask you to perform the following
experiment:
=Experiment.=--Place some kernels of corn or other large seeds on a
plate between the folds of a piece of wet cloth. Cover with a pane of
glass or another plate. Keep the cloth moist till the seeds sprout and
the young plants have roots two or three inches long. Now have at hand
a plate, two pieces of glass, 4 by 6 inches, a piece of white cloth
about 4 by 8 inches, a spool of dark thread, and two burnt matches, or
small slivers of wood. A shallow tin pan may be used in place of the
plate. Lay one pane of glass on the plate, letting one end rest in the
bottom of the plate and the other on the opposite edge of the plate.
At one end of the piece of cloth cut two slits on opposite sides about
an inch down from the end and reaching nearly to the middle. Wet the
cloth and spread it on the glass. Take one of the sprouted seeds, lay
it on the cloth, tie pieces of thread around the main root at
intervals of one-quarter inch from tip to seed. Tie carefully, so that
the root will not be injured. Place the second pane of glass over the
roots, letting the edge come just below the seed, slipping in the
slivers of wood to prevent the glass crushing the roots. Wrap the two
flaps of the cloth about the seed. Pour some water in the plate and
leave for development. (Fig. 12.) A day or two of waiting will show
conclusively that the lengthening takes place at the tip only, or just
back of the tip. Is this fact of any value to the farmer? Yes. The
soft tender root tips will force their way through a mellow soil with
greater ease and rapidity than through a hard soil, and the more rapid
the root growth the more rapid the development of the plant. This
teaches us again the lesson of deep, thorough breaking and pulverizing
of the soil before the crop is planted.
We have learned that the roots grow out into the soil in search of
moisture and food, which they absorb for the use of the plant. How
does the root take in moisture and food? Many people think that there
are little mouths at the tips of the roots, and that the food and
moisture are taken in through them. This is not so, for examination
with the most powerful microscopes fails to discover any such mouths.
Sprout seeds of radish, turnip or cabbage, or other seeds, on dark
cloth, placed in plates and kept moist. Notice the fuzz or mass of
root hairs near the ends of the tender roots of the seedlings (Fig.
13). Plant similar seed in sand or soil, and when they have started
to grow pull them up and notice how difficult it is to remove all of
the sand or dirt from the roots. This is because the delicate root
hairs cling so closely to the soil grains. The root hairs are
absorbing moisture laden with plant food from the surface of the soil
particles. The root hairs are found only near the root tips. As the
root grows older, its surface becomes tougher and harder, and the
hairs die, while new ones appear on the new growth just back of the
root tips, which are constantly reaching out after moisture and food.
The moisture gets into the root hairs by a process called osmose. The
following interesting experiment will give you an idea of this process
or force of osmose.
[Illustration: FIG. 10.
A plow stopped in the furrow, to show what it does to the roots of
plants when used for after-cultivation. Notice the point of the plow
under the roots.]
[Illustration: FIG. 11.
A corn-plant ten days after planting the seed. To show how quickly the
roots reach out into the soil. Some of the roots were over 18 inches
long.]
=Experiment.=--Procure a wide-mouthed bottle, an egg, a glass tube
about three inches long and a quarter-inch in diameter, a candle, and
a piece of wire a little longer than the tube. Remove a part of the
shell from the large end of the egg without breaking the skin beneath.
This is easily done by gently tapping the shell with the handle of a
pocket-knife until it is full of small cracks, and then, with the
blade of the knife, picking off the small pieces. In this way remove
the shell from the space about the size of a nickel. Remove the shell
from the small end of the egg over a space about as large as the end
of the glass tube. Next, from the lower end of the candle cut a piece
about one-half inch long. Bore a hole in this just the size of the
glass tube. Now soften one end of the piece of candle with the hole
in it and stick it on to the small end of the egg so that the hole in
the candle comes over the hole in the egg. Heat the wire, and with it
solder the piece of candle more firmly to the egg, making a
water-tight joint. Place the glass tube in the hole in the piece of
candle, pushing it down till it touches the egg. Then, with the heated
wire, solder the tube firmly in place. Now run the wire down the tube
and break the skin of the egg just under the end of the tube. Fill the
bottle with water till it overflows, and set the egg on the bottle,
the large end in contact with the water (Fig. 14). In an hour or so
the contents of the egg will be seen rising in the glass tube. This
happens because the water is making its way by osmose into the egg
through the skin, which has no openings, so far as can be discovered.
If the bottle is kept supplied with water as fast as it is taken up by
the egg, almost the entire contents of the egg will be forced out of
the tube. In this way water in which plant food is dissolved enters
the slender root hairs and rises through the plant.
=Experiment.=--This process of osmose may also be shown as follows
(Fig. 15): Remove the shell from the large end of an egg without
breaking the skin, break a hole in the small end of the egg and empty
out the contents of the egg; rinse the shell with water. Fill a
wide-mouthed bottle with water colored with a few drops of red ink.
Fill the egg-shell partly full of clear water and set it on the bottle
of colored water. Colored water will gradually pass through the
membrane of the egg and color the water in the shell. Prepare another
egg in the same way, but put colored water in the shell and clear
water in the bottle. The colored water in the shell will pass through
the skin and color the water in the bottle. Sugar or salt may be used
in place of the red ink, and their presence after passing through the
membrane may be detected by taste.
CONDITIONS NECESSARY FOR ROOT GROWTH
We have learned some of the things that the roots do for plants and a
little about how the work is done. The next thing to find out is:
What conditions are necessary for the root to do its work?
We know that a part of the work of the root is to penetrate the soil
and hold the plant firmly in place. Therefore, it needs a firm soil.
We know that the part of the root which penetrates the soil is tender
and easily injured. Therefore, for rapid growth the root needs a
mellow soil.
We know that part of the work of the root is to take moisture from the
soil. Therefore, it needs a moist soil.
We know that part of the work of the root is to take food from the
soil. Therefore, it needs a soil well supplied with plant food.
We know that roots stop their work in cold weather. Therefore, they
need a warm soil.
Another condition needed by roots we will find out by experiment.
=Experiment.=--Take two wide-mouthed clear glass bottles (Fig. 16);
fill one nearly full of water from the well or hydrant; fill the other
bottle nearly full of water that has been boiled and cooled; place in
each bottle a slip or cutting of Wandering Jew (called also inch
plant, or tradescantia, and spiderwort), or some other plant that
roots readily in water. Then pour on top of the boiled water about a
quarter of an inch of oil--lard oil or cotton-seed oil or salad oil.
This is to prevent the absorption of air. In a few days roots will
appear on the slip in the hydrant water, while only a very few short
ones, if any, will appear in the boiled water, and they will soon
cease growing. Why is this? To answer this question, try another
experiment. Take two bottles, filled as before, one with hydrant water
and the other with boiled water; drop into each a slip of glass or a
spoon or piece of metal long enough so that one end will rest on the
bottom and the other against the side of the bottle, and let stand for
an hour or so (Fig. 17). At the end of that time bubbles of air will
be seen collecting on the glass or spoon in the hydrant water, but
none in the boiled water. This shows us that water contains more or
less air, and that boiling the water drives this air out. The cutting
in the boiled water did not produce roots because there was no air in
it and the oil kept it from absorbing any.
=Experiment.=--Into some tumblers of moist sand put cuttings of
several kinds of plants that root readily (Fig. 18), geranium,
tradescantia, begonia, etc. Put cuttings of same plants into tumblers
filled with clay that has been wet and stirred very thoroughly, until
it is about the consistency of cake batter. Keep the sand and puddled
clay moist; do not allow the clay to crack, which it will do if it
dries. The cuttings in the sand will strike root and grow, while most,
if not all, those in the clay will soon die. The reason for this is
that the sand is well ventilated and there is sufficient air for root
development, while the clay is very poorly ventilated, and there is
not sufficient air for root growth.
These experiments show us that to develop and do their work roots need
air or a well-ventilated soil.
We have found the conditions which are necessary for the growth and
development of plant roots, namely:
A firm, mellow soil.
A moist soil.
A soil supplied with available plant food.
A warm soil.
A ventilated soil.
These are the most important facts about plant growth so far as the
plant grower is concerned. In other words, these conditions which are
necessary for root growth and development are the most important
truths of agriculture, or they are the foundation truths or principles
upon which all agriculture is based. Having found these conditions,
the next most important step is to find out how to bring them about in
the soil, or, if they already exist, how to keep them or to improve
them. This brings us, then, to a study of soils.
[Illustration: FIG. 12.
To show where growth in length of the root takes place. Forty hours
before the photograph was taken the tip of the root was ¼ inch from
the lowest thread. The glass cover was taken from this in order to get
a good picture of the root.]
[Illustration: FIG. 13.
Radish seeds sprouted on dark cloth. To show root hairs.]
[Illustration: FIG. 14.
To show how water gets into the roots of plants. Water passed up into
the egg through the skin, or membrane, and forced the contents up the
glass tube until it began to overflow.]
[Illustration: FIG. 15.
To show osmose (see page 19).]
CHAPTER III
SOILS
The soil considered agriculturally, is that part of the earth's crust
which is occupied by the roots of plants and from which they absorb
food and moisture.
RELATION OF SOIL TO PLANTS
We have learned that plant roots penetrate the soil to hold the plant
in a firm and stable position, to absorb moisture and with it plant
food. We learned also that for roots to do these things well, the soil
in which they grow must be mellow and firm, and must contain moisture
and plant food, air must circulate in its pores and it must be warm.
How can we bring about these conditions? To answer this question
intelligently it will be necessary for us to study the soil to find
out something about its structure, its composition, its
characteristics; also, how it was made and what forces or agencies
were active in making it. Are these forces acting on the soil at the
present time? Do they have any influence over the conditions which are
favorable or unfavorable to plant growth? If so, can we control them
in their action for the benefit or injury of plants?
We will begin this soil study with an excursion and a few experiments.
Go to the field. Examine the soil in the holes dug for the root
lessons, noticing the difference between the upper or surface soil and
the under or subsoil. Examine as many kinds of surface soils and
subsoils as possible, also decayed leaf mould, the black soil of the
woods, etc. If there are in the neighborhood any exposed embankments
where a road has been cut through a hill, or where a river or the sea
water has cut into a bank of soil, visit them and examine the exposed
soils.
=Experiment.=--Place in separate pans, dishes, plates, boxes, or on
boards, one or two pints each of sand, clay, decayed vegetable matter
or leaf mould or woods soil, and garden soil. The soil should be fresh
from the field. Examine the sand, clay and leaf mould, comparing them
as to color; are they light or dark, are they moist or not? Test the
soils for comparative size of particles by rubbing between the fingers
(Fig. 19), noticing if they are coarse or fine, and for stickiness by
squeezing in the hand and noting whether or not they easily crumble
afterwards.
=Experiment.=--Take samples, about a teaspoonful, of sand, clay and
leaf mould. Dry them and then place each in an iron spoon or on a
small coal shovel and heat in stove to redness. It will be found that
the leaf mould will smoke and burn, and will diminish in amount,
while the sand and clay will not.
=Experiment.=--Take two wide-mouthed bottles; fill both nearly full of
water. Into one put about a teaspoonful of clay and into the other the
same amount of sand; shake both bottles thoroughly and set on table to
settle (Fig. 20). It will be found that the sand settles very quickly
and the clay very slowly.
As the result of our three experiments we will find something as
follows:
Sand is light in color, moist, coarse, not sticky, settles quickly in
water, and will not burn.
Clay is darker in color, moist, very fine, quite sticky, settles
slowly in water, and will not burn.
Leaf mould or humus is very dark in color, moist, very fine, slightly
sticky, and burns when placed in the fire.
=Experiment.=--We now have knowledge and means for making simple tests
of soils. Repeat the last three experiments with the garden soil. We
will find, perhaps, that it is dark in color and some of it burns away
when placed in the fire, therefore it contains organic matter or
decaying vegetable matter or humus, as it is called. This sample has
perhaps fine particles and coarse particles; part of it will settle
quickly in water while part settles very slowly, and it is sticky.
Therefore we conclude that there are both clay and sand in it. If we
shake a sample of it in a bottle of water and let it settle for
several days, we can tell roughly from the layers of soil in the
bottom of the bottle the relative amounts of sand and clay in the
soil. Also if we weigh a sample before and after burning we can tell
roughly the amount of organic matter in the soil. Test a number of
soils and determine roughly the proportions of sand, clay and organic
matter in them.
=Experiment.=--Take the pans of soil used in our first soil experiment
and separate the soils in the pans into two parts by a trench across
the centre on the pan. Now wet the soil in one side of the pan and
stir it with a stick or a spoon, carefully smooth the surface of the
soil in the other side of the pan and pour or sprinkle some water on
it, but do not stir it. Set the pans aside till the soils are dry.
This drying may take several days and in the meantime we will study
the classification of soils.
[Illustration: FIG. 16.
To show that roots need air. Bottle _A_ was supplied with fresh water,
and bottle _B_ with water that had been boiled to drive the air out
and then cooled.]
[Illustration: FIG. 17.
Bottle _A_ contains fresh water, bottle _B_ contains boiled water.
Notice the air bubbles in bottle _A._]
[Illustration: FIG. 18.
Tumblers _A_ and _C_ contained moist sand, _B_ and _D_ contained
puddled clay. Cuttings in _B_ and _D_ died, because there was not
sufficient ventilation in the clay for root-development.]
CLASSIFICATION OF SOILS
Soil materials and soils are classified as follows:
_Stones._--Coarse, irregular or rounded rock fragments or pieces of
rock.
_Gravel._--Coarse fragments and pebbles ranging in size from several
inches in diameter down to 1/25 inch.
_Sand._--Soil particles ranging from 1/25 of an inch down to 1/500 of
an inch in diameter. Sand is divided into several grades or sizes.
Coarse sand 1/25 to 1/50 of an inch.
Medium sand 1/50 to 1/100 of an inch.
Fine sand 1/100 to 1/250 of an inch.
Very fine sand 1/250 to 1/500 of an inch.
These grades of sand correspond very nearly with the grains of
granulated and soft sugar and fine table salt.
_Silt._--Fine soil particles ranging from 1/500 to 1/5000 of an inch
in diameter. It feels very fine and smooth when rubbed between the
fingers, especially when moist. A good illustration of silt is the
silicon used for cleaning knives, a small amount of which can be
obtained at most any grocery store. By rubbing some of this between
the fingers, both dry and wet, one can get a fair idea of how a silty
soil should feel. Silt when wet is sticky like clay.
_Clay._--The finest of rock particles, 1/5000 to 1/250000 of an inch
in diameter, too small to imagine. Clay when wet is very soft,
slippery and very sticky. Yellow ochre and whiting from the paint shop
are good illustrations of clay.
_Humus_, or decaying vegetable and animal matter. This is dark brown
or almost black in color--decaying leaves and woods soil are examples.
Soils composed of the above materials:
_Sands or Sandy Soils._--These soils are mixtures of the different
grades of sand and small amounts of silt, clay and organic matter.
They are light, loose and easy to work. They produce early crops, and
are particularly adapted to early truck, fruit and bright tobacco, but
are too light for general farm crops. To this class belongs the
so-called Norfolk Sand. This is a coarse to medium, yellow or brown
sand averaging about five-sixths sand and one-sixth silt and clay and
is a typical early truck soil found all along the eastern coast of the
United States.
"It is a mealy, porous, warm sand, well drained and easily cultivated.
In regions where trucking forms an important part of agriculture, this
soil is sought out as best adapted to the production of watermelons,
canteloupes, sweet potatoes, early Irish potatoes, strawberries, early
tomatoes, early peas, peppers, egg plant, rhubarb and even cabbage and
cauliflower, though the latter crops produce better yields on a
heavier soil."
A very similar sand in the central part of the country is called Miami
Sand and, on the Pacific Coast, Fresno Sand. These names are given to
these type soils by the Bureau of Soils of the United States
Department of Agriculture.
_Loams or Loamy Soils_, consist of mixtures of the sands, silt and
clay with some organic matter. The term loam is applied to a soil
which, from its appearance in the field and the feeling when handled,
appears to be about one-half sand and the other half silt and clay
with more or less organic matter. These are naturally fine in texture
and quite sticky when wet. They would be called clay by many on
account of their stickiness. They are good soils for general farming
and produce good grain, grass, corn, potatoes, cotton, vegetables,
etc.
_Sandy Loams_, averaging about three-fifths sand and two-fifths silt
and clay. These soils are tilled easily and are the lightest desirable
soil for general farming. They are particularly adapted to corn and
cotton and in some instances are used for small fruits and truck
crops.
_Silt Loam_ consists largely of silt with a small amount of sand,
clay, and organic matter. These soils are some of the most difficult
to till, but when well drained they are with careful management good
general farming soils, producing good corn, wheat, oats, potatoes,
alfalfa and fair cotton.
_Clay Loams._--These soils contain more clay than the silt loams. They
are stiff, sticky soils, and some of them are difficult to till. They
are generally considered the strongest soils for general farming. They
are particularly adapted to wheat, hay, corn and grass.
_Gravelly loams_ are from one-fourth to two-thirds coarse grained; the
remaining fine soil may be sandy loam, silt or clay loam. They are
adapted to various crops according to the character of the fine soil.
Some of them are best planted to fruit and forest.
_Stony Loam._--Like the gravelly loam the stony loams are one-fourth
to three-fourths sandy, silty or clay loam, the remainder being rock
fragments of larger size than the gravel. These fragments are
sometimes rough and irregular and sometimes rounded. The stones
interfere seriously with tillage, and naturally the soils are best
planted with forest or fruit.
_Clay Soils._--Clay soils are mixtures of sand, silt, clay and humus,
the clay existing in quite large quantities, there being a greater
preponderance of the clay characteristics than in the clay loams; they
are very heavy, sticky, and difficult to manage. Some clay soils are
not worth farming. Those that can be profitably tilled are adapted to
wheat, corn, hay and pasture.
_Adobe Soils._--These are peculiar soils of the dry West. They are
mixtures of clay, silt, some sand and large amounts of humus. Their
peculiar characteristic is that they are very sticky when wet and bake
very hard when dry and are, therefore, very difficult to manage,
though they are generally very productive when they are moist enough
to support crops.
_Swamp Muck_ is a dark brown or black swamp soil consisting of large
amounts of humus or decaying organic matter mixed with some fine sand
and clay. It is found in low wet places.
_Peat_ is also largely vegetable matter, consisting of tough roots,
partially decayed leaves, moss, etc. It is quite dense and compact and
in some regions is used for fuel.
HOW WERE SOILS MADE?
As a help in finding the answer to this question collect and examine a
number of the following or similar specimens:
_Brick._--Take pieces of brick and rub them together. A fine powder or
dust will be the result.
_Stones._--Rub together pieces of stone; the same result will follow,
except that the dust will be finer and will be produced with greater
difficulty because the stones are harder. Some stones will be found
which will grind others without being much affected themselves.
_Rock Salt or Cattle Salt._--This is a soft rock, easily broken. Place
on a slate or platter one or two pieces about the size of an egg or
the size of your fist. Slowly drop water on them till it runs down and
partly covers the slate, then set away till the water dries up. Fine
particles of salt will be found on the slate wherever the water ran
and dried. This is because the water dissolved some of the rock.
_Lime Stone._--This is harder. Crush two samples to a fine powder and
place one in water and the other in vinegar. Water has apparently no
effect on it, but small bubbles are seen to rise from the sample in
vinegar. The vinegar which is a weak acid is slowly dissolving the
rock. The chemists tell us water will also dissolve the limestone, but
very slowly. There are large areas of soil which are the refuse from
the dissolving of great masses of limestone.
We find that the rocks about us differ in hardness: they are ground to
powder when rubbed together, some are easily dissolved in water,
others are dissolved by weak acids.
Geologists tell us that the whole crust of the earth was at one time
made up of rocks, part of which have been broken down into coarse and
fine particles which form the gravel, sand and clay of our soils. The
organic matter of our soils has been added by the decay of plants and
animals. Several agencies have been active in this work of breaking
down the rocks and making soils of them. If we look about we can
perhaps see some of this work going on now.
_Work of the Sun._--Examine a crockery plate or dish that has been
many times in and out of a hot oven, noticing the little cracks all
over its surface. Most substances expand when they are heated and
contract when they are cooled. When the plate is placed in the oven
the surface heats faster than the inner parts, and cools faster when
taken out of the oven. The result is that there is unequal expansion
and contraction in the plate and consequently tension or pulling of
its parts against each other. The weaker part gives way and a crack
appears. If hot water is put into a thick glass tumbler or bottle, the
inner surface heats and expands faster than the outer parts and the
result is tension and cracking. If cold water be poured on a warm
bottle or piece of warm glass, it cracks, because there is unequal
contraction. In the early part of a bright sunny afternoon feel of the
surface of exposed rocks, bricks, boards, or buildings on which the
sun has been shining. Examine them in the same way early the next
morning. You will find that the rocks are heated by the sun just as
the plate was heated when put into the oven, and when the sun goes
down the rocks cool again. This causes tension in the rocks and
little cracks and checks appear in them just as in the heated plate,
only more slowly. This checking may also be brought about by a cool
shower falling on the sun heated rocks just as the cool water cracked
the warm glass. Many rocks if examined closely will be found to be
composed of several materials. These materials do not expand and
contract alike when heated and cooled and the tendency for them to
check is greater even than that of the plate. This is the case with
most rocks.
[Illustration: FIG. 19.--COMPARING SOILS.]
[Illustration: FIG. 20.--WATER TEST OF SOILS.
Bottle _A_ contains sand and water, bottle _B_ clay and water. The
sand settles quickly, the clay very slowly.]
_Work of Rain._--Rain falling on the rocks may dissolve a part of them
just as it dissolved the rock salt; or, working into the small cracks
made by the sun, may wash out loosened particles; or, during cold
weather it may freeze in the cracks and by its expansion chip off
small pieces; or, getting into large cracks and freezing, may split
the rock just as freezing water splits a water pitcher or the water
pipes.
_Work of Moving Water._--Visit some neighboring beach or the banks of
some rapid stream. See how the waves are rolling the sand and pebbles
up and down the beach, grinding them together, rounding their corners
and edges, throwing them up into sand beds, and carrying off the finer
particles to deposit elsewhere. Now visit a quiet cove or inlet and
see how the quiet water is laying down the fine particles, making a
clay bed. Notice also how the water plants along the border are
helping. They act as an immense strainer, collecting the suspended
particles from the water, and with them and their bodies building beds
of soil rich in organic matter or humus.
The sun, besides expanding and cracking the rocks by its heat, helps
in another way to make soils. It warms the water that has been
grinding soil on the beach or along the river banks and causes some of
it to evaporate. This vapor rises, forms a cloud and floats away in
the air. By and by the vapor forms into rain drops which may fall on
the top of some mountain. These rain drops may wash loosened particles
from the surface or crevices of exposed rocks. These drops are joined
by others until, by and by, they form a little stream which carries
its small burden of rock dust down the slope, now dropping some
particles, now taking up others. Other little streams join this one
until they form a brook which increases in size and power as it
descends the mountain side. As it grows by the addition of other
streams it picks up larger pieces, grinds them together, grinds at its
banks and loads itself with rocks, pebbles, sand and clay. As the
stream reaches the lower part of the mountain where the slope is less
steep, it is checked in its course and the larger stones and pebbles
are dropped while the sand and finer particles are carried on and
deposited on the bottom of some broad quiet river farther down, and
when the river overflows its banks, are distributed over the
neighboring meadows, giving them a new coating of soil and often
adding to their fertility. What a river does not leave along its
course it carries out to sea to help build the sand bars and mud flats
there. The rain drops have now gotten back to the beach where they
take up again the work of grinding the soil.
The work of moving water can be seen in almost any road or cultivated
field during or just after a rain, and particularly on the hillsides,
where often the soil is loosened and carried from higher to lower
parts, making barren sand and clay banks of fertile hillsides and
destroying the fertility of the bottom lands below.
We have already noticed the work of freezing water in splitting small
and large fragments from the rocks. Water moving over the surface of
the earth in a solid form, or ice, was at an earlier period in the
history of the earth one of the most powerful agencies in soil
formation. Away up in Greenland and on the northern border of this
continent the temperature is so low that most if not all of the
moisture that falls on the earth falls as snow. This snow has piled up
until it has become very deep and very heavy. The great weight has
packed the bottom of this great snow bank to ice. On the mountains
where the land was not level the masses of snow and ice, centuries
ago, began to slide down the slopes and finally formed great rivers of
solid water or moving ice.
The geologists tell us that at one time a great river of ice extended
from the Arctic region as far south as central Pennsylvania and from
New England to the Rocky Mountains. This vast river was very deep and
very heavy and into its under surface were frozen sand, pebbles,
larger stones and even great rocks. Thus it acted as a great rasp or
file and did an immense amount of work grinding rocks and making
soils. It ground down mountains and carried great beds of soil from
one place to another. When this great ice river melted, it dropped its
load of rocks and soils, and as a result we find in that region of the
country great boulders and beds of sand and clay scattered over the
land.
_Work of the Air._--The air has helped in the work of wearing down the
rocks and making soils. If a piece of iron be exposed to moist air a
part of the air unites with part of the iron and forms iron rust. In
the same way when moist air comes in contact with some rocks part of
the air unites with part of the rock and forms rock rust which
crumbles off or is washed away by water. Thus the air helps to break
down the rocks. Moving air or wind picks up dust particles and carries
them from one field to another. On sandy beaches the wind often blows
the sand along like snow and piles it into drifts. The entire surface
of sandy regions is sometimes changed in this way. Sands blown from
deserts sometimes bury forests which with their foliage sift the fatal
winding sheet from the dust-laden winds.
_The Work of Plants._--Living plants sometimes send their roots into
rock crevices; there they grow, expand, and split off rock fragments.
Certain kinds of plants live on the surface of rocks. They feed on
the rocks and when they die and decay they keep the surface of the
rocks moist and also produce carbonic acid which dissolves the rocks
slowly just as the vinegar dissolved the limestone in our experiment.
Dead decaying roots, stems, and leaves of plants form largely the
organic matter of the soil. When organic matter has undergone a
certain amount of decay it is called humus, and these soils are called
organic soils or humus soils. The black soils of the woods, swamps and
prairies, contain large amounts of humus.
_Work of Animals._--Earth worms and the larvæ of insects which burrow
in the soil eat soil particles which pass through their bodies and are
partially dissolved. These particles are generally cast out on the
surface of the soil. Thus these little animals help to move soil, to
dissolve soil, and to open up passages for the entrance of air and
rain.
SOIL TEXTURE
We have seen that the soil particles vary in size and that for the
best development of the plant the particles of the soil must be so
arranged that the delicate rootlets can readily push their way about
in search of food, or, in other words, that the soil must have a
certain texture. By the texture of the soil we mean the size of its
particles and their relation to each other. The following terms are
used in describing soil textures: Coarse, fine, open, close, loose,
hard, stiff, compact, soft, mellow, porous, leachy, retentive, cloddy,
lumpy, light, heavy. Which of these terms will apply to the texture of
sand, which to clay, which to humus, which to the garden soil, which
to a soil that plant roots can easily penetrate? We find then that
texture of the soil depends largely on the relative amounts of sand,
silt, clay and humus that it contains.
CHAPTER IV
RELATION OF SOILS TO WATER
IMPORTANCE OF WATER TO PLANTS
We learned in a previous paragraph that plant roots take moisture from
the soil. What becomes of this moisture? We will answer this question
with an experiment.
=Experiment.=--Take a pot or tumbler in which a young plant is
growing, also a piece of pasteboard large enough to cover the top of
the pot or tumbler; cut a slit from the edge to the centre of the
board, then place it on top of the pot, letting the stem of the plant
enter the slit. Now close the slit with wax or tallow, making it
perfectly tight about the stem. If the plant is not too large invert a
tumbler over it (Fig. 21), letting the edge of the tumbler rest on the
pasteboard; if a tumbler is not large enough use a glass jar. Place in
a sunny window. Moisture will be seen collecting on the inner surface
of the glass. Where does this come from? It is absorbed from the soil
by the roots of the plant and is sent with its load of dissolved plant
food up through the stem to the leaves. There most of the moisture is
passed from the leaves to the air and some of it is condensed on the
side of the glass.
By experiments at the Cornell University Agricultural Experiment
Station, Ithaca, N.Y., it has been found that during the growth of a
sixty bushel crop of corn the plants pump from the soil by means of
their roots, and send into the air through their leaves over nine
hundred tons of water. A twenty-five bushel crop of wheat uses over
five hundred tons of water in the same way. This gives us some idea of
the importance of water to the plant and the necessity of knowing
something of the power of the soil to absorb and hold moisture for the
use of the plant. Also the importance of knowing if we can in any way
control or influence the water-holding power of the soil for the good
of the plant.
SOURCES OF SOIL WATER
From what sources does the soil receive water? From the air above, in
the form of rain, dew, hail and snow, falling on the surface, and from
the lower soil. This water enters the soil more or less rapidly.
ATTITUDE OF THE SOILS TOWARDS WATER
Which soils have the greater power to take in the rain which falls on
their surface?
[Illustration: FIG. 21.
To show what becomes of the water taken from the soil by roots.
Moisture, sent up from the roots, has been given off by the leaves and
has condensed on the glass.]
[Illustration: FIG. 22.--PERCOLATION EXPERIMENT.
To show the relative powers of soils to take in water falling on the
surface. _A_, sand; _B_, clay; _C_, humus; _D_, garden soil.]
=Experiment.=--Take four student-lamp chimneys. (In case the chimneys
cannot be found get some slender bottles like salad oil bottles or
wine bottles and cut the bottoms off with a hot rod. While the rod
is heating make a shallow notch in the glass with the wet corner of a
file in the direction you wish to make the cut. When the rod is hot
lay the end of it lengthwise on the notch. Very soon a little crack
will be seen to start from the notch. Lead this crack around the
bottle with the hot rod and the bottom of the bottle will drop off.)
(Fig. 23.) Make a rack to hold them. Tie a piece of cheese cloth or
other thin cloth over the small ends of the chimneys. Then fill them
nearly full respectively, of dry, sifted, coarse sand, clay, humus
soil, and garden soil. Place them in the rack; place under them a pan
or dish. Pour water in the upper ends of the tubes until it soaks
through and drips from the lower end (Fig. 22). Ordinary sunburner
lamp chimneys may be used for the experiment by tying the cloth over
the tops; then invert them, fill them with soil and set in plates or
pans. The sand will take the water in and let it run through quickly;
the clay is very slow to take it in and let it run through; the humus
soil takes the water in quite readily. Repeat the experiment with one
of the soils, packing the soil tightly in one tube and leaving it
loose in another. The water will be found to penetrate the loose soil
more rapidly than the packed soil. We see then that the power of the
soil to take in rainfall depends on its texture or the size and
compactness of the particles.
If the soil of our farm is largely clay, what happens to the rain that
falls on it? The clay takes the water in so slowly that most of it
runs off and is lost. Very likely it carries with it some of the
surface soil which it has soaked and loosened, and thus leaves the
farm washed and gullied.
What can we do for our clay soils to help them to absorb the rain more
rapidly? For immediate results we can plow them and keep them loose
and open with the tillage tools. For more permanent results we may mix
sand with them, but sand is not always to be obtained and is expensive
to haul. The best method is to mix organic matter with them by plowing
in stable manures, or woods soil, or decayed leaves, or by growing
crops and turning them under. The organic matter not only loosens the
soil but also adds plant food to it, and during its decay produces
carbonic acid which helps to dissolve the mineral matter and make
available the plant food that is in it.
Clay soils can also be made loose and open by applying lime to them.
=Experiment.=--Take two bottles or jars, put therein a few spoonsful
of clay soil, fill with water, put a little lime in one of them, shake
both and set them on the table. It will be noticed that the clay in
the bottle containing lime settles in flakes or crumbs, and much
faster than in the other bottle. In the same manner, lime applied to a
field of clay has a tendency to collect the very fine particles of
soil into flakes or crumbs and give it somewhat the open texture of a
sandy soil. Lime is applied to soil for this purpose at the rate of
twenty bushels per acre once in four or five years.
Which soils have the greater power to absorb or pump moisture from
below?
=Experiment.=--Use the same or a similar set of tubes as in the
experiment illustrated in Fig. 23. Fill the tubes with the same kinds
of dry sifted soils. Then pour water into the pan or dish beneath the
tubes until it rises a quarter of an inch above the lower end of the
tubes (Fig. 24). Watch the water rise in the soils. The water will be
found to rise rapidly in the sand about two or three inches and then
stop or continue very slowly a short distance further. In the clay it
starts very slowly, but after several hours is finally carried to the
top of the soil. The organic matter takes it up less rapidly than the
sand, faster than the clay, and finally carries it to the top. By this
and further experiments it will be found that the power of soils to
take moisture from below depends on their texture or the size and
closeness of their particles.
We found the sand pumped the water only a short distance and then
stopped.
What can we do for our sandy soils to give them greater power to take
moisture from below? For immediate results we can compact them by
rolling or packing. This brings the particles closer together, makes
the spaces between them smaller, and therefore allows the water to
climb higher. For more lasting results we can fill them with organic
matter in the shape of stable manures or crops turned under. Clay may
be used, but is expensive to haul.
Which soils have greatest power to hold the water which enters them?
=Experiment.=--Use the same or similar apparatus as for the last
experiment. After placing the cloth caps over the ends of the tubes
label and carefully weigh each one, keeping a record of each; then
fill them with the dry soils and weigh again. Now place the tubes in
the rack and pour water in the upper ends until the entire soil is
wet; cover the tops and allow the surplus water to drain out; when the
dripping stops, weigh the tubes again, and by subtraction find the
amount of water held by the soil in each tube; compute the percentage.
It will be found that the organic matter will hold a much larger
percentage of water than the other soils; and the clay more than the
sand. The tube of organic soil will actually hold a larger amount of
water than the other tubes. (See also Fig. 25.)
In the experiment on page 40 we noticed that the sand took in the
water poured on its surface and let it run through very quickly. This
is a fault of sandy soils.
What can we do for our sandy soils to help them to hold better the
moisture which falls on them and tends to leach through them? For
immediate effect we can close the pores somewhat by compacting the
soil with the roller. For more lasting effects, we can fill them with
organic matter.
Which soils will hold longest the water which they have absorbed? Or
which soils will keep moist longest in dry weather?
[Illustration: FIG. 23.
To show how bottles may be used in place of lamp chimneys shown in
Figs 22 and 24.]
[Illustration: FIG. 24.--CAPILLARITY OF SOILS
To show the relative powers of soils to take water from below.]
[Illustration: FIG. 25.--WATER-ABSORBING AND WATER-HOLDING POWERS OF
SOILS.]
=Experiment.=--Fill a pan or bucket with moist sand, another with
moist clay, and a third with moist organic matter; set them in the sun
to dry and notice which dries last. The organic matter will be found
to hold moisture much longer than the other soils. The power of the
other soils to hold moisture through dry weather can be improved by
mixing organic matter with them.
We find then that the power of soils to absorb and hold moisture
depends on the amount of sand, clay, or humus which they contain, and
the compactness of the particles. We see also how useful organic
matter is in improving sandy and clayey soils.
THE EFFECT OF WORKING SOILS WHEN WET
By this time the soils we left in the pans (see page 26), sand, clay,
humus and garden soil, must be dry. If so, examine them. We find that
the clay which was stirred when wet has dried into an almost bricklike
mass, while that which was not stirred is not so hard, though it has a
thick, hard crust. The sand is not much affected by stirring when wet.
The organic matter which was stirred when wet has perhaps stiffened a
little, but very easily crumbles; the unstirred part was not much
affected by the wetting and drying.
The garden soil after drying is not as stiff as the clay nor as loose
as the sand and humus. This is because it is very likely a mixture of
all three, the sand and the humus checking the baking. This teaches
us that it is not a good plan to work soils when they are wet if they
are stiff and sticky; and that our stiff clay soils can be kept from
drying hard or baking by the use of organic matter. "And that's a
witness" for organic matter.
The relation of the soil to moisture is very important, for moisture
is one of the greatest factors if not the greatest in the growth of
the crop.
The power to absorb or soak up moisture from any source is greatest in
those soils whose particles are smaller and fit closer together.
It is for this reason that strong loams and clay soils absorb and hold
three times as much water as sandy soils do, while peaty or humus
soils absorb a still larger proportion.
The reason why crops burn up so quickly on sandy soils during dry
seasons is because of their weak power to hold water.
The clay and humus soils carry crops through dry weather better
because of their power to hold moisture and to absorb or soak up
moisture from below. It is for this reason also that clay and peaty
soils more often need draining than sandy soils.
When rain falls on a sandy soil it enters readily, but it is apt to
pass rapidly down and be, to a great extent, lost in the subsoil, for
the sand has not sufficient power to hold much of it.
When rain falls on a clay soil it enters less readily because of the
closeness of the particles, and during long rains or heavy showers
some of the water may run off the surface. If the surface has been
recently broken and softened with the plow or cultivator the rain
enters more readily. What does enter is held and is not allowed to run
through as in the case of the sand.
Humus soil absorbs the rain as readily as the sand and holds it with a
firmer grip than clay.
This fact gives us a hint as to how we may improve the sand and clay.
Organic matter mixed with these soils by applying manures or plowing
under green crops will cause the sand to hold the rain better and the
clay to absorb it more readily.
CHAPTER V
FORMS OF SOIL WATER
Water which comes to the soil and is absorbed exists in the soil
principally in two forms: Free water and capillary water.
FREE WATER
Free water is that form of water which fills our wells, is found in
the bottoms of holes dug in the ground during wet seasons and is often
found standing on the surface of the soil after heavy or long
continued rains. It is sometimes called ground water or standing water
and flows under the influence of gravity.
Is free water good for the roots of farm plants? If we remember how
the root takes its food and moisture, namely through the delicate root
hairs; and also remember the experiment which showed us that roots
need air, we can readily see that free water would give the root hairs
enough moisture, but it would at the same time drown them by cutting
off the air. Therefore free water is not directly useful to the roots
of house plants or farm plants, excepting such as are naturally
swamp plants, like rice, which grows part of the time with its
roots covered with free water.
[Illustration: FIG. 26.--CAPILLARY TUBES.
To show how water rises in small tubes or is drawn into small spaces.]
[Illustration: FIG. 27.--CAPILLARY PLATES.
Water is drawn to the highest point where the glass plates are closest
together.]
[Illustration: FIG. 28.
A cone of soil to show capillarity. Water poured about the base of
this cone of soil has been drawn by capillary force half-way to the
top.]
[Illustration: FIG. 29.
To show the relative amounts of film-moisture held by coarse and fine
soils. The colored water in bottle _A_ represents the amount of water
required to cover the half pound of pebbles in the tumbler _B_ with a
film of moisture. The colored water in bottle _C_ shows the amount
required to cover the soil grains in the half pound of sand in tumbler
_D._]
CAPILLARY WATER
If you will take a number of glass tubes of different sizes, the
largest not more than one-fourth of an inch in diameter, and hold them
with one end of each in water or some colored liquid, you will notice
that the water rises in the tubes (Fig. 26), and that it rises highest
in the smallest tube. The force which causes the water to rise in
these tubes is called the capillary force, from the old Latin word
_capillum_ (a hair), because it is most marked in hair-like tubes, the
smaller the tube the higher the water will rise. The water which rises
in the tubes is called capillary water.
Another method of illustrating capillary water is to tie or hold
together two flat pieces of glass, keeping two of the edges close
together and separating the opposite two about one-eighth of an inch
with a sliver of wood. Then set them in a plate of water or colored
liquid and notice how the water rises between the pieces of glass,
rising higher the smaller the space (Fig. 27). It is the capillary
force which causes water to rise in a piece of cloth or paper dipped
in water.
Take a plate and pour onto it a cone-shaped pile of dry sand or fine
soil; then pour water around the base of the pile and note how the
water is drawn up into the soil by capillary force (Fig. 28).
Capillary water is the other important form of water in the soil. This
is moisture which is drawn by capillary force or soaks into the spaces
between the soil particles and covers each particle with a thin film
of moisture.
FILM WATER
Take a marble or a pebble, dip it into water and notice the thin layer
or film of water that clings to it. This is a form of capillary water
and is sometimes called film water or film moisture. Take a handful of
soil that is moist but not wet, notice that it does not wet the hand,
and yet there is moisture all through it; each particle is covered
with a very thin film of water.
Now this film water is just the form of water that can supply the very
slender root hairs without drowning them, that is, without keeping the
air from them. And the plant grower should see to it that the roots of
his plants are well supplied with film water and are not drowned by
the presence of free water. Capillary water may sometimes completely
fill the spaces between the soil particles; when this occurs the roots
are drowned just as in the case of free water as we saw when cuttings
were placed in the puddled clay (see Fig. 18). Free water is
indirectly of use to the plant because it serves as a supply for
capillary and film moisture.
Now I think we can answer the question which was asked when we were
studying the habit of growth of roots but was left unanswered at the
time (see page 14). The question was this: Of what value is it to the
farmer to know that roots enter the soil to a depth of three to six
feet? We know that roots will not grow without air. We also know that
if the soil is full of free water there is no air in it, and,
therefore, roots of most plants will not grow in it. It is, therefore,
of interest to the farmer to see that free water does not come within
at least three or four feet of the surface of the soil so that the
roots of his crops may have plenty of well ventilated soil in which to
develop. If there is a tendency for free water to fill the soil a
large part of the time, the farmer can get rid of it by draining the
land. We get here a lesson for the grower of house plants also. It is
that we must be careful that the soil in the pots or boxes in which
our plants are growing is always supplied with film water and not wet
and soggy with free water. Water should not be left standing long in
the saucer under the pot of a growing plant. It is best to water the
pot from the top and let the surplus water drain into the saucer and
then empty it out.
Which soils have the greatest capacity for film water?
=Experiment.=--Place in a tumbler or bottle one-half pound of pebbles
about the size of a pea or bean; pour a few drops of water on them and
shake them; continue adding water and shaking them till every pebble
is covered with a film of water; let any surplus water drain off. Then
weigh again; the difference in the two weights will be approximately
the weight of the film water that the pebbles can carry. Repeat this
with sand and compare the two amounts of water. A striking
illustration can be made by taking two slender bottles and placing in
them amounts of colored water equal to the amounts of film water held
by the pebbles and sand respectively. In the accompanying illustration
(Fig. 29), _A_ represents the amount of water that was found necessary
to cover the pebbles in tumbler _B_ with a film of moisture. _C_ is
the amount that was necessary to cover with a film the particles of
sand in _D_. The finer soil has the greater area for film moisture. It
has been estimated that the particles of a cubic foot of clay loam
have a possible aggregate film surface of three-fourths of an acre.
CHAPTER VI
LOSS OF SOIL WATER
LOSS OF SOIL WATER AND MEANS OF CHECKING THE LOSS
We noticed in previous paragraphs that soil might at times have too
much water in it for proper ventilation and so check the growth of the
roots of the plant. Now is it possible that soil water may be lost or
wasted and if so can we check the loss?
In the experiment to find out how well the soils would take in the
rainfall (page 40) we noticed that the clay soil took in the water
very slowly and that on a field of clay soil part of the rain water
would be likely to run off over the surface and be lost. Free water
may be lost then, by surface wash.
We noticed methods of checking this loss, namely, pulverizing the soil
with the tillage tools and putting organic matter into it to make it
absorb the rain more readily.
We noticed that water poured on the sand ran through it very quickly
and was apt to be lost by leaching or percolation. This we found could
be checked by rolling the soil and by putting organic matter into it
to close the pores.
We learned that roots take water from the soil for the use of the
plant and send it up to the leaves, which in turn send it out into the
air, or transpire it, as this process is called. We learned also that
the amount transpired is very great. Now water that is pumped up and
transpired by the crops we are growing we consider properly used. But
when weeds grow with the crop and pump and transpire water we consider
this water as lost or wasted.
Water may be lost then by being pumped up and transpired by weeds. And
this is the way weeds do their greatest injury to crops during dry
weather. The remedy is easily pointed out. Kill the weeds or do not
let them get a start.
There is another way, which we are not apt to notice, by which water
may be lost from the soil. When the soil in the pans in a previous
experiment (page 26) had been wet and set aside a few days it became
very dry. How did the water get out of this soil? That at the surface
of the soil evaporated or was changed into vapor and passed into the
air. Then water from below the surface was pumped up by capillary
force to take its place just as the water was pumped up in the tubes
of soil. This in turn was evaporated and the process repeated till all
of the water in the soil had passed into the air. Now this process is
going on in the field whenever it is not raining or the ground is not
frozen very hard.
Water then may be lost by evaporation.
How can we check this loss?
Suppose we try the experiment of covering the soil with some material
that cannot pump water readily.
=Experiment.=--Take four glass fruit jars, two-quart size, with
straight sides. If you cannot get them with straight sides cut off the
tops with a hot iron just below the shoulder; tin pails will do if the
glass jars cannot be had. Fill these with moist soil from the field or
garden, packing it till it is as hard as the unplowed or unspaded
soil. Leave one of them in this condition; from two of them remove an
inch or two of soil and replace it in the case of one with clean, dry,
coarse sand, and in the case of the other with chaff or straw cut into
half-inch lengths. Stir the soil in the fourth one to a depth of one
inch, leaving it light and crumbly. Now weigh the jars and set them
aside. Weigh each day for several days. The four jars illustrated in
Fig. 30 were prepared in this way and allowed to stand seven days. In
that time they lost the following amounts of water:
Amounts of water lost from jars of prepared soil in seven days.
No. 1 packed soil--lost 5.5 oz. equal to about 75 tons per acre.
No. 2 covered with straw--lost 2 oz. equal to about 27 tons per acre.
No. 3 covered with dry sand--lost 0 oz. equal to about tons per acre.
No. 4 covered with crumbled soil--lost 2.5 oz., equal to about 34 tons
per acre.
Why did not 2, 3 and 4 lose as much water as No. 1?
The soil in jar No. 1 was packed and water was pumped to the surface
by capillary force and was evaporated as fast as it came to the
surface.
In No. 2 the water could rise rapidly until it reached the straw, then
it was stopped almost entirely. But the straw being coarse, the air
circulated in it more or less freely and there was a slow loss by
evaporation. In jar No. 3 the water could rise only to the sand, which
was so coarse that the water could not climb on it to the surface, and
the air circulated in the sand so slowly that there was not sufficient
evaporation to affect scales weighing to one-quarter ounce. No. 4 lost
less than No. 1 because, as in the case of the sand, the water could
not climb rapidly to the surface on the coarse crumbs of soil. The
loss that did take place from No. 4 was what the air took from the
loosely stirred soil on the surface with a very little from the lower
soil. Simply stirring the surface of the sod in No. 4 reduced the loss
of water to less than half the loss from the hard soil in No. 1.
This experiment gives us the clew to the method of checking loss of
water from the soil by evaporation. It is to keep the water from
climbing up to the surface, or check the power of the soil to pump the
water to the surface by making it loose on top. This loose soil is
called a soil mulch. Everything that we do to the soil that loosens
and crumbles the surface tends to check the loss of water by
evaporation from the soil below.
[Illustration: FIG. 30.--TO SHOW THE EFFECT OF A SOIL MULCH
1. Packed soil, lost in 7 days 5.5 ozs. water, equal to 75 tons per
acre.
2. Packed soil, covered with straw, lost in 7 days 2 ozs. water, equal
to 27 tons per acre.
3. Packed soil, covered with sand, lost in 7 days 0 ozs. water, equal to
tons per acre.
4. Packed soil, covered with soil mulch, lost in 7 days 2.5 ozs.
water, equal to 34 tons per acre.]
CHAPTER VII
SOIL TEMPERATURE
We learned that roots need heat for their growth and development. Now
what is the relation of the different kinds of soil toward heat or
what are their relative powers to absorb and hold heat?
=Experiment.=--Some days before this experiment, spread on a dry floor
about a half bushel each of sand, clay and decayed leaf mould or black
woods soil. Stir them occasionally till they are thoroughly dry. When
they are dry place them separately in three boxes or large flower pots
and keep dry. In three similar boxes or pots place wet sand, wet clay,
and wet humus. Place a thermometer in each of the soils, placing the
bulb between one and two inches below the surface (Fig. 31). Then
place the soils out of doors where the sun can shine on them and leave
them several days. If a rain should come up protect the dry soils.
Observe and make a record of the temperatures of each soil several
times a day. Chart the average of several days observations. Fig. 32
shows the averages of several days observations on a certain set of
soils.
It will be noticed that the temperature of the soils increased until
the early part of the afternoon and after that time they lost heat.
[Illustration: FIG. 31.--SOIL TEMPERATURE EXPERIMENT.
Thermometer in pot of soil.]
HOW SOILS ARE WARMED
=Experiment.=--Hold your hand in bright sunlight or near a warm stove
or radiator. Your hand is warmed by heat radiated from the sun or warm
stove through the air to your body. In the same manner the rays of the
sun heat the surface of the soil.
=Experiment.=--Take the stove poker or any small iron rod and hold one
end of it in the fire or hold one end of a piece of wire in a candle
or lamp flame. The end of the rod or wire will quickly become very hot
and heat will gradually be carried its entire length until it becomes
too hot to hold. This carrying of the heat from particle to particle
through the length of the rod is called heating by conduction. Now
when the warm rays of the sun reach the soil, or a warm wind blows
over it, the surface particles are warmed and then pass the heat on to
the next ones below, and these in turn pass it to others and so on
till the soil becomes heated to a considerable depth by conduction.
A clay soil will absorb heat by conduction faster than a sandy soil
because the particles of the clay lie so close together that the heat
passes more readily from one to another than in the case of the
coarser sand.
If the soil is open and porous, warm air and warm rains can enter
readily and carry heat to the lower soil.
You have noticed how a pile of stable manure steams in cold weather.
You doubtless know that manure from the horse stable is often used to
furnish heat for hotbeds and for sweet potato beds.
Now the heat which warms the manure and sends the steam out of it, and
warms the hotbed and sweet potato bed, is produced by the decaying or
rotting of the manure. More or less heat is produced by the decay of
all kinds of organic matter. So if the soil is well supplied with
organic matter, the decay of this material will add somewhat to the
warmth of the soil.
HOW SOILS LOSE HEAT
Wet one of your fingers and hold your hand up in the air. The wet
finger will feel colder than the others and will gradually become dry.
This is because some of the heat of your finger is being used to dry
up the water or change it into a vapor, or in other words to evaporate
it.
In the same manner a wet soil loses heat by the evaporation of water
from its surface.
=Experiment.=--Heat an iron rod, take it from the fire and hold it
near your face or hand. You will feel the heat without touching the
rod. The heat is radiated from the rod through the air to your body
and the rod gradually cools. In the same way the soil may lose its
heat by radiating it into the air. A clay soil will lose more heat by
radiation than a sandy soil because the clay is more compact.
CONDITIONS WHICH INFLUENCE SOIL TEMPERATURE
It will be noticed that the dry soils are warmer than the wet ones.
Why is this? Scientists tell us that it takes a great deal more heat
to warm water than it does to warm other substances. Therefore when
soil is wet it takes much more heat to warm it than if it were dry.
It will be seen that of the dry soils the humus is the warmest. Why?
=Experiment.=--Take two thermometers, wrap the bulb of one with a
piece of black or dark colored cloth and the bulb of the other with a
piece of white cloth, then place them where the sun will shine on the
cloth covered bulbs. The mercury in both thermometers will be seen to
rise, but in the thermometer with the dark cloth about the bulb it
will rise faster and higher than in the other. This shows that the
dark cloth absorbs heat faster than the white cloth. In the same
manner a dark soil will absorb heat faster than a light colored soil;
therefore it will be warmer if dry.
Why was the dry clay warmer than the dry sand?
Because its darker color helped it to absorb heat more rapidly than
the sand, and, as the particles were smaller and more compact, heat
was carried into it more rapidly by conduction.
Why were the wet humus and clay cooler than the wet sand?
As they were darker in color and the clay was more compact than the
sand, they must have absorbed more heat, but they also held more
water, and, therefore, lost more heat by evaporation.
[Illustration: FIG. 32.
Charts showing average temperature of a set of dry and wet soils
during a period of five days. _H_, humus; _C_, clay; _S_, sand.]
[Illustration: FIG. 33.
To show the value of organic matter. 1 contains clay subsoil; 2, clay
subsoil and fertilizer; 3, clay subsoil and organic matter. All
planted at the same time.]
Of the dry soils, then, the humus averaged warmest, because, on
account of its dark color, it absorbed heat more readily than the
others. The dry clay was warmer than the sand on account of its color
and compact texture. Of the wet soils the sand was the warmest,
because, on account of its holding less moisture, less heat was
required to raise its temperature and there was less cooling by
evaporation, while the other soils, although they absorbed more heat
than the sand, lost more on account of greater evaporation, due to
their holding more moisture. Why are sandy soils called warm soils and
clay soils said to be cold?
How may we check losses of heat from the soil?
If we make a mulch on the surface of the soil evaporation will be
checked and therefore loss of heat by evaporation will be checked
also. The mulch will also check the conduction of heat from the lower
soil to the surface and therefore check loss of heat by radiation from
the surface.
VALUE OF ORGANIC MATTER
Figure 33 illustrates a simple way to show the value of organic matter
in the soil. The boxes are about twelve inches square and ten inches
deep. They were filled with a clay subsoil taken from the second foot
below the surface of the field. To the second box was added sufficient
commercial fertilizer to supply the plants with all necessary plant
food. To the third box was added some peat or decayed leaves, in
amount about ten per cent. of the clay subsoil. The corn was then
planted and the boxes were all given the same care. The better growth
of the corn in the third box was due to the fact that the organic
matter not only furnished food for the corn but during its decay
prepared mineral plant food that was locked up in the clay, and also
brought about better conditions of air and moisture by improving the
texture of the soil. The plants in the second box had sufficient plant
food, but did not make better growth because poor texture prevented
proper conditions of air and moisture. "And that's another witness"
for organic matter. Decaying organic matter or humus is really the
life of the soil and it is greatly needed in most of the farm soils of
the eastern part of the country. It closes the pores of sandy soils
and opens the clay, thus helping the sand to soak up and hold more
moisture and lessening excessive ventilation, and at the same time
helping the roots to take a firmer hold. It helps the clay to absorb
rain, helps it to pump water faster, helps it to hold water longer in
dry weather, increases ventilation, favors root penetration and
increases heat absorption. We can increase the amount of organic
matter in the soil by plowing in stable manure, leaves and other
organic refuse of the farm, or we can plow under crops of clover,
grass, grain or other crops grown for that purpose.
CHAPTER VIII
PLANT FOOD IN THE SOIL
We learned in previous paragraphs that the roots of plants take food
from the soil, and that a condition necessary for the root to do its
work for the plant was the presence of available plant food in
sufficient quantities.
What is plant food? For answer let us go to the plant and ask it what
it is made of.
=Experiment.=--Take some newly ripened cotton or cotton wadding, a
tree branch, a cornstalk, and some straw or grass. Pull the cotton
apart, then twist some of it and pull apart; in turn break the branch,
the cornstalk and the straw. The cotton does not pull apart readily
nor do the others break easily; this is because they all contain long,
tough fibres. These fibres are called woody fibre or cellulose. The
cotton fibre is nearly pure cellulose.
=Experiment.=--Get together some slices of white potato, sweet potato,
parsnip, broken kernels of corn, wheat and oats, a piece of laundry
starch and some tincture of iodine diluted to about the color of weak
tea. Rub a few drops of the iodine on the cut surfaces of the
potatoes, parsnip, and the broken surfaces of the grains. Notice that
it turns them purple. Now drop a drop of the iodine on the laundry
starch. It turns that purple also. This experiment tells us that
plants contain starch.
=Experiment.=--Chew a piece of sorghum cane, sugar cane, cornstalk,
beet root, turnip root, apple or cabbage. They all taste sweet and
must therefore contain sugar.
Examine a number of peach and cherry trees. You will find on the trunk
and branches more or less of a sticky substance called gum.
=Experiment.=--Crush on paper seeds of cotton, castor-oil bean,
peanuts, Brazil nuts, hickory nuts, butternuts, etc. They make grease
spots; they contain fat and oil.
=Experiment.=--Chew whole grains of wheat and find a gummy
mucilaginous substance called wheat gum, or wet a pint of wheat flour
to a stiff dough, let it stand about an hour, and then wash the starch
out of it by kneading it under a stream of running water or in a pan
of water, changing the water frequently. The result will be a tough,
yellowish gray, elastic mass called gluten. This is the same as the
wheat gum and is called an albuminoid because it contains nitrogen and
is like albumen, a substance like the white of an egg.
If we crush or grate some potatoes or cabbage leaves to a pulp and
separate the juice, then heat the clear juice, a substance will
separate in a flaky form and settle to the bottom of the liquid. This
is vegetable albumen.
[Illustration: FIG. 34.
Soy-bean roots. Showing nodules of tubercles, the homes of
nitrogen-fixing bacteria.]
[Illustration: FIG. 35.
Garden-pea roots, showing tubercles or nodules, the homes of
nitrogen-fixing bacteria.]
=Experiment.=--Crush the leaves or stems of several growing plants and
notice that the crushed and exposed parts are moist. In a potato or an
apple we find a great deal of moisture. Plants then are partly made of
water. In fact growing plants are from 65 to 95 per cent. water.
=Experiment.=--Expose a plant or part of a plant to heat; the water is
driven off and there remains a dry portion. Heat the dry part to a
high degree and it burns; part passes into the air as smoke and part
remains behind as ashes.
We have found then the following substances in plants: Woody fibre or
cellulose, starch, sugar, gum, fats and oils, albuminoids, water,
ashes. Aside from these are found certain coloring matters, certain
acids and other matters which give taste, flavor, and poisonous
qualities to fruits and vegetables. More or less of all these
substances are found in all plants. Now these are all compound
substances. That is, they can all be broken down into simpler
substances, and with the exception of the water and the ashes, the
plants do not take them directly from the soil.
The chemists tell us that these substances are composed of certain
chemical elements, some of which the plant obtains from the air, some
from the soil and some from water.
The following table gives the substances found in plants, the elements
of which they are composed, and the sources from which the plants
obtain them:
----------------------------------------------------------+
Substances found | Elements of which | Sources from |
in plants. | they are made. | which plants |
| | obtain them. |
-------------------+---------------------+----------------+
Cellulose or | | |
woody fibre | Carbon | Air |
Starch |---------------------+----------------+
Sugar | | |
Gum | Oxygen | Water |
Fat and Oil | Hydrogen | |
-------------------+---------------------+----------------+
| Carbon | Air |
+---------------------+----------------+
Albuminoids | Oxygen | Water |
| Hydrogen | |
+---------------------+----------------+
| _Nitrogen_ | |
| Sulphur | |
| Phosphorus | |
-------------------+---------------------| Soil +
| _Phosphorus_ | |
| _Potassium_ | |
Ashes | _Calcium_ | |
| Magnesium | |
| Iron | |
-------------------+---------------------+----------------+
Water | Oxygen | Soil |
| Hydrogen | |
-----------------------------------------+----------------+
Here is a brief description of these chemical elements.
Oxygen, a colorless gas, forms one-fifth of the air.
Hydrogen, a colorless gas, forms a part of water.
Carbon, a dark solid, forms nearly one-half of all organic matter;
charcoal is one of its forms. The lead in your pencil is another
example.
Nitrogen, a colorless gas, forms four-fifths of the air. Found in all
albuminoids.
Sulphur, a yellow solid.
Phosphorus, a yellowish white solid.
Potassium, a silver white solid.
Calcium, a yellowish solid. Found in limestone.
Magnesium, a silver white solid.
Iron, a silver gray solid.
Of these elements the nitrogen, sulphur, phosphorus, potassium,
calcium, magnesium, and iron must not only exist in the soil but must
also be there in such form that the plant can use them. The plant does
not use them in their simple elementary form but in various compounds.
These compounds must be soluble in water or in weak acids.
Of these seven elements of plant food the nitrogen, phosphorus, and
potassium and calcium are of particular importance to the farmer,
because they do not always exist in the soil in sufficient available
quantities to produce profitable crops. Professor Roberts, of Cornell
University, tells us that an average acre of soil eight inches deep
contains three thousand pounds of nitrogen. The nitrogen exists
largely in the humus of the soil and it is only as the humus decays
that the nitrogen is made available. Here is another reason for
keeping the soil well supplied with organic matter. The decay of this
organic matter is hastened by working the soil; therefore good tillage
helps to supply the plant with nitrogen.
If the nitrogen becomes available when there is no crop on the soil it
will be washed out by rains and so lost. Therefore the soil,
especially if it is sandy, should be covered with a crop the year
through. Many lands lose large amounts of plant food by being left
bare through the fall and winter, especially in those parts of the
country where the land does not freeze. The phosphorus, potassium and
calcium also exist in most soils in considerable quantities, but often
are not available; thorough tillage and the addition of organic matter
will help to make them available, and new supplies may be added in the
form of fertilizers. Calcium is found in nearly all soils in
sufficient quantities for most crops, but sometimes there is not
enough of it for such crops as clover, cowpea, alfalfa, etc. It is
also used to improve soil texture. The entire subject of commercial
fertilizers is based almost entirely on the fact of the lack of these
four elements in the soil in sufficient available quantities to grow
profitable crops. The plant gets its phosphorus from phosphoric acid,
its potassium from potash, and its calcium from lime.
There is a class of plants which have the power of taking free
nitrogen from the air. These are the leguminous plants; such as
clover, beans, cowpeas, alfalfa, soy bean, etc. They do it through the
acid of microscopic organisms called bacteria which live in nodules or
tubercles on the roots of these plants (Figs. 34-35). Collect roots of
these plants and find the nodules on them. The bacteria take nitrogen
from the air which penetrates the soil and give it over to the plants.
Here is another reason for good soil ventilation.
This last fact brings us to another very important property of soils.
Soils have existing in them many very small plants called bacteria.
They are so very small that it would take several hundred of them to
reach across the edge of this sheet of paper. We cannot see them with
the naked eye but only with the most powerful microscopes. Some of
these minute plants are great friends to the farmer, for it is largely
through their work that food is made available for the higher plants.
Some of them break down the organic matter and help prepare the
nitrogen for the larger plants. Others help the leguminous plants to
feed on the nitrogen of the air. To do their work they need warmth,
moisture, air, and some mineral food; these conditions we bring about
by improving the texture of the soil by means of thorough tillage and
the use of organic matter.
CHAPTER IX
SEEDS
CONDITIONS NECESSARY FOR SEEDS TO SPROUT
In the spring comes the great seed-planting time on the farm, in the
home garden and in the school garden. Many times the questions will be
asked: Why didn't those seeds come up? How shall I plant seeds so as
to help them sprout easily and grow into strong plants? To answer
these questions, perform a few experiments with seeds, and thus find
out what conditions are necessary for seeds to sprout, or germinate.
For these experiments you will need a few teacups, glass tumblers or
tin cans, such as tomato cans or baking-powder cans; a few plates,
either of tin or crockery; some wide-mouth bottles that will hold
about half a pint, such as pickle, olive, or yeast bottles or
druggists' wide-mouth prescription bottles; and a few pieces of cloth.
Also seeds of corn, garden peas and beans.
=Experiment.=--Put seeds of corn, garden peas, and beans (about a
handful of each) to soak in bottles or tumblers of water. Next day,
two hours earlier in the day, put a duplicate lot of seeds to soak.
When this second lot of seeds has soaked two hours, you will have two
lots of soaked seeds of each kind, one of which has soaked twenty-four
hours and the other two hours. Now take these seeds from the water and
dry the surplus water from them by gently patting or rubbing a few at
a time in the folds of a piece of cloth, taking care not to break the
skin or outer coating of the seed. Place them in dry bottles, putting
in enough to cover the bottoms of the bottles about three seeds deep;
cork the bottles. If you cannot find corks, tie paper over the mouths
of the bottles. Label the bottles "Seeds soaked 24 hours," "Seeds
soaked 2 hours," and let them stand in a warm place several days. If
there is danger of freezing at night, the bottles of seeds may be kept
in the kitchen or living room where it is warm, until they sprout.
Observe the seeds from day to day. The seeds that soaked twenty-four
hours will sprout readily (Fig. 36), while most, if not all, of those
that soaked only two hours will not sprout. Why is this? It is because
the two-hour soaked seeds do not receive sufficient moisture to carry
on the process of sprouting.
Our experiment teaches us that seeds will not sprout until they
receive enough moisture to soak them through and through.
This also teaches that when we plant seeds we must so prepare the soil
for them and so plant them that they will be able to get sufficient
moisture to sprout.
=Experiment.=--Soak some beans, peas or corn, twenty-four hours;
carefully dry them with a cloth. In one half-pint bottle place enough
of them to cover the bottom of the bottle two or three seeds deep;
mark this bottle A. Fill another bottle two-thirds full of them and
mark the bottle B (Fig. 37). Cork the bottles and let them stand for
several days. Also let some seeds remain soaking in the water. The few
seeds in bottle A will sprout, while, the larger number in bottle B
will not sprout, or will produce only very short sprouts. Why do not
the seeds sprout easily in the bottle which is more than half full?
To answer this question try the following experiment:
=Experiment.=--Carefully loosen the cork in bottle B (the bottle
containing poorly sprouted seeds), light a match, remove the cork from
the bottle and introduce the lighted match. The match will stop
burning as soon as it is held in the bottle, because there is no fresh
air in the bottle to keep the match burning. Test bottle A in the same
way. What has become of the fresh air that was in the bottles when the
seeds were put in them? The seeds have taken something from it and
have left bad air in its place; they need fresh air to help them
sprout, but they have not sprouted so well in bottle B because there
was not fresh air enough for so many seeds. The seeds in the water do
not sprout because there is not enough air in the water. Now try
another experiment.
[Illustration: FIG. 36.
To show that seeds need water for germination. The beans in bottle _A_
were soaked 2 hours, those in bottle _B_ were soaked 24 hours. They
were then removed from the water and put into dry bottles.]
[Illustration: FIG. 37.
To show that seeds need air for germination. The beans in both bottles
were soaked 24 hours, and then were put into dry bottles Bottle _A_
contained sufficient air to start the few seeds. Bottle _B_ had not
enough. The water in the tumbler _C_ did not contain sufficient air
for germination. See experiment, page 72.]
[Illustration: FIG. 38.
To show that seeds need air for germination. Corn planted in puddled
clay in tumbler _A_ could not get sufficent air for sprouting. The
moist sand in tumbler _B_ admitted sufficient air for germination.]
=Experiment.=--Fill some tumblers or teacups or tin cans with wet sand
and others with clay that has been wet and then thoroughly stirred
till it is about the consistency of cake batter or fresh mixed mortar.
Take a tumbler of the wet sand and one of the wet clay and plant two
or three kernels of corn in each, pressing the kernels down one-half
or three-quarters of an inch below the surface; cover the seeds and
carefully smooth the surface. In other tumblers plant peas, beans, and
other seeds. Cover the tumblers with saucers, or pieces of glass or
board to keep the soil from drying. Watch them for several days. If
the clay tends to dry and crack, moisten it, fill the cracks and
smooth the surface. The seeds in the sand will sprout but those in the
clay will not (see Fig. 38). Why is this? Water fills the small spaces
between the particles of clay and shuts out the fresh air which is
necessary for the sprouting of the seeds.
This teaches us that when we plant seeds we must so prepare the soil,
and so plant the seeds that they will get enough fresh air to enable
them to sprout, or, in other words, the soil must be well ventilated.
=Experiment.=--Plant seeds of corn and beans in each of two tumblers;
set one out of doors in a cold place and keep the other in a warm
place in the house. The seeds kept in the house will sprout quickly
but those outside in the cold will not sprout at all. This shows us
that seeds will not sprout without heat.
If the weather is warm place one of the tumblers in a refrigerator.
Why don't we plant corn in December?
Why not plant melons in January?
Why not plant cotton in November?
The seeds of farm crops may be divided into two classes according to
the temperatures at which they will germinate or sprout readily and
can be safely planted.
Class A. Those seeds that will germinate or sprout at an average
temperature of forty-five degrees in the shade, or at about the time
the peach and plum trees blossom:
Barley Beet Parsley
Oats Carrot Parsnip
Rye Cabbage Onion
Wheat Cauliflower Pea
Red Clover Endive Radish
Crimson Clover Kale Turnip
Grasses Lettuce Spinach
These can be planted with safety in the spring as soon as the ground
can be prepared, and some of them, if planted in the fall, live
through the winter.
Class B. Those seeds that will germinate or sprout at an average
temperature of sixty degrees in the shade, or when the apple trees
blossom:
Alfalfa Soy Bean Squash
Cow Pea Pole Bean Cucumber
Corn String Bean Pumpkin
Cotton Melon Tomato
Egg Plant Okra Pepper
We are now ready to answer the question: What conditions are necessary
for seeds to sprout or germinate? These conditions are:
The presence of enough moisture to keep the seed thoroughly soaked.
The presence of fresh air.
The presence of more or less heat.
This teaches us that when we plant seeds in the window box or in the
garden or on the farm we must so prepare the soil and so plant the
seeds that they will be able to obtain sufficient moisture, heat, and
air for sprouting. The moisture must be film water, for if it is free
water or capillary water filling the soil pores, there can be no
ventilation and, therefore, no sprouting.
SEED TESTING
In a previous experiment (page 73) the seeds planted in the wet clay
did not sprout (see Fig. 38). In answer to the question, "Why is
this?" some will say the seeds were bad. It often happens on the farm
that the seeds do not sprout well and the farmer accuses the seedsman
of selling him poor seed, but does not think that he himself may be
the cause of the failure by not putting the seeds under the proper
conditions for sprouting. How can we tell whether or not our seeds
will sprout if properly planted? We can test them by putting a number
of seeds from each package under proper conditions of moisture, heat
and air, as follows:
For large seeds take two plates (see Fig. 39) and a piece of cloth as
wide as the bottom of the plate and twice as long. Count out fifty or
one hundred seeds from a package, wet the cloth and wring it out.
Place one end of the cloth on the plate, place the seeds on the cloth
and fold the other end of the cloth over them. On a slip of paper mark
the number of seeds and date, and place on the edge of the plate. Now
cover the whole with another plate, or with a pane of glass to keep
from drying. Set the plate of seeds in a warm room and examine
occasionally for several days. If the cloth tends to dry, moisten it
from time to time. As the seeds sprout take them out and keep a record
of them. Or leave them in the plate and after four or five days count
those that have sprouted. This will give the proportion of good seeds
in the packages.
For small seeds fold the cloth first and place the seeds on top of it.
Another good tester for small seeds is made by running about an inch
of freshly mixed plaster of Paris into a small dish or pan and
moulding flat cavities in the surface by setting bottles into it. The
dish or pan and bottles should be slightly greased to prevent the
plaster sticking to them. When the cast has hardened it should be
turned out of the mould and set in a large dish or pan. One hundred
small seeds are then counted out and put into one of the cavities,
others are put into the other cavities. Water is then poured into the
pan till it rises half way up the side of the plaster cast or porous
saucer. The whole thing is then covered to keep in the moisture (Fig.
40).
Another method is to get boxes of finely pulverized sand or soil and
carefully plant in it fifty or one hundred seeds of each kind to be
tested. Then by counting those that come up, the proportion of good
seeds can easily be found.
In every case the testers should be kept at a temperature of about
seventy degrees or about that of the living room.
HOW THE SEEDS COME UP
Plant a few seeds of corn, beans and garden peas in boxes or tumblers
each day for several days in succession. Then put seeds of corn, beans
and garden peas to soak. After these have soaked a few hours, examine
them to find out how the seed is constructed. Note first the general
shape of the seeds and the scar (Fig. 41-4) on one side as in the bean
or pea and at one end or on one edge in the corn. This scar, also
called hilum, is where the seed was attached to the seed vessel.
Cut into the bean and pea, they will be found to be protected by a
tough skin or coat. Within this the contents of the seed are divided
into two bodies of equal size lying close to each other and called
seed leaves or cotyledons (Fig. 41-5). Between them near one end or
one side will be found a pair of very small white leaves and a little
round pointed projection. The part bearing the tiny leaves was
formerly, and is sometimes now, called the plumule, but is generally
called the epicotyl, because it grows above or upon the cotyledons.
The round pointed projection was formerly called the radicle, but is
now spoken of as the hypocotyl, because it grows below or under the
cotyledons.
Examine a dry kernel of corn and notice that on one side there is a
slight oval-shaped depression (Fig. 41-1). Now take a soaked kernel
and cut it in two pieces making the cut lengthwise from the top of the
kernel through the centre of the oval depression and examine the cut
surface. A more or less triangular-shaped body will be found on the
concave side of the kernel (see Figs. 41-2 and 41-3). This is the one
cotyledon of the corn. Besides this will be found quite a mass of
starchy material packed in the coverings of the kernel and in close
contact with one side of the cotyledon. This is sometimes called the
endosperm.
Within the cotyledon will be found a little growing shoot pointed
toward the top of the kernel. This is the epicotyl, and another
growing tip pointed toward the lower end of the kernel; this is the
hypocotyl or the part which penetrates the soil and forms roots.
Now examine the seeds that were planted in succession. Some will be
just starting a growing point down into the soil. Some of them have
probably come up and others are at intermediate stages.
How did the bean get up?
After sending down a root the hypocotyl began to develop into a strong
stem which crooked itself until it reached the surface of the soil and
then pulled the cotyledons or seed-leaves after it (Fig. 42). These
turn green and after a time shrink and fall off.
The pea cotyledons were left down in the soil, the epicotyl alone
pushing up to the surface. The corn pushed a slender growing point to
the surface leaving the cotyledon and endosperm behind in the soil but
still attached to the little plant (Fig. 43).
USE OF COTYLEDONS AND ENDOSPERM
=Experiment.=--Plant some beans in a pot or box of soil and as soon as
they come up cut the seed-leaves from some of them and watch their
growth for several days. It will soon be seen that the plants on which
the seed-leaves were left increase in size much more rapidly than
those from which the seed-leaves were removed (see Figs. 43 and 44).
Sprout some corn in the seed tester. When the seedlings are two or
three inches long, get a wide-mouthed bottle or a tumbler of water and
a piece of pasteboard large enough to cover the top. Cut a slit about
an eighth of an inch wide from the margin to the centre of the
pasteboard disk. Take one of the seedlings, insert it in the slit,
with the kernel under the pasteboard so that it just touches the
water. Take another seedling of the same size, carefully remove the
kernel from it without injuring the root, and place this seedling in
the slit beside the first one (Fig. 45). Watch the growth of these two
seedlings for a few days. Repeat this with sprouted peas. In each case
it will be found that the removal of the seed-leaves or the kernel
checks the growth of the seedling. Therefore, it must be that the
seed-leaves which appear above ground, as in the case of the bean, or
the kernel of the corn which remains below the surface of the soil,
furnish the little plant with food until its roots have grown strong
enough to take sufficient food from the soil.
[Illustration: FIG. 39.
A seed-tester, consisting of two plates and a moist cloth.]
[Illustration: FIG. 40.--A SEED-TESTER.
A plaster cast with cavities in the surface for small seeds.]
[Illustration: FIG. 41.
1. Corn-kernel showing depression at _z_. 2. Section of same after
soaking. 3. Corn-kernel after germination has begun. The seed-coat _a_
has been partly removed. 4. Bean showing scar or hilum at _h_. 5. The
same, split open. 6. Bean with one cotyledon removed, after sprouting
had begun. _a_, Seed-coat; _b_, cotyledon; _c_, epicotyl; _d_,
hypocotyl; _e_, endosperm. (Drawings by M.E. Feltham.)]
CHAPTER X
SEED PLANTING
HOW DEEP SHOULD SEEDS BE PLANTED?
=Experiment.=--Plant several kernels of corn in moist soil in a glass
tumbler or jar. Put one kernel at the bottom and against the side of
the glass, place the next one a half inch or an inch higher and an
inch and a half to one side of the first seed and against the glass.
Continue this till the top of the glass is reached (Fig. 2). Leave the
last seed not more than one-fourth inch below the top of the soil. The
soil should be moist at the start and the seeds should all be against
the glass so they can be seen. This can best be done by planting as
you fill the glass with soil. Plant peas and beans in the same way. Do
not water the soil after planting. Set aside in a warm place and wait
for the seeds to come up.
Another method of performing this experiment is to make a box having
one side glass (Fig. 46). The length and the depth of the box will
depend upon the size of the glass you use. Fill the box nearly full of
moist soil and plant seeds of corn and beans and peas at depths of
one-quarter inch, one inch, two inches, three inches, and four
inches. These seeds can best be put in as the box is being filled.
Hold each individual seed against the glass with a stick so that when
planted they may be seen through the glass. Protect the seeds and
roots from light by using a sheet of cardboard, tin or wrapping paper
or a piece of board, and set in a warm place.
Many of the seeds planted only one-quarter inch deep will not sprout
because the soil about them will probably dry out before they take
from it enough moisture to sprout. The one and two-inch deep seeds
will probably come up all right. Of the three and four-inch deep
seeds, the corn and peas will probably make their way to the surface
because they send up only a slender shoot, which can easily force its
way through the soil. The deep-planted beans will make a strong effort
but will not succeed in forcing their way to the surface because they
are not able to lift the large seed-leaves through so much soil, and
will finally give up the struggle. If any of the deeper beans do get
up, the seed-leaves will probably be broken off and the little plant
will starve and be dwarfed. This experiment teaches us that we should
plant seeds deep enough to get sufficient moisture for sprouting and
yet not so deep that the young seedlings will not be able to force
their way to the surface.
Seeds which raise their cotyledons above the soil should not be
planted as deep as those which do not. Large, strong seeds like corn,
peas, etc., which do not lift their cotyledons above the surface,
can be planted with safety at a depth of from one to four or five
inches.
[Illustration: FIG. 42.
To show how the bean plant gets up. Notice the curved hypocotyls
pulling the seed-leaves or cotyledon out of the soil.]
[Illustration: FIG. 43.
To show how the corn-plant gets out of the soil. A slender growing
point pushes straight up through the soil, leaving the kernel behind.]
[Illustration: FIG. 44.
To show the use of the cotyledons. These are the plants shown in
tumbler 2, Fig 42, forty-eight hours after removing the cotyledons
from plant _B._ Plant _B_, although first up, has been handicapped by
the loss of its cotyledons.]
Seeds of carrot, celery, parsley, parsnip and egg plant are weak and
rather slow in germinating. It is customary to plant them rather
thickly in order that by the united strength of many seeds they may
more readily come to the surface. This point should be observed also
in planting seeds in heavy ground that is liable to pack and crust
over before the seeds germinate.
Seed should always be sown in freshly stirred soil and may be planted
by hand or with a machine.
For the home garden and the school garden, and when only small
quantities of any one variety are planted, a machine is hardly
desirable and hand planting is preferable.
The rows are marked out with the garden marker, or the end of a hoe or
rake handle (Fig. 47), using a line or the edge of a board as a guide.
The seeds are then carefully and evenly dropped in the mark or furrow.
The covering is done with the hand or a rake or hoe, and the soil is
pressed over the seeds by patting it with the covering tool or walking
on the row and pressing it with the feet. This pressing of the soil
over the seeds is to bring the particles of soil close to each other
and to the seed so that film water can climb upon them and moisten the
seed sufficiently for sprouting.
A convenient way of distributing small seeds like those of turnip and
cabbage, is to take a small pasteboard box or tin spice or
baking-powder box, and punch a small hole in the bottom near one end
or side. Through this the seeds can be sifted quite evenly.
For the larger operations of the farm and market garden, hand and
horse-power drills and broadcasters are generally used, though some
farmers still plant large fields by hand.
The grasses and clovers are generally broadcasted by hand or machine,
and are then lightly harrowed and are generally rolled.
The small grains (wheat, oats, etc.) are broadcasted by many farmers,
but drilling is considered better. With the grain drill the seed is
deposited at a uniform depth and at regular intervals. In
broadcasting, some of the seeds are planted too deep, and some too
shallow, and others are left on the surface of the soil.
From experiment it has been found that there is a loss of about
one-fifth of the seed when broadcasted as compared with drilling.
As in the case of grass seed, the grains are generally rolled after
sowing.
Corn is planted by hand, or by hand- and horse-corn-planters, which
drop a certain number of seeds at any required distance in the row.
There are a number of seed drills made for planting vegetable seeds
which are good machines.
The main points to be considered in seed drills or seed planting
machines are:
Simplicity and durability of structure.
Ease of draft.
Uniformity in quantity of seed planted, and in the distances apart and
depth to which they are planted.
The distances apart at which seeds are planted vary according to the
character of the plant. Bushy, spreading plants and tall plants
require more room than low and slender-growing plants.
Visit the neighboring hardware stores and farms and examine as many
seed-growing tools as possible to see how they are constructed and how
properly used. Practice planting with these tools, if possible.
Illustrations of grain drills and other seed-planting machines will be
found in seed catalogues, hardware catalogues, and in the advertising
columns of agricultural papers.
SEED CLASSIFICATION
In order to become familiar with the farm and garden seeds, obtain
samples of as many of them as possible. Put them in small
bottles--homoeopathic vials for instance--or stick a few of each
kind on squares of cardboard. Arrange them in groups according to
resemblances or relationships, comparing not only the seeds but the
plants on which they grew. If you cannot recall the plants, and there
is no collection available, study the illustrations in seed catalogues
which can be obtained from seedsmen. The following groups contain
most of the farm and garden seeds, excepting flower seeds:
GRASS FAMILY: MUSTARD FAMILY: NIGHTSHADE FAMILY:
Corn, Mustard, Potato,
Wheat, Cabbage, Tomato,
Oats, Cauliflower, Egg Plant,
Rye, Collards, Pepper.
Barley, Brussels Sprouts,
Sorghum, Kale, GOOSEFOOT FAMILY:
Orchard Grass, Kohl Rabi, Beet,
Red Top Grass, Radish, Chard,
Timothy, Ruta Baga, Spinach,
Kentucky Blue Grass. Turnips, Mangle Wurzel.
Watercress.
GOURD FAMILY: PEA OR LEGUME FAMILY:
Canteloupe, THISTLE FAMILY: Garden Pea,
Citron, Artichoke, Canada Field Pea,
Cucumber, Cardoon, Cow Pea,
Gourd, Chicory, Soy Bean,
Muskmelon, Dandelion, Bush Bean,
Pumpkin, Endive, Lima Bean,
Squash, Lettuce, Velvet Bean,
Watermelon, Salsify, Vetch,
Cymling. Sunflower, Clover,
Tansy. Alfalfa.
PARSLEY FAMILY:
Caraway, LILY FAMILY: MALLOW FAMILY:
Carrot, Asparagus, Okra,
Celery, Garlic, Cotton.
Coriander, Leek,
Cumin, Onion.
Fennel,
Parsley,
Parsnip.
[Illustration: FIG. 45.
To show the use of the kernel to the young corn-plant. The kernel was
carefully removed from the plant on the right when both plants were of
the same size. The result is a dwarfing of the plant.]
[Illustration: FIG. 46.
To show how deeply seeds should be planted. Seeds 1 and 5 did not
sprout because they were not deep enough to get sufficient moisture.
The corn-plants from sprouting seeds 2, 3 and 4 all pushed their
slender growing points to the surface. Of the beans, No. 6 succeeded
in pulling the cotyledons to the surface, and has made a good plant.
Nos. 7 and 8, although they made a hard struggle, were not able to
raise the cotyledons through so great a depth of soil, and finally
gave up the struggle.]
TRANSPLANTING
The seeds of some crops--cabbage, tomato, lettuce, for example--are
planted in window boxes, hot-beds, cold frames or a corner of the
field or garden. When the seedlings have developed three or four
leaves or have become large enough to crowd one another, they are
thinned out or are transplanted into other boxes, frames or plots of
ground, or are transplanted into the field or garden.
The time and method of transplanting depend largely on
The condition of the plant.
The condition of the soil.
The condition of the atmosphere.
For best results in field planting the plant should be well grown,
strong and stocky, with well developed roots and three or four strong
leaves.
The soil should be thoroughly prepared, moist and freshly stirred. A
moist day just before a light shower is the best time. These
conditions being present, the plants are carefully lifted from the
seed bed with as little disturbance of the roots as possible and
carried to the field or garden. Some plants, like cabbage, will stand
considerable rough treatment, while others, like the eggplant, require
greater care.
In the field or garden a hole is made for each plant with the hand, a
stick or dibber or any convenient tool, the roots of the plant are
carefully placed in it and the soil is pressed about them. If the
soil is moist and freshly stirred, new roots will generally start in a
very short time.
Plants that have been grown in pots, small boxes or tin cans, as
tomatoes and eggplants are sometimes grown, may be quickly
transplanted in the field in the following manner: Open the furrow
with a small plow, knock the plants out of the pots or cans and place
them along the land side of the furrow at the proper distances, then
turn the soil back against them with the plow.
When there is a large number of plants to be set, as in planting
cabbage, sweet potatoes, etc., by the acre, it is not always
convenient to wait for a cloudy day or to defer operations till the
sun is low in the afternoon. In such cases the roots of the plants
should be dipped in water or in thin mud just before setting them, or
a little water may be poured into each hole as the plant is put in.
The soil should always be well firmed about the roots. The firming of
the soil about the roots of a newly set plant is as important as
firming it over planted seeds. The soil should be packed so tightly
that the individual leaves will be torn off when an attempt is made to
pull the plant up by them.
In dry or warm weather it is a good plan to trim the tops of plants
when setting them. This can be done readily with some plants, such as
cabbage and lettuce, by taking a bundle of them in one hand and with
the other twisting off about half of their tops.
[Illustration: FIG. 47.
Operations of seed-planting: 1, making the drill; 2, dropping the
seeds; 3, covering the seeds; 4, packing the soil over the seeds.]
[Illustration: FIG. 48.
A collection of planting machines. The large central machine is a
grass and grain planter. The one on the left, a potato planter. The
one on the right, a corn, bean, and pea planter. The three smaller
machines in front are hand seed planters.]
The proper time to transplant fruit and ornamental trees and shrubs
is during the fall, winter and early spring, which is their dormant or
resting season, as this gives the injured roots a chance to recover
and start new rootlets before the foliage of the plant makes demands
on them for food and moisture.
In taking up large plants many roots are broken or crushed. These
broken and injured roots should be trimmed off with a smooth cut. The
tree or shrub is then placed in the hole prepared for it and the soil
carefully filled in and packed about the roots. After the plant is
set, the top should be trimmed back to correspond with the loss of
root. If the plant is not trimmed, more shoots and leaves will start
into growth than the damaged roots can properly furnish with food and
water, and the plant will make a weak growth or die.
There are on the market a number of hand transplanting machines which,
from their lack of perfection, have not come into general use. Many of
them require more time to operate than is consumed in hand planting. A
number of large machines for transplanting are in successful and
satisfactory use on large truck and tobacco farms. These machines are
drawn by horses and carry water for watering each plant as it is set.
Practice transplanting in window boxes or in the open soil and see how
many of your plants will survive the operation.
CHAPTER XI
SPADING AND PLOWING
We have learned the important conditions necessary for the sprouting
of seeds and for the growth and development of roots. We have also
learned something about the soil, its properties, and its relation to,
or its behavior toward these important conditions. We are therefore
prepared to discuss intelligently methods of treating the soil to
bring about, or maintain, these conditions.
SPADING THE SOIL
The typical tool for preparing the soil for root growth is a spade or
spading fork (Fig. 49). With this tool properly used we can prepare
the soil for a crop better than with any other.
In spading, the spade or fork should be pushed into the soil with the
foot the full length of the blade and nearly straight down. The handle
is then pulled back and the spadeful of earth is pried loose, lifted
slightly, thrown a little forward, and at the same time turned. The
lumps are then broken by striking them with the blade or teeth of the
tool. All weeds and trash should be covered during the operation. A
common fault of beginners is to put the spade in the soil on a slant
and only about half the length of the blade, and then flop the soil
over in the hole from which it came, often covering the edge of the
unspaded soil. The good spader works from side to side across his
piece of ground, keeping a narrow trench or furrow between the spaded
and unspaded soil, into which weeds and trash and manure may be drawn
and thoroughly covered, and also to prevent covering the unspaded
soil. If this work has been well done with the ordinary spade or fork
and finished with a rake, the result will be a bed of soil twelve to
fifteen inches deep, fine and mellow and well prepared for root
penetration, for good ventilation, for the absorbing and holding of
moisture and warmth.
This method should always be employed for small gardens and flower
beds.
PLOWING
For preparing large areas of soil the plow is the tool most generally
used.
WHY DO WE SPADE AND PLOW?
To break and pulverize the soil and make it soft and mellow, so the
roots of plants may enter it in search of food, and get a firm hold
for the support of the plant which is above ground.
To make the soil open and porous, so that it can more readily absorb
rain as it falls on the surface.
To check loss of water by evaporation.
To admit air to the roots of plants. Also to allow air to act
chemically on the mineral and organic matter of the soil and make them
available to the crop.
To raise the temperature of soils in the spring, or of damp soils at
any time.
To mix manures and organic matter with the soil. The more thoroughly
manure is distributed through the soil the more easily plants will get
it and the greater will be its effect on the soil.
To destroy the insect enemies of the plant by turning them up to the
frost and the birds.
To kill weeds. Weeds injure crops:
They waste valuable moisture by pumping it up from the soil and
sending it out into the air through their leaves. In this way they do
their greatest injury to crops.
They crowd and shade the crop.
They take plant food which the plant should have.
Spading and plowing bring about conditions necessary for the sprouting
or germination of seeds.
Spading and plowing also tend to bring about conditions necessary for
the very important work of certain of the soil bacteria.
PARTS OF A PLOW
It will be found that a good farm plow has the following parts (Fig.
50):
_A standard_ or stock, the central part of the plow to which many of
the other parts are attached.
[Illustration: FIG. 49.--SPADING-FORK AND SPADE.]
[Illustration: FIG. 50.--A WOOD BEAM-PLOW
_a_, stock; _b_, beam; _c_, handles; _d_, clevis, _e_, shackle, _f_,
share; _g_, mould board; _h_, landside; _k_, jointer or skimmer, _l_,
truck or wheel, _p_, point or nose, _s_, shin.]
_A beam_, to which the power is attached by which the plow is drawn.
Some plows have wooden beams and others have iron beams.
_Handles_ by which the plowman guides and steadies the plow and also
turns it at the corners of the plowed ground in going about the field.
_A clevis_, which is attached to the end of the beam and is used to
regulate the depth of plowing. To the clevis is attached a _draft
ring_ or _shackle_, to which the horse or team is fastened. To make
the plow run deep the draft ring or shackle is placed in the upper
holes or notches of the clevis; to make it run shallow the ring is
placed in the lower holes. On some plows there are only notches in the
clevis for holding the ring, they answer the same purpose as holes.
The clevis is also used on some plows to regulate the width of the
furrow. By moving the draft ring or shackle towards the plowed land
the plow is made to cut a wider furrow, moving it away from the plowed
land causes the plow to cut narrower.
Some plows have a double clevis so that the draft ring may be raised
or lowered, or moved to right or left. With some plows the width of
the furrow is adjusted by moving the beam at its attachment to the
handles.
_A share_, called by some the point, which shears the bottom of the
furrow slice from the land. The share should be sharp, especially for
plowing in grass land and land full of tough roots. If the share,
particularly the point, becomes worn so that it bevels from beneath
upwards it will be hard to keep the plow in the soil, for it will tend
to slide up to the surface. If this happens the share must be renewed
or sharpened. Plows are being made now with share and point separate,
and both of these reversible (Fig. 51), so that if either becomes worn
on the under side it can be taken out and turned over and put back and
it is all right, they thus become self-sharpening.
_A mouldboard._ This turns and breaks the furrow slice. The degree to
which the mouldboard pulverizes depends on the steepness of its slant
upward and the abruptness of its curve sidewise. The steeper it is and
the more abrupt the curve, the greater is its pulverizing power. A
steep, abrupt mouldboard is adapted to light soils and to the heavier
soils when they are comparatively dry. This kind of a plow is apt to
puddle a clay soil if it is quite moist. For breaking new land a plow
with a long, gradually sloping share and mouldboard is used.
_A landslide_, which keeps the plow in place.
_A coulter._ Some plows have a straight knife-like coulter (Fig. 52)
which is fastened to the beam just in front of the mouldboard and
serves to cut the furrow slice from the land. In some plows this is
replaced by an upward projection of the share; this is wide at the
back and sharp in front and is called the shin of the plow from its
resemblance to the shin bone. The coulter is sometimes made in the
form of a sharp, revolving disk (Fig. 53), called a rolling coulter.
This form is very useful in sod ground and in turning under vines and
tall weeds. It also lessens the draft of the plow.
_A jointer_ or skimmer which skims stubble and grass from the surface
of the soil and throws them into the bottom of the furrow where they
are completely covered. The jointer helps also to pulverize the soil.
_A truck_ or wheel, attached under the end of the beam. This truck
makes the plow run steadier. This is sometimes used to make the plow
run shallower by setting it low down. This is not right, for it then
acts as a brake and makes the plow draw harder. The depth of the
furrow should be adjusted at the clevis.
A plow not only has parts but it has character also.
CHARACTERISTICS OF A GOOD PLOW
A good plow should be strong in build and light in weight.
The draft should be as light as possible.
The plow should run steadily.
A good plow should not only turn the soil but should pulverize it as
well.
When plowing, the team should be hitched to the plow with as short
traces as possible, and the plow should be so adjusted that it will
cut furrows of the required width and thickness with the least
possible draft on the team and the least exertion on the part of the
plowman.
THE FURROW SLICE
In plowing, the furrow slice may be cut thin and wide and be turned
over flat. This method is adapted to breaking new land and heavy sod
land.
It may be cut thick and narrow and be turned up on edge.
Or it may be cut of such a width and depth that the plow will turn it
at an angle of about forty-five degrees. By this last method the
greatest amount of soil can be turned at least expense of labor; the
furrow slice can be more thoroughly broken; the greatest surface is
exposed to the action of the air, and plant food is more evenly
distributed through the soil.
HOW DEEP SHALL WE PLOW?
We learned in a previous chapter that the roots of farm plants develop
largely in that part of the soil which is worked by the plow;
therefore, to have as much tilled soil as possible for root growth, we
should generally plow as deep as possible without turning too much of
the subsoil to the surface. Lands that have been plowed deep should be
deepened gradually by plowing up a half-inch to an inch of subsoil
each year until the plow reaches a depth of at least nine or ten
inches.
There is an opinion among many farmers that sandy soils should not be
plowed deep. But as these soils are apt to be leachy it seems best to
fill them with organic matter to as great a depth as possible to
increase their water-holding power, and this can best be done by
plowing farm manures in deep.
[Illustration: FIG. 51.--A SLIP-NOSE SHARE. _N_, A SLIP-NOSE.]
[Illustration: FIG. 52.--_C_, STRAIGHT KNIFE COULTER.]
[Illustration: FIG. 53.
An iron beam-plow, with rolling coulter and double clevis.]
[Illustration: FIG. 54.--A ROLLING COULTER HARROW.]
[Illustration: FIG. 55.--SPRING-TOOTHED HARROWS.]
In many parts of the South the farmers use very small plows and small
animals to draw them. The result is that the soil is not prepared to a
sufficient depth to allow of the large root development necessary for
large crops. These farmers need larger tools and heavier animals if
they expect to make much improvement in the yield of their crops.
These small plows and this shallow plowing have done much to aid the
washing and gulleying of the hill farms by rain. The shallow layer of
loose soil takes in the rain readily, but as the harder soil beneath
does not take the water as readily, the shallow plowed soil soon
fills, then becomes mud, and the whole mass goes down the slope. The
land would wash less if it had not been plowed at all, and least of
all if it were plowed deep, for then there would be a deep reservoir
of loose soil which would be able to hold a large amount of water
until the harder lower soil could take care of it.
BREAKING OUT THE MIDDLES
Some farmers have a way when getting the land ready for a crop, of
plowing the rows first and then "breaking out the middles" or spaces
between after the crop is planted. This is a poor practice, as it
interferes with thorough preparation of the soil. The ground can be
more thoroughly plowed and broken up before the crop is planted than
afterwards. This practice of leaving the middles interferes with
proper harrowing and after-cultivation.
THROWING THE LAND UP IN RIDGES
Many farmers throw the land up into ridges with the plow and then
plant on the ridge. When land is thrown into ridges a greater amount
of surface is exposed to the air and a greater loss of moisture by
evaporation takes place, therefore ridge culture is more wasteful of
soil water than level culture. For this reason dry soils everywhere
and most soils in dry climates should, wherever practicable, be left
flat. On stiff, heavy soils which are slow to dry out, and on low
bottom lands it may be desirable to ridge the land to get the soil
dried out and warmed quicker in the spring. Late fall and early
planter truck crops are often planted on the southern slopes of low
ridges thrown up with the plow for warmth and protection from cold
winds.
TIME TO PLOW
The time of plowing will depend somewhat on the nature of the soil,
climate and the crop.
More plowing is done in the spring just before planting spring and
summer crops than at any other time, excepting in localities that
plant large areas of winter grain and truck. This spring plowing
should be done early, for the spring plowing tends to dry the loosened
soil somewhat and allows it to become warm at an earlier date, and at
the same time the loosened soil tends to hold water in the lower soil
for future use by the crop and allows the soil to take in spring rains
more readily. If a cover crop or green manure crop is to be turned
under in the spring it should be done early so as to prevent the crop
to be turned under from pumping too much water out of the soil and
thus interfering with the growth of the crop for which the land is
being prepared.
There are some particular advantages to be gained by fall plowing in
heavy soils:
Immediately after harvest the land is usually dry and easy to work.
The soil plowed at this time and left rough is acted upon physically
by frost which pulverizes it, and chemically by rain and air which
renders plant food available.
Insects are turned up and exposed to frost and birds.
A great number of weeds are destroyed and the land is more easily
fitted for crops in the spring. Fall plowing should be done as early
as possible, especially in the dryer regions, to catch all water
possible. It is not advisable to plow sandy soils in the fall lest
plant food be washed out of them.
When possible a cover crop should be put on fall plowed land where
there is likely to be loss of plant food by leaching.
BARE FALLOW
The term "fallowing" is sometimes applied to the operation of plowing,
and sometimes the land is left bare without a crop sometime after
plowing; this is called "bare fallowing" the land.
Bare fallowing should not be practiced on all soils. It is adapted:
To dry climates and dry seasons where it is desirable to catch and
save every possible drop of rainfall, and where plant food will not be
washed out of the exposed soils by rains.
To heavy clay lands.
To lands that are foul with weeds and insects.
To sour soils which are sweetened by exposure to air and rain.
Light sandy soils should not be subjected to bare fallow unless they
are very foul with weeds. They should always be covered with a crop to
prevent loss of plant food by leaching.
CHAPTER XII
HARROWING AND ROLLING
HARROWING
After spading or plowing the next operation in the preparation of the
soil is generally raking, harrowing or dragging. The objects of these
operations are:
To break lumps and clods left by the plow and spade and to further
pulverize the soil.
Harrowing and raking aid in controlling soil ventilation, and put the
soil in better condition to absorb moisture.
They check the loss of moisture by making a mulch of fine loose earth
on the surface.
The harrow and rake destroy the weeds.
The harrow brings about conditions favorable to the even distribution
of seeds.
It is also the tool generally used to cover seeds sown broadcast.
Harrowing is generally done just before planting, and with some crops
just after, to cover seeds or to smooth the ground. Harrowing is also
done in the first stages of growth of some crops to kill weeds and
make a soil mulch. The harrow should always follow the plow within a
few hours unless it is desired to leave the land in a bare fall or
winter fallow. At other times of the year the lumps of earth are apt
to dry out and become hard and difficult to break. If there is but one
work team on the farm it is a good plan during the plowing season to
stop the plow in time to harrow the day's plowing before the day's
work ends.
HARROWS
There are several types of harrows in use. They may be classified
according to the style of their teeth or cutting parts; they are as
follows:
Rolling cutter harrows.
Spring-toothed harrows.
Spike-toothed harrows.
Coulter-toothed harrows.
Chain harrows.
Brush harrows.
Plank or drag harrows.
These types vary in the depth to which they cut, and the degree to
which they pulverize the soil.
_Rolling cutter harrows._ Harrows of this type (see Fig. 54) consist
of one or more revolving shafts on which are arranged a number of
concave disks. These disks are either entire, notched, or made of
several pieces fastened together. Examples of these are the disk,
cutaway and spading harrows. These harrows cut and move the soil
deeper than the other types. They are especially adapted to work on
heavy clay soils.
The value of this type of harrow as moisture preservers depends on the
manner in which they are used. If the disks are so set that they cover
but a portion of the surface with a mulch of fine earth they leave a
ridge exposed to the action of the wind and sun and the rate of
evaporation is greatly increased. The disks should be set at such an
angle that the whole surface shall be stirred or covered. Soils which
need the disk harrow should generally be gone over again with some
shallower working tool to smooth the surface. An objection to the
rolling cutters is that unless great care is taken they will leave the
land in ridges and valleys.
The two gangs of disks throw the earth in opposite directions. They
are generally set to throw it from the centre and the result is a
shallow double furrow the width of the machine. By lapping each time
the furrow is partially filled, but to get the land smooth a smoothing
harrow should be used after the rolling cutter.
_Spring-toothed harrows_ (Fig. 55). Spring-toothed harrows with their
curved spring teeth enter the soil readily, draw moderately easy and
pass over obstructions without much difficulty. They are very useful
in new land that is full of roots and stumps and also stony land. They
pulverize the soil to an average depth. They leave the soil in ridges.
The ridges can be leveled by a smoother in the shape of a piece of
plank attached to the rear of the harrow. On newly plowed grass land
they tend to tear up the sod and leave it on the surface. They also
tend to drag out coarse manures when plowed in.
The original and more common form of the spring-toothed harrow is a
floating harrow when at work. That is, it rests on the points of the
teeth and is dragged or floated over the ground. A newer form of
spring-toothed harrow, sometimes called the fallow cultivator, is
mounted on high wheels and its action is largely controlled by them.
This form of harrow is claimed to do much better work than the
floating harrow and may in a large measure displace the rolling
cutter. The weight of this harrow is entirely taken from the soil
except in the wheel tracks, and the entire action is that of
pulverizing and lightening the soil.
_Spike-toothed harrows_ (Fig. 56). The teeth of these harrows are
round, square or diamond-shaped spikes fastened into a wood or iron
frame. The teeth are set in a vertical position or are inclined to the
rear. These harrows are shallow in their action; they run easily but
tend to compact the soil more than the other types and are therefore
better adapted to loose soils and to finishing off after the work of
the deep cutting harrows. They are also used for covering seeds.
[Illustration: FIG. 56.--SPIKE-TOOTHED HARROWS.]
[Illustration: FIG. 57.--A COULTER-TOOTHED HARROW.]
[Illustration: FIG. 58.--A PLANK HARROW.]
_Coulter-toothed harrows._ The coulter-toothed harrows (Fig. 57) have
teeth resembling the coulter of a plow twisted or bent into various
shapes. The Acme is a good example of this class of harrow. It cuts,
turns and pulverizes the surface soil somewhat after the manner of the
plow. It prepares a fine mulch and leaves an excellent seed bed. It
is an excellent harrow to finish off with after using a rolling
cutter.
_Chain harrows._ The chain harrow consists of a web of chains linked
together. They have a wonderful power for breaking clods and are
useful for collecting weeds. They shake the dirt from the weeds and
roll them into heaps. Chain harrows tend to compact the soil.
_Brush harrows._ The brush harrow is a primitive form made by
fastening brush to a long pole. Brush harrows are quite useful for
brushing in seed and for pulverizing manure broadcasted on grass
lands.
_Plank harrows._ The plank harrow (see Fig. 58) is made of several
planks fastened together so that each plank overlaps the next one to
it, like the clapboards of a house. This harrow is as good as a roller
in fining and smoothing the surface soil. It is an excellent tool to
use alternately with a spike or coulter-toothed harrow on lumpy soil.
This tool rasps or grinds many of the lumps or clods which slip by the
harrow teeth and presses others into the ground so that the harrow
following can get a grip on them. It is a harrow that can be made on
any farm. This planker is an excellent tool to smooth the surface, for
broadcasting small seeds and for planting truck crops.
ROLLING
The objects of rolling are:
To compress the surface soil so that the harrow will do its work more
efficiently, also to break clods or lumps that may have resisted the
action of the harrow.
To smooth the surface of the soil for an even distribution of small
seeds, and to firm the soil around such seeds after they are planted
so that they will keep moist and sprout readily.
To give compactness to soils that are light and loose and thus enable
them to hold moisture and plant food better.
To press into the ground the roots of plants partly dislodged by the
frost.
To remove the conditions favorable to the development of many kinds of
insects.
To sink surface stones so that they will not interfere with harvesting
the crop.
Light porous soils may be rolled at any time, but clay soils can be
rolled to advantage only when they are stiff and cloddy.
Spring-sown grain is often rolled as soon as sown. This is all right
in ordinary spring weather, but if showers are frequent and the soil
is quite moist the rolling should be omitted till after the grain is
up. The same practice will apply to autumn-sown grain also. If the
soil is dry the rolling helps it to pump water up to the seeds. But if
it is moist and showers are frequent the combined action of the
roller and the rain is to make so thick a crust that many of the seeds
will not be able to force their way through it or will be smothered by
poor ventilation. After the grain is up the rolling may be done to
advantage, as it then makes a firm soil about the roots of the plants,
a condition of benefit to grain crops.
The most simple form of roller is a solid or hollow cylinder of wood
fastened into a frame by which it is drawn. Some rollers have spikes
or blunt attachments fastened to their surfaces for breaking clods. A
roller that is quite popular consists of a cylinder of pressed steel.
CHAPTER XIII
LEAVES
FACTS ABOUT LEAVES
We found in an earlier lesson that all of our farm plants have roots,
stems, leaves, flowers, fruit and seeds. We studied the root first as
being the most important part of the plant to the farmer. The seed was
the next part studied, for that was considered the next most
important, because the seed is the main reliance for new plants. The
part next in importance is the leaf and that we will now study.
If you will go into the field and observe the leaves on a number of
plants, you will find that the following facts are true:
They are all green.
They are flat and thin.
Many of them are very broad.
Some of the leaves on a single branch are larger than others on the
same branch, and some have longer stems than others.
Most of them have a rather dark glossy upper surface and a lighter
rougher under surface.
[Illustration: FIG. 59.
To show transpiration. Plant _A_ was set in the sunlight, plant _B_
was left in the darker part of the room. _A_ has transpired much more
than _B_, showing that sunlight is necessary for this work.]
[Illustration: FIG. 60.--AMOUNT OF TRANSPIRATION
This plant transpired within 48 hours an amount of water equal to the
colored liquid in the bottle standing on the jar, more than 6 ounces.]
The leaves on the lower branches of the trees are spread out in a more
or less flat layer and have their glossy surfaces all turned up,
while those on branches in the tops of trees or shrubs are arranged
all around the branch, the glossy surface being turned up.
What are the reasons for these facts?
A study of the work of the leaves and the conditions necessary for
them to perform their work will help us to answer this question.
THE USES OF LEAVES TO PLANTS
=Experiment.=--(See Fig. 59). Take a pot or tumbler in which a young
plant is growing, also a piece of pasteboard large enough to cover the
top of the pot; cut a slit from the edge to the centre of the
pasteboard, then place it on the top of the pot, letting the plant
enter the slit. Now close the slit with wax or tallow, making it
perfectly tight about the stem. If the plant is not too large, invert
a tumbler over it, letting the edge of the tumbler rest on the
pasteboard; if a tumbler is not large enough use a glass jar. If a
potted plant is not convenient a slip or a seedling bean or pea placed
in a tumbler of water will serve the purpose. Prepare several and
place some in a sunny window and leave others in the room where it is
darker, and observe them from time to time. In the case of those
plants that were set in the sunny window moisture will be seen
collecting on the inner surface of the tumbler. Where does this come
from? It is absorbed from the soil by the roots and is sent with its
load of dissolved plant food up through the stems to the leaves.
There most of the water is passed from the leaves to the air and is
condensed on the sides of the glass. A work of leaves then is to throw
off or to transpire moisture and thus make room for a new supply of
food-laden moisture. This water is thrown off through little pores or
mouths or stomata which are very small and very numerous on the under
side of the leaf. It will be noticed that the plant not placed in the
sunlight transpires very little moisture, showing that sunlight helps
the leaves in this work of transpiration.
How much water does a plant transpire or throw off from its leaves?
=Experiment.=--(See Fig. 60). Fill a common quart fruit jar or can
with soil and plant in it a kernel of corn, a bean, a cotton seed or
seed of some other plant. After the plant has grown to be twelve or
fifteen inches high, cut a piece of pasteboard a little larger than
the top of the jar, cut a hole in the centre as large as the stem of
the plant and make a slit from edge to centre. Soak the pasteboard in
melted wax or paraffine candle. Cool it and then place it over the
jar, slipping it around the plant stem. Now solder the pasteboard to
the jar with melted candle making the joints tight all the way around.
Then close up the slit and the hole about the stem. The jar is now
completely sealed and there is no way for water to escape except
through the plant. The plant should be well watered before the jar is
closed. Now weigh the jar and set in the sunlight. Weigh again the
next day. The difference in the two weights will represent the amount
of water transpired by the plant. The weighings may be repeated until
moisture gives out. If it is desired to continue this experiment some
time, a small hole should be cut in the pasteboard before it is
fastened to the jar. This hole is for adding water to the jar from
time to time. The hole should be kept closed with a cork. The amount
of water added should always be weighed and account taken of it in the
following weighings. While this plant is growing it will be well to
wrap the jar with paper to protect the roots from the light.
It has been found that the amount of water necessary to grow a plant
to maturity is equal to from 300 to 500 times the weight of the plant
when dry.
This gives us an idea of the very great importance of water to plants.
=Experiment.=--Take a few leaves from a plant of cotton, bean, clover
or other plant that has been growing in the sunlight; boil them for a
few minutes to soften the tissues, then place them in alcohol for a
day or until the green coloring matter is extracted by the alcohol.
Wash the leaves by taking them from the alcohol and putting them in a
tumbler of water. Then put them in saucers in a weak solution of
iodine. The leaf will be seen to gradually darken; this will continue
until it becomes dark purple or almost black (Fig. 61). We have
already learned that iodine turns starch this color, so we conclude
that leaves must contain starch. (Five or ten cents worth of tincture
of iodine from a drug store diluted to about the color of weak tea
will be sufficient for these leaf experiments.)
=Experiment.=--If a potted plant was used for the last experiment, set
it away in a dark closet after taking the leaves for the experiment. A
day or two after, take leaves from it before removing it from the
closet. Boil these leaves and treat them with alcohol as in the
previous experiment. Then wash them and test them with iodine as
before. No starch will be found in the leaves (Fig. 62). The starch
that was in them when placed in the closet has disappeared. Now paste
some thick paper labels on some of the leaves of a plant exposed to
the sunlight. After a few hours remove the leaves that have the labels
on them, boil, treat with alcohol and test with the iodine. In this
case starch will be found in all parts of the leaf except the part
over which the label was pasted (Fig. 63). If the sunlight is intense
and the label thin, some starch will appear under it.
According to these last experiments, leaves contain starch at certain
times, and this starch seems to appear when the leaf is in the
sunlight and to disappear when the light is cut off. The fact is that
the leaves manufacture starch for the plant and sunlight is necessary
for this work. The starch is then changed to sugar which is carried by
the sap to other parts of the plant where it is again changed to
starch to be built into the plant structure or stored for future use.
=Experiment.=--Take leaves from a plant of silver-leaf geranium
growing in the sunlight. If this plant cannot be had, the leaves from
some other variegated white and green leaved plant will do. Boil these
leaves, treat with alcohol, wash and test with iodine (Fig. 64).
Starch will be found in the leaf wherever there was green coloring
matter in it, while the parts that were white will show no starch. The
green coloring matter seems to have something to do with the starch
making, in fact starch is manufactured only where it is present. This
coloring matter is called chlorophyl or leaf green.
We are told by the chemists that this starch is made from carbon and
water. There exists in the air a gas called carbonic acid gas; this
gas is composed of carbon and oxygen. It is breathed out of the lungs
of animals and is produced by the burning and decay of organic matter.
The under side of the leaf contains hundreds of little pores or mouths
called stomata. This gas mixed with air enters these mouths. The green
part of the leaf aided by the sun takes hold of the gas and separates
the carbon from the oxygen. The oxygen is allowed to go free, but the
carbon is made to unite with water and form starch.
=Experiment.=--The escape of this oxygen gas may be seen by taking
some water weed from either fresh or salt water and placing it in a
glass jar of the kind of water from which it came, then set the jar in
the sunlight. After a time bubbles of gas will be seen collecting and
rising to the surface. If a mass of weed like the green scum of fresh
water ponds or green sea lettuce be used, the bubbles of gas will
become entangled in the mass and will cause it to rise to the surface
of the water. At the same time prepare another jar of the weed and
place it somewhere out of the sun; very few bubbles will be seen to
rise and the weed will settle to the bottom of the jar (Fig. 65).
All of the food of the plant, whether taken from the air or from the
soil is digested in the leaves, and sunlight and air are necessary for
this work.
Another function of leaves then is to digest food for the plant.
Important functions of leaves then are:
To transpire moisture sent up by the roots.
To manufacture starch by combining some of the water sent up by the
roots with carbon taken from the air.
To digest the starch and food sent up by the roots.
To do these things well leaves must be connected with a strong,
healthy root system and must have plenty of light and air.
We are now ready to give reasons for the facts about leaves mentioned
in the first part of the chapter (see page 109).
Leaves are green because the green coloring matter is necessary for
the leaf to do its work.
Leaves are flat and thin and broad in order that they may present a
large surface to the air and sunlight.
[Illustration: FIG. 61.
To show that growing leaves contain starch. 1. Represents a green
cotton leaf as picked from the plant. 2. Is the same leaf after taking
out the green coloring matter; the leaf is white. 3. The same leaf
after treatment with weak iodine turned to a dark purple, showing the
presence of starch. (Drawings by M.E. Feltham.)]
[Illustration: FIG. 62.
To show that starch disappears from the leaf when the plant is placed
in the dark. The plant from which was taken the leaf represented in
Fig 61, was immediately placed in a dark closet for 24 hours. Then
leaf 4 was taken from it; 5 represents this leaf after the chlorophyl
was taken from it: it is white; 6 is the same after treatment with
iodine. The leaf remains white, showing no starch. (Drawings by M.E.
Feltham.)]
[Illustration: FIG. 63.
To show that sunlight is necessary for starch-making by leaves. Leaf 7
had a paper label stuck to its upper surface a couple of hours while
the plant was exposed to sunlight; 8 is the same leaf after the
chlorophyl was taken out, and 9 represents it after treatment with
iodine. The leaf turned purple in all parts except the part that was
shaded by the label. Starch was removed from the portion under the
label, but was not renewed because the label kept out the necessary
sunlight. (Drawings by M.E. Feltham.)]
[Illustration: FIG. 64.
To show that chlorophyl is necessary for starch formation in the leaf.
10 is a variegated leaf from a silver-leaved geranium; the center is
an irregular patch of green, with an irregular border of white. 11,
after taking out the green. 12, after iodine treatment, the leaf turns
purple only where it was originally green, showing that no starch
forms in the white border. (Drawings by M.E. Feltham.)]
Some leaves on the branch are larger than others because in the
struggle for light and air they have had a better chance than the
others or they have had more of the food which has come up from the
root.
Some of the leaves have developed longer stems than others in their
effort to reach out after light and air.
Most leaves have the little mouths through which air is taken in and
water and oxygen given out on the rough side, and that side is turned
down toward the earth probably so that rain and dust will not choke
the little pores.
The leaves of the lower branches tend to spread out in a broad, flat
plane because in the effort to get light no leaf will grow directly
under and in the shadow of another, while on those branches which grow
straight up from the top of the tree the leaves can get light from all
sides and so arrange themselves around the stem.
Is it of any value to the plant grower to know these facts about
leaves? It is, for knowing these things he can better understand the
necessity of caring for the leaves of his growing plants to see that
their work is not interfered with.
HOW THE WORK OF SOME LEAVES IS INTERFERED WITH
Many people who grow house plants have trouble in keeping them well
clothed with leaves, for instance, the geranium and the rubber plant.
The leaves are constantly turning yellow and dropping off or drying
up. This sometimes occurs from over-watering or not sufficiently
watering the soil in the pot or box. If the watering is all right the
trouble may occur in this way: The air of the house is quite dry,
especially in winter. As a result transpiration from the leaf may be
excessive. More water is transpired than is necessary, consequently
more is pumped by the roots and with it more food is sent to the leaf
than it can take care of. As the excess of water is transpired the
excess of food is left in the leaf. The tendency is to clog its pores
and therefore interfere with its work, and gradually weaken and
finally kill it. The remedy for this is to spray the leaves frequently
so as to keep the air about them moist and so check transpiration.
Keeping a vessel of water near them helps also as this tends to keep
the air moist. Dust sometimes chokes the leaves. Washing or spraying
remedies this.
Sometimes house plants, and out-door plants as well, become covered
with a small, green insect called the plant louse or aphis. This
insect has a sharp beak like a mosquito and it sucks the juices from
the leaf and causes it to curl up, interfering with its work and
finally killing it. Frequent spraying with water will tend to keep
these away. A surer remedy against them is to spray the plants with
weak tobacco water made by soaking tobacco or snuff in water, or to
fumigate them with tobacco smoke. Sometimes the under side of the
leaf becomes infested with a very small mite called red spider
because it spins a web. These mites injure the leaf by sucking sap
from it. They can be kept in check by frequent spraying for they do
not like water. If, then, we are careful to frequently spray the
leaves of our house plants we will have very little trouble from
aphis, red spider or over transpiration. The aphis, or plant louse, is
often very numerous on out-door plants, for instance, the rose,
chrysanthemum, cabbage, and fruit trees. They vary in color from green
to dark brown or black. They are treated in the same way as those on
the house plants. Some familiar out-door insects which interfere with
leaf work are the common potato bug, the green cabbage worm, the rose
slug, the elm tree leaf beetle, the canker worm, the tomato worm.
These insects and many others eat the leaves (Fig. 67). They chew and
swallow their food and are called chewing insects. All insects which
chew the leaves of plants can be destroyed by putting poison on their
food. The common poisons used for this purpose are Paris green and
London purple, which contain arsenic, and are used at the rate of one
teaspoonful to a pail of water or one-fourth pound to a barrel of
water. This is sprinkled or sprayed on the leaves of the plants.
Another poison used is white hellebore. This loses its poisoning
qualities when exposed to the air for a time. Therefore it is safer to
use about the flower garden and on plants which are soon to be used as
food or whose fruit is to be used soon, like cabbages and current
bushes. This hellebore is sifted on the plant full strength, or it may
be diluted by mixing one part of hellebore with one or two parts of
flour, plaster, or lime. It is also used in water, putting one ounce
of hellebore in three gallons of water and then spraying it on the
plants. Plants may be sprayed by using a watering pot with a fine rose
or sprinkler, or an old hair-brush or clothes-brush. For large plants
or large numbers of smaller plants spray pumps of various sizes are
used. Sometimes chewing insects on food plants and sucking insects on
all plants are treated by spraying them with soapy solutions or oily
solutions which injure their bodies.
The work of the leaf is also interfered with by diseases which attack
the leaves and cause parts or the whole leaf to turn yellow or brown
or become blistered or filled with holes. The common remedy for most
of these diseases is called the "Bordeaux Mixture." It is prepared as
follows: Dissolve four pounds of blue vitriol (blue stone, or copper
sulphate) in several gallons of water. Then slake four pounds of lime.
Mix the two and add enough water to make a barrelful. The mixture is
then sprayed on the plants.
For more detailed directions for spraying plants and combating insects
and diseases write to your State Experiment Station and to the United
States Department of Agriculture at Washington, D.C.
[Illustration: FIG. 65.
To show the giving off of gas by leaves, and that sunlight is
necessary for it. The jars contain seaweed. _A_ was set in the sun and
developed enough gas to float part of the plant. _B_ was left in the
darker part of the room and developed very little gas.]
[Illustration: FIG. 66.
Seedling radishes reaching for light.]
[Illustration: FIG. 67.
Elm leaves injured by the "imported elm-tree leaf beetle," a chewing
insect.]
The work of the leaves of house plants is often interfered with by not
giving them sufficient sunlight. Garden and field plants are
sometimes planted so thick that they crowd each other and shut the
light and air from each other, or weeds are allowed to grow and do the
same thing, the result being that the leaves cannot do good work and
the plant becomes weak and sickly. Weeds are destroyed by pulling them
up and exposing their roots to the sun. This should be done before the
weeds blossom, to prevent them from producing fresh seeds for a new
crop of weeds. Some weeds have fleshy roots--for example, dock,
thistle--in which food is stored; these roots go deep in the ground,
and when the upper part of the plant is cut or broken off the root
sends up new shoots to take the place of the old. Some have
underground stems in which food is stored for the same purpose. The
surest way to get rid of such weeds, in fact, of all weeds, is to
prevent their leaves from growing and making starch and digesting food
for them. This is accomplished by constantly cutting off the young
shoots as soon as they appear above the soil, or by growing some crop
that will smother them. The constant effort to make new growth will
soon exhaust the supply of stored food and the weed will die.
CHAPTER XIV
STEMS
WHAT ARE STEMS FOR?
Visit the farm or garden and the fields to examine stems and study
their general appearances and habits of growth. Notice that many
plants, like the trees, bushes and many vegetable and flowering
plants, have stems which are very much branched, while others have
apparently single stems with but few or no branches. Examine these
stems carefully and note that there are leaves on some part of all of
them and that just above the point where each leaf is fastened to the
stem there is a bud which may sometime produce a new branch (Fig. 68).
If the stems of trees and other woody plants be examined in the winter
after the leaves have fallen, it will be seen that the buds are still
there, and that just below each bud is a mark or leaf scar left by the
fallen leaf. These buds are the beginnings of new branches for another
year's growth. On some branches will be found also flowers and fruit
or seed vessels.
Buds and leaves or buds and leaf scars distinguish stems from roots.
Some plants have stems under the soil as well as above it. These
underground stems resemble roots but can be distinguished from them by
the rings or joints where will be found buds and small scale-like
leaves (Fig. 69). Quitch-grass or wiregrass, Burmuda grass, white
potato and artichoke are examples of underground stems.
Now study the habit of growth of these stems. Notice that:
Some plants grow erect with strong, stiff stems, for example, corn,
sunflower, maple, pine, elm and other trees. Many of these erect stems
have branches reaching out into the air in all directions. Stand under
a tree close to the stem or trunk and look up into the tree and notice
that the leaves are near the outer ends of the branches while in the
centre of the tree the branches are nearly bare. Why is this? If you
remember the work of leaves and the conditions necessary for their
work you will be able to answer this question. Leaves need light and
air for their work, and these erect, branching stems hold the leaves
up and spread them out in the light and air.
Notice that where several trees grow close together, they are
one-sided, and that the longest and largest branches are on the
outside of the group and that they have more leaves than the inner
branches. Why? Why do the trees in thick woods have most of the living
branches and bear most of their leaves away up in the top of the tree?
Some stems instead of standing up erect climb up on other plants or
objects by means of springlike tendrils which twist about the object
and so hold up the slender stem. On the grape vine these tendrils are
slender branches. On the sweet pea and garden pea they are parts of
the leaves. The trumpet creeper and English ivy climb by means of air
roots. The nasturtium climbs by means of its leaf stems.
Other stems get up into the light and air with their leaves by twining
about upright objects. For example, the morning glory and pole bean.
Some stems will be found that spread their leaves out to the sun by
creeping over the ground. Sweet potato, melon, squash, and cucumber
vines are examples of such plants.
One use of the stems of plants then is to support the leaves, flowers
and fruit, and expose them to the much needed light and air.
=Experiment.=--Get a piece of grape vine and cut it into pieces four
or five inches long; notice that the cut surface appears to be full of
little holes. Cut a piece from between joints, place one end in your
mouth and blow hard. It will be found that air can be blown through
the piece of vine. Now pour about an inch of water in a tumbler or cup
and color it with a few drops of red ink. Then stand some of the
pieces of grape vine in the colored water. In a few hours the colored
water will appear at the upper ends of the sticks. Capillary force has
caused the colored water to rise through the small tubes in the vine.
Repeat this experiment with twigs of several kinds of trees and soft
green plants, as elm, maple, sunflower, corn, etc. It will not be
possible to blow through these twigs, but the red water will rise
through them by osmose, and in a few hours will appear at the upper
ends. If some leaves are left on the stems the colored water will
appear in them. Some white flowers can be colored in this way.
In this manner the stem carries plant food dissolved in water from the
roots to the leaves, and after the leaves have digested it carries it
back to various parts of the plant.
The stem then serves as a conductor or a passage for food and moisture
between roots and leaves.
Visit a strawberry bed or search for wild strawberry plants. Notice
that from the older and larger plants are sent out long, slender,
leafless stems with a bud at the tip. These stems are called runners.
Find some runners that have formed roots at the tip and have developed
a tuft of leaves there, forming new plants. Find some black raspberry
plants and notice that some of the canes have bent over and taken root
at the tips sending up a new shoot and thus forming a new plant. You
know how rapidly wire grass and Bermuda grass will overrun the garden
or farm. One way in which they do this is by sending out underground
stems which take root at the joints and so form new plants.
Another use of the stem then is to produce new plants.
On the farm we make use of this habit of stems when we wish to
produce new white potato plants. We cut an old potato in pieces and
plant them. The buds in the eyes grow and form new plants. One way of
getting new grape plants is to take a ripened vine in the fall and cut
it in pieces with two or three buds and plant them so that one or both
of the buds are covered with soil. The pieces will take root and in
the spring will send up new shoots and thus form new plants.
You can obtain new plants from geranium, verbena, nasturtium and many
other flowering plants, by cutting and planting slips or parts of the
stems from them.
In parts of the South new sweet potato plants are obtained by cutting
parts of the stems from growing plants and planting them.
Florists produce large numbers of new plants by taking advantage of
this function of stems.
=Experiment.=--Take a white potato which is a thickened stem and place
it in a warm, dark place. It will soon begin to sprout or send out new
stems, and as these new stems grow the potato shrinks and shrivels up.
Why is this? It is because the starch and other material stored in the
potato are being used to feed the new branches. When we plant potatoes
in the garden and field the new plants produced from the eyes of the
potato are fed by the stored material until they strike root and are
able to take care of themselves.
All stems store food for the future use of the plant.
Annual plants, or those which live but one year, store food in their
stems and leaves during the early part of their growth. During the
fruiting or seed forming season this food material is transferred to
the seeds and there stored, and the stems become woody. This is a fact
to bear in mind in connection with the harvesting of hay or other
fodder crops. If we let the grass stand until the seeds form in the
head, the stem and leaves send their nourishment to the seeds and
become woody and of less value than if cut before the seeds are fully
formed.
In plants of more than one year's growth the stored food is used to
give the plant a start the following season, or for seed production.
The rapid growth of leaf and twig on trees and shrubs in spring is
made from the food stored in the stem the season before.
Sago is a form of starch stored in the stem of the sago palm for the
future use of the plant.
Maple sugar is made from the food material stored in the trunk of the
maple tree for the rapid growth of twig and leaf in the spring.
Cane sugar is the food stored in the sugar cane to produce new plants
the next season.
If we examine the stem of a tree that has been cut down we find that
it is woody, that the wood is arranged in rings or layers and that the
outer part of the stem is covered with bark. We will notice also that
the wood near the centre of the tree is darker than the outer part.
This inner part is called the heart wood of the tree. The lighter
wood is called the sap wood. It is through the outer or sap wood that
the water taken in by the root is passed up to the leaves where the
food which it carries is digested and then sent back to the plant. The
returning digested food is sent back largely through the bark. Between
the bark and the wood is a very thin layer which is called cambium.
This is the active growing tissue of the stem. In the spring it is
very soft and slippery and causes the bark to peel off easily. This
cambium builds a new ring of wood outside of the old wood and a new
ring of bark on the inside of the bark. In this way the tree grows in
diameter.
Now if the bark is injured, or any part of the stem, all parts below
the wound are cut off from the return supply of digested food and
their growth is checked. When such a wound does occur, or if a wound
is made by cutting off a branch, the cambium sets to work to repair
the damage by pushing out a new growth which tends to cover the wound.
We can help this by covering the wound and keeping the air from it to
prevent its drying and to keep disease from attacking it before it is
healed.
HOW THE WORK OF THE STEM MAY BE INTERFERED WITH
If there are any peach trees near by, examine the trunks close to the
ground, even pulling away the soil for a few inches. You will very
likely find a mass of gummy substance oozing from the tree. Pull this
away and in it and in the wood under it will be found one or more
yellowish white worms. These are tree borers. They will be found in
almost all peach trees. They interfere with the work of the stem and
in many cases kill the trees. These worms may be kept somewhat in
check by keeping papers wrapped about the lower part of the tree. But
the surest way to keep them in check is to dig them out, spring and
fall, with a knife and wire.
Borers attack the other fruit trees and also ornamental trees and
shrubs.
Rabbits sometimes gnaw the bark from trees during severe winters.
Careless workmen sometimes injure the bark of trees by allowing plows
and mowing machines or other tools which they are using among them to
come in contact with the trees and injure the bark.
Young trees purchased from the nursery generally have a label fastened
to them with a piece of wire. Unless this wire is removed or is
carefully watched and enlarged from time to time it will cut into the
bark as the stem grows and interfere with its work and often kill the
top of the tree or injure a main branch.
These are a few ways in which the work of the stem is sometimes
checked and the plant injured thereby.
CHAPTER XV
FLOWERS
In our study of the parts of plants the flower and fruit have been
given the last place because in the growing of most farm plants a
knowledge of the functions of the flower is of less importance than
that of the roots, leaves and stems. However, a knowledge of these
parts is necessary for successful fruit culture and some other
horticultural industries.
As with the other parts of the plant our study will not be exhaustive
but will be simply an attempt to bring out one or two important truths
of value to most farmers.
In the study of flowers the specimens used for study will depend upon
the time of the year in which the studies are made and need not
necessarily be the ones used here for illustration.
FUNCTION OR USE OF FLOWERS TO PLANTS
Of what use is the flower to the plant?
You have doubtless noticed that most flowers are followed by fruit or
seed vessels. In fact, the fruit and seeds are really produced from
the flower, and the work of most flowers is to produce seeds in order
to provide for new plants.
[Illustration: FIG. 68.
A horse-chestnut stem showing leaves, buds, and scars where last
year's leaves dropped off.]
[Illustration: FIG. 69.--AN UNDERGROUND STEM
Buds show distinctly at points indicated by _b_.]
To understand how this comes about it will be necessary to study the
parts of the flower and find out their individual uses or functions.
PARTS OF A FLOWER
If we take for our study any of the following flowers: cherry, apple,
buttercup, wild mustard, and start from the outside, we will find an
outer and under part which in most flowers is green. This is called
the calyx (Figs. 70-74). In the buttercup and mustard the calyx is
divided into separate parts called sepals. In the cherry, peach and
apple, the calyx is a cup or tube with the upper edge divided into
lobes.
Above the calyx is a broad spreading corolla which is white or
brightly colored and is divided into several distinct parts called
petals. The petals of one kind of flower are generally different in
shape, size and color from those of other flowers. In some flowers the
petals are united into a corolla of one piece which may be
funnel-shaped, as in the morning glory or petunia of the garden, or
tubular as in the honeysuckle, wheel-shaped as in the tomato and
potato, or of various other forms.
Within the corolla are found several bodies having long, slender stems
with yellow knobs on their tips. These are called stamens. The slender
stems are called stalks or filaments and the knobs anthers. The
anthers of some of the stamens will very likely be found covered with
a fine, yellow powder called pollen. This pollen is produced within
the anther which, when ripe, bursts and discharges the pollen.
The stamens vary greatly in number in different kinds of flowers. In
the centre of the cherry, peach, or mustard flower will be found an
upright slender body called the pistil. In the peach and cherry the
pistil has three parts, a lower rounded, somewhat swollen part called
the ovary, a slender stem arising from it called the style, and a
slight enlargement at the top of the style called the stigma. The
stigma is generally roughened or sticky. If the ovary is split open,
within it will be found a little body called an ovule, which is to
develop into a seed.
In the apple flower the pistils will be found to have one ovary with
five styles and stigmas and in the ovary will be several ovules.
In the buttercup will be found a large number of small pistils, each
consisting of an ovary and stigma.
The parts of different flowers will be found to vary in color, in
shape, in relative size and in number. In some flowers one or more of
the parts will be found wanting.
Examine a number of flowers and find the parts.
FUNCTIONS OF THE PARTS OF THE FLOWERS
Now what are the uses of these parts of the flower?
[Illustration: FIG. 70.--FLOWER OF CHERRY.
_a_, pistil; _b_, stamen; _c_, corolla; _d_, calyx; _e_, section of
flower showing ovary with ovule. (Drawing by M.E. Feltham.)]
[Illustration: FIG. 71.
1. Flower of apple; _b_, stamens; _c_, corolla; _d_, calyx. 2. Section
of same; _a_, style; _e_, compound ovary; _f_, filament; _g_, anther.
(Drawing by M.E. Feltham.)]
[Illustration: FIG. 72.
_A._ Pistil of flowering raspberry; _e_, ovary; _t_, style; _s_,
stigma. _B._ Stamen of flowering raspberry; _f_, filament; _g_,
anther; _p_, pollen.]
[Illustration: FIG. 73.--FLOWER OF BUTTERCUP.
_c_, petals; _d_, sepals; _h_, ripened pistils, or fruit. (Drawing by
M.E. Feltham.)]
If we watch a flower of the peach or cherry from week to week, we will
see that the pistil develops into a peach or cherry which bears within
a seed from which a new plant will be produced if the seed is
placed under conditions necessary for germination or sprouting.
The pistils of the flowers of other plants will be found to develop
into fleshy fruits, hard nuts, dry pods or husks containing one or
more seeds.
The work of the pistil or pistils of flowers then is to furnish seeds
for the production of new plants.
The botanists tell us that a pistil will not produce seeds unless it
is fertilized by pollen from the same kind of flower falling on its
stigma.
The work of the stamen then is to produce pollen to fertilize the
pistils. Pistils and stamens are both necessary for the production of
fruit and seed. They are therefore called the essential or necessary
parts of the flower.
The botanists also tell us that nature has provided that in most cases
the pistils shall be fertilized by the pollen of some other flower
than their own, as this produces stronger seeds.
How is the pollen carried from flower to flower?
Go into the garden or field and watch the bees and butterflies flying
about the flowers, resting on them and crawling into them. They are
seeking for nectar which the flower secretes. As they visit plant
after plant, feeding from many flowers, their bodies become more or
less covered with pollen as they brush over the stamens. Some of this
pollen in turn gets rubbed off on the stigmas of the pistils and they
become fertilized. Thus the bees and some other insects have become
necessary as pollen carriers for some of the flowers and the flowers
in turn feed them with sweet nectar.
This gives us a hint as to one use of the corollas which spreads out
such broad, brightly-colored, conspicuous petals. It must be that they
are advertisements or sign boards to attract the bees and to tell them
where they can find nectar and so lead them unconsciously to carry
pollen from flower to flower to fertilize the pistils. The act of
carrying pollen to the pistil is called pollination, and carrying
pollen from the stamens of one flower to the pistil of another flower
is called cross pollination.
If we examine a blossom bud just before it opens we will see only the
calyx. Everything else will be wrapped up inside of it. Evidently,
then, the calyx is a protecting covering for the other parts of the
flower until blossoming time.
The corolla will be found carefully folded within the calyx and also
helps protect the stamens and pistil.
Some flowers do not produce bright-colored corollas to attract the
bees, for examples, the flowers of the grasses, wheat, corn, and other
grains, the willows, butternuts, elms, pines and others. But they
produce large amounts of pollen which is carried by the wind to the
pistils.
You have sometimes noticed in the spring that after a rain the pools
of water are surrounded by a ring of yellow powder and you have
perhaps thought it was sulphur. It was not sulphur but was composed of
millions of pollen grains from flowers. One spring Sunday I laid my
hat on the seat in church. When I picked it up at the end of the
service I found considerable dust on it. I brushed the dust off, but
on reaching home I found some remaining and noticed that is was
yellow, so I examined it with a magnifying glass and found that it was
nearly all pollen grains. Then I rubbed my finger across a shelf in my
room and found it slightly dusty; the magnifying glass showed me that
this dust was half pollen. This shows what a great amount of pollen is
produced and discharged into the air, and it shows that very few
pistils could escape even if they were under cover of a building.
To make sure of cross pollination nature has in some cases placed the
stamens and pistils in different flowers on the same plant. This will
be found true of the flowers of the squashes, melons and cucumber.
Below some of the flower buds will be seen a little squash, melon or
cucumber (Fig. 75). These are the ovaries of pistils and the stigmas
will be found within the bud or will be seen when the bud opens. But
no stamen will be found here. Other flowers on these plants will be
found to possess only stamens. These staminate flowers produce pollen
and then die. They do not produce any fruit, but their pollen is
necessary for the little cucumbers, squashes and melons to develop.
Another example is the corn plant. Here the pistils are on the ear,
the corn silk being the styles and stigmas, while the pollen is
produced in the tassel at the top of the plant.
With some plants we find that not only are the pistils and stamens in
separate flowers but the staminate and pistilate flowers are placed on
different plants. This will be found true of the osage orange and the
willow.
In many flowers that have both stamens and pistils or are perfect
flowers the stigmas and pollen ripen at different times.
With some varieties of fruit it is found that the pistils cannot be
fertilized by pollen of the same variety. This is true of most of our
native plums. For example, the pistils of the wild goose plum cannot
be fertilized by pollen of wild goose plums even if it comes from
other trees than the one bearing the pistils. They must have pollen
from another variety of plum.
VALUE OF A KNOWLEDGE OF THE FLOWER
Many times it happens that a farmer or a gardener wants to start a
strawberry bed and buys plants of a variety of berries that have the
reputation of being very productive. He plants them and cultivates
them carefully, and at the proper time they blossom very freely, and
there is promise of a large crop, yet very few berries appear and this
continues to be the case. Not satisfied with them he buys another
variety and plants near them, and after that the old bed becomes very
productive. Now why is this? It happens that the flowers of some
varieties of strawberries have a great many pistils but no stamens,
or very few stamens, and there is not pollen enough to fertilize all
of the blossoms, and when such a variety is planted it is necessary to
plant near it some variety that produces many stamens and therefore
pollen enough to fertilize both varieties in order to be sure of a
crop. Those strawberries which produce flowers with only pistils are
called pistilate varieties, while those with both stamens and pistils
are called perfect varieties (Fig. 78). In planting them there should
be at least one row of a perfect variety to every four or five
pistilate rows.
[Illustration: FIG. 74.
A magnolia flower showing central column of pistils and stamens, the
pistils being above and the stamens below them.]
[Illustration: FIG. 75.--FLOWERS OF SQUASH.
_A_, pistillate flower; _B_, staminate flower. A means of insuring
cross-pollination.]
We have learned that certain varieties of plums cannot be fertilized
by pollen from the same variety, and to make them fruitful some other
variety must be planted among them to produce pollen that will make
them fruitful. This is more or less true of all our fruits. Therefore
it is not best generally to plant one variety of fruit by itself. Not
knowing this some orchardists have planted large blocks of a single
variety of fruit which has been unfruitful till some other varieties
have been planted near them or among them.
A knowledge of the necessity of pollination is very important to those
gardeners who grow cucumbers, tomatoes, melons and other fruiting
plants in greenhouses. Here in most cases the pollination is done by
hand.
We noticed that nature provides that most of the flowers shall be
cross pollinated. This is particularly true of the flowers of the
fruit trees, and for this reason it is impossible to get true
varieties of fruit from seed. For example, if we plant seeds of the
wine sap apple, the new trees produced from them will not produce the
same kind of apple but each tree will produce something different and
they will very likely all be poorer than the parent fruit. This is
because of the mixture of pollens which fertilize the pistils. Knowing
this fact the nurseryman plants apple seeds and grows apple seedlings.
When these get to be the size of a lead pencil he grafts them, that
is, he digs them up, cuts off the tops away down to the root and then
takes twigs from the variety he wishes to grow and sets or splices
these twigs in the roots of the seedlings and then plants them. The
root and the new top unite and produce a tree that bears the same kind
of fruit as that produced by the tree from which the twig was taken.
These are a few of the reasons why it is well to know something about
flowers and their work.
[Illustration: FIG. 76.--FLOWER OF A LILY.
Notice how the stigma and the anthers are kept as far as possible from
each other to guard against self-pollination and to insure
cross-pollination.]
[Illustration: FIG. 77.
Bud and flower of jewel-weed, or "touch-me-not." _A._ Interior of bud.
Stamens are seen, but there appears to be no pistil. _B._ Section of
bud showing the pistil concealed behind the stamens. _C._ Bee entering
flower comes in contact with stamens and is loaded with pollen. _D._
Same bee entering older flower. The stamens have ripened and been
pushed off by the lengthened pistil, which is brushed by the back of
the bee, and thus is pollinated. This is a contrivance to insure
cross-pollination.]
[Illustration: FIG. 78.
_A._ Pistillate flower of strawberry.
_B._ Perfect flower of strawberry. (Drawing by M.E. Feltham.)]
FRUIT
The pistil develops and forms the fruit of the plant. This fruit bears
seed for the production of new plants. This fruit may be a dry pod
like the bean or pea, or it may be a fleshy fruit like the apple or
plum. Now the developing pistil or fruit may be checked in its work of
seed production by insects and diseases, and to secure good fruit it
is in many cases necessary to spray the fruits just as the leaves
are sprayed, to keep these insects and diseases in check.
The fruits of most plants, like the leaves, need light and air for
their best development, and it sometimes happens that the branches of
the fruit trees grow so thick that the fruits do not get sufficient
light and air. This makes it necessary to thin the branches or in
other words to prune the tree. Some trees also start more fruit than
they can properly feed and as a result the ripened fruits are small
and the tree is weakened. This makes it necessary to thin the fruits
while they are young and undeveloped.
PART II
Soil Fertility as Affected by Farm Operations and Farm Practices
THE FIRST BOOK OF FARMING
PART II
_Soil Fertility as Affected by Farm Operations and Farm Practices_
CHAPTER XVI
A FERTILE SOIL
What is a fertile soil?
The expression a fertile soil is often used as meaning a soil that is
rich in plant food. In its broader and truer meaning a fertile soil is
one in which are found all the conditions necessary to the growth and
development of plant roots.
These conditions, as learned in Chapter II, are as follows:
The root must have a firm yet mellow soil.
It must be well supplied with moisture.
It must be well supplied with air.
It must have a certain amount of heat.
It must be supplied with available plant food.
In order to furnish these needs or conditions the soil must possess
certain characteristics or properties.
These properties may be grouped under three heads:
Physical properties; the moisture, heat and air conditions needed by
the roots.
Biological properties; the work of very minute living organisms in the
soil.
Chemical properties; plant food in the soil.
PHYSICAL PROPERTIES OF A FERTILE SOIL
Three very important physical properties of a fertile soil are its
Power to take water falling on the surface.
Power to absorb water from below.
Power to hold water.
The fertile soil must possess all three of these powers. The relative
degrees to which these three powers or properties are possessed
determine more than anything else the kind of crops or the class of
crops that will grow best on a given soil.
These powers depend, as we learned in Chapter IV, on the texture of
the soil or the relative amounts of sand, silt, clay and humus
contained in the soil.
The power of admitting a free circulation of air through its pores is
also an important property of a fertile soil, for air is necessary to
the life and growth of the roots. This property is dependent also on
texture.
Two other important properties of a fertile soil are power to absorb
and power to hold heat. These depend upon the power of the soil to
take in warm rain and warm air, and also upon density and color. The
denser or more compact soil and the darker soil having greater power
to absorb heat.
The compactness of the soil which gives it greater powers to absorb
heat weakens its powers to hold it, because the compactness allows
more rapid conduction of heat to the surface, where it is lost by
radiation.
The more moisture a soil holds, the weaker is its heat-holding power,
because the heat is used in warming and evaporating water from the
surface of the soil.
These important properties or conditions of moisture, heat and air,
are, as we have seen, dependent on soil texture and color, which in
turn are dependent upon the relative amounts of sand, clay and humus
in the soil. We are able to control soil texture and therefore these
physical properties to a certain degree by means of tillage and the
addition of organic matter or humus (see Chapter IV).
BIOLOGICAL PROPERTIES OF A FERTILE SOIL
Biology is the story or science of life; and the biological properties
of the soil have to do with living organisms in the soil.
The soil of every fertile field is full of very small or microscopic
plants called bacteria or germs. They are said to be microscopic
because they are so small that they cannot be seen without the aid of
a powerful magnifying glass or microscope. They are so small that it
would take about 10,000 average-sized soil bacteria or soil germs
placed side by side to measure one inch.
A knowledge of three classes of these soil germs is of great
importance to the farmer. These three classes of germs are:
Nitrogen-fixing germs.
Nitrifying germs.
Denitrifying germs.
NITROGEN-FIXING GERMS
We learned in Chapter VIII that nitrogen is one of the necessary
elements of plant food, and that although the air is four-fifths
nitrogen, most plants must take their nitrogen from the soil. There
is, however, a class of plants called legumes which can use the
nitrogen of the air. Clover, alfalfa, lucern, cowpea, soy bean, snap
bean, vetch and similar plants are legumes. These legumes get the
nitrogen from the air in a very curious and interesting manner. It is
done through the aid of bacteria or germs.
Carefully dig up the roots of several legumes and wash the soil from
them. On the roots will be found many small enlargements like root
galls; these are called nodules or tubercles. On clover roots these
nodules are about the size of the head of a pin while on the soy bean
and cowpea they are nearly as large as a pea (see Fig. 34). These
nodules are filled with bacteria or germs and these germs have the
power of taking nitrogen from the air which finds its way into the
soil. After using the nitrogen the germ gives it to the plant which
then uses it to build stem, leaves and roots. In this way the legumes
are able to make use of the nitrogen of the soil air, and these germs
which help them to do it by catching the nitrogen are called
nitrogen-fixing germs.
The work of these germs makes it possible for the farmer to grow
nitrogen, so to speak, on the farm.
By growing crops of legumes and turning them under to decay in the
soil, or leaving the roots and stubble to decay after the crop is
harvested, he can furnish the following crop with a supply of nitrogen
in a very cheap manner and lessen the necessity of buying fertilizer.
NITRIFYING GERMS
Almost all the nitrogen of the soil is locked up in the humus and
cannot in that condition be used by the roots of plants. The nitrogen
caught by the nitrogen-fixing germs and built into the structure of
leguminous plants which are grown and turned under to feed other
plants cannot be used until the humus, which is produced by their
partial decay, is broken down and the nitrogen built into other
substances upon which the root can feed. The breaking down of the
humus and building of the nitrogen into other substances is the work
of another set of bacteria or germs called nitrifying germs.
These nitrifying germs attack the humus, break it down, separate the
nitrogen, cause it to unite with the oxygen of the air and thus build
it into nitric acid which can be used by plant roots. This nitric acid
if not immediately used will unite with lime or potash or soda or
other similar substances and form nitrates, as nitrate of lime,
nitrate of potash or common saltpetre. These nitrates are soluble in
water and can be easily used by plant roots. If there are no plant
roots to use them they are easily lost by being washed out of the
soil. The work of the nitrifying germs is called nitrification.
To do their work well the nitrogen-fixing germs and the nitrifying
germs require certain conditions.
The soil must be moist.
The soil must be well ventilated to supply nitrogen for the
nitrogen-fixing germs and oxygen for the nitrifying germs.
The soil must be warm. Summer temperature is the most favorable. Their
work begins and continues slowly at a temperature of about forty-five
degrees and increases in rapidity as the temperature rises until it
reaches ninety or ninety-five.
The nitrifying germs require phosphoric acid, potash and lime in the
soil.
Direct sunlight destroys these bacteria, therefore they cannot work at
the surface of the soil unless it is shaded by a crop.
From this we see that these bacteria or germs work best in the soil
that has conditions necessary for the growth and development of plant
roots.
DENITRIFYING GERMS
These germs live on the coarse organic matter of the soil. Like the
nitrifying germs they need oxygen, and when they cannot get it more
readily elsewhere they take it from the nitric acid and nitrates. This
allows the nitrogen of the nitrates to escape as a free gas into the
air again, and the work of the nitrogen-fixing and nitrifying germs is
undone and the nitrogen is lost. This loss of nitrogen is most apt to
occur when the soil is poorly ventilated, because of its being very
compact, or when the soil spaces are filled with water. This loss of
nitrogen by denitrification can be checked by keeping the soil well
ventilated.
CHEMICAL PROPERTIES OF A FERTILE SOIL
By the term chemical properties we have reference to the chemical
composition of the soil, the chemical changes which take place in the
soil, and the conditions which influence these changes.
The sand, clay and humus of the soil are made up of a great variety of
substances. The larger part of these act simply as a mechanical
support for the plants and also serve to bring about certain physical
conditions. Only a very small portion of these substances serve as the
direct food of plants and the chemical conditions of these substances
are of great importance.
In Chapter VIII we learned that plants are composed of several
elements and that seven necessary elements are taken from the soil.
These seven are nitrogen, phosphorus, potassium, magnesium, calcium,
iron and sulphur.
Now a fertile soil must contain these seven elements of plant food and
they must be in such form that the plant roots can use them.
Plant roots can generally get from most soils enough of the magnesium,
calcium, iron, and sulphur to produce well developed plants. But the
nitrogen, phosphorus and potassium, although they exist in sufficient
quantities in the soil, are often in such a form or condition that the
roots cannot get enough of one or more of them to produce profitable
crops. For this reason these three elements are of particular
importance to the farmer for, in order to keep his soil fertile, he
must so treat it that these elements will be made available or he must
add more of them to the soil in the proper form or condition.
_Nitrogen in the soil._--Plant roots use nitrogen in the form of
nitric acid and salts of nitrogen called nitrates. But the nitrogen of
the soil is very largely found in the humus with the roots cannot use.
A chemical change must take place in it and the nitrogen be built into
nitric acid and nitrates. This, we have learned, is done through the
aid of the nitrifying germs.
_Phosphoric acid in the soil._--Phosphorus does not exist pure in the
soil. The plant finds it as a phosphoric acid united with the other
substances forming phosphates. These are often not available to
plants, but can to a certain extent be made available through tillage
and by adding humus to the soil.
_Potash in the soil._--The plant finds potassium in potash which
exists in the soil. Potash like phosphoric acid often exists in forms
which the plant cannot use but may be made available to a certain
extent by tillage, the addition of humus, and the addition of lime to
the soil.
_Lime in the soil._--Most soils contain the element calcium or lime,
the compound in which it is found, in sufficient quantities for plant
food. But lime is also of importance to the farmer and plant grower
because it is helpful in causing chemical changes in the soil which
tend to prepare the nitrogen, phosphoric acid and potash for plant
use. It is also helpful in changing soil texture.
The chemical changes which make the plant foods available are
dependent on moisture, heat, and air with its oxygen, and are
therefore dependent largely on texture, and therefore on tillage.
When good tillage and the addition of organic matter and lime do not
render available sufficient plant food, then the supply of available
food may be increased by the application of manure and fertilizers.
It will be seen that all these classes of properties are necessary to
furnish all the conditions for root growth.
The proper chemical conditions require the presence of both physical
and biological properties and the biological work in the soil
requires both chemical and physical conditions.
From the farmer's standpoint the physical properties seem to be most
important, for the others are dependent on the proper texture,
moisture, heat and ventilation which are controlled largely by
tillage.
Therefore the first effort of the farmer to improve the fertility of
his soil should be to improve his methods of working the soil.
Every one of these properties of the fertile soil, and consequently
every one of the conditions necessary for the growth and development
of plant roots, is influenced in some way by every operation performed
on the soil, whether it be plowing, harrowing, cultivating, applying
manure, growing crops, harvesting, or anything else, and the
thoughtful farmer will frequently ask himself the question: "How is
this going to effect the fertility of my soil or the conditions
necessary for profitable crop production?"
MAINTENANCE OF FERTILITY
The important factors in maintaining or increasing the fertility of
the soil are:
The mechanical operations of tillage, especially with reference to the
control of soil water.
The application of manures and fertilizers, especially with reference
to maintaining a supply of humus and plant food.
Methods or systems of cropping the soil, with reference to economizing
fertility.
CHAPTER XVII
SOIL WATER
The more important tillage tools and tillage operations we studied in
Chapters XI and XII. They will be noticed here only in connection with
their influence over soil water, for in the regulation of this
important factor in soil fertility the other conditions of fertility
are also very largely controlled.
IMPORTANCE OF SOIL WATER
"Of all the factors influencing the growth of plants, water is beyond
doubt the most important," and the maintaining of the proper amount of
soil water is one of the most important problems of the thinking
farmer in controlling the fertility of his soil.
NECESSITY OF SOIL WATER
The decay of mineral and organic matter in the soil, and the
consequent setting free of plant food, can take place only in the
presence of moisture. The plant food in barn manures and crops plowed
under for green moisture, can be made available only when there is
sufficient moisture in the soil to permit breaking down and
decomposition.
The presence of moisture in the soil is necessary for the process of
nitrification to take place.
Soil moisture is necessary to dissolve plant food. Plant roots can
absorb food from the soil only when it is in solution, and it seems to
be necessary that a large quantity of water pass through the plant
tissues to furnish the supply of mineral elements required by growth.
Moisture is necessary to build plant tissues. The quantity of water
entering into the structure of growing plants varies from sixty to as
high as ninety-five per cent, of their total weight.
During the periods of active growth there is a constant giving off of
moisture by the foliage of plants and this must be made good by water
taken from the soil by their roots.
In a series of experiments at the University of Wisconsin Agricultural
Experiment Station, it was found that in raising oats, every ton of
dry matter grown required 522.4 tons of water to produce it; for every
ton of dry matter of corn there were required 309.8 tons of water; a
ton of dry red clover requires 452.8 tons of water to grow it. At the
Cornell University Agricultural Experiment Station, a yield of
potatoes at the rate of 450 bushels per acre represented a water
requirement of 1310.75 tons of water.
SOURCES AND FORMS OF SOIL WATER
The soil which is occupied by the roots of plants receives moisture in
the form of rain, snow and dew from above and free and capillary water
rising from below.
"Free water is that form of water which fills our wells, is found in
the bottom of holes dug in the ground during wet seasons, and is often
found standing on the surface of the soil after heavy or long
continued rains. It is sometimes called 'ground water' or 'standing
water,' and flows under the influence of gravity." Free water is not
used directly by plants unless they are swamp plants, and its presence
within eighteen inches of the surface is injurious to most farm
plants. Free water serves as the main source of supply for capillary
water.
"Capillary water is water which is drawn by capillary force or soaks
into the spaces between the soil particles and covers these particles
with a thin film of moisture." It is a direct source of water to
plants. Capillary water will flow in any direction in the soil, the
direction of flow being determined by texture and dryness, the flow
being stronger toward the more compact and drier parts. If the soil is
left lumpy and cloddy then capillary water cannot rise readily from
below to take the place of that which is lost by evaporation. If,
however, the soil is fine and well pulverized, the water rises freely
and continuously to supply the place of that taken by plant roots or
evaporation from the surface.
TOO MUCH WATER
Some farm lands contain too much water for the growth of farm crops;
for example, bottom lands which are so low that water falling on the
surface cannot run off or soak down into the lower soil. The result is
that the spaces between the soil particles are most of the time filled
with water, and this checks ventilation, which is a necessary factor
in soil fertility. This state of affairs occurs also on sloping
uplands which are kept wet by spring water or by seepage water from
higher lands. Some soils are so close and compact that water falling
on the surface finds great difficulty in percolating through them, and
therefore renders them too wet for profitable cropping during longer
or shorter periods of the year. Nearly all such lands can be improved
by removing the surplus water through drains. (See Chapter XXV.)
Percolation and ventilation of close compact soils can be improved by
mixing lime and organic matter with them.
NOT ENOUGH WATER
In some sections of the country, particularly the arid and semi-arid
sections of the West, the soil does not receive a sufficient supply
of rain water for the production of profitable yearly crops. These
soils are rendered unfertile by the lack of this one all important
factor of fertility. They can be made fertile and productive by
supplying them with sufficient water through irrigation.
The crop-producing power of some lands is lowered even in regions
where the rainfall is sufficient, because these lands are not properly
prepared by tillage and the addition of organic matter to absorb and
hold the water that comes to them, or part of the water may be lost or
wasted by lack of proper after-tillage or after-cultivation. This
state of affairs is of course improved by better preparation to
receive water before planting the crop and better methods of
after-cultivation to save the water for the use of the crop.
LOSS OF SOIL WATER
Aside from what is used by the crops the soil may lose its water in
the following ways:
Rain water which comes to the soil may be lost by running off over the
surface of the land. This occurs especially on hilly farms and in the
case of close, compact soils.
Water may be lost from the soil by leaching through the lower soil.
Water may be lost from the soil by evaporation from the surface.
The soil may lose water by the growth of weeds which are continually
pumping water up by their roots and transpiring it from their leaves
into the air.
HOW SOME FARM OPERATIONS INFLUENCE SOIL WATER
Plowing and soil water. One of the first effects of deeply and
thoroughly plowing a close, compact soil, is that rain will sink into
it readily and not be lost by surface wash. In many parts of the
country, especially the South, great damage is done by the surface
washing and gulleying of sloping fields.
The shallow layer of soil stirred up by small plows and practice of
shallow plowing so prevalent in the South takes in the rain readily,
but as the harder soil beneath does not easily absorb the water the
shallow layer of plowed soil soon fills, then becomes mud, and the
whole mass goes down the slope. Where the land is plowed deep there is
prepared a deep reservoir of loose soil that is able to hold a large
amount of water till the harder lower soil can gradually absorb it.
The soil stirred and thoroughly broken by the plow serves not only as
a reservoir for the rainfall, but also acts as a mulch over the more
compact soil below it, thus checking the rapid use of capillary water
to the surface and its consequent loss by evaporation. The plow which
breaks and pulverizes the soil most thoroughly is the one best adapted
to fit the soil for receiving and holding moisture.
If the plowing is not well done or if the land is too dry when plowed
and the soil is left in great coarse lumps and clods, the air
circulates readily among the clods and takes from them what little
moisture they may have had and generally the soil is left in a worse
condition than if it had not been plowed at all.
Fall plowing on rolling land and heavy soil leaving the surface rough
helps to hold winter snows and rains when they fall, giving to such
fields a more even distribution of soil water in the spring.
Spring plowing should be done early, before there is much loss of
water from the surface by evaporation.
Professor King, of the University of Wisconsin Agricultural Experiment
Station, carried on an experiment to see how much soil water could be
saved by early plowing. He selected two similar pieces of ground near
each other and tested them for water April 29th. Immediately after
testing one piece was plowed. Seven days later, May 6th, he tested
them for water again and found that both had lost some water, but that
the piece which was not plowed had lost 9.13 pounds more water per
square foot of surface than the plowed piece. This means that by
plowing one part a week earlier than the other he saved in it water
equal to a rainfall of nearly two inches or at the rate of nearly 200
tons of water per acre.
HOEING, RAKING, HARROWING, AND CULTIVATING
These operations when properly and thoroughly done tend to supplement
the work of the plow in fitting the soil to absorb rain and in making
a mulch to check loss by surface evaporation. The entire surface
should be worked and the soil should be left smooth and not in ridges.
Rolling cutters and spring-toothed harrows are apt to leave ridges and
should have an attachment for smoothing the surface or be followed by
a smoothing harrow. Cultivators used to make mulches to save water
should have many narrow teeth rather than few broad ones. If a large
broad-toothed tool is used to destroy grass and large weeds it should
be followed by a smoother to level the ridges and thus lessen the
evaporating surface. The soil should be cultivated as soon after a
rain as it can be safely worked.
Rolling compacts the soil and starts a quicker capillary movement of
water toward the surface and a consequent loss by evaporation. When
circumstances will permit, the roller should be followed by a light
harrow to restore the mulch.
Ridging the land tends to lessen the amount of moisture in the soil
because it increases the evaporating surface. It should be practiced
only on wet land or in early spring to secure greater heat.
Drains placed in wet land remove free water to a lower depth and
increase the depth of soil occupied by capillary water and therefore
increase the body of soil available to plant roots.
MANURES AND SOIL WATER
Humus, as we learned in Chapter IV, has a very great and therefore
important influence over the water-absorbing and water-holding powers
of soils. Therefore, any of the farm practices that tend to increase
or diminish the amount of humus in the soil are to be seriously
considered because of the effect on the water content of the soil. For
this reason the application of barn manures and green crops turned
under tend to improve the water conditions of most soils.
The mixing of heavy applications of coarse manures or organic matter
with light sandy soils may make them so loose and open that they will
lose moisture rapidly. When this practice is necessary the land should
be rolled after the application of the manure.
METHODS OF CROPPING AND SOIL WATER
Constant tillage hastens the decay of organic matter in the soil.
Hence any method or system of cropping which does not occasionally
return to the soil a new supply of humus tends to weaken the powers of
the soil toward water.
All of the operations and practices which influence soil water also
affect the other conditions necessary to root growth; namely, texture,
ventilation, heat, and plant food, and those operations and practices
which properly control and regulate soil water to a large degree
control and regulate soil fertility.
SELECTION OF CROPS WITH REFERENCE TO SOIL WATER
While climatic conditions determine the general distribution of
plants, the amount of water which a soil holds and can give up to
plants during the growing season determines very largely the crops to
which it is locally best adapted.
With crops that can be grown on a wide range of soils the water which
the soil can furnish largely determines the time of maturing, the
yield, and often the quality of the crop. With such a crop a small
supply of water tends to hasten maturity at the expense of yield.
The sweet potato, when wanted for early market and high prices, is
grown on the light sandy soils called early truck soils. These soils
hold from five to seven per cent, of water. That is, the texture is
such that during the early part of the growing season one hundred
pounds of this soil is found to hold an average of from five to seven
pounds of water under field conditions. This soil, holding little
water, warms up early and thus hastens growth. Then as the warmer
summer weather advances, the water supply diminishes, growth is
checked, and the crop matures rapidly. On account of the small amount
of water and the early checking of growth, the yield of the crop is
less than if grown on a soil holding more water, but the earlier
maturity makes it possible to realize a much higher price per bushel
for the crop. A sweet potato grown on such a light soil is dry and
starchy, a quality which brings a higher price in the northern markets
than does the moist, soggy potato grown on heavier soils which contain
more water and produce larger yields.
Early white potatoes, early cabbage, water melons, musk-melons,
tomatoes and other early truck and market garden crops are also grown
on light soil holding from five to seven per cent. of water. The main
crop of potatoes and cabbage and the canning crop of tomatoes are
grown on the loam soils holding from ten to eighteen per cent. of
water. Such soils produce a later though much larger yield.
Upland cotton produces best on a deep loam that is capable of
furnishing a uniform supply of about ten or twelve per cent. of water
during the growing season.
Sea Island Cotton grows best on a light, sandy soil holding only five
per cent. of water.
On light, sandy soils the Upland Cotton produces small plants with
small yield of lint, while on clay and bottom land, which are apt to
have large amounts of water, the plants grow very large and produce
fewer bolls, which are very late in maturing.
Corn, while it will grow on a wide range of soils, produces best on
loam or moist bottom lands holding about fifteen per cent. of water
during the growing season.
The grasses and small grains do best on cool, firm soils holding
eighteen to twenty-two per cent. of water.
Sorghum or "Molasses Cane" grows best on good corn soil, while the
sugar cane of the Gulf States requires a soil with twenty-five per
cent. of water for best growth.
While the amount of water which a soil will hold is determined largely
by texture, it is also considerably influenced by the amount and
frequency of rainfall and the location of the soil as to whether it be
upland or bottom land.
The average percentage of water held by a soil during the growing
season may be approximately determined in the following manner:
Sample the soil in one of the following methods:
Take to the field a spade, a box that will hold about half a bushel,
and a pint or quart glass jar with a tight cover. If a cultivated
field, select a place free from grass and weeds. Dig a hole one foot
deep and about eighteen inches square. Trim one side of the hole
square. Now from this side cut a slice about three inches thick and
one foot deep, quickly place this in the box and thoroughly break
lumps and mix together, then fill jar and cork tightly.
Another method is to take a common half-inch or two-inch carpenter's
auger and bore into the soil with it. Pull it out frequently and put
the soil which comes up with it into the jar until you have a sample
a foot deep. If one boring twelve inches deep does not give sufficient
soil make another boring or two close by and put all into the jar.
Take the sample, by whatever method obtained, weigh out ten or twenty
ounces of the moist soil and dry it at a temperature just below 212
degrees. When it is thoroughly dry weigh again. The difference between
the two weights will be the amount of water held by the sample. Now
divide this by the weight of the dry sample and the result will be the
per cent. of water held by the soil.
Several samples taken from different parts of the field will give an
average for the field. Repeat this every week or oftener through the
season and an approximate estimate of the water-holding capacity of
the soil will be obtained and consequently an indication of the crops
to which the soil is best adapted.
EXAMPLE.
Weight of a soil sample, 20 ounces.
When dried this sample weighs 17¾ ounces.
20 - 17¾ = 2¼, the water held by the soil.
2.25 ÷ 17.75 = .12 plus.
This soil held a little over twelve per cent. of water. If this soil
continues to give about the same result for successive tests during
the growing season, the results would indicate a soil adapted to
cotton, late truck or corn.
CHAPTER XVIII
THE AFTER-CULTIVATION OF CROPS
The term "after-cultivation" is here used in referring to those
tillage operations which are performed after the crop is planted.
Synonymous terms are "cultivation," "inter-tillage," "working the
crop."
After-cultivation influences the texture, ventilation, heat, plant
food and moisture factors of fertility, but most particularly the
moisture factor.
Under ordinary circumstances the greatest benefit derived from
after-cultivation when properly performed is the saving of soil water
for the use of the crop.
LOSS OF WATER BY EVAPORATION
Soil water is seldom at rest unless the soil be frozen solid. When
rain falls on a fertile soil there is a downward movement of water.
When the rain ceases, water begins to evaporate from the surface of
the soil. Its place is taken by water brought from below by
capillarity. This is in turn evaporated and replaced by more from
below. This process continues with greater or less rapidity according
to the dryness of the air and the compactness of the soil.
LOSS OF WATER THROUGH WEEDS
We learned in a former chapter that during their growth farm plants
require an amount of water equal to from 300 to 500 times their dry
weight. Weeds require just as much water and some of them probably
more than the cultivated plants. This water is largely absorbed by the
roots and sent up to the leaves where it is transpired into the air
and is lost from the soil, and therefore is unavailable to the growing
crop until it again falls onto the soil.
In some parts of the country, particularly the semi-arid West, the
rainfall is not sufficient to supply the soil with enough water to
grow such crops as it could otherwise produce. In the moister regions
the rainfall is not evenly distributed throughout the growing season,
and there are longer or shorter intervals between rains when the loss
of water through evaporation and weeds is apt to be greater than the
rainfall. For these reasons it is best to check these losses and save
the water in the soil for the use of the crops.
SAVING THE WATER
This can be done by:
Preventing the growth of weeds and by checking losses by evaporation
with a soil mulch.
TIME TO CULTIVATE
A seedling plant is easiest killed just as it has started into growth.
The best time to kill a plant starting from an underground stem or a
root is just as soon as it appears above the surface in active growth.
The best time to cultivate, then, to kill weeds is as soon as the
weeds appear. At this time large numbers can be killed with the least
of effort. Do not let them get to be a week or two old before getting
after them.
In planting some crops the ground between the rows becomes trampled
and compact. This results in active capillarity which brings water to
the surface and it is lost by evaporation.
Every rainfall tends to beat the soil particles together and form a
crust which enables the capillary water to climb to the surface and
escape into the air. This loss by evaporation should be constantly
watched for and the soil should be stirred and a mulch formed whenever
it becomes compact or a crust is formed.
The proper time to cultivate, then, to save water is as soon as weeds
appear or as soon as the surface of the soil becomes compact or
crusted by trampling, by the beating of rain or from any other cause,
whether the crop is up or not. The cultivation should start as soon
after a rain as the soil is dry enough to work safely.
The surface soil should always be kept loose and open. The efficacy
of the soil mulch depends on the thoroughness and frequency of the
operation. It is particularly beneficial during long, dry periods.
During such times it is not necessary to wait for a rain to compact
the soil; keep the cultivators going, rain or no rain.
TOOLS FOR AFTER-CULTIVATION
The main objects of after-cultivation are to destroy weeds and to form
a soil mulch for the purpose of controlling soil moisture. These ends
are secured by shallow surface work. It is not necessary to go more
than two or three inches deep. Deeper work will injure the roots of
the crop. Therefore the proper tools for after-cultivation in the
garden are the hoe and rake and for field work narrow-toothed harrows
and cultivators or horse-hoes which stir the whole surface thoroughly
to a moderate depth. These field tools are supplemented in some cases
by the hand hoe, but over wide areas of country the hoe never enters
the field.
A light spike-toothed harrow can be used on corn, potatoes, and
similar crops, and accomplish the work of cultivation rapidly until
they get to be from four to six inches high; after that cultivators
which work between the rows should be used.
A very useful class of tools for destroying weeds in the earlier
stages are the so-called "weeders." They somewhat resemble a horse hay
rake and have a number of flexible wire teeth which destroy shallow
rooted weeds but slip around the more firmly rooted plants of the
crop. These weeders must be used frequently to be of much value, for
after a weed is well rooted the weeder cannot destroy it.
There is a larger class of hand wheel hoes which are very useful in
working close planted garden and truck crops. They either straddle the
row, working the soil on both sides at the same time, or, running
between the rows, work the soil to a width of from six to eighteen
inches.
For best results with the weeder and hand wheel hoes the soil should
be thoroughly prepared before planting by burying all trash with the
plow and breaking all clods with harrow and roller.
The objection made to the deep-working implements, like the plow, is
that they injure the crop by cutting its feeding roots, and this has
been found by careful experiment and observation to diminish the crop.
Some farmers object to using a light harrow for cultivation in the
early stages of the crop because they say the harrow will destroy the
crop as well as the weeds. This danger is not so great as it seems.
The seeds of the crop are deeper in the soil than the seeds of the
weeds which germinate and appear so quickly. The soil has also been
firmed about them. Hence they have a firmer hold on the soil and but
few of them are destroyed if the work is carefully done.
In working crops not only should weeds be destroyed but also surplus
plants of the crop, as these have the same effect as weeds; namely,
they occupy the soil and take plant food and moisture which if left to
fewer plants would produce a larger harvest.
HILLING AND RIDGING
Except in low, wet ground, the practice of hilling or ridging up crops
is now considered by those who have given the matter thorough study,
to be unnecessary, flat and shallow culture being cheaper. It saves
more moisture, and for this reason, in the majority of cases, produces
larger crops.
Sometimes during very long-continued periods of wet weather weeds and
grass become firmly established among the plants of the crop. Under
such circumstances it is necessary to use on the cultivator teeth
having long, narrow sweeps that will cut the weeds just beneath the
surface of the soil. Sometimes a broad-toothed tool is used that will
throw sufficient soil over the large weeds near the rows to smother
them.
The condition to be met and the effect of the operation should always
be given serious thought.
We have considered after-cultivation as influencing soil fertility by
checking a loss of water by evaporation and weed transpiration, and
this is its main influence but other benefits follow.
Keeping the surface soil loose and open benefits fertility because it
directly aids the absorption of rain, favors ventilation, and has a
beneficial influence over soil temperature. Indirectly through these
factors it aids the work of the beneficial soil bacteria and the
chemical changes in the process of preparing plant food for crop use.
CHAPTER XIX
FARM MANURES
FUNCTIONS OF MANURES AND FERTILIZERS
In Chapter II we learned that the roots of plants for their growth and
development need a soil that is firm yet mellow, moist, warm,
ventilated and supplied with plant food. We also learned that of the
plant foods there is often not enough available nitrogen, phosphoric
acid, potash and lime for the needs of the growing plants.
Manures and fertilizers are applied to the soil for their beneficial
effects on these necessary conditions for root growth and therefore to
assist in maintaining soil fertility.
CLASSIFICATION OF MANURES AND FERTILIZERS
Manures may be classified as follows:
{ Barn or stable manures,
Farm manures. { Green-crop manures,
{ Composts.
Commercial { Materials furnishing nitrogen,
fertilizers { " " phosphoric acid,
or artificial { " " potash,
manures. { " " lime.
IMPORTANCE OF FARM MANURES
Of these two classes of manures the farmer should rely chiefly on the
farm manures letting the commercial fertilizers take a secondary place
because:
Farm manures are complete manures; that is they contain all the
necessary elements of plant food.
Farm manures add to the soil large amounts of organic matter or humus.
The decay of organic matter produces carbonic acid which hastens the
decay of mineral matter in the soil and so increases the amount of
available plant food.
The organic matter changes the texture of the soil.
It makes sandy soils more compact and therefore more powerful to hold
water and plant food.
It makes heavy clay soils more open and porous, giving them greater
power to absorb moisture and plant food. This admits also of better
circulation of the air in the soil, and prevents baking in dry
weather.
Farm manures influence all of the conditions necessary for root growth
while the commercial fertilizers influence mainly the plant food
conditions.
The farm manures are good for all soils and crops.
They are lasting in their effects on the soil.
BARN OR STABLE MANURE
Barn or stable manure consists of the solid and liquid excrement of
any of the farm animals mixed with the straw or other materials used
as bedding for the comfort of the animals and to absorb the liquid
parts.
The liquid parts should be saved, as they contain more than half of
the nitrogen and potash in the manure.
The value of barn manure for improving the soil conditions necessary
for root growth depends in a measure upon the plant food in it, but
chiefly upon the very large proportion of organic matter which it
contains when it is applied to the soil.
These factors are influenced somewhat: by the kind of animal that
produces the manure; by the kind of food the animal receives; by the
kind and amount of litter or bedding used; but they depend
particularly on the way the manure is cared for after it is produced.
LOSS OF VALUE
Improper care of the manure may cause it to diminish in value very
much.
_Loss by leaching._
If the manure is piled against the side of the stable where water from
the roof can drip on it, as is often the case, or if it is piled in an
exposed place where heavy rain can beat on it, the rain water in
leaching through the manure washes out of it nitrogen and potash,
which pass off in the dark brown liquid that oozes from the base of
the pile.
_Loss by heating or fermenting._
When barn manure is thrown into piles it soon heats and throws off
more or less steam and gas. This heating of the manure is caused by
fermentation or the breaking down of the materials composing the
manure and the forming of new compounds. This fermentation is produced
by very small or microscopic plants called bacteria.
The fermentation of the manure is influenced by the following
conditions:
A certain amount of heat is necessary to start the work of the
bacteria. After they have once started they keep up and increase the
temperature of the pile until it gets so hot that sometimes a part of
the manure is reduced to ashes. The higher the temperature the more
rapid the fermentation. This can be seen particularly in piles of
horse manure.
The bacteria which produce the most rapid fermentation in manure need
plenty of air with its oxygen. Therefore fermentation will be more or
less rapid according as the manure is piled loosely or in a close
compact mass.
A certain amount of moisture is necessary for the fermentation to take
place, but if the manure is made quite wet the temperature is lowered
and the fermentation is checked. The water also checks the
fermentation by limiting the supply of air that can enter the pile.
The composition of the manure influences the fermentation. The
presence of considerable amounts of soluble nitrogen hastens the
rapidity of the fermentation.
Now when the manure ferments a large part of the organic matter in it
is broken down and changed into gases. The gas formed most abundantly
by the fermentation is carbonic acid gas, which is produced by the
union of oxygen with carbon of the organic matter. The formation of
this gas means a loss of humus. This loss can be noticed by the fact
that the pile gradually becomes smaller.
The next most abundant product of the fermentation is water vapor
which can often be seen passing off in clouds of steam.
When manure ferments rapidly the nitrogen in it is changed largely
into ammonia. This ammonia combines with part of the carbonic acid gas
and forms carbonate of ammonia, a very volatile salt which rapidly
changes to a vapor and is lost in the atmosphere. This causes a great
loss of nitrogen during the rapid decomposition of the manure. This
loss can be detected by the well known odor of the ammonia which is
particularly noticeable about horse stables and piles of horse manure.
Besides these gases a number of compounds of nitrogen, potash, etc.,
are formed which are soluble in water. It is these that form the dark
brown liquid that sometimes oozes out from the base of the manure
heap.
At the Cornell University Agricultural Experiment Station, the
following experiment was carried out to find out how much loss would
take place from a pile of manure:
"Four thousand pounds of manure from the horse stable were placed out
of doors in a compact pile and left exposed from April 25th to
September 22d. The results were as follows:"
----------------------------+-------------+--------------+----------
| April 25. | Sept. 22. | Loss
| | | per cent.
----------------------------+-------------+--------------+----------
Gross weight | 4,000 lbs. | 1,730 lbs. | 57
Nitrogen | 19.6 " | 7.79 " | 60
Phos. acid | 14.8 " | 7.79 " | 47
Potash | 36 " | 8.65 " | 76
Value of plant food per ton | $2.30 | $1.06 |
----------------------------+-------------+--------------+----------
This shows a loss of more than half the bulk of the manure and more
than half the plant food contained in it.
CHECKING THE LOSSES
The first step to be taken in preserving the manure or in checking
losses is to provide sufficient bedding or litter in the stable to
absorb and save all the liquid parts.
The losses from fermentation of hot manures like horse manure may be
largely checked by mixing with the colder manure from the cow stable.
Losses from fermentation may also be checked.
By piling compactly, which keeps the air out.
By moistening the pile, which lowers the temperature and checks the
access of oxygen.
The manure may be hauled directly to the field each day and spread on
the surface or plowed in. This method is the best when practicable
because fermentation of the manure will take place slowly in the soil
and the gases produced will be absorbed and retained by the soil.
Gypsum or land plaster is often sprinkled on stable floors and about
manure heaps to prevent the loss of ammonia.
Copperas or blue stone, kainite and superphosphate are sometimes used
for the same purpose. There is, however, nothing better nor so good
for this purpose as dry earth containing a large percentage of humus.
Losses from washing or leaching by rain may be prevented by piling the
manure under cover or by hauling it to the field as soon as produced
and spreading it on the surface or plowing it under.
APPLYING THE MANURE TO THE SOIL
From ten to twenty tons per acre is considered a sufficient
application of barn manure for most farm crops. Larger amounts are
sometimes applied to the soil for truck and market garden crops.
Barn manures are applied to the soil by these methods:
The manure is sometimes hauled out from the barn and placed in a large
pile in the field or in many small piles where it remains for some
time before being spread and plowed or harrowed in.
Some farmers spread it on the field and allow it to lie some time
before plowing it in.
It is sometimes spread as soon as hauled to the field and is
immediately plowed in or mixed with the soil. This last is the safest
and most economical method so far as the manure alone is concerned.
When the manure is left in a large pile it suffers losses due to
fermentation and leaching.
At the Cornell University Agricultural Experiment Station, five tons
of manure from the cow stable, including three hundred pounds of
gypsum which was mixed with it, were exposed in a compact pile out of
doors from April 25th to September 22d. The result was as follows:
----------------------------+-------------+-------------+----------
| April 25 | Sept 22 | Loss
| | | per cent.
----------------------------+-------------+-------------+----------
Gross weight | 10,000 lbs. | 5,125 lbs. | 49
Nitrogen | 47 " | 28 " | 41
Phos. acid | 32 " | 26 " | 19
Potash | 48 " | 44 " | 8
Value of plant food per ton | $2.29 | $1.60 |
----------------------------+-------------+-------------+----------
When distributed over the field in small piles and allowed to remain
so for some time, losses from fermentation take place, and the rain
washes plant food from the pile into the soil under and immediately
about it. This results in an uneven distribution of plant food over
the field, for when the manure is finally scattered and plowed in,
part of the field is fertilized with washed out manure while the soil
under and immediately about the location of the various piles is
often so strongly fertilized that nothing can grow there unless it be
rank, coarse weeds.
[Illustration: FIG. 79.--A CROP OF COWPEAS.]
[Illustration: FIG. 80.--RED CLOVER.]
When the manure is spread on the surface and allowed to lie for some
time it is apt to become dry and hard, and when finally plowed in,
decays very slowly.
When the manure is plowed in or mixed with the soil as soon as applied
to the field there results an even distribution of plant food in the
soil, fermentation takes place gradually and all gases formed are
absorbed by the soil, there is very little loss of valuable nitrogen
and organic matter, and the fermentation taking place in the soil also
aids in breaking down the mineral constituents of the soil and making
available the plant food held by them.
Therefore it seems best to spread the manure and plow it in or mix it
with the soil as soon as it is hauled to the field, when not prevented
by bad weather and other more pressing work.
PROPER CONDITION OF MANURE WHEN APPLIED
A large part of the value of barn manure lies in the fact that it
consists largely of organic matter, and therefore has an important
influence on soil texture, and during its decay in the soil produces
favorable chemical changes in the soil constituents. Therefore it will
produce its greatest effect on the soil when applied fresh. For this
reason it is generally best to haul the manure to the field and mix
it with the soil as soon after it is produced as possible.
If coarse manures are mixed with light, sandy soils it is best to
follow with the roller, otherwise the coarse manure may cause the soil
to lie so loose and open that both soil and manure will lose moisture
so rapidly that fermentation of the manure will be stopped and the
soil will be unfit for planting.
If it is desired to apply manure directly to delicate rooted truck and
vegetable crops it is best to let it stand for some time until the
first rank fermentation has taken place and the manure has become
rotten.
A good practice is to apply the manure in its fresh condition to
coarse feeding crops like corn, and then follow the corn by a more
delicate rooted crop which requires the manure to be in a more
decomposed condition than is necessary for the corn. In this case the
corn is satisfied and the remaining manure is in proper condition for
the following crop when it is planted.
Another practice is to broadcast the coarse manure on grass land and
then when the hay is harvested the sod and remaining manure are plowed
under for the following crop.
A study of root development in Chapter II. tells us that most of the
manure used for cultivated crops should be broadcasted and thoroughly
mixed with the soil. A small amount may be placed in the drill or hill
and thoroughly mixed with the soil for crops that are planted in rows
or furrows in order to give the young plant a rapid start. For the
vegetable garden and flower garden and lawns, it is best to apply only
manure that has been piled for some time and has been turned over
several times so that it is well rotted and broken up.
There may not be a single farm where it will be possible to carry out
to the letter these principles applying to the treatment and
application of barn manures.
This is because climate, crops and conditions vary in different parts
of the country and on different farms. Therefore we should study
carefully our conditions and the principles and make our practice so
combine the two as to produce the best and most economical results
under the circumstances.
If we can get manure out in the winter it will very much lessen the
rush of spring work.
In some parts of the country on account of deep snows, heavy rainfall
and hilly fields, it is not advisable to apply manure in the winter.
This will necessitate storing the manure.
If conditions are such that we can get the manure on to the land as
soon as it is made, it should be applied to land on which a crop is
growing or land which is soon to be planted. If land is not intended
for an immediate crop, put a cover crop on it.
COMPOSTS
Composts are collections of farm trash or rubbish, as leaves, potato
tops, weeds, road and ditch scrapings, fish, slaughter-house refuse,
etc., mixed in piles with lime, barn manure, woods-earth, swamp muck,
peat and soil.
The object of composting these materials is to hasten their decay and
render available the plant food in them.
There are certain disadvantages in composting, namely:
Expense of handling and carting on account of bulk.
Low composition.
Loss of organic matter by fermentation.
Compost heaps serve as homes for weed seeds, insects and plant
diseases.
Nevertheless, all waste organic matter on the farm should be saved and
made use of as manure. These materials when not too coarse may be
spread on the surface of the soil and plowed under; they should never
be burned unless too coarse and woody or foul with weed seeds, insects
and disease.
[Illustration: FIG. 81.--SOY BEANS IN YOUNG ORCHARD.]
[Illustration: FIG. 82.--A YOUNG ALFALFA PLANT JUST COMING INTO
FLOWER.]
CHAPTER XX
FARM MANURES--CONCLUDED
GREEN-CROP MANURES
Green-crop manures are crops grown and plowed under for the purpose of
improving the fertility of the soil.
The main object of turning these crops under is to furnish the soil
with humus. Any crop may be used for this purpose.
By growing any of the class of crops called Legumes we may add to the
soil not only humus but also nitrogen. Cowpeas, beans, clover, vetch
and plants having foliage, flowers, seed pods and seeds like them are
called Legumes.
Most of the farm plants take their nitrogen from the soil. This
nitrogen is taken in the form of nitric acid and nitrogen salts
dissolved in soil water. The legumes, however, are able to use the
free nitrogen which forms four-fifths of the atmosphere. This they do
not of their own power but through the aid of very minute plants
called bacteria or nitrogen-fixing germs. These germs are so small
that they cannot be seen without the use of a powerful microscope. It
would take ten thousand average sized bacteria placed side by side to
measure one inch.
These little germs make their homes in the roots of the legumes,
causing the root to enlarge at certain points and form tubercles or
nodules (Figs. 34 and 35).
Carefully dig up a root of clover, cowpea, soy bean or other legume
and wash the soil from it. You will find numbers of the little
tubercles or nodules. On the clover they will be about the size of a
pin head or a little larger. On the soy bean they will be nearly as
large as the beans. These nodules are filled with colonies or families
of bacteria which take the free nitrogen from the air which penetrates
the soil and give it over to the plant in return for house rent and
starch or other food they may have taken from the plant.
In an experiment at Cornell University Agricultural Experiment
Station, in 1896, clover seeds were sown August 1st, and the plants
were dug November 4th, three months and four days after the seeds were
sown. The clovers were then weighed and tested and the following
results were obtained:
----------------+----------------------------------------------
| NITROGEN IN AN ACRE OF CLOVERS.
+---------------+----------------+-------------
| Lbs. in tops. | Lbs. in roots. | Lbs., total.
----------------+---------------+----------------+-------------
Crimson Clover | 125.28 | 30.66 | 155.94
Mammoth Clover | 67.57 | 78.39 | 145.96
Red Clover | 63.11 | 40.25 | 103.36
----------------+---------------+----------------+-------------
A large part of the nitrogen found in these plants was undoubtedly
taken by the roots from the soil air.
Besides adding humus and nitrogen to the soil the legumes, being
mostly deep-rooted plants, are able to take from the subsoil food
which is out of reach of other plants. This food is distributed
throughout the plant and when the plant is plowed under the food is
deposited in the upper soil for the use of shallow-rooted plants.
BENEFITS
The benefits derived from green crop manuring then are as follows:
We add to the soil organic matter or humus which is so helpful in
bringing about the conditions necessary for root growth.
By using the legumes for our green manure crops we may supply the soil
with nitrogen taken from the air.
We return to the surface soil not only the plant food taken from it
but also plant food brought from the subsoil by the roots of the green
manure plants.
CHARACTER OF BEST PLANTS FOR GREEN CROP MANURING
The plants best adapted to green crop manuring are deep-rooted,
heavy-foliaged plants. Of these the legumes are by far the best, as
they collect the free nitrogen from the air which other plants cannot
do. This enables the farmer to grow nitrogen which is very expensive
to buy.
THE TIME FOR GROWING GREEN MANURE CROPS
Green manure crops may be grown at any time that the soil is not
occupied by other crops, provided other conditions are suitable. Land
which is used for spring and summer crops often lies bare and idle
during fall and winter. A hardy green manure crop planted after the
summer crop is harvested will make considerable growth during the fall
and early spring, and this can be plowed under for the use of the
following summer crops. If there is a long interval of time during
spring or summer when the land is bare, that is a good time for a
green manure crop.
Green manure crops are often planted between the rows of other crops
such as corn or cotton at the last working of the crop for the benefit
of the crop which is to follow.
It is advisable to arrange for a green manure crop at least once in
three or four years.
LEGUMINOUS GREEN MANURE CROPS
_Cowpea_. (Field pea, stock pea, black pea, black-eyed pea, clay pea,
etc.) (Fig. 79.)
The cowpea is perhaps the most important leguminous plant grown for
soil improvement in the South. It will grow anywhere south of the
Ohio River and can be grown with fair success in many localities
farther north.
It is a tender annual, that is, it is killed by frost and makes its
entire growth from seed to seed in a single season. It should
therefore be planted only during the spring and summer. This crop not
only has power like the other legumes to take nitrogen from the air,
but it is also a strong feeder, that is, it can feed upon mineral
plant food in the soil that other plants are unable to make use of.
For this reason it will grow on some of the poorest soils, and is a
good plant with which to begin the improvement of very poor land. It
is a deep-rooted plant. On the farm of the Hampton Normal and
Agricultural Institute cowpea roots have been traced to the depth of
sixty-one inches.
Cowpeas will grow on almost any land that is not too wet. From one and
one-half to three bushels of seed are used per acre. These are sown
broadcast and harrowed in or are planted in drills or furrows and
cultivated a few times. Aside from its value as a green manure crop
the cowpea is useful as food for man and the farm animals. The green
pods are used as string beans or snaps. The ripened seeds are used as
a food and the vines make good fodder for the farm animals.
"Experiments at the Louisiana Experiment Station show that one acre of
cowpeas yielding 3,970.38 pounds of organic matter, turned under, gave
to the soil 64.95 pounds of nitrogen, 20.39 pounds of phosphoric acid
and 110.56 pounds of potash."--Farmer's Bulletin, 16 U.S. Dept. of
Agriculture.
"It is now grown in all the States south of the Ohio River, and in
1899 there were planted nearly 800,000 acres to the crop. Basing our
estimate on the amount of nitrogen stored in the soil by this crop, it
is fair to say that fully fifteen million pounds of this valuable
substance were collected and retained as a result of the planting of
the cowpea alone. This at fifteen cents per pound (the market price of
nitrogen) would be worth something more than $2,000,000 for nitrogen
alone."--Year Book of the Department of Agriculture, 1902.
_The Clovers._--These are the most extensively grown plants for green
manure purposes in the United States. They are deep-rooted, and are
able to use mineral food that is too tough for other plants. They
furnish large crops of hay or green forage and a good aftermath and
sod to turn under as green manure, or the entire crop may be plowed
under.
_Red Clover_ is the most widely planted (Fig. 80). It is a perennial
plant and grows from the most northern States to the northern border
of the Gulf States. It grows best on the loams and heavier soils well
supplied with water, but not wet. It is sown broadcast at the rate of
from ten to twenty pounds of seed per acre. In the North it is
generally sown in the spring on fields of winter grain. In the South,
September and October are recommended as the proper sowing times. It
is the custom to let it grow two years, cutting it for hay and seed,
and then to turn the aftermath and sod under.
_Mammoth Red Clover_, also called sapling clover and pea-vine clover,
closely resembles the red clover, but is ranker in growth and matures
two or three weeks later. It is better adapted to wet land than the
red clover.
_Crimson Clover_, also called German clover and Italian clover, is a
valuable green manure crop in the central and southern States east of
the Mississippi. It is a hardy annual in that section and is generally
sown from the last of July to the middle of October, either by itself
or with cultivated crops at their last working. Fifteen and twenty
pounds of seed are used to the acre. It makes a good growth during the
fall and early winter and is in blossom and ready to cut or plow under
in April or May. It grows at a season when the cowpea will not live.
Crimson clover will grow on soils too light for other clovers.
The _Soy Bean_, also called soja bean and Japanese pea, is another
leguminous crop used for green manuring (Fig. 81). It was introduced
into this country from Japan and in some localities is quite
extensively planted. It grows more upright than the cowpea and
produces a large amount of stem and foliage which may be used for
fodder or turned under for green manure The seeds are used for food
for man and beast. The soy bean is planted and cared for in the same
manner as the cowpea.
The _Canadian Field Pea_ is sometimes grown in the north as a green
manure crop.
_White Sweet Clover_, white melitot or Bokhara clover, grows as a weed
from New England to the Gulf of Mexico. In the Gulf States it is
regarded as a valuable forage and green manure plant. One or two pecks
of seed per acre are sown in January or February.
_Alfalfa_, or lucern, though grown more for a forage crop than for
green manuring, should be mentioned here, for wherever grown and for
whatever purpose, its effects on the soil are beneficial (Fig. 82).
This plant requires a well prepared soil that is free from weeds.
Twenty to twenty-five pounds of seed are planted per acre. In the
north the seeding is generally done in the spring after danger of
frost is past, as frost kills the young plants. In the South fall
seeding is the custom in order to give the young plants a long start
ahead of the spring weeds. One seeding if well cared for lasts for
many years. Alfalfa is pastured or cut for hay, four to eight tons
being the yield. Many fields run out in five or six years and the sod
is plowed under. This plant sends its roots thirteen, sixteen, and
even thirty feet into the soil after water and food, and when these
roots decay they furnish the lower soil with organic matter and their
passages serve as drains and ventilators in the soil. Alfalfa is grown
extensively in the semi-arid regions of the country.
NON-LEGUMINOUS GREEN MANURE PLANTS
Among the non-leguminous green manure plants are rye, wheat, oats,
mustard, rape, buckwheat. Of these the rye and buckwheat are most
generally used, the rye being a winter crop and the other a warm
weather plant. They are both strong feeders and can use tough plant
food. They do not add new nitrogen to the soil though they furnish
humus and prepare food for the weaker feeders which may follow them.
CHAPTER XXI
COMMERCIAL FERTILIZERS
THE RAW MATERIALS
Next to the soil itself, the farmer's most important sources of plant
food are the farm manures. But most farms do not produce these in
sufficient quantities to keep up the plant food side of fertility.
Therefore the farmer must resort to other sources of plant food to
supplement the farm manures.
There is a large class of materials called Commercial Fertilizers,
which, if judiciously used, will aid in maintaining the fertility of
the farm with economy.
We learned in a previous chapter that the plant foods, nitrogen,
phosphoric acid, potash and lime, are apt to be found wanting in
sufficient available quantities to supply the needs of profitable
crops. We learned also that lime is useful in improving the texture of
the soil and in making other plant foods available. Now the commercial
fertilizers are used to supply the soil with these four substances and
they may be classified according to the substance furnished as
follows:
Sources of nitrogen,
" " phosphoric acid,
" " potash,
" " lime.
SOURCES OF NITROGEN
Nitrogen is the most expensive of plant foods to buy, therefore
special attention should be given to producing it on the farm by means
of barn manures and legumes plowed under.
The principal commercial sources of nitrogen are: Nitrate of soda,
sulphate of ammonia, dried blood, tankage, dry ground fish,
cotton-seed meal.
_Nitrate of Soda_ or Chile saltpetre containing 15.5 per cent. of
nitrogen, is found in large deposits in the rainless regions of
western South America. In the crude state as it comes from the mine it
contains common salt and earthy matter as impurities. To remove these
impurities the crude nitrate is put into tanks of warm water. The
nitrate dissolves and the salt and earthy matter settle to the bottom
of the tank. The water with the nitrate in solution is then drawn off
into other tanks from which the water is evaporated, leaving the
nitrate, a coarse, dirty looking salt which is packed in
three-hundred-pound bags and shipped.
Plants that take their nitrogen from the soil take it in the form of
nitrate. Hence nitrate of soda, which is very soluble in water, is
immediately available to plants and is one of the most directly
useful nitrogen fertilizers. It is used for quick results and should
be applied only to land that has a crop or is to be immediately
planted, otherwise it is liable to be lost by leaching.
_Sulphate of Ammonia_ contains 20 per cent. of nitrogen. It is a white
salt, finer and cleaner looking than the nitrate. It is a by-product
of the gas works and coke ovens. The nitrogen in it is quite readily
available.
_Dried Blood_ contains 8 to 12 per cent. of nitrogen. This is blood
collected in slaughter-houses and dried by steam or hot air. It decays
rapidly in the soil and is a quick acting nitrogen fertilizer.
_Tankage_ contains 4 to 8 per cent. of nitrogen and 7 to 20 per cent.
of phosphoric acid. Slaughter-house waste, such as meat and bone
scrap, are boiled or steamed to extract the fat. The settlings are
dried and ground and sold as tankage. It is much slower in its action
than dried blood and supplies the crop with both nitrogen and
phosphoric acid.
_Dried Fish Scrap_ is a by-product of the fish oil factories and the
fish canning factories. It contains 7 to 9 per cent. of nitrogen and 6
to 8 per cent. of phosphoric acid. It undergoes nitrification readily
and is a quick acting organic source of nitrogen and phosphoric acid.
_Cotton-seed Meal_ contains 7 per cent. of nitrogen, about 2.5
phosphoric acid, and 1.5 per cent. of potash. It is a product of the
cotton oil factories and is obtained by grinding the cotton seed cake
from which the oil has been pressed. It is a most valuable source of
nitrogen for the South.
The nitrogen in the dried blood, tankage, fish scrap and cotton-seed
meal, being organic nitrogen, must be changed by the process of
nitrification to nitric acid or nitrate before it is available. They
are therefore better materials to use for a more gradual and
continuous feeding of crops than the nitrate of soda or sulphate of
ammonia.
Scrap leather, wool waste, horn and hoof shavings are rich in nitrogen
but they decay so slowly that they make poor fertilizers. They are
used by fertilizer manufacturers in making cheap mixed fertilizers.
SOURCES OF PHOSPHORIC ACID
The principal commercial sources of phosphoric acid are:
Phosphate Rocks.
Bones.
Fish scrap.
Phosphate slag.
The _Phosphate Rocks_ are found in shallow mines in North and South
Carolina, Georgia, Florida and Tennessee, and also as pebbles in the
river beds. They are the fossil remains of animals. After being dug
from the mines the rock is kiln dried and then ground to a very fine
powder called "floats" which is used on the soil. The phosphoric acid
in the floats is insoluble and becomes available only as the phosphate
decays. This is too slow for most plants so it is treated with oil of
vitriol or sulphuric acid to make it available. The phosphoric acid in
the ground rock is combined with lime, forming a phosphate of lime
which is insoluble. When treated with the oil of vitriol or sulphuric
acid, the sulphuric acid takes lime from the phosphate and forms
sulphate of lime or gypsum. The phosphoric acid is left combined with
the smallest possible amount of lime and is soluble in water. It is
then called soluble or water soluble phosphoric acid.
Now if this soluble form remains unused it begins to take on lime
again and turns back toward its original insoluble form. After a time
it gets to such a state that it is no longer soluble in water but is
soluble in weak acids. It is then said to be reverted phosphoric acid.
Reverted phosphoric acid is also called citrate soluble phosphoric
acid, because in testing fertilizers the chemists use ammonium citrate
to determine the amount of reverted phosphoric acid.
This form still continues to take on lime and by and by gets back to
the original insoluble form called insoluble phosphoric acid.
The soluble phosphoric acid and reverted phosphoric acid are available
to plant roots. The insoluble form is not.
The rock phosphates contain from 26 to 35 per cent. of insoluble
phosphoric acid. The acid phosphates or dissolved rock phosphates
contain from 12 to 16 per cent. of available phosphoric acid and from
1 to 4 per cent. of insoluble.
_Bone Fertilizers._ Bones have long been a valuable and favored source
of phosphoric acid. In addition to phosphoric acid they contain some
nitrogen which adds to their value. They are organic phosphates and
are quite lasting in their effect on the soil as they decay slowly.
The terms "Raw Bone," "Steamed Bone," "Ground Bone," "Bone Meal,"
"Bone Dust," "Bone Black," "Dissolved Bone," indicate the processes
through which the bone has passed in preparation, or the condition of
the material as put on the market and used on the soil.
Ground bone, bone meal, bone dust, indicate the mechanical conditions
of the bones.
The bones are sometimes ground "raw" just as they come from the
slaughter-house or kitchen, or they are sometimes first "steamed" to
extract the fat for soap, and the nitrogenous matter for glue.
_Raw Bone._ Analysis: Nitrogen, 2.5 to 4.5 per cent. Available
phosphoric acid, 5 to 8 per cent. Insoluble phosphoric acid 15 to 17
per cent.
_Steamed Bone_ contains 1.5 to 2.5 per cent. of nitrogen, 6 to 9 per
cent. of available phosphoric acid and 16 to 20 per cent. of insoluble
phosphoric acid.
Steamed bone pulverizes much finer than raw bone and decays more
rapidly in the soil because the fat has been extracted from it.
_Dissolved Bone._ Ground bone is sometimes treated with sulphuric acid
to render the phosphoric acid in it more available. It is then called
dissolved bone and contains thirteen to fifteen per cent. of
available phosphoric acid and two to three per cent. of nitrogen.
_Dissolved Bone Black._ Bone charcoal is used for refining sugar. It
is then turned over to the fertilizer manufacturers who sell it as
"Bone Black" or treat it with sulphuric acid and then put it on the
market as dissolved bone black.
The bone black contains thirty to thirty-six per cent. of insoluble
phosphoric acid.
The dissolved bone black contains 15 to 17 per cent. of available
phosphoric acid and 1 to 2 per cent. insoluble.
"_Thomas Slag_," "_Phosphate Slag_," "_Odorless Phosphate_."
Phosphorous is an impurity in certain iron ores. In the manufacture of
Bessemer steel this is extracted by the use of lime which melts in the
furnace, unites with the phosphorous and brings it away in the slag.
This slag is ground to a fine powder and used as a fertilizer. It
contains 11 to 23 per cent. of phosphoric acid, most of which is
available.
_Superphosphate._ The term superphosphate is applied to the phosphates
that have been treated with sulphuric acid to make the phosphoric acid
available. Dissolved bone, dissolved bone black, and the dissolved
phosphate rocks are superphosphates.
_Fish Scrap_, mentioned as a source of nitrogen, is also a valuable
source of phosphoric acid, containing 6 to 8 per cent., which is quite
readily available owing to the rapid decay of the scrap.
SOURCES OF POTASH
The chief sources of potash used for fertilizers are the potash salts
from the potash mines at Stassfurt, Germany, where there is an immense
deposit of rock salt and potash salts.
The principal products of these mines used in this country are the
crude salts:
_Kainite_, containing 12 per cent. of potash.
_Sylvinite_, containing 16 to 20 per cent. of potash, and the higher
grade salts manufactured from the crude salts:
_Muriate of Potash_, containing 50 per cent. potash.
_High grade Sulphate of Potash_, containing 50 per cent. potash.
_Low grade Sulphate of Potash_, containing 25 per cent. potash.
_Wood Ashes_, if well kept and not allowed to get wet and leach,
contain 4 to 9 per cent. of potash.
_Cotton Hull Ashes_ contain 20 to 30 per cent, of potash and 7 to 9
per cent. of phosphoric acid.
The potash in all these forms is soluble in water and equally
available to plants. The crude salts, kainite and sylvinite, and the
muriate contain chlorine and are not considered good for potatoes and
tobacco as the chlorine lowers the quality of these products.
In tobacco regions tobacco refuse is a valuable source of potash, the
stems are about five per cent. potash.
LIME
_Lime_ is generally supplied to the soil in the form of quicklime made
by burning lime stone or shells. Other forms are gypsum or land
plaster, gas lime (a refuse from gas works) and marl. Most soils
contain sufficient lime for the food requirements of most plants. Some
soils, however, are deficient in lime and some crops, particularly the
legumes, are benefitted by direct feeding with lime.
Lime is valuable for its effect on the soil properties which
constitute fertility.
Physically lime acts on the texture of the soil making clay soils
mealy and crumbly, and causing the lighter soils to adhere or stick
together more closely.
Chemically, lime decomposes minerals containing potash and other plant
foods, thus rendering them available for the use of plants. It also
aids the decay of organic matter and sweetens sour soils.
Biologically lime aids the process of nitrification.
The action of lime is greatest in its caustic or unslacked form.
Too much or too frequent liming may injure the soil. It should be
carefully tried in a small way, and its action noted, before using it
extensively.
A common way of using lime is to place twenty to forty bushels on an
acre in heaps of three to five bushels, covering them with soil until
the lime slacks to a fine powder. The lime is then spread and harrowed
in. Lime tends to hasten the decay of humus. It should not be applied
oftener than once in four or five years.
_Gypsum_, a sulphate of lime, is similar to lime in its action on the
soil. Its most important effect is the setting free of potash from its
compounds.
_Gas lime_ should be used with great care as it contains substances
that are poisonous to plant roots. It is best to let it lie exposed to
the weather several months before using.
_Marl_ is simply soil containing an amount of lime varying from five
to fifty per cent. It has value in the vicinity of marl beds but does
not pay to haul very far.
CHAPTER XXII
COMMERCIAL FERTILIZERS--CONTINUED
MIXED FERTILIZERS
_What they are._
There are a large number of business concerns in the country which buy
the raw materials described in Chapter XXI, mix them in various
proportions, and sell the product as mixed or manufactured
fertilizers. If these mixtures contain the three important plant
foods, nitrogen, phosphoric acid and potash, they are sometimes called
"complete" manures or fertilizers. In some parts of the country all
commercial fertilizers are called "guano."
_Many brands._
These raw materials are mixed in many different proportions and many
dealers have special brands for special crops. There are consequently
large numbers of brands of fertilizers which vary in the amounts,
proportions and availability of the plant foods they contain. For
instance, in 1903, twenty-three fertilizer manufacturers offered for
sale ninety-six different brands in the State of Rhode Island. In
Missouri one hundred and ten brands, made by sixteen different
manufacturers, were offered for sale. Eighty-three manufacturers
placed six hundred and forty-four brands on the market in New York
State during the same year. Of one hundred and twenty brands
registered for sale in Vermont in the spring of 1904, there were
seventeen mixtures for corn and thirty-four for potatoes.
The result of this is more or less confusion on the part of the farmer
in purchasing fertilizers, and with many a farmer it is a lottery as
to whether or not he is buying what his crop or his soil needs.
Some of the manufacturers are not above using poor, low grade, raw
materials in making these mixtures.
This means that the farmer should make himself familiar with the
subject of fertilizers if he desires to use them intelligently and
economically.
_Safeguard for the farmer._
As a safeguard to the buyer of fertilizers the State laws require that
every brand put on the market shall be registered and that every bag
or package sold shall have stated on it an analysis showing the
amounts of nitrogen, or its equivalent in ammonia, the soluble
phosphoric acid, the reverted phosphoric acid, the insoluble
phosphoric acid, and the potash.
This registration is generally made at the State experiment station,
and the director of the station is instructed to take samples of these
brands and have them analyzed, and publish the results together with
the analysis guaranteed by the maker.
These analyses are published in bulletin form and should be in the
hands of every farmer who makes a practice of using commercial
fertilizers.
The manufacturers of fertilizers comply with the law by printing on
the bag or package the per cents of plant food in the fertilizers, and
these statements in the great majority of cases agree favorably with
the analyses of the experiment stations, but they do not in all cases
state what materials were used to furnish the different kinds of plant
food, and it is not always possible to find this out by analysis.
_Low grade materials._
For instance in mixing a fertilizer one manufacturer may use dried
blood to furnish nitrogen and another may use leather waste or horn
shavings. The latter contains more nitrogen than the dried blood, but
they are so tough and decay so slowly that they are of little benefit
to a quick growing plant.
_Inflating the guarantee._
Although the dealer states correctly the per cents of plant food in
the fertilizer, he is quite frequently inclined to repeat this in a
different form, and thus give the impression that the mixture contains
more than it really does.
The dealers also give the nitrogen as ammonia because it makes a
larger showing.
Phosphoric acid is often stated as "bone phosphate" because in this
the amount appears to be greater.
For example, an analysis taken from a fertilizer catalogue reads as
follows:
Ammonia 2 to 3 per cent.
Available Phosphoric Acid 8 to 10 "
Total Phosphoric Acid 11 to 14 "
Total Bone Phosphate 23 to 25 "
Actual Potash 10 to 12 "
Sulphate of Potash 18 to 20 "
A better statement would be as follows:
Nitrogen 1.65 per cent.
Available Phosphoric Acid 8 "
Total Phosphoric Acid (furnished in Bone Phosphate) 11 "
Potash (furnished in Sulphate of Potash) 10 "
Ammonia is reduced to terms of nitrogen by multiplying by .824. All
bone phosphate is forty-six per cent. phosphoric acid. When bone
phosphate is given instead of phosphoric acid it simply makes the
mixture appear to have more in it, and when both phosphoric acid and
bone phosphate are stated one is merely a repetition of the other. The
same is true of the statements, potash and sulphate of potash, one is
a repetition of the other only a different form.
VALUATION
The experiment stations not only publish comparative analyses of the
registered fertilizers but they also compute the market values of the
plant food contained in them and compare these valuations with the
selling price of the fertilizers.
They also furnish a list of trade values of the plant foods in raw
materials for the convenience of fertilizer buyers in testing the
values of the brands offered them on the markets.
In the following list are given the "trade values agreed upon by the
Experiment Stations of Massachusetts, Rhode Island, Connecticut, New
Jersey and Vermont, after a careful study of prices ruling in the
larger markets of the southern New England and Middle States."
Trade values of fertilizing ingredients in raw materials and chemicals
for 1904:
Cents per lb.
Nitrogen in Nitrates 16
Nitrogen in Ammonia Salts 17½
Organic Nitrogen in dry and fine ground fish, blood,
and meat, and in mixed fertilizers 17½
Organic Nitrogen in fine ground bone and tankage 17
Organic Nitrogen in coarse bone and tankage 12½
Phosphoric Acid soluble in water 4½
Phosphoric Acid soluble in ammonium citrate 4
Phosphoric Acid in fine ground bone and tankage 4
Phosphoric Acid in coarse bone and tankage 3
Phosphoric Acid (insoluble in water and in ammonium
citrate) in mixed fertilizer 2
Potash as high-grade sulphate and in mixtures free
from muriate (chloride) 5
Potash as muriate 4¼
For example, in calculating the commercial value of the plant food in
a fertilizer we will take the formula mentioned on page 205, namely:
Ammonia 2 to 3 per cent.
Available Phosphoric Acid 8 to 10 "
Total Phosphoric Acid 11 to 14 "
Total Bone Phosphate 23 to 25 "
Actual Potash 10 to 12 "
Sulphate of Potash 18 to 20 "
This fertilizer is evidently a mixture of bone meal and sulphate of
potash and the plant food contained in it is as follows:
Nitrogen 1.65 per cent.
Available Phosphoric Acid 8 "
Insoluble Phosphoric Acid 3 "
Potash 10 "
One hundred pounds of the mixture would contain:
Pounds. Value per
100 lbs.
Nitrogen 1.64 value at 17½¢ .29
Available Phosphoric Acid 8 " " 4¢ .32
Insoluble Phosphoric Acid 3 " " 2¢ .06
Potash 10 " " 5¢ .50
-----
Total $1.17
In one ton the whole value would be twenty times this or $23.40. Add
to this $8, which is about the average charge for mixing, bagging,
shipping, selling and profit, and we find that $32 is probably the
lowest figure at which this fertilizer could be purchased on the
markets, and very likely the price would be higher as we have taken
the lowest guaranteed per cent. of plant food for our basis of
calculation.
Fertilizers are generally mixed and sold to the farmer on the ton
basis.
LOW GRADE MIXTURES
Most dealers, to meet a certain demand, furnish mixtures ranging from
$15 to $25 per ton. These mixtures are necessarily low grade and are
more expensive than the higher priced high grade mixtures.
For example:
A certain potato fertilizer on the market, which we will call mixture
A, has the following guaranteed analysis:
Ammonia 7 to 8 per cent.
Available Phosphoric Acid 6 to 7 "
Actual Potash 5 to 6 "
A ton of this would contain:
Pounds.
Nitrogen 115.4 value at 17½¢ $20.19
Available Phosphoric Acid 120 " " 4¢ 4.80
Potash 100 " " 5¢ 5.00
----- ------
Totals 335.4 $29.99
Add to this the average charge for mixing, bagging, selling, profit,
etc., $8, and the cost will be $37.99.
The selling price of this fertilizer would probably be not less than
$40. Now suppose the farmer thinks this a high priced and expensive
fertilizer and looks about for something cheaper. He finds a low grade
potato fertilizer, which we will call mixture B, that has the
following guarantee:
Ammonia 3½ to 4 per cent.
Available Phosphoric Acid 3 to 3½ "
Actual Potash 2½ to 3 "
Just one-half the guarantee of the high grade mixture A. A ton of this
contains:
Pounds.
Nitrogen 57.7 value at 17½¢ $10.10
Available Phosphoric Acid 60 " " 4¢ 2.40
Potash 50 " " 5¢ 2.50
----- ------
Totals 167.7 $15.00
Add average charge for mixing, etc. 8.00
------
$23.00
The selling price of this would very likely be not less than $25.
This seems at first sight to be cheaper and more reasonable. But let
us see.
In a ton of mixture A he gets 335.4 pounds of plant food for $40, or
at an average cost of twelve cents per pound, while in a ton of
mixture B he gets 167.7 pounds of plant food for $25, or at an average
cost of fifteen cents per pound.
To put it another way, in a ton of the high grade mixture A, he gets
335.4 pounds of plant food for $40. To get the same amount of plant
food, 335.4 pounds, in the low grade mixture, B, it will be necessary
to buy two tons at a cost of $50.
A low grade fertilizer is always expensive even if the plant food is
furnished by high grade materials.
BUY ON THE PLANT FOOD BASIS
The farmer generally buys his fertilizer on the ton basis. A better
method is to buy just as the fertilizer manufacturers buy the raw
materials they use for mixing, namely, on the basis of actual plant
food in the fertilizer. The dealers have what they call the "unit
basis," a "unit" meaning one per cent. of a ton or twenty pounds of
plant food. A ton of nitrate of soda, for instance, contains 310
pounds or 15½ units of nitrogen, which at $3.20 cents per unit would
cost $49. Buy your mixture of a reliable firm, find out the actual
amounts of the plant foods in the mixture and pay a fair market price
for them.
CHAPTER XXIII
COMMERCIAL FERTILIZERS--CONCLUDED
THE HOME MIXING OF FERTILIZERS
When a considerable amount of fertilizer is used a better plan than
buying mixed fertilizer is to buy the raw materials and mix them
yourself. For example, a farmer is about to plant five acres of
cabbages for the market. He finds that a certain successful cabbage
grower recommends the use of fifty pounds nitrogen, fifty pounds
phosphoric acid and seventy pounds potash per acre. For the five acres
this will mean 250 pounds nitrogen, 250 pounds phosphoric acid and 350
pounds potash. To furnish the nitrogen he can buy 1,613 pounds of
nitrate of soda or 2,500 pounds dried blood or 1,250 pounds sulphate
of ammonia, or a part of each. To furnish the phosphoric acid he can
buy 1,786 pounds acid phosphate. Seven hundred pounds of either
sulphate or muriate of potash will furnish the potash. These materials
can be easily mixed by spreading in alternate layers on a smooth floor
and then shovelling over the entire mass several times. The mixture
can be further improved by passing it through a sand or coal screen or
sieve.
By following this method of buying the raw materials and mixing them
on the farm, the farmer can reduce his fertilizer bill by quite a
considerable amount and at the same time can obtain just the kinds and
proper amounts of plant foods needed by his crops.
KIND AND AMOUNT TO BUY
The farmer should make the best use of farm manures and through
tillage to render plant food available for his crops before turning to
commercial fertilizer for additional plant food.
If he grows leguminous crops for green manuring, for feeding stock or
for cover crops, he can in many cases secure, chiefly through them,
sufficient high priced nitrogen for the needs of his crops, and it is
necessary only occasionally to purchase moderate amounts of phosphoric
acid, potash and lime.
For special farming and special crops it may be necessary to use the
commercial fertilizer more freely.
It is impossible to say here just what amounts or what kinds of
fertilizer should be purchased, because no two farms are exactly alike
as to soil, methods of cropping or methods of tillage.
There are certain factors, however, which will serve as a general
guide and which should be considered in determining the kind and
amount of fertilizer to buy.
These factors are:
The crop.
The soil.
The system of farming.
THE CROP
Crop roots differ in their powers of feeding, or their powers of
securing plant foods. Some roots can use very tough plant foods, while
others require it in the most available form. Some roots secure
nitrogen from the air. The cowpea roots, for example, can take
nitrogen from the air and they can use such tough phosphoric acid and
potash that it seldom pays to feed them directly with fertilizers.
A bale per acre crop of cotton requires for the building of roots,
stems, leaves, bolls, lint and seed:
103 pounds of Nitrogen.
41 " " Phosphoric Acid.
65 " " Potash.
and yet experiment and experience have proved that the best fertilizer
for such a crop contains the following amounts of plant food:
Nitrogen 20 pounds
Phosphoric Acid 70 "
Potash 20 "
This means that cotton roots are fairly strong feeders of nitrogen and
potash, but are weak on the phosphoric acid side.
The small grains, wheat, oats, barley and rye, can use tough
phosphoric acid and potash, but are weak on nitrogen, and as they make
the greater part of their growth in the cool spring before
nitrification is rapid, they are benefitted by the application of
nitrogen, particularly in the form of nitrate, which is quickly
available.
Clover, peas, beans, etc., have the power of drawing nitrogen from the
air, but draw from the soil lime, phosphoric acid and potash. Hence
the phosphates, potash manures and lime are desirable for these crops.
Root and tuber crops are unable to use the insoluble mineral elements
in the soil, hence they require application of all the important plant
foods in readily available form. Nitrogen is especially beneficial to
beets. Turnips are benefitted by liberal applications of soluble
phosphoric acid. White and sweet potatoes require an abundance of
potash.
If we are growing tender, succulent market garden crops, we need
nitrogenous manures, which increase the growth of stem and foliage.
Fruit trees are slow growing plants and do not need quick acting
fertilizers.
The small fruits, being more rapid in growth, require more of the
soluble materials.
A dark, healthy green foliage indicates a good supply of nitrogen,
while a pale yellowish green may indicate a need of nitrogen.
A well developed head of grain, seed pod or fruit indicates liberal
supplies of phosphoric acid and potash.
THE SOIL
Soils that are poor in humus are generally in need of nitrogen.
Heavy soils are generally supplied with potash but lack phosphoric
acid.
Sandy soils are apt to be poor in potash and nitrogen.
SYSTEM OF FARMING
A system of general or diversified farming embracing crop products and
stock raising, requires much less artificial manuring than does a
system which raises special crops or quick growing crops in rapid
succession, as in the case of truck farming or market gardening.
TESTING THE SOIL
Every farmer should be more or less of an investigator and
experimenter.
The factors mentioned previously as indicating the presence or absence
of sufficient quantities of certain plant foods serve as a general
guide, but are not absolute. The best method of determining what plant
foods are lacking in the soil is to carry on some simple experiments.
The following plan for soil testing with plant foods is suggestive: To
test the soil for a possible need of the single plant foods, a series
of five plots may be laid off. These plots should be long and narrow
and may be one-twentieth, one-sixteenth, one-tenth, one eighth acre or
larger. A plot one rod wide and eight rods long will contain
one-twentieth acre. The width of the plot may be adjusted to
accommodate a certain number of rows of crop and the length made
proper to include an even fraction of an acre. A strip three or four
feet in width should be left between each two plots. These strips are
to be left unfertilized and are for the purpose of preventing one plot
being affected by the plant food of another.
The plots are all plowed, planted and cared for alike, the only
difference in treatment being in the application of plant food. If the
plots are one-twentieth acre in size, plant foods may be applied as
follows.
+----------------------------+
PLOT 1. | Nitrate of Soda 8 lbs. |
+----------------------------+
+----------------------------+
PLOT 2. | Acid Phosphate 16 lbs. |
+----------------------------+
+----------------------------+
PLOT 3. | Nothing. |
+----------------------------+
+----------------------------+
PLOT 4. | Muriate of Potash 8 lbs. |
+----------------------------+
+----------------------------+
PLOT 5. | Lime 1 bushel. |
+----------------------------+
Plot 3 is a check plot for comparison.
The measuring of the plots, weighing and application of the
fertilizers, planting and care of the crops, weighing and measuring at
harvest, should be carefully and accurately done.
A number of additional plots may be added if desired to test the
effect of plant foods in combination. For instance:
+----------------------------+
PLOT 6. | Nitrate of Soda 8 lbs. |
| Acid Phosphate 16 " |
+----------------------------+
+----------------------------+
PLOT 7. | Nitrate of Soda 8 lbs. |
| Muriate of Potash 8 " |
+----------------------------+
+----------------------------+
PLOT 8. | Nothing. |
| |
+----------------------------+
+----------------------------+
PLOT 9. | Muriate of Potash 8 lbs. |
| Acid Phosphate 16 " |
+----------------------------+
+----------------------------+
PLOT 10. | Nitrate of Soda 8 lbs. |
| Acid Phosphate 16 " |
| Muriate of Potash 8 " |
+----------------------------+
If the amount of fertilizer is too small to distribute evenly over the
plot, mix it thoroughly with a few quarts of dry earth or sand to give
it more bulk and then apply it.
In the use of fertilizers it should always be remembered that small
crops are not always due to lack of plant food, but may be caused by
an absence of the other conditions necessary for root growth and
development. The soil may not be sufficiently moist to properly supply
the plants with water. Too much water may check ventilation. Poor
tillage may check root development. Unless the physical conditions are
right the possible effects of additional plant food in the form of
fertilizers are greatly diminished. The farmer who gets the largest
return from fertilizers is the one who gives greatest attention to the
physical properties of the soil. He makes use of organic matter and is
very thorough in his methods of tillage. Every farmer should apply to
his State Experiment Station for bulletins on the subject of
fertilizers.
CHAPTER XXIV
THE ROTATION OF CROPS
SYSTEMS OF CROPPING
There are two methods or systems of cropping the soil:
The One Crop System, or the continuous cropping of the soil year after
year with one kind of crop.
The Rotation of Crops or the selection of a given number of different
crops and growing them in regular order.
The purpose of this chapter is to inquire into the effect of these two
systems of cropping:
On the soil conditions necessary for the best growth and development
of the crops.
On the market value of the crops.
On the increase of or the protection from injurious diseases and
insects.
On the distribution of labor throughout the year.
On the caring for farm stock.
On the providing for home supplies.
This inquiry and the conclusion will be based on the following facts
learned in the foregoing chapters.
Plant roots need for their growth and development (see Chapter II):
A mellow yet firm soil.
A moist soil.
A ventilated soil.
A warm soil.
A soil supplied with plant food.
Decaying organic matter or humus is one of the most important
ingredients of our soils. Because:
It greatly influences soil texture and therefore the conditions
necessary for root growth.
Its presence or absence greatly influences the attitude of soils
toward water, the most important factor in plant growth. Its presence
helps light, sandy soils to hold more water and to better pump water
from below, while it helps close, heavy soils to better take in the
water which falls on their surface. Its absence causes an opposite
state of affairs.
The presence of organic matter checks excessive ventilation in too
open, sandy soil by filling the pores, and improves poor ventilation
in heavy clay soils by making them more open.
Humus, on account of its color, influences the heat absorbing powers
of soils.
The organic matter is constantly undergoing more or less rapid decay
unless the soil be perfectly dry or frozen solid. Stirring and
cultivating the soil hasten this decay.
As the organic matter decays it adds available plant food to the soil,
particularly nitrogen.
As it decays, it produces carbonic acid and other acids which are
able to dissolve mineral plant food not soluble in pure water and thus
render it available to plants.
Plants, although they require the same elements of plant food, take
them in different amounts and different proportions.
Plants differ in the extent and depth of root growth and therefore
take food from different parts of the soil. Some are surface feeders
while others feed on the deeper soil.
Plants differ in their power to take plant food from the soil; some
are weak feeders, and can use only the most available food; others are
strong feeders, and can use tougher plant food.
Plants vary in the amount of heat they require to carry on their
growth and development.
THE ONE CROP SYSTEM
We are now ready for the question. What effect has the continuous
cultivation, year after year, of the same kind of crop on the soil
conditions necessary to the best growth and development of that crop
or any other crop? Suppose we take cotton for example.
How does cotton growing affect soil humus?
During the cultivation of cotton, the organic matter or humus of the
soil decays in greater quantities than are added by the stalks and
leaves of the crop. Therefore, cotton is a humus wasting crop, and
the continuous cultivation of this crop tends to exhaust the supply
of organic matter in the soil.
How does cotton growing affect soil texture?
Cotton growing wastes soil humus and therefore injures soil texture by
making the lighter soils more loose and open, and the heavier soils
more dense and compact.
How does cotton growing affect soil water?
By wasting humus cotton growing injures soil texture and so weakens
the water holding and water pumping power of light soils and weakens
the water absorbing power of heavy soils. Therefore the continuous
cultivation of cotton weakens the power of the soil over water, that
most important factor in crop growth.
How does cotton growing affect soil ventilation?
Continuous cotton culture, by wasting humus, injures texture and
therefore injures soil ventilation, causing too much ventilation in
the lighter soils and too little in heavier soils.
How does cotton culture affect plant food in the soil?
Continuous cotton growing wastes plant food:
Because it wastes organic matter which contains valuable plant food,
particularly nitrogen.
Because by wasting organic matter it increases the leaching of the
lighter soils and the surface washing of the heavier soils.
Because its roots occupy largely the upper soil and do not make use of
much food from the lower soil.
Because it grows only during the warm part of the year and there is
no crop on the land to check loss of plant food from leaching and
surface wash during the winter.
Because it is a weak feeder of phosphoric acid, and can use only that
which is in the most available form. In applying fertilizer to cotton
it is necessary for best results to apply at least twice as much
phosphoric acid as the crop can use, because it can use only that
which is in the most available form and the remainder is left in the
soil unused.
Continuous cotton culture then has an injurious effect on all the
important soil conditions necessary to its best growth and
development, and the result is a diminishing yield or an increasing
cost in maintaining fertility by the use of fertilizer.
How does continuous cotton culture affect the economics of the farm?
The injury to the soil conditions necessary to root growth diminishes
the yield and therefore increases the cost of production.
The poor soil conditions tend not only to diminish yield but also to
diminish the quality of the crop, which tends to lower the price
received for the cotton.
Keeping the land constantly in cotton tends to increase the insect
enemies and the diseases of the crop.
The continuous growing of cotton does not permit the constant
employment of one set of laborers throughout the year.
The continuous growing of cotton generally means that most of the
farm goes into cotton. A small patch of corn is planted for the stock,
which are apt to suffer from a lack of variety in food.
The same is true with reference to home supplies. Very few vegetables
are grown for the table and there is little milk, butter or eggs for
home use or exchange for groceries or drygoods at the store.
Thus we see that the continuous growing of cotton on the soil, year
after year, has a bad effect on conditions necessary to its best
growth and development and also on the economics of the farm.
These facts are true to a greater or less degree in the case of nearly
all of the farm crops. The grain crops are often considered as humus
makers because of the stubble turned under, but Professor Snyder, of
Minnesota, found that five years' continuous culture of wheat resulted
in an annual loss of 171 pounds of nitrogen per acre, of which only
24.5 was taken by the crop, the remaining 146.5 pounds were lost
through a waste of organic matter.
THE ROTATION OF CROPS
Now, suppose that instead of growing cotton on the same soil year
after year, we select four crops--cotton, corn, oats and cowpea--and
grow them in regular order, a rotation practiced in some parts of the
South.
We will divide the farm into three fields and number them 1, 2 and 3,
and will plant these crops as indicated by the following diagrams:
[Illustration: Plan of farm.]
Plan for planting.
FIELD 1. FIELD 2. FIELD 3.
+----------------+----------------+----------------+
| | OATS, | CORN, |
1st year | | harvested in | followed by |
or 1905. | COTTON | spring, | oats, |
| | followed by | planted in |
| | COWPEAS. | fall. |
+----------------+----------------+----------------+
| CORN, | | OATS, |
2d year | followed by | | harvested in |
or 1906. | oats, | COTTON. | spring, |
| planted in | | followed by |
| fall. | | COWPEAS. |
+----------------+----------------+----------------+
| OATS, | CORN, | |
3d year | harvested in | followed by | |
or 1907. | spring, | oats, | COTTON. |
| followed by | planted in | |
| COWPEAS. | fall. | |
+----------------+----------------+----------------+
Each of these crops occupies one-third of the farm each year, and yet
the crop on each field changes each year so that no one kind of crop
is grown on any field oftener than once in three years. The cotton is
grown for market, the corn partly to sell, partly to feed, the oats to
feed and the cowpeas to plow under. All cotton and corn refuse is
plowed under.
What effect will such a system have on the conditions necessary for
plant growth? Suppose we follow the crops on Field 1. Cotton, corn,
and oats are humus wasting crops but the pea crop which is grown the
third year is plowed under, and largely, if not entirely, remedies the
loss by furnishing a new supply of organic matter, and the ill effects
which we noticed would follow the loss of organic matter due to the
continuous growing of cotton are avoided, soil texture is preserved,
soil ventilation is not injured, and the power of the soil over water
is preserved.
What is the effect on plant food in the soil?
Before answering this question let us see what amounts of plant foods
these crops take out of the soil.
We will assume that the soil is a good loam at the start and will
produce:
One bale of five hundred pounds of lint cotton per acre, sixty bushels
shelled corn per acre, thirty bushels oats per acre, or two tons
cowpea hay per acre.
Such a yield of crop would take from the soil the following amounts of
plant food per acre:
----------------------+-----------+------------+------------
| | Phosphoric |
| Nitrogen, | Acid, | Potash,
| pounds. | pounds. | pounds.
----------------------+-----------+------------+---------
Cotton (whole plant) | 103 | 41 | 65
Corn (whole plant) | 84 | 26 | 61
Oats (whole plant) | 32 | 13 | 27
Cowpea | 78 | 23 | 66
----------------------+-----------+------------+---------
Now suppose we sell the lint of the cotton, keeping all the rest of
the plant, including the seed, on the farm and turning it back into
the soil.
Of the corn suppose we sell one-half the grain and keep the other half
and the fodder for use on the farm.
Suppose the oats be made into oat hay and be fed on the farm and the
cowpeas be turned under.
Assuming that the cowpeas take half their nitrogen from the air.
This will mean that in the course of three years we take out of the
soil of each acre in the crops:
Nitrogen. Phosphoric Acid. Potash.
258 pounds. 103 pounds. 219 pounds.
but we return to the soil in crop refuse and manure from the stock:
Nitrogen. Phosphoric Acid. Potash.
256 pounds. 87 pounds. 197 pounds.
This assumes that we have taken from the farm in products sold:
------------------+-----------+------------+------------+
| Nitrogen. | Phosphoric | Potash. |
| | Acid. | |
------------------|-----------|------------|------------|
Cotton Lint | 2 | 1 | 2 |
Corn | 28 | 12 | 10 |
Animal products | 11 | 3 | 10 |
+-----------+------------+------------+
Totals | 41 | 16 | 22 |
------------------+-----------+------------+------------+
The plant food charged to animal products is twenty per cent. of that
in the grain and forage fed to the stock.
At the end of the three years the plant food account will balance up
with:
Nitrogen a gain of 2 pounds.
Phosphoric Acid a loss of 16 "
Potash a loss of 22 "
This result is of course approximate. There will be some loss of
nitrogen through leaching and denitrification. Some of the potash and
phosphoric acid will be converted into unavailable forms. This can be
made good by applying to the cotton a fertilizer containing twenty
pounds of nitrogen, sixty pounds of phosphoric acid and twenty pounds
of potash.
Additional nitrogen and organic matter can be grown to turn under by
planting crimson clover in the cotton at the last working for a winter
cover crop to be turned under for the corn, and by planting cowpeas or
soy beans between the rows of corn.
If this is done it may not be necessary to add any nitrogen in the
fertilizer, letting that supply only phosphoric acid and potash.
If commercial fertilizer is used on the cotton, it would be a good
plan to apply the manure from the stock to the corn.
To follow our crop on Field 1 through the three years we will have,
first, cotton drawing large amounts of plant food from the soil and
diminishing the humus of the soil.
Growing a winter crop of crimson clover, turning back all the cotton
refuse except the lint and oil, and applying the barn manure will
furnish ample plant food for the corn and replenish the organic
matter.
The corn is a rather stronger feeder of phosphoric acid than cotton
and will be able to get sufficient from that left by the cotton.
The oats will be able to get a full ration after the corn, and the
cowpeas will readily take care of themselves on the score of plant
food and will put the soil in fine condition for cotton again.
The peas may be left on the ground to turn under in the spring at
cotton planting time, or they may be plowed under in the early fall
and a crimson clover or vetch cover crop planted, which will be plowed
under for the cotton.
These same facts will be true of each of the three fields. The humus
and, therefore, texture will be taken care of; ventilation, soil
temperature and plant food will be controlled to advantage.
Each of the crops will be represented on the farm each year and the
yields of each crop will be better than if grown continuously alone.
The quality and therefore the market value will be greater. Insects
and disease will be easier kept in control, and stock will be more
economically furnished with a variety of foods.
BENEFITS DERIVED FROM ROTATION OF CROPS
Rotation of crops economizes the natural plant food of the soil and
also that which is applied in the form of manure and fertilizer. This
is because:
Crops take food from the soil in different amounts and different
proportions.
Crops differ in their feeding powers.
Crops differ in the extent and depth to which they send their roots
into the soil in search of food and water.
Crops differ in the time of year at which they make their best
growths.
Rotation helps to maintain or improve the texture of the soil because
the amount of humus in the soil is maintained or increased by turning
under green manure and cover crops which should occur in every
well-planned rotation.
Rotation helps to maintain or increase the plant food in the surface
soil. When crops like cowpeas or clover which take mineral food from
the subsoil and nitrogen from the air, are plowed under, they give up
the plant food in their leaves, stems and upper roots to the surface
soil, and thus help to maintain or increase fertility.
Rotation tends to protect crops from injurious insects and diseases.
If one kind of crop is grown continuously on one piece of land the
soil becomes infested with the insects and diseases which injure that
particular crop. If the crop is changed, the insects and diseases find
difficulty in adapting themselves to the change and consequently
diminish in numbers.
Rotation helps to keep the soil free from weeds. "If the same kind of
crop were grown year after year on the same field, the weeds which
grow most readily along with that crop would soon take possession of
the soil." For example, chick weed, dock, thistle, weeds peculiar to
grain and grain crops tend to increase if the land is long occupied by
these crops.
Rotation helps the farmer to make a more even distribution of labor
throughout the year. This is because crops differ as to the time of
year at which they are planted and harvested.
Rotation of crops enables the farmer to provide for his stock more
economically. Live stock fares better on a variety of food, which is
more cheaply secured by a system of rotation than otherwise.
THE TYPICAL ROTATION
A typical rotation for general farming should contain at least:
One money crop which is necessarily an exhaustive crop.
One manurial crop which is a soil enricher.
One feeding crop which diminishes fertility only a little.
One cleansing crop, a hoed or cultivated crop.
CONDITIONS WHICH MODIFY THE ROTATION
There are certain conditions which tend to modify the rotation or to
influence the farmer in his choice of crops. They are as follows:
First of all the climate will set a limit on the number and varieties
of crops from which a choice can be made for a given locality.
The kind of farming which he chooses to carry on, whether stock
raising, grain farming, truck farming, or a combination of two or more
of these, or others.
Kind of soil. Certain soils are best adapted to particular crops. For
example, heavy soils are best suited to wheat, grass, clover,
cabbages, etc. Light, sandy soils to early truck, certain grades of
tobacco, etc.
The demand for crops and their market value.
Facilities for getting crops to market, good or bad country roads,
railroads and water transportation.
The state of the land with respect to weeds, insect pests and plant
diseases.
GENERAL RULES
A few general rules may be made use of in arranging the order of the
crops in the rotation though they cannot always be strictly followed.
Crops that require the elements of plant food in the same proportion
should not follow each other.
Deep-rooted crops should alternate with shallow-rooted crops.
Humus makers should alternate with humus wasters.
Every well arranged rotation should have at least one crop grown for
its manurial effect on the soil, as a crop of cowpeas, or one of
clover, to be turned under.
The objection often made to this last rule is that, aside from the
increase in fertility, there is no direct return for the time, labor
and seed, and the land brings no crop for a year. It is not necessary
to use the entire crop for green manuring--a part of it may be used
for hay or for pasture with little loss of the manurial value of the
crop, provided the manure from that part of the crop taken off is
returned and the part of the crop not removed is turned under.
LENGTH OF THE ROTATION
The length of the rotation may vary from a two-course or two crop
rotation to one of several courses. Crimson clover may be alternated
with corn, both crops being grown within a year.
A three-course rotation, popular in some parts of the country, is
wheat, clover, and potatoes; potatoes being the money crop and
cleansing crop, wheat a secondary money crop or feeding crop, and
clover the manurial and feeding crop.
A popular four-course rotation is corn, potatoes or truck, small
grain, clover; the potatoes being the chief money crop, corn the
feeding crop, the small grain the secondary money or feeding crop, and
clover the manurial and feeding crop.
On many New England farms near towns, hay and straw are the chief
money crops. Here the rotation is grass two or more years, then a
cleansing crop and a grain crop. A Canadian rotation is wheat, hay,
pasture, oats, peas. A rotation for the South might be corn, crimson
clover, cotton, crimson clover; this rotation covering a period of two
years. A South Carolina rotation is oats, peas, cotton, corn--a
three-year rotation. It might be improved as follows: Oats, peas,
crimson clover, cotton, crimson clover, corn.
CHAPTER XXV
FARM DRAINAGE
Some farm lands contain so much water that the conditions of fertility
are interfered with and therefore the crop producing power of these
lands is lowered.
HOW SURPLUS WATER AFFECTS FERTILITY
This surplus water diminishes fertility by reducing the area of film
water in the soil.
It checks soil ventilation.
It tends to keep the soil cold.
It dilutes plant food in the soil.
It interferes with proper tillage.
INDICATIONS OF A NEED OF DRAINAGE
The above-mentioned state of affairs occurs sometimes in fields at the
foot of hills, or on sloping uplands which receive spring water or
seepage water from higher lands. Some fields are underlaid by a close,
compact subsoil which so checks percolation that the surface soil is
too wet for tillage operations the greater part of the year. In such
cases:
A need of drainage is generally indicated by the presence of more or
less free water standing on the surface.
In some lands the surface water does not appear as free water standing
on the surface. In such cases:
A need of drainage is indicated by the curling and wilting of the
leaves of corn and other crops during dry, hot weather. This curling
and wilting is due to the fact that during the early growth of the
crop free water stands so high in the soil that the crop roots are
confined to a shallow layer of soil. When dry, hot weather comes, the
free water recedes, the upper soil dries out, and the roots cannot get
sufficient water to supply the demands of transpiration, hence the
curling and wilting of the leaves.
If drains are placed in this soil, the free water will be kept at a
lower level in the spring and the plant roots will develop deeper in
the soil, where there will be constant supply of film water during the
dryer and warmer summer weather.
The wiry and spindling growth of grass and grain crops may indicate
too much water.
The growth of moss on the surface of the ground and the cracking of
the soil in dry weather are also indications of too much water.
DRAINS
How can we get rid of this surplus free water?
We can make passageways through the soil to a lower level and then
let gravity pull the water through them to lower ground below. These
passageways are called drains.
Drains may be classed as:
Surface drains which are shallow, open channels made in the soil with
a plow, hoe or other tool, to carry off surface water. They are
temporary and need frequent renewing.
Open-ditch drains are deeper, more permanent water passageways around
or across the fields.
Surface and open-ditch drains take only surface water. They also carry
off surface soil and manures washed into them. They frequently become
choked or stopped by trash and soil, and are in the way of cultivation
and harvesting operations.
Covered drains, under drains or blind ditches are water passageways
made of brush, poles, stones, tiles, etc. (Figs. 80-81), placed in the
bottoms of ditches and then covered with soil.
INFLUENCE OF COVERED OR UNDER DRAINS ON FERTILITY
_Influence on soil water._
Covered or under drains take not only surface water, but also remove
free water from the soil beneath down to nearly the level of the
bottom of the drains, and thus increase the area of film water.
Removing the free water enables the soil to absorb more readily rain
water falling on the surface and therefore checks surface wash and the
gullying of fields.
_Influence on soil ventilation._
Lowering the free water allows a deeper penetration of air and,
therefore, a deeper root development and enables crops to better
resist dry periods.
_Influence on soil temperature._
Lowering the free water in the soil influences soil temperature:
By diminishing the amount of water to be heated.
By checking evaporation.
By letting warm showers sink down into the soil.
By increasing ventilation and therefore permitting the circulation of
warm air in the soil.
The cropping season is lengthened by causing the soil to be warmer and
drier earlier in the spring and later in the fall.
_Influence on plant food in the soil._
Covered or under drains check losses of plant food that occur with
surface and open ditch drains. They render available more plant food,
for lowering free water and increasing ventilation:
Deepen the feeding area of the roots.
Aid the process of nitrification.
Aid chemical changes which make plant food available.
Check denitrification.
LOCATION OF DRAINS
As gravity is the force that is to take the surplus water from the
soil, the outlet of the drainage system should be at the lowest part
of the area to be drained.
[Illustration: FIG. 83.--CROSS-SECTIONS OF STONE-DRAINS.]
[Illustration: FIG. 84.
_A._ Cross-section of a pole-drain. _B._ Cross-section of a
tile-drain.]
[Illustration: FIG. 85.--A COLLECTION OF DRAINAGE TOOLS.]
[Illustration: FIG. 86.
_A_ represents a poorly laid tile-drain. It is poorly graded, and has
partly filled with soil. It has lost more than half its water carrying
capacity. _B_ was properly graded, and has kept free from sediment.]
The main drains should be located in the lowest parts of the fields,
indicated by courses taken by water after a rain or by small streams
running through the farm.
The lateral drains, if surface or open ditch drains, should run across
the slopes; if under drains, they should run up and down the slopes.
_Grade or slope of the drain._
The grade of the drain should be sufficient to cause a flow of the
water. In the case of open ditches it should not be steep enough to
cause too rapid a current and a consequent serious washing of the
banks of the ditch. Large, deep ditches will carry water with a grade
of one inch to a hundred feet.
_Tile drains._
Covered or under drains are made of brush, poles, planks, stones,
tiles, etc. (Figs. 83-84). Where tiles can be obtained at reasonable
prices they are considered best. Tiles are made of clay and are burnt
like brick. They are more lasting than wood and are easier and cheaper
to lay than stone, unless the stone must be gotten rid of.
The most approved form of drain tile is the round or circular form.
These are made in sizes ranging from two and one-half to six and eight
inches in diameter, and in pieces one foot in length.
The size used depends on the length of the drain, the amount of water
to carry, the frequency of heavy rainfalls and the character of the
soil.
The distance apart varies from twenty-five feet in heavy soils to
over two hundred feet in light soils. The usual depth is about three
feet, though the farther apart the deeper they are put.
A lateral tile drain should enter a main at an acute angle to prevent
too great a check in the current.
In putting in a drainage system the first thing to be done is to make
a plan of the ground and determine the slope of the land and the grade
of the drain. The ditches are then staked out and the digging
proceeds. In digging the ditches plows are sometimes used to throw out
the top soil, then the work is finished with spades and shovels.
Professional ditchers use special tools and they take out only
sufficient earth to make room for the tiles (Fig. 85). The tiles are
then laid end to end, the joints covered with a piece of sod, some
grass, straw, paper or clay, to prevent loose soil sifting in. As the
tiles are laid, enough soil is placed on them to hold them in place
until the ditch is filled.
In laying the tiles an even grade should be maintained (Fig. 86). A
lessening of the grade checks the current of water and tends to cause
a stoppage of the drain.
The water gets into the drain through the joints where the tiles come
together.
The outlet of a tile drain should be protected by brick work or should
be of glazed tile such as the so-called terra-cotta tile, to prevent
injury by frost.
The mouth of the drain should be protected by a screen of wire to
prevent the entrance of rats and other small animals.
GLOSSARY
=Acid=, a chemical name given to many sour substances.
=Albumen=, a nitrogenous organic compound.
=Albuminoid=, a nitrogenous substance resembling albumen.
=Ammonia=, a gas containing nitrogen produced by the decay of organic
matter.
=Annual=, a plant that lives only one year; corn and sunflower are
examples.
=Anther=, the part of a stamen that bears the pollen.
=Available=, that which can be used.
=Bacteria=, very small plants, so small that they cannot be seen
without the aid of a powerful microscope. They are sometimes called
"germs." Some of them are beneficial, some do great harm and some
produce disease.
=Biennial=, a plant that lives two years, usually producing seeds the
second year.
=Bordeaux mixture,= a mixture of copper sulphate, lime and water used
to prevent plant diseases. It was invented in Bordeaux, France.
=Bud=, an undeveloped branch.
=Calyx=, the outermost part of a flower.
=Cambium=, the active growing layer between the bark and the wood of a
tree.
=Capillary=, Hair-like. A name given to very small spaces through
which water flows by the force of capillary attraction.
=Carbohydrate=, an organic substance made of oxygen, hydrogen and
carbon, but containing no nitrogen; cellulose or woody fibre, sugar,
starch are examples.
=Carbon=, a chemical element. Charcoal is nearly pure carbon.
=Carbonic acid gas=, a gas consisting of carbon and oxygen. It is
produced from the lungs of animals, and by the decay or burning of
organic matter.
=Catch crop=, a crop growing during the interval between regular
crops.
=Cereal=, a name given to the grain crops that are used for food.
=Chlorophyl=, the green matter in plants.
=Commercial fertilizers=, materials containing plant food which are
bought and sold in the markets to improve the soil.
=Compost=, a mixture of decaying organic matter used to enrich the
soil.
=Cross pollination=, the pollination of a flower by pollen brought
from some other flower.
=Cover crop=, a crop to cover the soil during the interval between
regular corps.
=Cultivator=, a farm implement used to loosen the surface of the soil
and to kill weeds after a crop has been planted.
=Cutting=, a part of a plant placed in moist soil, water or other
medium with the object of its producing roots and making a new plant.
=Dormant=, said of plants when they are resting or inactive. Most
plants are dormant during the winter season.
=Drainage=, the method by which surplus water is removed from the
land.
=Element=, a substance that cannot be divided into simpler substances.
=Fermentation=, the process by which organic substances are broken
down or changed and new substances formed.
=Fertility=, that state or condition of the soil which enables it to
produce crops.
=Fibre=, long thread-like structure.
=Flocculate=, to make crumbly.
=Free water=, standing water or water which flows under the influence
of gravity.
=Function=, the particular action of any part of an organism.
=Furrow=, the trench left by the plow.
=Furrow slice=, the strip of earth which is turned by the plow.
=Germinate=, to sprout.
=Grafting=, the process of inserting a cion or bud in a stock plant.
=Green manure crops=, crops intended to be plowed under to improve the
soil.
=Harrow=, an implement used to pulverize the surface of the soil.
=Heavy soils=, soils that are hard to work; stiff, cloddy soils.
=Horticulture=, that branch of agriculture which deals with the
growing of fruits, vegetables, flowers and ornamental plants.
=Humus=, partially decayed animal and vegetable matter in the soil.
=Hydrogen=, a gaseous, chemical element, one of the constituents of
water.
=Inter-tillage=, tillage between plants.
=Irrigation=, the practice of supplying plants with water by
artificial means.
=Kainite=, a potash salt used in making fertilizer.
=Kernel=, a single seed or grain.
=Leaching=, passing through and going off in drainage water.
=Legume=, a plant belonging to the bean, pea and clover family.
=Light soils=, soils which are loose and open and easy to work.
=Loam=, a mixture of sand, clay and organic matter.
=Mould board=, the curved part of the plow which turns the furrow
slice.
=Mulch=, a covering on the soil. It may be of straw, leaves,
pulverized soil or other material.
=Nectar=, a sweet substance in flowers from which bees make honey.
=Nitrate=, a soluble form of nitrogen.
=Nitrification=, the changing of nitrogen into a nitrate.
=Nitrogen=, a gas forming four-fifths of the air. Nitrogen is a very
necessary food of plants.
=Organic matter=, substances produced by the growth of plants and
animals.
=Osmose=, the movement of fluids through membranes or thin partitions.
=Oxygen=, a gas which forms one-fifth of the air. Its presence is
necessary to the life of all green plants and all animals.
=Ovary=, the part of the pistil that bears the developing seeds.
=Ovule=, an immature seed in the ovary.
=Perennial=, living through several years.
=Phosphoric acid=, an important plant food found in phosphates.
=Pistil=, the part of the flower which produces seeds.
=Propagate=, to increase in number.
=Pollen=, the powdery substance produced by stamens.
=Pollination=, the transfer of pollen from stamens to pistils.
=Potash=, an important plant food.
=Pruning=, removing parts of a plant for the good of what remains.
=Retentive=, holding, retaining, said of soil which holds water.
=Reverted=, said of phosphoric acid in the process of becoming
insoluble.
=Rotation of crops=, a change of crops in regular order.
=Sap=, the juice or liquid contents of plants.
=Seed bed=, the earth in which seeds are sown.
=Seedling=, a young plant just from the seed. Also a plant raised from
a seed in distinction from one produced from a graft or a cutting.
=Sepal=, one of the parts of the calyx.
=Slip=, a cutting placed in water or moist soil or other substance to
produce roots and form a new plant.
=Soil=, that part of the earth's crust into which plants send their
roots for food and water.
=Stamen=, that part of a flower which bears the pollen.
=Stigma=, the part of the pistil which receives the pollen.
=Stomata=, breathing pores in plants.
=Subsoil=, that part of the soil which lies beneath the soil that is
worked with the tillage tools.
=Sap root=, a main root that runs straight down into the soil.
=Tillage=, stirring the soil.
=Transpiration=, the giving off of water from plants.
=Tubercle=, a small nodular growth on the roots of plants.
=Under drainage=, drainage from below.
=Vitality of seeds=, the ability of seeds to grow.
INDEX
Acid phosphates, 196.
Adobe soils, 30.
After-cultivation, 158, 164.
benefits from, 164.
flat, 169.
frequency of, 167.
saves water, 164.
shallow, 15, 167, 169.
time for, 166.
tools for, 167.
Agencies active in making soils, 32.
Agents, with which farmer works, 5.
most important, 6.
Agriculture, foundation facts and principles of, 22.
Air, and the farmer, 5.
in relation to germination, 72.
necessary for root growth, 20.
work of, in making soils, 36.
Albuminoids in plants, 64, 66.
Alfalfa or lucern, 68.
roots, 13.
soils, 29.
Ammonia in fertilizers, 204, 205.
in barn manures, 175.
lost by fermentation, 175.
sulphate of, 194.
Analysis of plants, 163-166.
of fertilizers, 203.
Animals, 5.
and the farmer, 5.
dependent on plants, 6.
work of, in making soils, 37.
Annual plants, 125.
Anthers, 129.
Aphis, 116.
Apple, flower of, 129, 130.
Ash in plants, 65, 66.
Ashes, a source of potash, 199.
cotton hull, 199.
Bacteria, 68, 143.
and the farmer, 5, 144.
denitrifying, 144.
in manures, 174.
in the roots of legumes, 68.
in the soil, 68, 143.
nitrifying, 144.
nitrogen-fixing, 144.
Bare fallow, 100.
when advisable, 100.
Barn manures, 171.
application of, 177.
condition of, 179.
effect of on soil texture, 172.
loss of value of, 173.
meaning of term, 173.
Beet, 6.
Beets, 4.
nitrogen for, 214.
Biological properties of a fertile soil, 143.
Biology, 143.
Blood, dried, 194.
as a fertilizer, 194.
nitrogen in, 194.
Bokhara clover, 190.
Bone, dissolved, 197.
dust, 197.
ground, 197.
Bone fertilizers, 197.
meal, 197.
raw, 197.
steamed, 197.
Bone black, 197.
dissolved, 198.
Bones, 195, 197.
Bordeaux mixture, 118.
Breaking out the middles, 97.
Brick, 30.
Brush harrow, 102, 105.
Buds, 120.
Buildings, 5.
and the farmer, 5.
Bureau of soils, United States, 28.
Department of Agriculture, 28.
Buttercup, flower of, 129, 130.
Cabbage, fertilizer for, 211.
soil, 28, 161.
transplanting, 87, 88.
worm, 117.
Cabbages, 4.
Calcium in plants, 66, 67.
in soils, 68.
Calyx, 129.
function of, 132.
Cambium, 126.
Canadian field pea, 189.
Canteloupe soil, 28.
Capillary force, 49.
meaning of term, 49.
tubes, 49.
water, 153.
Carbon in plants, 66.
Carbonic acid in soil, 37.
Carrots, 4, 6.
Cauliflower soil, 28.
Celery, 4.
Cellulose in plants, 63, 66.
Chain harrow, 102, 105.
Chemical properties of a fertile soil, 147.
Cherry flower, 129, 130.
Chlorophyl in leaves, 113.
Classification of soils, 26.
Clay, 27, 38.
and lime, 42.
loams, 29.
power to absorb water, 41, 42.
relation to water, 25, 41, 43.
soils, 29.
soils injured by working when wet, 45.
to improve texture of, 42.
water-holding power, 44.
Clevis, 93.
Climbing plants, 121.
Clover, 68.
Bokhara, 190.
crimson, 189.
mammoth, 189.
red, 188.
Clovers, as green manure-crops, 188.
as nitrogen gatherers, 184.
nodules on roots of, 184.
Commercial fertilizers, 171, 192.
amount to buy, 212.
home mixing, 211.
kind to buy, 212.
raw materials, 192.
(See also Fertilizers.)
Composts, 171, 181.
Conditions necessary for root growth, 20.
Corn, a humus waster, 226.
depth of root growth of, 13.
flower of, 132.
germination of, 78, 79.
in rotation, 226, 229, 234.
plant, 6.
pollination of, 133.
rapid growth of roots of, 13.
roots cut by plow, 14.
soils, 28, 29, 30, 161.
structure of seed, 78.
water used by, 40.
Corolla, 129.
function of, 132.
Cotton, 5, 161.
a humus waster, 221.
in rotation, 225-229.
plant, 6.
plant food removed by, 227.
Sea Island, 161.
soils, 28, 29, 161.
upland, 161.
Cotton hull ashes, 199.
Cotton-seed meal, 194.
Cotyledons, 77.
use of, 79.
Coulter of plow, 94.
Coulter-toothed harrow, 102, 104.
Cow manure, 178.
losses by exposure, 178.
Cowpeas, 68, 186.
for green manuring, 186.
plant food in, 187.
root growth of, 12.
soils for, 187.
Cropping and soil water, 159, 160.
Crops, cleansing, 232.
feeding, 232.
in rotation, 219.
manurial, 232.
money, 232.
Cucumber flower, 133.
Cultivation.
(See After-cultivation.)
Denitrification, 147.
conditions favoring, 147.
Denitrifying germs, 144, 147.
Draft ring of plow, 93.
Draining, need of, 235.
Drains, 158-239.
and capillary water, 237.
covered, 237.
Drains, effect on film water, 237.
effect on plant food, 238.
effect on soil temperature, 238.
effect on soil water, 237.
grade of, 239.
lateral, 239.
location of, 238.
main, 239.
open ditch, 237.
surface, 237.
tile, 239.
Dried blood, 194.
as a fertilizer, 194.
nitrogen in, 194.
Early crops, soils for, 27, 28.
Egg experiments to show osmose, 18, 19.
Egg plant, soil for, 28.
Elements in plants, 66.
Elm tree leaf beetle, 117.
Endosperm, 78.
use of, 79.
Epicotyl, 78.
Essential organs of flowers, 131.
Evaporation, loss of water by, 54.
loss of heat by, 59.
Excursion,
to examine soils, 24.
to see plow cutting roots, 14.
to study roots, 11.
to study leaves, 108.
to study stems, 120.
to visit farm, 4.
Experiment to show,
air necessary for germination, 73.
amount of transpiration, 110.
capillarity, 49.
capacity of soils for film water, 51.
checking loss of water by evaporation, 55.
chlorophyl necessary for starch making, 113.
effect of soil mulch, 55.
depth of planting seeds, 81.
effect of lime on clay soil, 42.
effect of working soil when wet, 26, 45.
exclusion of oxygen by leaf, 113.
film water, 50.
growth in length of roots, 16.
heat necessary for germination, 73.
how food and water get into the root, 18, 19.
how soils are warmed, 58.
how soils lose heat, 59.
importance of roots, 7.
moisture necessary for germination, 71.
no starch formed in dark, 112.
osmose, 18, 19.
plants contain albuminoids, 64.
plants contain ashes, 65.
plants contain cellulose, 63.
plants contain gum, 64.
plants contain oil, 64.
plants contain starch, 64.
plants contain sugar, 64.
plants contain water, 65.
power of soils to absorb rain, 40.
power of soils to hold water, 44, 45.
power of soils to pump water, 43.
roots absorb moisture, 9.
roots take food from soil, 9.
roots produce new plants, 10.
roots need air, 21.
soil characteristics, 24, 25.
soil temperature, 57, 60.
starch in leaf, 111.
stems carry sap, 122.
stems store food, 124.
transpiration, the fact, 109.
transpiration, amount, 111.
use of cotyledons, 79.
what becomes of water taken by roots, 39.
Fallow, bare, 100.
Fall plowing, 99.
Families of plants, 86.
Farm drainage, 235.
Farm manures, 171, 183.
classification of, 171.
importance of, 172.
Farmer deals with agents, laws and forces, 5.
Fat in plants, 64.
Fermentation of manures, 174.
Fertile soil, a, 141.
biological properties of, 142, 143.
chemical properties of, 142, 147.
most important properties of, 150.
physical properties of, 142.
Fertility of the soil, 150.
economizing the, 150.
maintaining the, 150.
Fertilizers, commercial, 68, 192.
analysis of, 203.
classification of, 171.
home mixing, 211.
how to know what kind is needed, 212.
importance of thorough mixing with the soil, 15.
manufactured, 202.
many brands, 202.
mixed, 202.
raw materials, 192.
sources of lime, 193, 200.
sources of nitrogen, 193.
sources of phosphoric acid, 193, 195.
sources of potash, 193, 199.
use of by farmer, 172, 192.
value of plant food in, 205.
Filament of stamen, 129.
Film water, 50.
Fish scrap as a fertilizer, 194.
Flower,
of apple, 129, 130.
of buttercup, 129, 130.
calyx, 129.
of cherry, 129, 130.
corolla, 129.
of cucumber, 133.
functions of parts of, 130.
of honeysuckle, 129.
of melon, 133.
parts of, 129.
of peach, 129, 130.
petals, 129.
of petunia, 129.
pistil, 130.
pollen, 130.
of potato, 129.
sepals, 129.
stamen, 129.
of squash, 133.
of tomato, 129.
of wild mustard, 129, 130.
Flowers, 8, 128.
essential parts of, 131.
functions of, 130.
Food of plants, 63.
Forces of nature and the farmer, 5.
Forest soils, 29.
Foundation facts and principles of agriculture, 22.
Free water in the soil, 48, 153.
injurious to roots, 153.
source of capillary and film water, 153.
Fresno sand, 28.
Fruit, 8, 136.
Fruit soils, 29.
Fruits, 27.
Furrow slice, 96.
Gas lime, 201.
Geranium, 6.
Germinating seeds,
need air, 73.
need heat, 73.
need water, 71.
Germs, 143.
denitrifying, 144, 147.
nitrifying, 144, 145.
nitrogen fixing, 144.
Goosefoot family, 86.
Gourd family, 86.
Grafting, 136.
Grain crops humus wasters, 224.
Grain soils, 28.
Grass, 5.
family, 86.
soils, 28, 29, 30, 162.
Gravel, 26.
Gravelly loams, 29.
Green-crop manures, 171, 183.
benefits from, 185.
best plants for, 185.
Green manure-crops, 186.
clovers as, 188.
cowpeas as, 186.
legumes as, 186.
non-leguminous, 191.
soy-bean as, 189.
time for growing, 186.
Gum in plants, 64, 66.
Gypsum, 201.
Habit of growth of roots, 11.
Handles of plow, 93.
Harrowing, 101, 158.
objects of, 101.
time for, 101.
Harrows, 4, 102.
brush, 102, 105.
chain, 102, 105.
coulter-toothed, 102, 104.
plank, 102, 105.
rolling cutter, 102, 103.
spike-toothed, 102, 104.
spring-toothed, 102, 103.
Hay soils, 29, 30.
Heat and the farmer, 5.
Heat necessary for germination, 73.
Hilling the crop, 169.
Hilum, 77.
Hoeing and soil water, 158.
Hoes, 4.
Horn shavings as fertilizer, 195.
Horse manure, 176.
losses when piled, 176.
House plants, watering of, 51.
How the bean gets up, 78.
How the corn gets up, 79.
Humus, 27, 38.
influence on soil texture, 62.
nitrogen in, 67.
a source of nitrogen, 67.
water-absorbing power of, 41.
water-holding power of, 44.
water-pumping power of, 43.
Hydrogen in plants, 66.
Hypocotyl, 78.
Ice, work of, in making soils, 35.
Insects, chewing, 117.
how to combat, 116, 117.
injure leaves, 116.
sucking, 116.
Insect pollination, 131.
Inter-tillage, 164.
Iodine, test for starch, 64.
Iron in plants, 66.
Jointer of plow, 95.
value as a pulverizer, 95.
Kainite, 199.
Knowledge of flowers, value of, 134.
Land plaster, 200.
Laws of nature, 5.
Leaf work, conditions necessary for, 114.
interfered with, 115, 118.
Leather as a fertilizer, 195.
Leaves, 8, 108.
digest food, 114.
facts about, 108.
functions of, 109.
manufacture starch, 112.
transpire water, 110.
Legume family, 86.
Legumes, definition of, 68.
nitrogen fixers, 68, 186, 144.
value as green manure plants, 144, 185.
Leguminous plants, 68.
Light necessary for leaf work, 114.
Lily family, 86.
Lime, 200.
amount to use, 200.
effect on sand, 200.
effect on clay, 200.
in soils, 149.
its action on soils, 149, 200.
sets free potash, 149.
sources of, 171, 200.
Lime stone soluble in water, 31.
Loam, 28.
Loamy soils, 28.
London purple, 117.
Loss of soil water, 53, 155.
Lucern, 13.
roots, 13.
Magnesium in plants, 66.
Maintenance of fertility, 150.
Materials composing soils, 26.
Mallow family, 86.
Manures, barn, 171, 173.
application of, 177.
care of, 173.
checking losses from, 176.
effect on soil texture, 172.
effect on soil water, 159.
functions of, 171.
losses from leaching, 173.
losses from heating, 174.
Many things the farmer deals with, 5.
Marigold, 6.
Marl, 201.
Melon flower, 133.
Miami sand, 28.
Microscopic organisms, 5.
Mixed fertilizers, 202.
inflating the guarantee, 204.
low grade, 204, 207.
many brands, 202.
valuation of, 205.
Morning-glory, 129.
Most important factor in the raising of crops, 151.
Mould board of plow, 94.
Muck, swamp, 30.
Mulch, soil, 56.
how made, 56.
to save water, 56.
Muriate of potash, 199.
Mustard, family, 86.
flower, 129, 130.
Muskmelon soils, 161.
Night shade family, 86.
Nitrates, what they are, 146.
availability of, 146, 193.
solubility of, 146.
Nitrate of soda, 193.
nitrogen, 193.
Nitric acid in soil, 146.
Nitrification, 146.
aided by plowing, 146.
aided by lime, 146.
conditions favorable to, 146.
Nitrifying germs, 144, 145.
Nitrogen, 66.
added to the soil by legumes, 68.
grown on the farm, 68.
in humus, 167.
in soils, 67, 148.
in plants, 66, 67.
in fertilizers, 192.
loss of, 67.
sources of, 171.
Nitrogen-fixing germs, 144.
Non-leguminous green manure-crops, 191.
Norfolk sand, 28.
Oats, soil for, 29.
Object of this book, 3.
Odorless phosphate, 198.
Oil in plants, 64, 66.
One-crop system, 221.
effect on fertility, 221.
Onion, 6.
Organic matter,
in soils, 32, 62, 220.
value of, 61.
Osmose, 18.
Ovary of flower, 130.
Ovules, 130.
Oxygen in plants, 66.
Paris green to destroy chewing insects, 117.
Parsley family, 86.
Parsnip root, depth of growth, 13.
Parsnips, 4.
Pasture, soils for, 30.
Pea family, 86.
soils, 28.
Peach borer, 127.
flower, 130.
Peanuts, 5.
Peat, 30.
Peppers, soil for, 28.
Percolation of water, 41.
Petals, 129.
Petunia, 129.
Pigweeds, 5, 6.
Pistil, 130.
function of, 131.
Phosphate, odorless, 198.
rock, 195.
slag, 195, 198.
Phosphoric acid, 195.
available, 195, 196.
in fertilizers, 195.
in soil, 148.
insoluble, 195, 196.
reverted, 196.
soluble, 196.
sources of, 171.
Phosphorus in plants, 66, 67.
in soils, 68.
Plank harrow, 102, 105.
Plant, analysis of, 63.
most important part of to plant itself, 7.
most important part of to plant grower, 7.
Plant diseases, 118.
Plant food, 63.
and the farmer, 5.
Plant food, in soil, 63.
in fertilizers, 68, 192, 205.
what it is, 63, 69.
Planting,
corn, 84.
grass seed, 84.
grain seed, 84.
method of, 83.
seeds, 81.
vegetable seeds, 84.
Plants, 5.
and the farmer, 5.
conditions for growth, 6.
composition of food of, 63.
for study, 6.
living, growing things, 6.
parts of, 6.
resemble one another, 6.
why raised, 6.
work of in making soils, 36.
Plow beam, 93.
coulter, 94.
characteristics of, 95.
clevis, 93.
cutting roots, 15.
draft ring, 93.
handles, 93.
jointer, 95.
landside, 94.
mouldboard, 94.
parts of, 92.
shackle, 93.
share, 93.
standard, 92.
truck, 95.
Plowing, 90.
depth of, 96.
effect on soil water, 156.
favors root growth, 14.
in fall, 99, 157.
in spring, 98, 157.
importance of deep, 15, 17.
objects of, 91, 92.
to save water, 92.
time for, 98.
Plows, 4.
Plumule, 78.
Pollen, 130.
Pollination, 131, 132, 135.
cross, 132, 133, 135.
of wild goose plum, 134.
Potash, 199.
in fertilizers, 199.
in soils, 149.
sources of, 171.
Potassium, in plants, 66, 67.
in soils, 68.
Potato, 6.
soils, 28, 29, 161.
Potato, sweet,
roots of, 13.
soils, 28, 160.
Properties of a fertile soil, 141.
Pruning, 137.
Quitch-grass, 121.
underground stem of, 121.
Radicle, 78.
Radish, shrunken root of, 10.
Ragweed, 5.
Rain, work of in making soils, 33.
on clay soils, 41.
on sandy soils, 41.
Rake, 101.
Rakes, 4.
Raking and soil water, 158.
Red spider, 117.
Rhubarb soil, 28.
Ridging the soil, 98, 158, 169.
Rock salt, 31.
Rollers, 107.
Rolling, 101, 106, 158.
autumn-sown grain, 106.
light soils, 106.
reason for, 106.
spring-sown grain, 106.
Rolling cutter harrows, 102.
Root, 8.
how it takes moisture, 18.
most important part of plant, 7.
Root hairs, 17, 18.
Roots,
absorb water, 9, 11, 17.
absorb plant food, 10, 11.
alfalfa, 13.
and fertilizers, 15.
growth of in length, 16.
conditions necessary for growth of, 8, 20, 141, 220.
corn, 13.
cowpea, 12.
depth of growth of, 12.
extent of growth of, 12.
habit of growth of, 11, 15.
hold plant in place, 9, 11, 15, 16.
important lessons from, 13, 15.
location of, 12, 13.
need firm soil, 20, 22, 23.
need mellow soil, 20, 22, 23.
need moist soil, 20, 22, 23.
need plant food in soil, 20, 22, 23.
need warm soil, 20, 22, 23.
need air in soil, 21, 22, 23.
produce new plants, 10, 11.
rapidity of growth of, 15.
soy-bean, 12.
store food, 10, 11.
sweet potato, 13.
tree, 13.
uses of, 9, 10, 11, 15.
work of, 9, 10, 15.
Rotation of crops, 219.
benefits from, 230.
conditions which modify, 232.
effect upon fertility, 224.
examples of, 234.
general rules for, 233.
length of, 233.
typical, 231.
Sampling soils, 163.
Sand, 26, 38.
Fresno, 28.
grades of, 26.
Miami, 28.
Norfolk, 28.
power to absorb water, 41, 43.
Sandy soils, 27.
adapted to early truck, 27.
effect of humus on, 43, 44, 220.
improving, 43.
water-holding power of, 44.
Sandy loam, 28.
Sapwood, 126.
Scythes, 4.
Seed leaves, 77.
Seed, 130.
classification of, 85.
crab,
drills, 4, 84.
planting, 81, 83.
Seeds, 8.
depth to plant, 81.
how they come up, 77.
how to test, 75.
which germinate at a temperature of 45 degrees, 74.
which germinate at a temperature of 60 degrees, 74.
Seeds to germinate,
need air, 72, 73, 75.
need heat, 73, 75.
need moisture, 71, 75.
Sepals, 129.
Shallow cultivation, 14, 15, 167, 169.
Share of plow, 93.
Shackle of plow, 93.
Silt, 27, 38.
Silt loam, 29.
Small fruit soils, 20.
Soil,
a fertile, 141.
definition of, 23.
formation of, 30, 237.
material composing, 147, 26.
mulch, 56.
temperature, 57, 60.
testing, 162, 215.
texture, 37, 142.
texture important, 142, 143.
ventilation, 68, 142.
warmed by sun, 58.
warmed by conduction, 58.
water, 40, 151.
Soils, 5, 23.
adobe, 30.
alfalfa, 29.
and the farmer, 5.
attitude of toward water, 40.
cabbage, 28, 161.
canteloupe, 28, 161.
capacity for film water, 51.
cauliflower, 28.
classified, 26.
clay, 29.
cloddy, 38.
close, 38.
coarse, 38.
compact, 38.
corn, 28, 29, 30, 161.
cotton, 28, 29, 161.
effect of working when wet, 26, 41.
egg plant, 28.
fine, 38.
forest, 29.
fruit, 27, 29.
general farming, 28, 29.
grain, 28, 162.
grass, 28, 29, 162.
gravelly, 29.
hard, 38.
hay, 29, 30.
heavy, 38.
how made, 30.
humus, 27, 38.
leachy, 38.
loamy, 28.
loose, 38.
lose heat, 59.
light, 38.
lime in, 67, 149.
loss of water from, 53, 153.
lumpy, 38.
mellow, 38.
oat, 29.
open, 38.
organic matter in, 220.
pasture, 30.
pea, 28.
peat, 30.
peppers, 28.
plant food in, 63.
potato, 28, 29, 161.
porous, 38.
relation of to water, 39, 46.
relation of to plants, 23.
retentive, 38.
rhubarb, 28.
sandy, 27.
small fruit, 28, 29.
soft, 38.
sorghum, 162.
stiff, 38.
stony, 29.
strawberry, 28.
swamp, 30.
testing, 162, 215.
tobacco, 27.
tomato, 28, 161.
truck, 27, 28, 29, 161.
vegetable, 28.
water-absorbing power of, 40, 43, 46, 142.
water-holding power of, 44, 142.
watermelon, 28, 161.
wheat, 29, 30.
Soil water, 150, 151.
amount of used by plants, 40.
and farm operations, 156.
control of, 53.
form of, 48, 153.
greatest factor in growth of crop, 46.
importance of, 39, 151.
loss of, 53, 155, 157, 164.
loss of by evaporation, 54.
loss of by weeds, 54, 165.
loss of by surface wash, 53.
necessity for, 151.
not enough, 154.
saving, 165.
sources of, 40, 153.
too much, 154.
Soil water influenced,
by cropping, 159.
by harrowing, 101, 103, 158.
by humus, 42, 43, 44, 45, 220.
by plowing, 91, 156.
by ridging, 98, 158.
by rolling, 106, 158.
Sorghum soils, 162.
Soy-bean, as a green manure crop, 189.
growth of roots, 12.
Spade, 90.
Spading, 90.
Spading-fork, 90.
Spike-toothed harrows, 102, 104.
Spraying, 118.
Spring plowing, 98.
Spring-toothed harrows, 102, 103.
Squash flowers, 133.
Stable manure, 171, 173.
Stamen, 129.
function of, 131.
Staminate flowers, 133.
Starch in plants, 64, 66.
iodine test for, 64.
Stems, 8, 120.
distinguished from roots, 120.
habit of growth of, 121.
structure of, 125.
underground, 121.
uses of, 120.
work of checked, 126.
Stigma, 130.
Stomata, 110.
Stones, 26, 31.
Stony loam, 29.
Strawberry flowers, 134.
perfect, 135.
pistillate, 135.
Study of plants begun, 6.
Style, 130.
Sugar cane, 5.
soil, 162.
Sugar in plants, 64, 66.
Sulphate of ammonia, 194.
Sulphate of potash, 199.
Sulphur in plants, 66.
Sun, work of in making soils, 32, 34.
Sunlight, and the farmer, 5.
necessary for leaf work, 110, 111, 112.
Superphosphates, 198.
Swamp muck, 30.
Sweet clover, 190.
Sweet potato roots, 13.
soils, 28, 160.
Sweet potatoes, 5.
Sylvinite, 199.
Systems of cropping, 119.
Tankage, 194.
as fertilizer, 194.
nitrogen in, 194.
phosphoric acid in, 194.
Temperature of soil, 57.
Tendrils, plants climb by, 122.
Testing seeds, 75.
Testing soils for water, 162.
for plant food, 215.
Texture of soils, 37, 143, 150.
Thinning fruit, 137.
Thistle, 6.
Thistle family, 86.
Thomas slag, 198.
as fertilizer, 198.
phosphoric acid in, 198.
Tillage and plant food, 67.
and fertility, 150.
Time to begin this study, 3.
Time to plow, 98.
Tobacco soils, 27.
Tomato soils, 161.
Tools, 5.
and the farmer, 5.
Transpiration, the fact, 110.
amount of, 111.
Transplanting, 87.
machines, 89.
Truck of plow, 95.
Truck soils, 27, 28, 29, 161.
Tubercles on roots of legumes, 68, 144.
Turnip, 6.
Type soils, 26.
Under drains, 237.
advantage of, 237.
Underground stems, 121.
Value of knowledge of flowers, 134.
Vegetables,
roots, 13, 14, 15.
soil for, 28.
Ventilation of soils, 68, 142.
necessary for germination, 73.
necessary for root growth, 21, 22, 23.
necessary for fixation of nitrogen, 144.
Water, absorption of by soil, 40, 43, 46, 142.
amount used by plants, 40.
capillary, 49, 153.
evaporation of, 54, 155.
free, 48, 153.
film, 50.
ground, 48.
importance of to plants, 39.
percolation of, 41.
relation of soils to, 39.
standing, 48.
work of in making soils, 33, 35.
Water and the farmer, 5.
Water in plants, 65.
Watering house plants, 51.
Watermelon soils, 28, 161.
Weeders, 167.
Weeds, 54.
how they injure crops, 54, 92.
how to kill, 119.
waste soil water, 54.
Wheat soils, 29, 30.
water used by, 40.
Wheel hoes, 168.
White hellebore, 117.
Wind pollination, 132.
Work of roots, 9, 10, 15.
Work of sun in making soils, 32, 34.
air in making soils, 36.
animals in making soils, 37.
moving ice in making soils, 35.
moving water in making soils, 33, 35.
plants in making soils, 36.
rain in making soils, 33.
Wood ashes, 199.
Wool waste as fertilizer, 195.
* * * * *
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