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.