a film of water surrounds
the soil grains.
7 he six points of contact
leave large air spaces which
retard capillary attraction
and permit an excessive
amount of air and heat to
evaporate what little moist-
ure may be in cloddy
The thousand marbles
make six thousand points
of contact thus showing how
much easier it is for moist-
ure to travel upward by
capillarity, the increased
surface for holding film
Water and diminished air
22 THE OLIVER PLOW BOOK
finely pulverized soil. Clay has the smallest soil particles ;
clay loam the next larger, loam larger than clay loam;
sandy loam larger than loam; and loamy sand larger than
sandy loam. This pan was filled with water, giving it
an opportunity to rise in the tubes by capillarity.
The five samples of soil in these tubes were taken from the same farm.
They are shown on pages 39, 41, 43, 45 and 47. At the top of each tube
is a granular mulch. The particles of earth are much coarser than those
of the finely compacted earth below. These tubes are eight inches high
and two inches in diameter. The earth was packed in each tube to bring
about an ideal condition for capillary attraction to act. The soil was
also placed in an ideal condition for germination of the seed and the
growth of the plant. The surface was not. Do not fail to observe the
effect of this granular mulch in the illustration on page twenty-four.
The illustration at the top of page twenty-three
shows the water is almost halfway to the top of
the finely pulverized earth in the tube of the loamy
sand; has a good start in the sandy loam; is just
beginning in the loam; is hardly perceptible in the clay
loam, and not at all in the clay. Thus, we observe that
up to this period capillary attraction is faster in the
sandy soils than the clay, and that the loam is about
The second illustration on page twenty-three shows
the water in the tube filled with clay has just started
INFLUENCE OF WATER
while that in the loamy sand tube has almost reached
the top. The clay loam, loam, and sandy loam are still
drawing water in about the same proportion as shown
in the previous illustration.
The illustration on page twenty-four shows the
water in the tube filled with loamy sand has reached
the cloddy portion, while that in the clay tube
has gone about one-fifth of the way to the top of the
tube. The water in the other three is still climbing in
the same proportion, thus showing conclusively that the
finer the soil particles are, the slower the water rises.
THE OLIVER PLOW BOOK
Another feature that must be taken into serious con-
sideration is that soils, in which water rises rapidly, dry
out equally fast, thus the sandy soils dry out much
quicker than the clay soils, all of which goes to show that
the finer the soil particles are, the stronger the attrac-
tion to hold the water.
Compare the water in the loamy sand and clay tubes illustrated on
page twenty-three with those illustrated above. The granular mulch on top
the tube of loamy sand stopped the upward trend of moisture as the
distance the water in the clay tube has travelled upward shows. The
moisture in the loamy sand tube has climbed from a point just below the
wire to the granular mulch while the water in the clay tube travelled
twice as far as it had, thus showing that the granular mulch stopped the
upward trend of moisture. This illustration serves to show the import-
ance of keeping the soil particles on the surface in an entirely different
arrangement from those below in order that capillary attraction may be
permitted to act up to this point and then stopped, thus peeping the
moisture in the ground.
Observe further the soil at the top of the tube filled
with loamy sand; that the water has not penetrated the
clods to any appreciable extent. Bearing in mind the
illustration of the tube with the clods in the center, it
will be observed that a granular surface on top is better
to prevent moisture from escaping into the air than the
finely pulverized soil. The reason for this is simply
that capillarity has been broken up between the com-
INFLUENCE OF WATER 25
pact sub-surface and the granulated top. For this reason
it is better to have the lower portion of the soil compact
and the layer on the surface coarse and granular than to
have it all finely pulverized.
When a farmer desires to plant a field infested with
cutworms, grubworms, wireworms, or some other pest
which can be eradicated by plowing, he wants to know
whether it is best to plow for the express purpose of kill-
ing the insects, for the conservation of moisture, or at a
time of the year when plowing can be easier done. He
must decide which is the most important and plow ac-
cordingly. The number of times that one would run
into difficulty with moisture when plowing to kill insect
pests would be very few because the ideal time to plow
to kill insect pests is during their larva state, which for
the most part is in the fall of the year.
If one plans on plowing sod with the expectation of
growing a crop it is better to fall plow for the moisture
conservation process and also for the killing of insect
pests. The small profit that may be made in pasturing
such fields is much less than the total accruing from
plowing in the fall previous to planting. This has been dem-
onstrated sufficiently to be stated as a fundamental fact.
If one studies carefully the conditions mentioned it is
evident that the damage done during dry periods can
be minimized by having the soil kept in the proper
physical condition by the right kind of tillage to save
moisture for use at this time.
From the foregoing it is obvious that soil moisture
very often determines whether a yield will be large or
small. The same needs for moisture are present,
north, east, south and west, and the same laws for con-
26 THE OLIVER PLOW BOOK
serving must be applied. The degree to which this
conservation must be practiced is determined solely by
the amount of moisture contained in the soil. In the
more humid districts it may be only necessary to adopt
a system for conserving the rains of summer and fall;
whereas, in the dryer territories it may be necessary to
practice a system of summer fallowing for an entire year
before enough moisture can be saved to insure a crop.
The big thing to remember is that moisture must be
present when the plants need it.
Those farms underlaid with clay soils are easier to till
for conserving moisture for future use than those which
have an endless depth of sand or gravel. If the sub-soil
is of such a nature that it will not hold moisture within
the distance which capillary attraction operates, the
problems are extremely difficult and almost beyond
control unless the soil is kept chock full of humus at a
depth deep enough to prevent surface heat from evapor-
ating the moisture.
Importance of Air in the Soil
WATER, heat and oxygen are necessary for the
germination of seeds. Oxygen must come from the
air, hence it is necessary, in the preparation of the
seed bed, to leave the ground in condition for the cir-
culation of air.
In view of the fact that seeds must germinate before
the plants can grow, the nearer the oxygen and moisture
are in the right proportion in the ground, the more
rapid will be the germination and growth of the plant.
In the development of plant food for growing plants
the elements that go to make nitrates are largely con-
fined to the first few feet of surface soil. If the soil is
loose enough to allow access of air, nitrification is more
rapid, hence plant growth is more rapid. It obviously
follows then that plowing and cultivating are necessary
for the development of plant food.
Air is also necessary to keep the ground in condition
for the retention of plant food after it has reached the
nitrate form. The roots of plants need oxygen in the
process of growing. Energy is required. The roots
penetrating through the ground absorb the oxygen and
thus acquire the needed energy for the work of pushing
the soil particles to one side.
Nitrogen, in the form of nitric acid, is the most im-
portant of all plant food elements. Oxygen gives life
or activity to prevent destruction of nitrates after they
have once been made. Wet soils, rich in organic
THE OLIVER PLOW BOOK
matter, often give off more free nitrogen than is used in
forming the nitrates in them. Thus they become
depleted on account of too much water and not enough
oxygen. Too much oxygen in the soil burns up the
fertility and has a tendency to form clods.
Seeds will not germinate in ground from which oxygen
has been completely excluded; neither will growth take
place. Water, completely filling pore spaces, excludes
oxygen. This is another way of saying that plants drown.
The human being drowns because oxygen is excluded
from the lungs; so do plants. Compact earth prevents
This illustration shows a soil that had been covered with water for a
long time. The excessive air spaces caused by these cracks are due to
the shrinking of the soil particles after the swelling caused by the water.
It is easy to see that the cracks penetrate deeply thus causing the air and
heat of the sun to evaporate the moisture from a great depth.
circulation of air and creates a condition fatal to growth,
even if the ground contains sufficient moisture. Some
authorities claim poisonous gases are formed by this
While the evil effects of excluding air from the soil
are many, it is equally true that too much air is harmful.
Air is just as essential in the forming of nitrates as
IMPORTANCE OF AIR IN SOIL 29
moisture. Consequently, if all the air were removed
from the ground there would be no forming of nitrates,
and plant food could not be produced. Too much air
makes cracks and fissures in the soil, drawing out
moisture, oftentimes to such a depth as not only to
stunt the crop, but kill it. Too much air in the soil in
the spring can easily cause the loss of enough moisture
to grow a crop.
It is a well known fact that the atmospheric pressure
on the earth's surface is 14.7 pounds per square inch at
sea level. The amount of nitrogen in these 14.7 pounds
of pressure is 77%. It is perfectly logical, if the
ground is broken up and thoroughly pulverized when
plowing, that this pressure of 14.7 pounds per square
inch will force the air into the soil taking with it 77% of
free nitrogen. It is the air circulating around every
particle of soil in conjunction with capillary moisture
that liberates plant food for the growing plants.
This field is similar to that shown on page twenty-eight but in a much
less aggravated form. However, if left to itself for any length of time it
is easily possible to see how the cracks would widen and deepen.
30 THE OLIVER PLOW BOOK
Scientists tell us that wheat, oats, barley, rye, etc.,
take up the nitrogen, which they use from the
roots, and then only in nitrates in dissolved form. Hence,
nitrogen must be available in the ground.
The more nitrates there are in the ground per acre
the greater chance the farmer has of growing increased
crops. He may have his phosphorous, potassium, cal-
cium and water, but unless he has the nitrogen which
he can get from the free air, he can never grow the proper
kind of crop.
Since the need for air in the soil is highly important it
behooves the plowman to be very careful to see that the
ground is thoroughly pulverized and that all large air
spaces are eliminated and the after preparation of the
seed bed made so as to keep the air and moisture mixed
in the ground in as nearly the perfect proportion as
possible. Enough has been said to show that the perfect
condition in all soils is when the soil has natural air
spaces between the soil particles. This is one reason
why Nature makes soil particles with irregular surfaces.
The best way for aerating the ground is to thoroughly
pulverize when plowing. To be sure of this requires a
study of the shapes and sizes of plow bottoms, because
different soils require different shapes, sizes and curva-
tures of bottoms to bring about the desired result.
Also the time of the year that the plowing is done with
relation to the time elapsing between the plowing and
planting has a great deal to do with the success of
In the chapter on the temperature of the soil atten-
tion is called to the difference in the temperature required
for the most propitious development of plant food and
the planting of wheat to resist the winter's freezing.
IMPORTANCE OF AIR IN SOIL
Observe how deeply fissures will penetrate the ground when conditions
are ripe. This condition can only be prevented by a mulch of earth on
the surface to keep moisture travelling upward from the ground water
level to the mulch, and the rays of heat and light from penetrating.
Summing up the importance of air in the soil, temper-
ature and plant food development, and the killing of
insect pests we find that early summer plowing, with
complete burying of stubble and trash on the bottom
of the furrow, is the best method for killing the Hessian
fly, and aerating the soil at a time when nitrates develop
best. At this time there is the least amount of rainfall
to wash away plant food and the soil is in the best
possible condition for the percolating and saving of
what rain does fall so that later in the fall when the
time comes for planting wheat it is at a cooler temper-
ature with plant food enough developed for giving the
wheat a remarkably good start, thus lessening its
chances of winter killing.
FOR centuries farmers have observed that some soils
are seemingly better adapted than others to grow
certain kinds of crops. These observations naturally
have led to what is called "wheat soil," "barley soil,"
"rye soil," etc. While these observations on the face
of them would lead one to think that some soils are
more adapted than others for crop growing, there is a
great deal of doubt as to their real merit because in the
light of present-day experiments crops have been grown
in pure sand which had been supplied with the plant
food elements and the amount of moisture necessary to
Climatic conditions have much to do with crop grow-
ing, consequently, when one begins to study what crops
that soil is to produce, he must take into consideration
the climatic conditions as well as the soil. Naturally
then, if a farmer can supply a soil with conditions
equivalent to climate, he can, to the extent of that
ability, grow plants in any soil.
The wheat and oat plants offer an interesting illus-
tration of this fact. Assuming that the proper fertility
is in the soil, whether it is sand or clay, climatic con-
ditions, that is, temperature and water, must determine
the growth. Up to the time of ear shooting wheat
needs wet, but not too warm weather; at flowering
time, dry, warm weather; during the ripening period,
medium moist weather, and dry weather for harvest.
The oat does best in moist and relatively cool weather.
It is not to be supposed that it is possible for a man
to control the temperature of the soil to the degree that
he can bring about climatic conditions for growing a
crop, but by the proper conservation of moisture and
cultivation of the soil it can be made warm in the spring
Ground in this condition becomes too hot in the summer for the suc-
cessful development of nitrates for growing corn. This soil, a silt loam,
requires very careful handling to prevent its powdering.
when it otherwise would be cool, and cool in the summer
when it otherwise would be hot. To this extent the
temperature of the ground can be controlled. This
aids very materially in the growing of crops. The
means for bringing this about center around the amount
of moisture in the ground and the rapidity with which it
34 THE OLIVER PLOW BOOK
is permitted to evaporate. The evaporation of moist-
ure is determined by the kind of soil, its compactness,
the amount of surface exposed to the rays of light, and
the wind. The greatest difference in temperature
between the different types of soil takes place in the
early spring thawing and the period immediately follow-
ing. This is of utmost importance to farmers especially
at planting time because a small amount of difference
in the temperature of the ground means speeding up or
retarding the rate of germination of the seed and the
growth of the plants. Other things being equal, it
logically follows that the sandy types of soil can be
planted earlier in the year than the clay types.
When' a soil is cultivated a larger area of its surface
is exposed, thus the amount of evaporation is very much
greater. The result of greater evaporation is that the
temperature of the cultivated soil rises much higher and
faster than that of the uncultivated, and permits earlier
planting. This is one of the strongest arguments for
fall plowing and leaving the ground rough. In the
spring of the year the additional exposed surface dries
out much more rapidly and thus permits earlier seeding.
The most interesting part of this process is that as soon
as a dry mulch of this earth is formed on the plowed
soil the loss of water by evaporation is reduced very
much, while the loss on the unplowed soil is still greater.
In the summer this reduces the temperature of the
mulched ground, while that of the unplowed ground is
A further observation is that the heat which is not
utilized in the evaporation of water is being rapidly
conducted downward in the unplowed ground, thus
causing it to dry out at great depth. On the cultivated
SOIL TEMPERATURE 35
or mulched land only a small part of the heat is con-
ducted downward. The other is radiated back to the
atmosphere by the dry ground on top. This is because
the mulch breaks up capillary attraction with the moist
soil below, acting somewhat as a blanket to hold the
moisture down and keep the heat out. When this mulch
becomes completely dry, as it often does, during the hot
summer, it radiates back large amounts of excessive
heat to the atmosphere, thus, we find the effect of this
mulch upon the soil as follows:
It prevents the soil from reaching a high temperature
during the day and a low temperature during the night;
it greatly warms the soil in the spring; it tends to con-
serve moisture in the lower strata and consequently
reduces the rate of cooling in the summer. The im-
portance of this is very manifest when one considers the
temperature necessary for the development of nitric acid.
Soluble nitrates do not form at a temperature below
41 Fahrenheit. The most favorable temperature is
between 60 and 85 Fahrenheit. They form very
slowly at 115 and at 130 will not form. It has been
determined that wheat germinating at a temperature of
40 Fahrenheit is more resistant to cold than wheat
which germinates at 64. Obviously, the temperature
for the greatest formation of nitrates, which are neces-
sary for the development of plant food, is too high for
the successful growing of wheat to withstand the winter's
freezing. This makes it necessary, if the most favorable
condition for wheat is to be brought about, to plow the
ground and keep the seed bed at a temperature of from
60 to 85 Fahrenheit in order that plant food may be
developed for the growing of plants which must be
grown at a cooler temperature.
Why Soils Must Be Handled
THE soil is the farmer's working capital. It is neces-
sary that this capital be used in the wisest possible
manner to earn the profit which justly belongs to him.
Carelessly handling the soil results in a loss just exactly
in the same manner as the mishandling of working
capital results in loss to a manufacturer. The broad
business principle underlying manufacturing and farm-
ing is identical but the tools and working capital of the
two are widely separate and hence must be handled in a
manner peculiar to each before either can achieve
Soil is a combination of disintegrated rocks, dead vege-
tation and many living forms, such as bacteria and
fungi. Broadly speaking, soil may be regarded as
matter in which a planted seed can grow to maturity.
The difference between soil and earth or ground, from a
practical standpoint is so slight that the terms are
When comparing the mode of life of the plant with
that of a human being, the soil around the plant may be
regarded as the dining room in which the plant eats, the
kitchen in which its food is prepared, the storehouse
where the food elements are kept in reserve, a reservoir
for the water and a ventilating system. When one
reflects upon the numerous results this working capital
is supppsed to produce, the more concerned one becomes
as to how it should be treated.
38 THE OLIVER PLOW BOOK
It is plainly evident that all these conditions are
necessary to bring about plant growth. When we
understand that plant growth, in the form of either
legitimate crops or weeds, consumes plant food, or
fertility and the water which is contained in the soil,
we see why it is necessary to replenish the fertility and
change the condition in this ground before new develop-
ment of plant food will take place. Plowing is the only
means known to human endeavor that will successfully
start this process. It is highly important then, that
one should understand the peculiarity of the soil he
desires to plow before he can do this efficiently.
There is scarcely a farm, regardless of how small it
may be, that is made up of less than two distinct soil
compositions. The fact that most farms are made up of
several soils, some of them radically different, means
the necessity for a thorough understanding of the types
because they must be handled in an entirely different
manner to bring about good results.
There are many soil combinations but the most
common are clay, loam, clay loam, sandy loam, loamy
sand, sand and muck. We will go into some detail in
the clay, loam and sandy soils because they are by far
the most common and will serve as illustrations of the
fact that each soil must be tilled according to its kind.
Indeed, there are many types of soils that are never
mentioned in books which have bountifully repaid the
tillage of farmers who studied their characteristics, and
by long, bitter experience learned how to handle them
for crop growing.
Clay is the hardest soil to till on account of the
peculiar effect water and air have upon it. It holds
DIFFERENT HANDLING OF SOILS
This sample of clay and the soils illustrated on pages 41, 43,
45 and 47 were taken from the same farm, comprising 240 acres.
These entirely different soils coming from one farm offer the strongest
evidence that every farmer should thoroughly understand soil composi-
tion. A careful examination will reveal the similarity of the speci-
mens to the land being plowed.
The same peculiarities of the clay soil in this plowed ground obtain in
the specimen above. Finely pulverized earth is not to be seen.
moisture longer than any other kind of soil with the
possible exception of peat; bakes hardest; forms
clods easiest and cracks into deeper fissures, per-
40 THE OLIVER PLOW BOOK
mitting great quantities of moisture to escape.
Clay never works up into a loose, mellow seed
bed, but rather one of clods or fine dust which
blows easily. Cultivated when wet, clay forms into
clods of different sizes, from that of a walnut to as
large as a person's head, depending upon the kind and
amount of cultivation. The grain is fine and has a
peculiarity not discernible in any other type of soil.
Moist clay is soft and sticky. It can be kneaded and
formed into various shapes and bodies. Small boys,
unable to buy marbles, use clay very successfully for
making them. A small piece of clay can be easily
smoothed and polished by the fingernail. While polish-
ing a greasy or soapy feeling will be noted. Moist clay,
when rubbed between the thumb and finger, has a slip-
pery feeling. Persons walking on a sloping bank of
wet clay are apt to have their feet slide out from under
them very suddenly. Clay in a powdered condition
when moistened, has a peculiar odor unlike anything
else. Clay in color may be red, yellow, blue, white,
black or chocolate.
For the most part clay soils when plowed too dry,
form large clods which are decidedly hard to break into
pulverized condition. If such soil lacks humus in
sufficient quantities to keep it friable, it nearly always