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The Farm That Won't Wear Out
By Cyril G. Hopkins
Preface
THE FARM THAT WON'T WEAR OUT
WAS FIRST published serially in THE COUNTRY GENTLEMAN, the privilege
having been granted the author of subsequent publication. It is now
issued in book form in response to numerous requests coming
especially from the Central, Eastern, and Southern States.
CYRIL G. HOPKINS.
CHAMPAIGN, ILL.
_"Population must increase rapidly, more rapidly than in former
times, and ere long the most valuable of all arts will be the art of
deriving a comfortable subsistence from the smallest area of
soil."--Lincoln._
_"It is not the land itself that constitutes the farmer's wealth,
but it is in the constituents of the soil, which serve for the
nutrition of plants, that this wealth truly consists."--Liebig._
CONTENTS
CHAPTER I: What Goes To Make Up Permanent Fertility
CHAPTER II: The Nitrogen Problem And Its Economical Solution
CHAPTER III: Phosphorus: The Master Key To Permanent Agriculture
CHAPTER IV: Permanent Soil Fertility: Its Relation to Profits and
Future Values
CHAPTER I
WHAT GOES TO MAKE UP PERMANENT FERTILITY
IT IS an old saying that "any fool can farm," and this was almost
the truth when farming consisted chiefly in reducing the fertility
of new, rich land secured at practically no cost from a generous
Government. But to restore depleted soils to high productive power
in economic systems is no fool's job, for it requires mental as well
as muscular energy; and no apologies should be expected from those
who necessarily make use of technical terms in the discussion of
this technical subject, notwithstanding the common foolish advice
that farmers should be given a sort of "parrot" instruction in
almost baby language instead of established facts and principles in
definite and permanent scientific terms. The farmer should be as
familiar with the names of the ten essential elements of plant food
as he is with the names of his ten nearest neighbors. Safe and
permanent systems of soil improvement and preservation may come with
intelligence--never with ignorance--on the part of the landowners.
When the knowledge becomes general that food for plants is just as
necessary as food for animals, then American agriculture will mean
more than merely working the land for all that's in it. This
knowledge is as well established as the fact that the earth is
round, although the people are relatively few who understand or make
intelligent application of the existing information.
Agricultural plants consist of ten elements, known as the essential
elements of plant food; and not a kernel of corn or a grain of
wheat, not a leaf of clover or a spear of grass can be produced if
the plant fails to secure any one of these ten elements. Some of
these are supplied to plants in abundance by natural processes;
others are not so provided and must be supplied by the farmer, or
his land becomes impoverished and unproductive.
Foods That Plants Live On
Two elements, carbon and oxygen, are contained in normal air in the
form of a gas called carbon dioxid, and this compound is taken into
the plant through the breathing pores, which are microscopic
openings located chiefly on the under side of the leaves. Some
plants have more than a hundred thousand breathing pores to the
square inch of leaf surface.
When plants or plant products are burned or decomposed the carbon of
the combustible material--grass, wood, coal, and so forth--unites
with the free oxygen of the atmosphere to re-form the carbon dioxid,
which thus returns as a gas to the air. Even the food taken into the
animal system, after being digested and carried into the blood, is
brought, into contact with the oxygen of the air--which also passes
into the blood through the cell walls of the lungs--and a form of
combustion takes place, the heat generated serving to warm the body
while the carbon dioxid passes back into the lungs and is exhaled
into the open air.
By these circulation processes the supply of carbon dioxid in the
atmosphere is renewed and maintained without any special effort on
the part of man. Hydrogen is one of the elements of which water is
composed. Water is taken into the plant through the roots, carried
through the stems to the leaves, and there, under the influence of
chlorophyll, sunlight and the life principle, the carbon, oxygen and
hydrogen are made to unite into some of the most important plant
compounds, such as the sugars, which are later transformed into
starch and fiber.
Though these three elements constitute the larger part of the mature
agricultural plant they are no more necessary for plant growth than
the seven which are supplied by the soil. Iron is one of the
essential elements of plant food; but the amount required by plants
is so small and the amount contained in the soil is so large that
soils have never been known to become deficient in iron. Though
sulfur is found in plants in very appreciable amounts and is known
to be essential to plant growth, it is evident that plants do not
need so much sulfur as they often contain, some of it being taken up
and merely tolerated, as is the case with all of the sodium and
silicon found in plants, neither of these being required for normal
growth, although commonly found in plants in very considerable
amounts. The supply of sulfur in normal soils is not large; but,
with the combustion and decay of organic materials--coal, wood,
grass, leaves, and so forth--sulfur passes into the air and is
brought back to the soil dissolved in rain or absorbed by direct
contact of soil and air. Thus under normal conditions the supply of
sulfur naturally provided is ample to meet the needs of the staple
farm crops, although there are some plants, such as cabbage, for
example, which may possibly be benefited by fertilizing with sulfur.
But there are five other essential elements of plant food, and these
require special consideration in connection with permanent soil
fertility. They are potassium, magnesium, calcium, phosphorus and
nitrogen. There are also five important points to be kept in mind in
relation to each of these elements: (1) the soil's supply, (2) the
crop requirements, (3) the loss by leaching, (4) the methods of
liberation, and (5) the means of renewal.
The neglect of one or more of these important points in relation to
one or more of these five elements has reduced the fertility of most
cultivated soils in the United States, has greatly impoverished the
older farm lands, and has brought agricultural abandonment to
millions of acres in the original thirteen states. On the other
hand, intelligent attention to these same factors will bring
restoration and high productive power to such lands.
England's Best Lesson in Farming
Where these five elements were supplied regularly to land on the
Rothamsted Experiment Station the average yield of wheat for the
thirty years, 1852 to 1881, was 35.9 bushels an acre, while 13.6 was
the average yield of similar unfertilized land; and during the next
thirty years--1882 to 1911--the corresponding average yields were 38
bushels an acre on the fertilized land, and 11.7 bushels where no
plant food was applied. These statements are not mere opinions, but
determined facts whose accuracy stands unquestioned.
On another field at Rothamsted, England, the average yield of barley
for the same sixty years was 43 bushels an acre where nitrogen,
phosphorus and calcium were regularly applied, 42.6 where all five
elements--including potassium and magnesium--were added, but only
14.3 on unfertilized land.
On still another Rothamsted experiment field, where a four-year crop
rotation of turnips, barley, clover (or beans) and wheat has been
practiced since 1848, the yield of turnips in 1908 was 717 pounds an
acre on unfertilized land and 35,168 pounds where the five important
elements of plant food had been regularly applied once every four
years--for the turnips only--since 1848. In 1909 the barley yielded
33.4 bushels an acre on the fertilized land, but only 10 bushels
where no plant food was applied. The yield of clover in 1910 was
8590 pounds an acre on the land fertilized for turnips, but only
1949 on the unfertilized land. The wheat following the clover with
no other fertilizer produced 24.5 bushels an acre in 1911, but 38
bushels where plant food is always applied for turnips grown three
years before.
These are the established facts from the longest accurate record,
and thus the most trustworthy data the world affords; and when one
hears promulgated the very pleasing doctrine that the rotation of
crops will maintain the fertility of the soil it is time to remember
that "to err is human."
Fertility in Normal Soils
Of the four important mineral elements, potassium is by far the most
abundant in common soils. Thus, as an average of ten residual soils
from ten different geological formations in the eastern part of
United States, two million pounds of subsurface soil were found to
contain:
Potassium 37,860 pounds
Magnesium 14,080 pounds
Calcium 7,810 pounds
Phosphorus 1,100 pounds
Even the depleted, and to some extent abandoned, gently undulating
upland "Leonardtown loam," which was farmed for generations and
which, according to the surveys of the Federal Bureau of Soils,
covers 41 per cent of St. Mary's County, Maryland, and more than
45,000 acres of Prince George's County--still contains in two
million pounds of surface soil--corresponding to the plowed soil of
an acre about 6-2/3 inches deep:
Potassium 18,500 pounds
Magnesium 3,480 pounds
Calcium 1,000 pounds
Phosphorus 160 pounds
The brown silt loam prairie soil of the early Wisconsin glaciation
is the most common type of the greatest soil area in the Illinois
Corn Belt. Two million pounds of this surface soil contain as an
average:
Potassium 36,250 pounds
Magnesium 8,790 pounds
Calcium 11,450 pounds
Phosphorus 1,190 pounds
The older gray silt loam prairie, the most extensive soil of
Southern Illinois, contains in two million pounds of soil:
Potassium 24,940 pounds
Magnesium 4,690 pounds
Calcium 3,420 pounds
Phosphorus 840 pounds
These data represent averages involving hundreds of soil analyses,
and they emphasize the fact that normal soils are rich in potassium
and poor in phosphorus. This is to be expected, for most soils are
made from the earth's crust, and normal soils should bear some
relation in composition to the average of the earth's crust, which
contains in two million pounds 49,200 pounds of potassium and 2,200
pounds of phosphorus, as shown by the weighted averages of analyses
involving about two thousand samples of representative rocks,
reported by the United States Geological Survey.
Measuring Fertility Losses
The plant food required for one acre of wheat yielding 50 bushels,
one acre each of corn and oats yielding 100 bushels, and one acre of
clover yielding four tons, includes for the total crops:
Potassium 320 pounds
Magnesium 68 pounds
Calcium 168 pounds
Phosphorus 77 pounds
If only the grain, including a yield of 4 bushels an acre of clover
seed, is considered, the straw, stalks and hay being returned to the
soil--either directly or in farm fertilizer--then the loss per acre
from four years of cropping as above would be as follows:
Potassium 51 pounds
Magnesium 16 pounds
Calcium 5 pounds
Phosphorus 42 pounds
The average annual loss by leaching from good soils in humid
sections is known by the results of many analyses to be about as
follows per acre:
Potassium 10 pounds
Calcium 300 pounds
Phosphorus 2 pounds
The average annual loss of magnesium in drainage water from good
soils is probably 30 pounds or more an acre, but the data thus far
secured are inconclusive with respect to that element.
A careful consideration of the trustworthy data clearly reveals the
fact that potassium is very abundant in normal soils, while
phosphorus is relatively very deficient; and, all things considered,
calcium--and probably magnesium--is of much greater significance
than potassium, from the standpoint of the maintenance of usable
plant food in the soil. It should be noted, too, that certain crops
which are exceedingly important for economic systems of permanent
agriculture require very large amounts of calcium as plant food.
Thus a four-ton crop of clover hay takes about 120 pounds of calcium
from the soil, or the same amount as of potassium; while such a crop
of alfalfa requires about 145 pounds of calcium, but only 96 pounds
of potassium. When it is known that the abandoned "Leonardtown loam"
still contains in two million pounds of surface soil 18,500 pounds
of potassium and only 1000 pounds of total calcium, the significance
of these chemical and mathematical data must be apparent.
The Liberation of Fertility
Probably there has never been a greater waste of time and effort in
the name of science than in the endeavor to determine the
"available" plant food in soils. The almost universal assumption has
been that the plant food in the soil exists in two distinct
conditions, "available" and "unavailable," and that the
determination of the "available" plant food would reveal both the
crop-producing power of the soil and the fundamental fertilizer
requirements for the improvement of the soil for crop production.
After ascertaining the total stock of plant food in the plowed soil,
the next important question is not how much is "available," but
rather how much can be made available during the crop season, year
after year. In other words we must make plant food available by
practical methods of liberation, by converting it from insoluble
compounds into soluble and usable forms; for plant food must be in
solution before the plant can take it from the soil. For the
present, space is taken only to emphasize the value of decaying
organic manures in the important matter of making plant food
available; and attention is also called to the fact that the
decomposition of the organic matter of the soil--including both
fresh materials and old humus--is hastened by tillage and by
underdrainage, which permit the oxygen of the air to enter the soil
more freely, oxygen being a most active agent in nitrification and
other decomposition processes of organic matter, as well as in the
more common combustion of wood, coal, and so forth.
The Renewal of Fertility
In rational systems of general farming the supply of any element
which is normally very abundant may be renewed from the subsoil by
even the very slight erosion which occurs on all ordinary lands in
humid sections. This statement applies to iron and potassium, and
often to magnesium.
If two million pounds of normal surface soil contain 30,000 pounds
of potassium, one inch an acre would contain 4500 pounds of that
element; and if a third of this--1500 pounds--were removed by
cropping and leaching before its removal by surface washing, then
two-thirds of a century could be allowed for the erosion of one inch
of soil, with crop yields of 50 bushels of wheat, 100 bushels of
corn and oats, and 4 bushels of clover seed to the acre, provided
the stalks, straw and clover hay were returned to the land, either
directly or in farm manure. This amount of surface washing is likely
to occur on land sufficiently undulating for good surface drainage,
provided the land is plowed and cultivated as frequently as would be
required for a four-year rotation as suggested above. Where hay,
straw, potatoes, root crops or common market garden crops are sold,
very much larger amounts of potassium leave the farm than in grain
farming or live-stock farming, and in such cases potassium must
ultimately be purchased and returned to the soil, either in
commercial form or in animal manures from the cities.
Thirty Bushels for Potassium
There are some soils, however, which are not normal--soils whose
composition bears no sort of relation to the average of the earth's
crust; such, for example, as peaty swamp soil or bog lands, which
consist largely of partly decayed moss and swamp grasses. These
soils are exceedingly poor in potassium, and they are markedly and
very profitably improved by potassium fertilizers, such as potassium
sulphate and potassium chloride--commonly but erroneously called
"muriate" of potash.
Thus, as an average of triplicate tests each year, the addition of
potassium to such land on the University of Illinois experiment
field near Manito, Mason county, increased the yield by 20.7 bushels
more corn to the acre in 1902, by 23.5 in 1903, by 29 in 1904 and by
36.8 in 1905; and the proceedings of the midsummer session of the
Illinois State Farmers' Institute for 1911 report that the use of
$22,500 in potassium salts on the peaty swamp lands in the
neighborhood of Tampico, Whiteside county, increased the value of
the corn crop in 1910 by $210,000, the average increase for
potassium being about 30 bushels of corn to the acre.
Some sand soils, particularly residual sands, which often consist
largely of quartz-silicon dioxid--are very deficient in potassium;
consequently the experiments or demonstrations conducted by the
potash syndicate at Southern Pines, North Carolina, show very marked
increases from the use of potassium salts on such soil, although the
result ought not to be used to encourage the use of such fertilizers
on normal soils, which are exceedingly rich in potassium.
Even in soils abundantly supplied with potassium temporary use may
well be made of soluble potassium salts when no adequate supply of
decaying organic matter can be provided. For this purpose,
kainit--which contains potassium and also magnesium and sodium in
chlorides and sulfates--is preferred to the more concentrated and
more expensive potassium salts. About 600 pounds an acre every four
years is a good application. The kainit will not only furnish
soluble potassium and magnesium but will also help to dissolve and
thus make available other mineral plant food naturally present or
supplied, such as natural phosphates. When the supply of organic
matter produced in crops and returned either in farm manure or in
crop residues becomes sufficiently abundant, then the addition of
kainit may be discontinued on normal soil.
Thus, as an average of 112 separate tests covering four different
years, on the Southern Illinois experiment field on worn, thin land,
at Fairfield, the use of 600 pounds an acre of kainit once in four
years increased the yield of corn by 10.7 bushels where no organic
manure was used, and by only 1.7 bushels when applied with eight
tons of farm manure.
Liming the Soil
In the form of ashes, marl or chalk, lime has been used as a
fertilizer for thousands of years. It serves two very important
purposes: to correct the acidity of sour soils and to supply calcium
and sometimes magnesium as plant food. Burned lime has also been
much used, but in more recent years the development of machinery for
crushing and pulverizing rock--especially in cement manufacture--has
made possible the production of pulverized natural limestone, and at
much less expense than for caustic lime made by burning and slaking.
Where ground limestone can be easily procured it takes the place of
burned lime, and it produces better results at less expense, even
though 1-3/4 tons of ground limestone are required to equal 1 ton of
quicklime in calcium content and in power to correct acidity.
Furthermore, ground limestone can be applied in any amount with no
injurious results, while caustic lime destroys the organic matter or
humus of the soil, dissipates soil nitrogen, is disagreeable to
handle, and may injure the crop unless applied in limited amounts or
several months before the crop is to be planted.
The most valuable and trustworthy investigation on record in regard
to the comparative value of burned lime and ground limestone has
been conducted by the Pennsylvania Experiment Station. A four-year
rotation of crops was practiced, including corn, oats, wheat and hay
(clover and timothy) on four different fields, each crop being
represented every year. After twenty years the results for the four
acres showed that the land treated with ground limestone had
produced 99 bushels more corn, 116 bushels more oats, 13 bushels
more wheat and 5.6 tons more hay than the land treated with about an
equivalent amount of burned lime. At the end of sixteen years the
analysis of the soil showed that the burned lime had destroyed 4.7
tons of humus and had dissipated 375 pounds of nitrogen to the acre,
as compared with the ground limestone, this loss being equivalent to
37-1/2 tons of farm manure.
Other trustworthy experiments by the Maryland and Ohio Experiment
Stations confirm the Pennsylvania results in showing better crop
yields when unburned lime carbonate was used; and more extensive
experiments by the Tennessee Experiment Station also agree with the
Pennsylvania data in regard to the destruction of organic matter and
loss of soil nitrogen from the use of burned lime. If dolomitic
limestone is used, magnesium as well as calcium is thus added to
the soil.
Limestone need not be very finely pulverized. If ground so that it
will pass through a ten-mesh sieve it is amply fine, assuming that
the entire product is used, including the finer dust produced in
grinding, and it is very possible that final investigations will
show that the entire product from a quarter-inch screen is even more
economical and profitable in permanent systems.
Limestone is quite easily soluble in soil water carrying carbonic
acid. It is thus readily available; in fact, it is too available to
be durable if very finely ground; and in humid sections the loss by
leaching far exceeds that removed by cropping. In practical economic
systems of farming about two tons an acre of ground limestone should
be applied every four years, or corresponding amounts for other
rotation periods.
The essential facts relating to potassium, magnesium and calcium and
to the use and value of different forms of lime have been stated
above, and they may be accepted with confidence for use in economic
systems of farming on normal soils.