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  • From: "TradingPostPaul" <tradingpost@riseup.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] The Soul Of Soil - facts about soil taken from a textbook published in 1909
  • Date: Wed, 21 Mar 2007 11:26:31 -0700


The Soul Of Soil
http://www.countrysidemag.com/issues/5_1999.htm#soil

Growing good crops that will bring health to man and beast requires fertile
soil. This does not mean chemicals from a bag, especially when spread
without understanding

There are two ways to farm or garden: You can rely on technology and
buy a bag of fertilizer and spread it on your land and hope for the best -
or you can learn what soils and plants really are and how they function.
The first is certainly the easiest, but the second is part of The Simple
Life, and by far the best. (And incidentally, if we're living in the
Information Age, just what is it that we supposedly know so much about, and
how important is it?)

Some people like to point out that the sum total of human knowledge is
now doubling every 18 months. This "information explosion" suggests that we
know far more than our grandparents, and their grandparents.

Yet, what do we "know" about even the most basic, the most important
elements of the world we live in. . . such as the soil that feeds us?
Probably much less than our ancestors!

Most people who rely on supermarkets and restaurants for their food
regard soil as dirt. . . something filthy, to be avoided, and certainly of
no great importance. To them, it's all the same, and it doesn't matter.

But if you grow your own food you are very aware that all soil is not
the same, and it certainly does matter, even to those who have no personal
contact with it beyond the food they purchase.

And that lack of knowledge - basic, life-giving essential knowledge -
allows the modern sophisticate to ignore the source of food and its
production techniques. Much worse, that ignorance allows the technological
and industrial society to make poor decisions regarding everything from
land use in housing and commercial developments, to policies regarding
agriculture, to the choice of foods that keep them alive.

Here are some facts about soil taken from a textbook published in 1909.
These facts were common knowledge 90 years ago, but have been overshadowed
by and largely forgotten during the "Green Revolution" and information
explosion.

Some people will say this is old and outdated information, and we
should concentrate instead on all the wonderful new scientific advances and
the latest data - such as gene splicing and cloning and terminator
technology.

I say it's time, and past time, that we take another look at the basics
so we can use, or reject, the modern science with not only knowledge but
with wisdom.

This is an edited and abridged chapter from a high school textbook,
Elements of Agriculture, by G. F. Warren. - Jd
--------------------------

Most people see soil as "dirt." They almost invariably think of it as a
dead thing. But in reality, soil is teeming with life, and it's full of
activities of the most complex and interesting kinds.

The almost universal idea is that soil consists of small particles of rock
that have been made fine by the process of weathering. But no crop could
grow on a soil composed entirely of rock particles. An agricultural soil
also needs soil water, soil air, decaying organic matter, and living
organisms in order to be productive. (Organic matter is defined as any
material that is, or once was, an organism or living thing, such as wood,
straw, manure, etc.)

Rock particles

Rock particles are 65 to 95 percent of the weight in most soils. (One
exception is muck soils, where nearly all the solid matter is made up of
organic materials. These are some of the most fertile soils on the planet.)
Organic matter usually constitutes 2 to 5 percent. (This was in 1909: many
farm soils today are much lower.) Most of the remaining weight is water.
The mineral matter furnishes the solid food, and acts as a reservoir for
holding the water. Both functions are dependent on the size of the soil
particles, which in turn has much to do with the value of the land. (This,
of course, is in reference to food production. Today, much real estate is
evaluated by location, location, and location, regardless of its food
production capabilities, meaning that even prime farmland is often
destroyed when someone can make more money by using it for a housing or
commercial development.)

If a soil is thoroughly shaken up with water and then allowed to settle for
a few minutes, the larger particles will be separated out. The riley water
can then be poured off and allowed to settle for a longer period, and the
next larger particles will have settled to the bottom. If the riley water
is again poured off, the soil is separated into three sizes of particles.
Any number of divisions can be made in this manner.

(That knowledge was exploding beyond the needs, and perhaps even the
understanding, of the common man, even in 1909, is demonstrated by this
footnote: "The common method of making the separation is to put the samples
of soil in bottles of water, and shake for a day in a shaking machine. This
separates the particles that are stuck together. A centrifugal machine is
used to aid in making the separations, as it is more rapid than waiting for
the particles to settle. The material is usually separated into three
grades by means of water. The sands are further separated by means of
sieves.")

The finest soil particles are called clay, the next smallest silt. The
larger particles are different grades of sand and gravel. The following
table shows the mechanical analyses of three important soil types as
separated by the Bureau of Soils:

The Norfolk sand is one of theeading truck soils of the Atlantic coast. A
large part of the vegetables for eastern cities are grown on this soil. The
Miami silt loam is one of the leading types of soil in the corn belt of the
Central West. The Wabash clay occurs along many river bottoms. It is used
for corn, oats, cotton and hay.

The mineral components of a soil are of course dependent upon the type and
origin of the rock it was derived from.

How soils are named

The soils that contain a large proportion of the finest particles are
called clay. At the other extreme we have sands and gravels. Soils that are
intermediate in texture are called loams. Those with a large proportion of
silt particles and not too much clay are called silt-loams.

Then these words are joined together to describe intermediate types. There
are gravelly loams, sandy loams, fine sandy loams, clay loams, etc.

Since many soils as thus named are very different in other respects, the
Bureau of Soils prefixes another name to distinguish them. These are
usually names of towns near which the soils were first mapped. (Today,
Miami silt loam might make one think of Florida; think Ohio instead.)

Local names used in any community are often misleading. In a region where
nearly all the soils are sandy, a loam soil is usually called a clay; while
in regions where most of the soils are heavy clays the same loam is likely
to be called sandy.

Soils are also named in many other ways. Glacial soils are those formed as
a result of glaciation. Arid soils are those that do not receive enough
rain to produce regular crops without irrigation. Humid soils are those
that receive sufficient rainfall to produce crops.

The importance of the size of soil particles

The size of the soil particles influences the water-holding power of the
soil, the amount of food that can be dissolved for plant use, the ease of
movement of water and air, the growth of organisms in the soil, and the
crop-producing power.

The rock particles of the soil can hold water on their surfaces only.
Therefore the water-holding power of the soil increases when the surface
area of the particles is decreased.

Dip a pebble in water and a film of water will remain on it when it is
removed. Wipe the pebble and the water will be gone, because no water has
soaked into it. If such a pebble is broken in two it will have more surface
area. The finer the material is broken, the more surface there will be, and
the more water it will hold.

The finest soil particles are extremely small - less than four
hundred-thousandths of an inch in diameter. The total surface area in a
cubic foot of such material would be very great. Such fine particles do not
always act as individuals in holding water: some of the particles usually
stick together.

A cubic foot of soil grains having a diameter of one-thousandth of an inch
(coarse silt) would have a surface area of 37,700 square feet. A column of
such soil one foot square and four feet deep would have a water-holding
surface of not less than 3.4 acres.

The water capacity of a soil is the amount of water it will hold when all
the free water is allowed to drain out. Some clay soils will retain about
40 percent of water. That is, 100 pounds of soil may retain 40 pounds of
water. A cubic foot of clay weighs about 80 pounds and could, therefore,
hold about 32 pounds of water. Sandy soils might have a water capacity as
low as five percent.

Which one would you rather garden in? The answer might not be as apparent
as it seems.

Plants cannot remove all the water from a soil. They die for lack of water
long before the soil is absolutely dry. They can use a larger proportion of
the water from a sandy soil than from a clay. In one study, in a sandy soil
with a capacity of 18 percent, corn was able to reduce the water to 4.17
percent. In a clay soil whose capacity was 26 percent, corn used the water
down to 11.79 percent. In this case, the sandy soil actually furnished more
water for the growth of the corn than had the clay.

Water

The rock particles are very slowly soluble. Soil water can act on the
surface of the particles only. Since smaller particles have more surface
area for a given volume of soil, they are able to furnish plant food more
rapidly. Finer soils are usually more fertile, but are less easily managed.

Air

About half the volume of a dry soil is air; that is, a cubic foot of such
soil contains about half a cubic foot of air. The small particles of which
a clay soil is composed do not pack so closely as do the larger sand
particles, because they are lighter. Therefore, there is more pore space in
clay than in sand.

But the spaces in a sandy soil are larger, so the air moves more freely,
making such a soil better aerated.

Temperature

The temperature of a soil is influenced by its color, topography, humus
content, and several other factors. But the chief factor is water capacity.

It requires about 20 heat units to raise the temperature of 100 pounds of
dry soil 1 degree F. To raise the temperature of the same weight of water 1
degree requires 100 heat units. This is why gardeners often speak of "wet"
and "cold" soils in the same breath.

But the effect of water is most striking when it evaporates. To evaporate
100 pounds of water requires 966.6 heat units. This explains why wet soils
are always cold soils. Clay soils are cold chiefly because of the large
amount of water that evaporates from them.

Few crops begin growth until the soil is 45-50 degrees. The best growth
usually doesn't take place until the soil is 70 degrees. It's easy to see
why gardeners want sandy soils for early truck crops.

However. . . another caution. No single soil is "best" for all crops. One
early soils researcher (Whitney) gives the following as the number of soil
particles per gram of soil adapted to different crops:

* Early truck 1,955,000,000
* Truck and small fruit 3,955,000,000
* Tobacco 6,786,000,000
* Wheat 10,228,000,000
* Grass and wheat 14,735,000,000

Warren said, "No person can comprehend such figures as these, but the
comparison is the valuable point. The table shows how much coarser the
truck soils are than the wheat soils."

But even if the clay soils would produce good truck (garden) crops, they
have another drawback: they are difficult to work. Vegetables already
require more labor than crops such as hay or wheat, and using soils that
are hard to work only adds to the labor cost.

Sandy and other well-drained soils are not only easier to till, but the
number of days on which they can be worked is much greater. They can be
tilled earlier in the spring, and more quickly after rains.

Flocculation

When a silt or clay soil is in good condition, many of the particles are
united into compound particles. Such a soil is "flocculated." Good
management of such a soil consists very largely in maintaining this
granulated condition. If such a soil is worked while wet, and if it then
dries, it will be greatly injured, sometimes so much as to damage the crop
for several years. Working a clay soil when wet makes "bricks" of it. The
crust that forms on the surface of a soil after it rains is due to this
breaking down of compound particles.

This became a more serious problem when farmers started using bigger and
bigger equipment, and worked more and more land. . . and forgot (or never
learned) what their forefathers knew about soil. With so much area to work,
waiting until the soil was ready was more often neglected, and if a
powerful tractor could work even wet soil, this was considered progress.
But such progress has ruined many soils.

If such a soil is too finely pulverized - which often happens when eager
but uninformed gardeners think they're "improving" their soil by getting
out the rototiller every time they see a weed - it "runs together" and
bakes because the granules have been broken up.

The relative fineness of the soil is called its texture, just as the word
is used when speaking of the texture of cloth. If the soil is composed of
very small particles that are flocculated, it can still be of a coarse
texture.

Structure refers to the arrangement of soil particles. If small particles
are united, it is possible to have a soil of fine texture and coarse
structure.

Soil water

In an agricultural sense, Warren wrote in 1909, the most important use of
soil is to act as a storehouse for water. The productiveness of soil is
limited by the amount of water that the soil can hold, and by the extent to
which growing crops are able to remove the water. The soil water is
important not only because it is the chief plant food, but because it acts
as a carrier of all the other plant foods that come from the soil.

Soil water is very different from rain water. It contains all the plant
foods in solution. The solution is very dilute, but plants use a large
amount of it.

The chief ways water exists in the soil are as film water and free water.
The particles can hold a certain amount of water on their surfaces, just as
one's hand remains wet when removed from water. Only a limited amount can
be held in this way. If too much water is present, it will drop off.

If more water is present in the soil than can be held as film moisture, it
will fill the pore spaces between the particles. If there is an outlet,
this free water will drain away and leave the film or capillary water.

Free water moves downward by gravity. Capillary water can move in any
direction, because the force of adhesion between the soil particles and the
water is strong enough to lift the water, just as oil is lifted in a lamp
wick.

After a heavy rain the soil may be filled with water. Gradually the free
water drains away and leaves capillary water only. The surface soil loses
some of the water by evaporation. This leaves it drier than the soil below.
Some of the water of the lower layer is then drawn up by capillary action.
In this way water may be removed from the soil very rapidly, particularly
when the weather is dry, warm and windy.

Water also evaporates within the soil, into the soil air. There is a
constant movement of this air in and out of the soil, and this aids in
drying a soil.

If there is not an abundance of rainfall, it is desirable to stop this
movement of water to the surface where it evaporates. Any loose mulch, like
straw, on the surface of the soil will accomplish this purpose. Capillary
water moves very slowly through dry soil, so one of the best methods for
preventing evaporation is to form a dust mulch on the surface. When
possible, the soil should be cultivated after every rain as soon as it is
in the proper condition for working. This cultivation will break up the
crust, break the capillary connection, and prevent much of the evaporation.
At the same time, it leaves the soil in a loose condition, ready to absorb
the next rain.

(Note, however, that this means shallow cultivation, not deep digging with
a rototiller.)

When seeds are planted it is often desirable to increase evaporation, so
that the seeds, which are near the surface, will be kept moist by the water
as it rises. This is the reason for packing seeds. Corn planters pack over
the rows of seed only. Rollers are often used to pack new plantings of
grasses and small grains such as oats and wheat. In the garden, the same
effect can be achieved by patting down the soil over the seeds with the
hand, or by placing a board over a row of seeds and standing on it.
Lightly. We're not talking about stomping down the rows, causing
compaction.

Amount of water

Too much water is as bad as too little. Optimum water content is 50 to 60
percent of the soil's capacity. In many areas the soil is saturated with
water during the early part of the growing season, and too dry later on,
injuring the crop at both extremes. However, a good soil, rich in humus,
modifies both extremes.

The most serious result of too much water in the soil is the exclusion of
air, which is essential for plant growth and for the activities of soil
organisms. It also prevents roots from growing deeply into the soil, makes
the soil cold, and delays farm or garden work. When the work cannot be done
at the proper time, weeds are more likely to gain a foothold. Wet land is
nearly always weedy land.

One of the first effects of too-wet soil is yellowing of leaves. This is
due to the lack of nitrogen. The fixation of atmospheric nitrogen ceases
when air is excluded from the soil by an overabundance of water. When air
is excluded from the soil, beneficial soil organisms become inactive. It is
from the air in the soil that these organisms and leguminous plants secure
free nitrogen for the use of crops. Not only does the fixation of nitrogen
cease when air is excluded from the soil, but under these conditions the
organisms that break down nitrogen compounds are very active, so that the
nitrogen that was fixed previously is being lost.

For optimum plant productivity, we want just the right balance of air and
water in the soil.

Organic matter

All productive soils contain decaying roots, leaves and animal life. This
partly decayed organic matter is called humus. It is humus that gives soils
their dark color.

Humus has many functions. It increases the water-holding power of soils,
which is particularly important on sandy land. It loosens heavy soil and
promotes aeration, which are of special importance on clay soils. It
furnishes food for bacteria. These, acting on the humus, change nitrogen to
nitric acid so that it is ready for plant food.

As humus decays, it also liberates carbon dioxide. This acts on the
minerals of the soil, making them soluble and ready for plant use.

Another extremely important function of humus is that it encourages the
growth of bacteria that fix free nitrogen from the soil air, making it
available as plant food.

The more air in the soil, the more rapidly the humus is decomposed. If a
soil is saturated with water, the oxidation practically stops and organic
matter accumulates. This is the way that peat and muck are formed. For crop
production, a moderate rate of decomposition is preferred. If too rapid,
the supply is exhausted; if too slow, the plant does not receive enough
food.

Life in the soil

As we have seen, soil is not a dead thing. It is much more than a
collection of rock particles. It is teeming with life. If all the living
things in the soil should die, the soil would soon fail to produce crops.

(Note: This "common knowledge" of a century ago was debunked by the
so-called Green Revolution, which held that the only function of soil was
to hold the plant roots while they were being fed artificial fertilizers.
Organic farmers never lost, or in some cases rediscovered, the old
knowledge. But today, even some high-tech agriculturists have sorted out
the information overload and are returning to the old wisdom.)

The 1909 high school students who studied Elements of Agriculture learned
pretty much what today's so-called "conventional" farmers who are turning
towards organic or sustainable farming are learning only now.

Keeping the soil productive, Warren wrote almost a century ago, is very
largely a matter of keeping these organisms thrifty. The roots and stems of
plants furnish food for bacteria and molds. The waste products furnish food
for other bacteria. Eventually, the food is in a form available for crops
to use again. Any break in the link will affect all of the chain. If the
organisms do not decompose the roots and stems properly, the new crops will
suffer. If there is not enough humus in the soil, the bacteria suffer and
the crops are immediately affected.

Earthworms serve a useful purpose in the soil by helping to break down the
organic matter. They also do much good by making the soil porous. A soil
that is full of earthworms is nearly always fertile.

The molds help in breaking down the organic matter, particularly the woody
matter. But the most important forms of life in the soil are the
microscopic organisms, yeasts and bacteria.

Soil bacteria

On an average, it takes about 25,000 bacteria placed end to end to measure
one inch. Of the very smallest ones, it takes about 150,000 to measure an
inch.

The small size of the bacteria is more than made up by their immense
numbers and by the rapidity with which they multiply. They reproduce by
simple division: one individual divides into two. Under favorable
conditions this can take place every 15-30 minutes. If each one divides
into two every quarter of an hour, there will be an immense number of them
at the end of a day, even if there was only one in the morning.

Warren noted that the limit of food supply and other conditions prevent
this rapid multiplication from continuing. He could not have foreseen his
students, and much more so their sons, not only adopting farming methods
that would knowingly limit that food supply, but also killing those
microorganisms by the application of chemical fertilizers and pesticides!

He continued by saying that bacteria are present in all soils, ranging from
less than 28,000,000 per ounce of soil (and far fewer than that in many
soils today) to many times that number. In fertile soils like gardens there
are many billions per ounce. There is usually a relationship between the
number and kinds of soil bacteria and fertility.

Bacteria may seem to be too small to be of much consequence, but they are
far from unimportant. We know how many contagious diseases are caused by
bacteria, so we must recognize their power. But while certain ones cause
disease, others are useful to us.

Bacteria are microscopic plants. We should look on them as we do other
plants. Some plants, such as corn and cotton, are useful. Others, like
poison ivy, are to be avoided.

We could not live were it not for the activities of the useful bacteria and
yeast plants.

A turn-of-the-century New Jersey Agricultural Bulletin put it this way:

"The different chemical changes produced by soil bacteria are quite
numerous. Some kinds are specialized for one series of changes, others for
changes of a different sort. Some will attack by preference carbohydrates
like starch or sugar, some will decompose woody tissue, some will cause the
decay of proteins, some of fats, etc. This division of labor allows an
effective decomposition of humus. Various gases and acids are produced in
the course of decay, and help to decompose the rock particles in the soil
and to render the mineral plant food contained in them available. The
insoluble protein compounds in the roots and stubble are broken down and
their nitrogen changed partly to ammonia. The particles of ammonia, as they
are thus generated by bacteria of many kinds, are at once pounced upon by a
special class of germs whose function it is to change the ammonia into
nitrate. Thanks, therefore, to the activities of many species of bacteria,
the nitrogen locked up in the humus and green manure is transformed
gradually into nitrate, and is then quite suitable for the building of
roots, stems, leaves and fruit."

If we accept all of this, and prefer it to the modern high-tech chemical
company ag college explanations and solutions, the next question is, how
can we maintain the fertility of the land? People who think they have so
much more information than these primitives of a hundred years ago will
simply buy a bag of fertilizer - probably without even knowing how to read
the label - and scatter it around without the foggiest notion of what
they're doing, and consider themselves progressive and educated. But what
can those of us who think do to improve our soils, and our world?

We can start by going back even further, and seeing how soils were formed.

How soils become productive

It has required untold ages for the soils of the world to be formed and to
become productive. At first the particles of rock were capable of
supporting only lichens and mosses. After generations of these plants died
and added their material to the soil, it became possible for other plants
to grow. For tens of thousands of years grasses grew, died, and decayed,
enriching the barren soil with humus. Trees shed their leaves, and
eventually fell back to the Earth themselves. Tiny root hairs probed into
cracks and crevices formed by freezing and thawing, and along with acids,
broke the rocks into ever-smaller particles. Birds and animals added to and
accelerated the process.

Thus soils were formed, over many thousands of years, and became ever more
fertile.

How rich virgin soils become less productive

There are people, still living, who can tell about wonderfully productive
crops grown on virgin soils. And they can also tell how, after a few years
of such crops, the soil became "worn out." Humans didn't have time to
replicate nature's method of creating soils, so for a time, they simply
wore out the land and moved on.

Then there was no more virgin land to exploit.

Humans (as a species) weren't smart enough to follow nature's methods. To
make things worse, they thought they were smarter than nature: they could
do the job much faster and more easily by using their technical knowledge.
But that's getting ahead of our story.

The first farming of a virgin soil has nearly always been grain farming.
(In the United States, this was due largely to economics; i.e., the
industrial system. It was much easier and cheaper to ship grain from the
frontier to the population centers than it was to ship meat, eggs or dairy
products.) Grain is grown every year, with no provision for keeping up the
humus supply, either by means of barnyard manure or by plowing under the
crop residues, even straw often being burned. Little barnyard manure is
produced, and that which is is either thrown away or allowed to lose most
of its value before being put on the land. G. F. Warren noted in 1909 that
"Very few farmers in any part of America have yet learned to handle manure
without losing one-half of its value." (In some regions this hasn't
changed. . . and the availability of chemical fertilizers has made it even
worse.)

The virgin soils, Warren continued, are so productive that farmers nearly
always make the mistake of thinking that they will always remain so. "But
the constant tillage exhausts the humus supply, and the virgin soils become
less and less productive. The change is so gradual and is so obscured by
the weather variations from year to year that the real state of affairs is
often not realized until the soil is so poor that it does not pay to farm
it."

Even in the early 1900s, according to Warren, sometimes commercial
fertilizers were resorted to. But he points out that while these might pay
for a few years, sooner or later some provision for renewing the humus
supply must be made, or the field must be temporarily abandoned to allow
nature to renew the supply by growing weeds. "Many fields in the older
sections of the United States are thus abandoned for a few years to
recuperate to such an extent that a small crop may be grown. A wiser way of
farming would be to begin to raise animals for manure production before the
soils become so exhausted."

The causes of decreased productivity

Warren said even more soil fertility was lost by wind and water erosion
than by cropping. In spite of a much wider recognition of this, soil
erosion remains a serious problem even as we enter the 21st century. In
fact, there are places where windbreaks planted after the Dust Bowl years
are now being torn out to accommodate ever-larger fields and equipment, and
by running after short-term profits rather than long-term interests.

Warren suggested keeping the soil in sod, keeping cover crops during the
winter, and terracing.

Productivity can be decreased when the soil no longer holds enough
moisture. This can be remedied by adding humus, Warren said.

The soil may cease to be favorable for the development of soil organisms.
Again, Warren suggests adding humus. . . and lime.

Constant cropping can exhaust the available supply of a specific plant
food. Each crop removes a certain amount of nitrogen, phosphorus and potash
(as well as others). If any one is lacking, the crop will suffer no matter
how much of the others is available. Usually it is not a shortage of the
absolute amount in the soil, but a shortage of that which the plant can
secure in usable form. Again, the addition of humus. . . to feed the soil,
so the soil can feed the plant. . . is called for.

The exhaustion of the humus supply is usually the fundamental cause for
decrease in crop yields, Warren said. If that was a problem in 1900, it has
become ten-fold worse. This affects crops in many ways. It may result in an
unfavorable physical condition of the soil that will limit the crop even
when there is no shortage of plant food. The soil may bake, or lose its
water-holding power. Since the humus furnishes nitrogen by its
decomposition and encourages the fixation of free nitrogen, the exhaustion
of humus will be accompanied by a shortage of nitrogen. Or because of the
lack of humus, the mineral elements may not be rapidly enough dissolved,
although present in abundance. In such a case, the addition of phosphoric
acid or potash might increase the crop, Warren said, but it would usually
be wiser to supply humus so as to render available the food that is already
in the soil. Once again: "Many soils are losing their fertility in all of
the waysmentioned above". . . and that was nearly 100 years ago. It's much
worse now.

Materials used as fertilizers

Naturally fertile soils were made that way over thousands, and sometimes
tens of thousands of years, by a combination of the basic rock, plant
growth and the return to the Earth of the plants, as well as the animals
that fed on them, and their waste products, all worked upon by the activity
of soil biology.

It's easy to see how early farmers could have learned to follow that
natural method, even if they didn't think about it. Perhaps someone noticed
that the grass was greener or the grain yield better around animal
droppings. The same effect could be seen around old campfires, or even
after grass or forest fires. Barnyard manure and wood ashes are among the
oldest fertilizers used by humans to maintain or restore natural fertility.

The Indians taught European settlers in America how to grow corn and use
fish as fertilizer. One account says, "According to the manner of the
Indians, we manured our ground with herrings, or rather shads, which we
have in great abundance and take with ease at our doors. You may see in one
township a hundred acres together set with these fish, every acre taking a
thousand of them, and an acre thus dressed will produce and yield as much
corn as three acres without fish."

Nitrogen

All nitrogen comes from the air. There is no nitrogen in stone. Nearly
four-fifths of the air is nitrogen. Warren said there are over 35,000 tons
of this gas over every acre of land. And yet, plants swimming in this sea
of nitrogen can be nitrogen starved, yellow and sickly. That's because no
plants except legumes are able to use atmospheric nitrogen.

A small amount of nitrogenous compounds are brought down with rain and
snow. This can amount to 2-3 pounds per acre per year. But about 40 pounds
is required for a fair wheat crop.

Nitrogen from the air can be "fixed" by bacteria on legumes. Some of the
old writings on farming note that pea-like plants have some effect on the
soil that benefits following crops. Only in the last 150 years has this
been explained. Until then, the Chinese saying that "beans are good for the
soil" was as good as any.

Note that the legumes themselves do not fix nitrogen. This is done by the
nitrogen-fixing bacteria that live in the root nodules of the plants. If
the right kind of bacteria are not in the soil, a legume cannot produce
nitrogen, for itself or for subsequent crops.

But other bacteria also increase nitrogen under the proper conditions.
Warren cites one early study from the New Jersey Experiment Station where
millet (not a legume) was grown in boxes without fertilizer, with one gram
of nitrogen added in the form of nitrate of soda, and one gram of nitrogen
added in the form of barnyard manure. A fourth box got no fertilizer, no
crop was grown, and the soil was kept bare.

The soil that was bare contained a gram more nitrogen in the fall than it
did in spring. There was a slight gain when millet was grown. When one gram
of nitrate of soda was added, the crop and soil contained 3.73 grams more
than was present at the beginning. But when the manure was used, the gain
soared to 10.48 grams.

These gains came from the air. The nitrogen was fixed by organisms acting
independently of legumes. The striking results with the barnyard manure,
Warren speculated, were probably due to the humus it contains, and perhaps
partly due to the organisms it brings with it. "This partly explains why
fertilizers alone cannot take the place of manure."

Grasses don't have the power to obtain nitrogen from the air, but when land
is left in sod there is usually a considerable gain in nitrogen. Every
farmer knows (or at least used to know) that a field that has been in sod
for a few years produces much better crops. This is partly due to the humus
added by the decaying roots, Warren said, and is undoubtedly partly due to
the fixation of nitrogen. Probably the humus has much to do with the
nitrogen fixation.

"In the regions where soils have been so farmed as to become unproductive,
the fields are commonly abandoned for one or more years, then they will
produce crops again. Where the soils are not quite so far exhausted, one or
two tilled crops are grown and are then followed by hay a few years, after
which small crops can once more be raised. The same principle should be
applied in regular farming. Under most conditions, the land should be in
sod one to three years out of every five. The poorer the land, the more
time it should be in sod. If legumes can be combined with this sod, so much
the better. The same results may be accomplished in other ways, as by
plowing down green manure crops."

Manure management

There are other organisms in the soil which accomplish the opposite
results. They act on nitrogen compounds and break them up so that the
nitrogen escapes into the air as free nitrogen. This is called
denitrification. When manure is left in loose piles, or simply spread on
the land without being worked in, much of the nitrogen is lost by
denitrification. Composting manure is the best way to retain the nitrogen
in it.

Nitrogen may also be lost by being made too soluble too rapidly, in which
case it may leach out of the soil. The humus in a sandy soil is likely to
be burned out so rapidly that the nitrogen may be lost in this way.

Dried blood or blood meal is usually about 12 percent nitrogen, and is
commonly used by organic gardeners.

Another organic fertilizer, bone meal, also contains nitrogen: about 4
percent. (At least it did in Warren's day: the package we have makes no
mention of this, so it probably doesn't contain any.) But bone meal is used
for its phosphorus.

For potash, Warrens (and many present-day organic gardeners) recommends
wood ashes. . . and barnyard manure.

Lime is usually spoken of as a soil amendment rather than a plant food or
fertilizer, but again, Warren recognizes the interdependence of nature,
including soil fertility. Lime helps to improve the physical condition of
some soils, it corrects acidity, and it helps liberate other plant foods,
but perhaps its most important effect is its influence on soil organisms.
If there isot sufficient lime in the soil, the fixation of atmospheric
nitrogen cannot go on properly, nor can the liberation of nitrogen from the
humus.

"The addition of lime to the soil so favors the preparation of nitrogen
food that its effect is often the same as nitrogen. If a soil is deficient
in lime it is unwise to go on farming it until this deficiency has been
corrected. The other fertilizers or barnyard manure cannot be used most
economically if there is not sufficient lime. On the other hand, lime does
not take the place of these fertilizing materials."

All of this provides a mere glimpse into a book written nearly one hundred
years ago, to explain to high school students facts known to few college
graduates today. . . probably including some with degrees in agriculture.
And yet, to those exploring organic methods, it's all "up-to-the-minute
news in depth."

The information explosion might have made us smarter. But now it's time to
become wiser.






  • [Livingontheland] The Soul Of Soil - facts about soil taken from a textbook published in 1909, TradingPostPaul, 03/21/2007

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