NATURAL MANURE.
We often hear about “natural” manure. I do not like the term, though I
believe it originated with me. It is not accurate; not definite enough.
“I do not know what you mean by natural manure,” said the Deacon,
“unless it is the droppings of animals.” --“To distinguish them,
I suppose,” said the Doctor, “from artificial manures, such as
superphosphate, sulphate of ammonia, and nitrate of soda.” --“No; that
is not how I used the term. A few years ago, we used to hear much in
regard to the ‘exhaustion of soils.’ I thought this phrase conveyed a
wrong idea. When new land produces large crops, and when, after a few
years, the crops get less and less, we were told that the farmers were
exhausting their land. I said, no; the farmers are not exhausting the
_soil_; they are merely exhausting the accumulated plant-food in the
soil. In other words, they are using up the _natural manure_.
“Take my own farm. Fifty years ago, it was covered with a heavy growth
of maple, beech, black walnut, oak, and other trees. These trees had
shed annual crops of leaves for centuries. The leaves rot on the ground;
the trees also, age after age. These leaves and other organic matter
form what I have called natural manure. When the land is cleared up and
plowed, this natural manure decays more rapidly than when the land lies
undisturbed; precisely as a manure-pile will ferment and decay more
rapidly if turned occasionally, and exposed to the air. The plowing and
cultivating renders this natural manure more readily available. The
leaves decompose, and furnish food for the growing crop.”
EXHAUSTION OF THE SOIL.
“You think, then,” said the Doctor, “that when a piece of land is
cleared of the forest, harrowed, and sown to wheat; plowed and planted
to corn, and the process repeated again and again, until the land no
longer yields profitable crops, that it is the ‘natural manure,’ and not
the soil, that is exhausted?”
“I think the _soil_, at any rate, is not exhausted, and I can easily
conceive of a case where even the natural manure is very far from being
all used up.”
“Why, then,” asked the Deacon, “is the land so poor that it will
scarcely support a sheep to the acre?”
“Simply because the natural manure and other plant-food which the soil
contains is not in an available condition. It lies dead and inert. It is
not soluble, and the roots of the plants cannot get enough of it to
enable them to thrive; and in addition to this, you will find as a
matter of fact that these poor ‘exhausted’ farms are infested with
weeds, which rob the growing crops of a large part of the scanty supply
of available plant-food.”
“But these weeds,” said the Deacon, “are not removed from the farm. They
rot on the land; nothing is lost.”
“True,” said I, “but they, nevertheless, rob the growing crops of
available plant-food. The annual supply of plant-food, instead of being
used to grow useful plants, is used to grow weeds.”
“I understand that,” said the Deacon, “but if the weeds are left on the
land, and the useful plants are sold, the farmer who keeps his land
clean would exhaust his land faster than the careless farmer who lets
his land lie until it is overrun with thistles, briars, and pig-weed.
You agricultural writers, who are constantly urging us to farm better
and grow larger crops, seem to overlook this point. As you know, I do
not take much stock in chemical theories as applied to agriculture, but
as you do, here is a little extract I cut from an agricultural paper,
that seems to prove that the better you work your land, and the larger
crops you raise, the sooner you exhaust your land.”
The Deacon put on his spectacles, drew his chair nearer the lamp on the
table, and read the following:
“There is, on an average, about one-fourth of a pound of potash to every
one hundred pounds of soil, and about one-eighth of a pound of
phosphoric acid, and one-sixteenth of a pound of sulphuric acid. If the
potatoes and the tops are continually removed from the soil, it will
soon exhaust the potash. If the wheat and straw are removed, it will
soon exhaust the phosphate of lime; if corn and the stalks, it will soon
exhaust the sulphuric acid. Unless there is a rotation, or the material
the plant requires is supplied from abroad, your crops will soon run
out, though the soil will continue rich for other plants.”
“That extract,” said I, “carries one back twenty-five years. We used to
have article after article in this strain. We were told that ‘always
taking meal out of the tub soon comes to the bottom,’ and always taking
potash and phosphoric acid from the soil will soon exhaust the supply.
But, _practically_, there is really little danger of our exhausting the
land. It does not pay. The farmer’s resources will be exhausted long
before he can exhaust his farm.”
“Assuming,” said the Doctor, who is fond of an argument, “that the above
statement is true, let us look at the facts. An acre of soil, 12 inches
deep, would weigh about 1,600 tons; and if, as the writer quoted by the
Deacon states, the soil contains 4 ozs. of potash in every 100 lbs. of
soil, it follows that an acre of soil, 12 inches deep, contains 8,000
lbs. of potash. Now, potatoes contain about 20 per cent of dry matter,
and this dry matter contains say, 4 per cent of ash, half of which is
potash. It follows, therefore, that 250 bushels of potatoes contain
about 60 lbs. of potash. If we reckon that the tops contain 20 lbs.
more, or 80 lbs. in all, it follows that the acre of soil contains
potash enough to grow an _annual_ crop of 250 bushels of potatoes per
acre for one hundred years.”
“I know farmers,” said Charley, “who do not get over 50 bushels of
potatoes per acre, and in that case the potash would last five hundred
years, as the weeds grown with the crop are left on the land, and do
not, according to the Deacon, exhaust the soil.”
“Good for you, Charley,” said the Doctor. “Now let us see about the
phosphoric acid, of which the soil, according to the above statement,
contains only half as much as it contains of potash, or 4,000 lbs. per
acre.
“A crop of wheat of 30 bushels per acre,” continued the Doctor,
“contains in the grain about 26 lbs. of ash, and we will say that half
of this ash is phosphoric acid, or 13 lbs. Allowing that the straw,
chaff, etc., contain 7 lbs. more, we remove from the soil in a crop of
wheat of 30 bushels per acre, 20 lbs. of phosphoric acid, and so,
according to the above estimate, an acre of soil contains phosphoric
acid to produce annually a crop of wheat and straw of 30 bushels per
acre for _two hundred years_.
“The writer of the paragraph quoted by the Deacon,” continued the
Doctor, “selected the crops and elements best suited to his purpose, and
yet, according to his own estimate, there is sufficient potash and
phosphoric acid in the first 12 inches of the soil to enable us to raise
unusually large crops until the next Centennial in 1976.
“But let us take another view of the subject,” continued the Doctor. “No
intelligent farmer removes all the potatoes _and tops_, all the wheat,
straw, and chaff, or all the corn and stalks from his farm. According to
Dr. Salisbury, a crop of corn of 75 bushels per acre removes from the
soil 600 lbs. of ash, but the _grain_ contains only 46 lbs. The other
554 lbs. is contained in the stalks, etc., all of which are usually
retained on the farm. It follows from this, that when only the grain is
sold off the farm, it takes more than thirteen crops to remove as much
mineral matter from the soil as is contained in the whole of one crop.
Again, the ash of the grain contains less than 3 per cent of sulphuric
acid, so that the 46 lbs. of ash, in 75 bushels of corn, contains less
than 1½ lbs. of sulphuric acid, and thus, if an acre of soil contains
2,000 lbs. of sulphuric acid, we have sufficient for an annual crop of
75 bushels per acre for fifteen hundred years!
“As I said before,” continued the Doctor, “intelligent farmers seldom
sell their straw, and they frequently purchase and consume on the farm
nearly as much bran, shorts, etc., as is sent to market with the grain
they sell. In the ‘Natural History of New York,’ it is stated that an
acre of wheat in Western New York, of 30 bushels per acre, including
straw, chaff, etc., removes from the soil 144 lbs. of mineral matter.
Genesee wheat usually yields about 80 per cent. of flour. This flour
contains only 0.7 per cent of mineral matter, while fine middlings
contain 4 per cent; coarse middlings, 5½ per cent; shorts, 8 per cent,
and bran 8½ per cent of mineral matter or ash. It follows from this,
that out of the 144 lbs. of mineral matter in the crop of wheat, less
than 10 lbs. is contained in the flour. The remaining 134 lbs. is found
in the straw, chaff, bran, shorts, etc., which a good farmer is almost
sure to feed out on his farm. But even if the farmer feeds out none of
his wheat-bran, but sells it all with his wheat, the 30 bushels of wheat
remove from the soil only 26 lbs. of mineral matter; and it would take
more than five crops to remove as much mineral matter as one crop of
wheat and straw contains. Allowing that half the ash of wheat is
phosphoric acid, 30 bushels remove only 13 lbs. from the soil, and if
the soil contains 4,000 lbs., it will take three hundred and seven
crops, of 30 bushels each, to exhaust it.”
“That is to say,” said Charley, “if all the straw and chaff is retained
on the farm, and is returned to the land without loss of phosphoric
acid.”
“Yes,” said the Doctor, “and if all the bran and shorts, etc., were
retained on the farm, it would take eight hundred crops to exhaust the
soil of phosphoric acid; and it is admitted that of all the elements of
plant-food, phosphoric acid is the one first to be exhausted from the
soil.”
I have sold some timothy hay this winter, and propose to do so whenever
the price suits. But some of my neighbors, who do not hesitate to sell
their own hay, think I ought not to do so, because I “write for the
papers”! It ought to satisfy them to know that I bring back 30 cwt. of
bran for every ton of hay I sell. My rule is to sell nothing but wheat,
barley, beans, potatoes, clover-seed, apples, wool, mutton, beef, pork,
and butter. Everything else is consumed on the farm--corn, peas, oats,
mustard, rape, mangels, clover, straw, stalks, etc. Let us make a rough
estimate of how much is sold and how much retained on a hundred-acre
farm, leaving out the potatoes, beans, and live-stock. We have say:
Sold.
15 acres wheat, @ 40 bushels per acre 18 tons
5 ” barley, @ 50 ” ” 6 ”
15 ” clover seed, 4 ” ” 1¾ ton.
------
Total sold 25¾ tons.
Retained on the farm.
15 acres corn, @ 80 bushels per acre 33½ tons.
Corn stalks from do. 40 ”
5 acres barley straw 8 ”
10 ” oats and peas, equal 80 bushels of oats 12¾ ”
Straw from do. 20 ”
15 acres wheat-straw 25 ”
15 ” clover-hay 25 ”
Clover-seed straw 10 ”
15 acres pasture and meadow, equal 40 tons hay 40 ”
5 ” mustard, equal 10 tons hay 10 ”
5 ” rape, equal 10 tons hay 10 ”
5 ” mangels, 25 tons per acre, 15 ”
equal to 3 tons dry
Leaves from do. 3 ”
-------
Total retained on the farm 252¼ tons.
It would take a good many years to exhaust any ordinary soil by such a
course of cropping. Except, perhaps, the sandy knolls, I think there is
not an acre on my farm that would be exhausted in ten thousand years,
and as some portions of the low alluvial soil will grow crops without
manure, there will be an opportunity to give the poor, sandy knolls more
than their share of plant-food. In this way, notwithstanding the fact
that we sell produce and bring nothing back, I believe the whole farm
will gradually increase in productiveness. The plant-food annually
rendered available from the decomposition and disintegration of the
inert organic and mineral matter in the soil, will be more than equal to
that exported from the farm. If the soil becomes deficient in anything,
it is likely that it will be in phosphates, and a little superphosphate
or bone-dust might at any rate be profitably used on the rape, mustard,
and turnips.
The point in good farming is to develop from the latent stores in the
soil, and to accumulate enough available plant-food for the production
of the largest possible yield of those crops which we sell. In other
words, we want enough available plant-food in the soil to grow 40
bushels of wheat and 50 bushels of barley. I think the farmer who raises
10 tons for every ton he sells, will soon reach this point, and when
once reached, it is a comparatively easy matter to maintain this degree
of fertility.
WHY OUR CROPS ARE SO POOR.
“If the soil is so rich in plant-food,” said the Deacon, “I again ask,
why are our crops so poor?”
The Deacon said this very quietly. He did not seem to know that he had
asked one of the most important questions in the whole range of
agricultural science. It is a fact that a soil may contain enough
plant-food to produce a thousand large crops, and yet the crops we
obtain from it may be so poor as hardly to pay the cost of cultivation.
The plant-food is there, but the plants cannot get at it. It is not in
an available condition; it is not soluble. A case is quoted by Prof.
Johnson, where a soil was analyzed, and found to contain to the depth of
one foot 4,652 lbs. of nitrogen per acre, but only 63 lbs. of this was
in an available condition. And this is equally true of phosphoric acid,
potash, and other elements of plant-food. No matter how much plant-food
there may be in the soil, the only portion that is of any immediate
value is the small amount that is annually available for the growth of
crops.
HOW TO GET LARGER CROPS.
“I am tired of so much talk about plant-food,” said the Deacon; “what we
want to know is how to make our land produce larger crops of wheat,
corn, oats, barley, potatoes, clover, and grass.”
This is precisely what I am trying to show. On my own farm, the three
leading objects are (1) to get the land drained, (2) to make it clean
and mellow, and (3) to get available nitrogen for the cereal crops.
After the first two objects are accomplished, the measure of
productiveness will be determined by the amount of available nitrogen in
the soil. How to get available nitrogen, therefore, is my chief and
ultimate object in all the operations on the farm, and it is here that
science can help me. I know how to get nitrogen, but I want to get it in
the cheapest way, and then to be sure that I do not waste it.
There is one fact fully established by repeated experiment and general
experience--that 80 lbs. of available nitrogen per acre, applied in
manure, will almost invariably give us a greatly increased yield of
grain crops. I should expect, on my farm, that on land which, without
manure, would give me 15 bushels of wheat per acre, such a dressing of
manure would give me, in a favorable season, 35 or 40 bushels per acre,
with a proportional increase of straw; and, in addition to this, there
would be considerable nitrogen left for the following crop of clover. Is
it not worth while making an earnest effort to get this 80 lbs. of
available nitrogen?
I have on my farm many acres of low, mucky land, bordering on the creek,
that probably contain several thousand pounds of nitrogen per acre. So
long as the land is surcharged with water, this nitrogen, and other
plant-food, lies dormant. But drain it, and let in the air, and the
oxygen decomposes the organic matter, and ammonia and nitric acid are
produced. In other words, we get _available_ nitrogen and other
plant-food, and the land becomes capable of producing large crops of
corn and grass; and the crops obtained from this low, rich land, will
make manure for the poorer, upland portions of the farm.