CHAPTER IV.
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.