Talks on Manures Part 34

3d. Much of our wheat is seriously injured by stagnant water _in the soil_, and standing water on the surface. I think we may safely say that one-third the wheat-crop of this county (Monroe Co., N.Y.), is lost for want of better tillage and better draining--and yet we think we have as good wheat-land and are as good farmers as can be found in this country or any other!

Unless we drain land, where drainage is needed, and unless we work land thoroughly that needs working, and unless we kill the weeds or check their excessive growth, it is poor economy to sow expensive manures on our wheat-crops.

But I do not think there is much danger of our falling into this error.

The farmers who try artificial manures are the men who usually take the greatest pains to make the best and most manure from the animals kept on the farm. They know what manures cost and what they are worth. As a rule, too, such men are good farmers, and endeavor to work their land thoroughly and keep it clean. When this is the case, there can be little doubt that we can often use artificial manures to great advantage.

"You say," said the Deacon, who had been looking over the tables while I was talking, "that mixed mineral manures and 50 lbs. of ammonia give 39 bushels per acre. Now these mixed mineral manures contain potash, soda, magnesia, and superphosphate. And I see where superphosphate was used without any potash, soda, and magnesia, but with the same amount of ammonia, the yield is nearly 46 bushels per acre. This does not say much in favor of potash, soda, and magnesia, as manures, for wheat. Again, I see, on plot 10_b_, 50 lbs. of ammonia, _alone_, gives over 43 bushels per acre. On plot 11_b_, 50 lbs. ammonia _and_ superphosphate, give 46 bushels. Like your father, I am inclined to ask, '_Where can I get this ammonia?_'"

CHAPTER XXVIII.

LIME AS A MANURE.

These careful, systematic, and long-continued experiments of Lawes and Gilbert seem to prove that if you have a piece of land well prepared for wheat, which will produce, without manure, say 15 bushels per acre, there is no way of making that land produce 30 bushels of wheat per acre, without directly or indirectly furnis.h.i.+ng the soil with a liberal supply of available nitrogen or ammonia.

"What do you mean by directly or indirectly?" asked the Deacon.

"What I had in my mind," said I, "was the fact that I have seen a good dressing of lime double the yield of wheat. In such a case I suppose the lime decomposes the organic matter in the soil, or in some other way sets free the nitrogen or ammonia already in the soil; or the lime forms compounds in the soil which attract ammonia from the atmosphere. Be this as it may, the facts brought out by Mr. Lawes' experiments warrant us in concluding that the increased growth of wheat was connected in some way with an increased supply of available nitrogen or ammonia."

My father used great quant.i.ties of lime as manure. He drew it a distance of 13 miles, and usually applied it on land intended for wheat, spreading it broad-cast, after the land had received its last plowing, and harrowing it in, a few days or weeks before sowing the wheat.

He rarely applied less than 100 bushels of stone-lime to the acre--generally 150 bushels. He used to say that a small dose of lime did little or no good. He wanted to use enough to change the general character of the land--to make the light land firmer and the heavy land lighter.

While I was with Mr. Lawes and Dr. Gilbert at Rothamsted, I went home on a visit. My father had a four-horse team drawing lime every day, and putting it in large heaps in the field to slake, before spreading it on the land for wheat.

"I do not believe it pays you to draw so much lime," said I, with the confidence which a young man who has learned a little of agricultural chemistry, is apt to feel in his newly acquired knowledge.

"Perhaps not," said my father, "but we have got to do something for the land, or the crops will be poor, and poor crops do not pay these times.

What would you use instead of lime?" --"Lime is not a manure, strictly speaking," said I; "a bushel to the acre would furnish all the lime the crops require, even if there was not an abundant supply already in the soil. If you mix lime with guano, it sets free the ammonia; and when you mix lime with the soil it probably decomposes some compounds containing ammonia or the elements of ammonia, and thus furnishes a supply of ammonia for the plants. I think it would be cheaper to buy ammonia in the shape of Peruvian guano."

After dinner, my father asked me to take a walk over the farm. We came to a field of barley. Standing at one end of the field, about the middle, he asked me if I could see any difference in the crop. "Oh, yes," I replied, "the barley on the right-hand is far better than on the left hand. The straw is stiffer and brighter, and the heads larger and heavier. I should think the right half of the field will be ten bushels per acre better than the other."

"So I think," he said, "and now can you tell me why?" --"Probably you manured one half the field for turnips, and not the other half." --"No."

--"You may have drawn off the turnips from half the field, and fed them off by sheep on the other half." --"No, both sides were treated precisely alike." --I gave it up --"Well," said he, "this half the field on the right-hand was limed, thirty years ago, and that is the only reason I know for the difference. And now you need not tell me that lime does not pay."

I can well understand how this might happen. The system of rotation adopted was, 1st clover, 2d wheat, 3d turnips, 4th barley, seeded with clover.

Now, you put on, say 150 bushels of lime for wheat. After the wheat the land is manured and sown with turnips. The turnips are eaten off on the land by sheep; and it is reasonable to suppose that on the half of the field dressed with lime there would be a much heavier crop of turnips.

These turnips being eaten off by the sheep would furnish more manure for this half than the other half. Then again, when the land was in gra.s.s or clover, the limed half would afford more and sweeter gra.s.s and clover than the other half, and the sheep would remain on it longer. They would eat it close into the ground, going only on to the other half when they could not get enough to eat on the limed half. More of their droppings would be left on the limed half of the field. The lime, too, would continue to act for several years; but even after all direct benefit from the lime had ceased, it is easy to understand why the crops might be better for a long period of time.

"Do you think lime would do any good," asked the Deacon, "on our limestone land?"--I certainly do. So far as I have seen, it does just as much good here in Western New York, as it did on my father's farm.

I should use it very freely if we could get it cheap enough--but we are charged from 25 to 30 cts. a bushel for it, and I do not think at these rates it will pay to use it. Even gold may be bought too dear.

"You should burn your own lime," said the Deacon, "you have plenty of limestone on the farm, and could use up your down wood."--I believe it would pay me to do so, but one man cannot do everything. I think if farmers would use more lime for manure we should get it cheaper. The demand would increase with compet.i.tion, and we should soon get it at its real value. At 10 to 15 cents a bushel, I feel sure that we could use lime as a manure with very great benefit.

"I was much interested some years ago," said the Doctor, "in the results of Prof. Way's investigations in regard to the absorptive powers of soils."

His experiments, since repeated and confirmed by other chemists, formed a new epoch in agricultural chemistry. They afforded some new suggestions in regard to how lime may benefit land.

Prof. Way found that ordinary soils possessed the power of separating, from solution in water, the different earthy and alkaline substances presented to them in manure; thus, when solutions of salts of ammonia, of potash, magnesia, etc., were made to filter slowly through a bed of dry soil, five or six inches deep, arranged in a flower-pot, or other suitable vessel, it was observed that the liquid which ran through, no longer contained any of the ammonia or other salt employed. The soil had, in some form or other, retained the alkaline substance, while the water in which it was previously dissolved pa.s.sed through.

Further, this power of the soil was found not to extend to the whole salt of ammonia or potash, but only to the alkali itself. If, for instance, sulphate of ammonia were the compound used in the experiments, the ammonia would be removed from solution, but the filtered liquid would contain sulphuric acid in abundance--not in the free or uncombined form, but united to lime; instead of sulphate of ammonia we should find sulphate of lime in the solution; and this result was obtained, whatever the acid of the salt experimented upon might be.

It was found, moreover, that the process of filtration was by no means necessary; by the mere mixing of an alkaline solution with a proper quant.i.ty of soil, as by shaking them together in a bottle, and allowing the soil to subside, the same result was obtained. The action, therefore, was in no way referable to any physical law brought into operation by the process of filtration.

It was also found that the combination between the soil and the alkaline substance was rapid, if not instantaneous, partaking of the nature of the ordinary union between an acid and an alkali.

In the course of these experiments, several different soils were operated upon, and it was found that all soils capable of profitable cultivation possessed this property in a greater or less degree.

Pure sand, it was found, did not possess this property. The organic matter of the soil, it was proved, had nothing to do with it. The addition of carbonate of lime to a soil did not increase its absorptive power, and indeed it was found that a soil in which carbonate of lime did not exist, possessed in a high degree the power of removing ammonia or potash from solution.

To what, then, is the power of soils to arrest ammonia, potash, magnesia, phosphoric acid, etc., owing? The above experiments lead to the conclusion that it is due to the _clay_ which they contain. In the language of Prof. Way, however,

"It still remained to be considered, whether the whole clay took any active part in these changes, or whether there existed in clay some chemical compound in small quant.i.ty to which the action was due. This question was to be decided by the extent to which clay was able to unite with ammonia, or other alkaline bases; and it soon became evident that the idea of the clay as a whole, being the cause of the absorptive property, was inconsistent with all the ascertained laws of chemical combination."

After a series of experiments, Prof. Way came to the conclusion that there is in clays a peculiar cla.s.s of double silicates to which the absorptive properties of soil are due. He found that the double silicate of alumina and lime, or soda, whether found naturally in soils or produced artificially, would be decomposed when a salt of ammonia, or potash, etc., was mixed with it, the ammonia, or potash, taking the place of the lime or soda.

Prof. Way's discovery, then, is not that soils have "absorptive properties"--that has been long known--but that they absorb ammonia, potash, phosphoric acid, etc., by virtue of the double silicate of alumina and soda, or lime, etc., which they contain.

Soils are also found to have the power of absorbing ammonia, or rather _carbonate_ of ammonia, from the air.

"It has long been known," says Prof. Way, "that soils acquire fertility by exposure to the influence of the atmosphere--hence one of the uses of fallows. * * I find that clay is so greedy of ammonia, that if air, charged with carbonate of ammonia, so as to be highly pungent, is pa.s.sed through a tube filled with small fragments of dry clay, _every particle of the gas is arrested_."

This power of the soil to absorb ammonia, is also due to the double silicates. But there is this remarkable difference, that while either the lime, soda, or potash silicate is capable of removing the ammonia from _solution_, the _lime_ silicate alone _has the power of absorbing it from the air_.

This is an important fact. Lime may act beneficially on many or most soils by converting the soda silicate into a lime silicate, or, in other words, converting a salt that will not absorb carbonate of ammonia from the air, into a salt that has this important property.

There is no manure that has been so extensively used, and with such general success as lime, and yet, "who among us," remarks Prof. Way, "can say that he perfectly understands the mode in which lime acts?" We are told that lime sweetens the soil, by neutralizing any acid character that it may possess; that it a.s.sists the decomposition of inert organic matters, and therefore increases the supply of vegetable food to plants: that it decomposes the remains of ancient rocks containing potash, soda, magnesia, etc., occurring in most soils, and that at the same time it liberates silica from these rocks; and lastly, that lime is one of the substances found uniformly and in considerable quant.i.ty in the ashes of plants, that therefore its application may be beneficial simply as furnis.h.i.+ng a material indispensable to the substance of a plant.

These explanations are no doubt good as far as they go, but experience furnishes many facts which cannot be explained by any one, or all, of these suppositions. Lime, we all know, does much good on soils abounding in organic matter, and so it frequently does on soils almost dest.i.tute of it. It may liberate potash, soda, silica, etc., from clay soils, but the application of potash, soda, and silica has little beneficial effect on the soil, and therefore we cannot account for the action of lime on the supposition that it renders the potash, soda, etc., of the soil available to plants. Furthermore, lime effects great good on soils abounding in salts of lime, and therefore it cannot be that it operates as a source of lime for the structure of the plant.

None of the existing theories, therefore, satisfactorily account for the action of lime. Prof. Way's views are most consistent with the facts of practical experience; but they are confessedly hypothetical; and his more recent investigations do not confirm the idea that lime acts beneficially by converting the soda silicate into the lime silicate.

Thus, six soils were treated with lime water until they had absorbed from one and a half to two per cent of their weight of lime. This, supposing the soil to be six inches deep, would be at the rate of about 300 bushels of lime per acre. The amount of ammonia in the soil was determined before liming, after liming, and then after being exposed to the fumes of carbonate ammonia until it had absorbed as much as it would. The following table exhibits the results:

----------------------------+------+------+------+------+------+------ No. 1. No. 2. No. 3. No. 4. No. 5. No. 6.

----------------------------+------+------+------+------+------+------ Ammonia in 1,000 grains of natural soil 0.293 0.181 0.085 0.109 0.127 0.083 Ammonia in 1,000 grains of soil after liming 0.169 0.102 0.040 0.050 ... 0.051 Ammonia in 1,000 grains of soil after liming and exposure to the vapor of ammonia 2.226 2.066 3.297 1.076 3.265 1.827 Ammonia in 1,000 grains of soil after exposure to ammonia without liming. 1.906 2.557 3.286 1.097 2.615 2.028 ----------------------------+------+------+------+------+------+------

No. 1. Surface soil of London clay.

No. 2. Same soil from 1 to 2 feet below the surface.

No. 3. Same soil 3 feet below the surface.

No. 4. Loam of tertiary drift 4 feet below the surface.

No. 5. Gault clay--surface soil.