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 furnishing 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 quantities 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 grass or clover, the limed half would afford more and sweeter grass 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 competition, 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 passed 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 quantity 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 quantity 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 class 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 passed 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 assists 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 quantity in the ashes of plants, that therefore its application may be beneficial simply as furnishing 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 destitute 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 1½ to 2 feet below the surface. No. 3. Same soil 3½ feet below the surface. No. 4. Loam of tertiary drift 4 feet below the surface. No. 5. Gault clay--surface soil. No. 6. Gault clay 4 feet below the surface.

It is evident that lime neither assisted nor interfered with the absorption of ammonia, and hence the beneficial effect of liming on such soils must be accounted for on some other supposition. This negative result, however, does not disprove the truth of Prof. Way’s hypothesis, for it may be that the silicate salt in the natural soils was that of lime and not that of soda. Indeed, the extent to which the natural soils absorbed ammonia--equal, in No. 3, to about 7,000 lbs. of ammonia per acre, equivalent to the quantity contained in 700 tons of barn-yard manure--shows this to have been the case.

_The lime liberated one-half the ammonia contained in the soil._

“This result,” says Prof. Way, “is so nearly the same in all cases, that we are justified in believing it to be due to some special cause, and probably it arises from the existence of some compound silicates containing ammonia, of which lime under the circumstances can replace one-half--forming, for instance, a double silicate of alumina, with half lime and half ammonia--such compounds are not unusual or new to the chemist.”

This loss of ammonia from a heavy dressing of lime is very great. A soil five inches deep, weighs, in round numbers, 500 tons, or 1,000,000 lbs. The soil, No. 1, contained .0293 per cent of ammonia, or in an acre, five inches deep, 293 lbs. After liming, it contained .0169 per cent, or in an acre, five inches deep, 169 lbs. The loss by liming is 124 lbs. of ammonia per acre. This is equal to the quantity contained in 1200 lbs. of good Peruvian guano, or 12½ tons of barn-yard manure.

In commenting on this great loss of ammonia from liming, Prof. Way observes:

“Is it not possible, that for the profitable agricultural use, the ammonia of the soil is too tightly locked up in it? Can we suppose that the very powers of the soil to unite with and preserve the elements of manure are, however excellent a provision of nature, yet in some degree opposed to the growth of the abnormal crops which it is the business of the farmer to cultivate? There is no absolute reason why such should not be the case. A provision of nature must relate to natural circumstances; for instance, compounds of ammonia may be found in the soil, capable of giving out to the agencies of water and air quite enough of ammonia for the growth of ordinary plants and the preservation of their species; but this supply may be totally inadequate to the necessities of man. * * * Now it is not impossible that the laws which preserve the supply of vegetable nutrition in the soil, are too stringent for the requirements of an unusual and excessive vegetation, such as the cultivator must promote.

“In the case of ammonia locked up in the soil, lime may be the remedy at the command of the farmer--his means of rendering immediately available stores of wealth, which can otherwise only slowly be brought into use.

“In this view, lime would well deserve the somewhat vague name that has been given it, namely, that of a ‘stimulant’; for its application would be in some sort an application of ammonia, while its excessive application, by driving off ammonia, would lead to all the disastrous effects which are so justly attributed to it.

“I do not wish to push this assumption too far,” says Prof. Way, in conclusion, “but if there be any truth in it, it points out the importance of employing lime in small quantities at short intervals, rather than in large doses once in many years.”

“The Squire, last year,” said the Deacon, “drew several hundred bushels of refuse lime from the kiln, and mixed it with his manure. It made a powerful smell, and not an agreeable one, to the passers by. He put the mixture on a twenty-acre field of wheat, and he said he was going to beat you.”

“Yes,” said I, “so I understood--but he did not do it. If he had applied the lime and the manure separately, he would have stood a better chance; still, there are two sides to the question. I should not think of mixing lime with good, rich farm-yard manure; but with long, coarse, strawy manure, there would be less injury, and possibly some advantage.”

“The Squire,” said the Deacon, “got one advantage. He had not much trouble in drawing the manure about the land. There was not much of it left.”

Lime does not always decompose organic matter. In certain conditions, it will _preserve_ vegetable substances. We do not want to mix lime with manure in order to preserve it; and if our object is to increase fermentation, we must be careful to mix sufficient soil with the manure to keep it moist enough to retain the liberated ammonia.

Many farmers who use lime for the first time on wheat, are apt to feel a little discouraged in the spring. I have frequently seen limed wheat in the spring look worse than where no lime was used. But wait a little, and you will see a change for the better, and at harvest, the lime will generally give a good account of itself.

There is one thing about lime which, if generally true, is an important matter to our wheat-growers. Lime is believed to hasten the maturity of the crop. “It is true of nearly all our cultivated crops,” says the late Professor Johnston, “but especially of those of wheat, that their full growth is attained more speedily when the land is limed, and that they are ready for the harvest from ten to fourteen days earlier. This is the case even with buckwheat, which becomes sooner ripe, though it yields no larger a return when lime is applied to the land on which it is grown.”

In districts where the midge affects the wheat, it is exceedingly important to get a variety of wheat that ripens early; and if lime will favor early maturity, without checking the growth, it will be of great value.

A correspondent in Delaware writes: “I have used lime as a manure in various ways. For low land, the best way is, to sow it broadcast while the vegetation is in a green state, at the rate of 40 or 50 bushels to the acre; but if I can not use it before the frost kills the vegetation, I wait until the land is plowed in the spring, when I spread it on the plowed ground in about the same quantity as before. Last year, I tried it both ways, and the result was, my crop was increased at least fourfold in each instance, but that used on the vegetation was best. The soil is a low, black sand.”

A farmer writes from New Jersey, that he has used over 6,000 bushels of lime on his farm, and also considerable guano and phosphates, but considers that the lime has paid the best. His farm has more than doubled in real value, and he attributes this principally to the use of lime.

“We lime,” he says, “whenever it is convenient, but prefer to put it on at least one year before plowing the land. We spread from 25 to 40 bushels of lime on the sod in the fall; plant with corn the following summer; next spring, sow with oats and clover; and the next summer, plow under the clover, and sow with wheat and timothy. We have a variety of soils, from a sandy loam to a stiff clay, and are certain that lime will pay on all or any of them. Some of the best farmers in our County commenced liming when the lime cost 25 cts. a bushel, and their farms are ahead yet, more in value, I judge, than the lime cost. The man who first commences using lime, will get so far ahead, while his neighbors are looking on, that they will never catch up.”

Another correspondent in Hunterdon Co., N.J., writes: “Experience has taught me that the best and most profitable mode of applying lime is on grass land. If the grass seed is sown in the fall with the wheat or rye, which is the common practice with us in New Jersey, as soon as the harvest comes off the next year, we apply the lime with the least delay, and while fresh slacked and in a dry and mealy state. It can be spread more evenly on the ground, and is in a state to be more readily taken up by the fine roots of the plants, than if allowed to get wet and clammy. It is found most beneficial to keep it as near the surface of the ground as practicable, as the specific gravity or weight of this mineral manure is so great, that we soon find it too deep in the ground for the fibrous roots of plants to derive the greatest possible benefit from its use. With this method of application are connected several advantages. The lime can be hauled in the fall, after the busy season is over, and when spread on the sod in this way, comes in more immediate contact with the grass and grass-roots than when the land is first plowed. In fields that have been limed in part in this manner, and then plowed, and lime applied to the remainder at the time of planting with corn, I always observe a great difference in the corn-crop; and in plowing up the stubble the next season, the part limed on the sod is much mellower than that limed after the sod was broken, presenting a rich vegetable mould not observed in the other part of the field.”

A farmer in Chester Co., Pa., also prefers to apply lime to newly-seeded grass or clover. He puts on 100 bushels of slaked lime per acre, either in the fall or in the spring, as most convenient. He limes one field every year, and as the farm is laid off into eleven fields, all the land receives a dressing of lime once in eleven years.

In some sections of the country, where lime has been used for many years, it is possible that part of the money might better be used in the purchase of guano, phosphates, fish-manure, etc.; while in this section, where we seldom use lime, we might find it greatly to our interest to give our land an occasional dressing of lime.

The value of quick-lime as a manure is not merely in supplying an actual constituent of the plant. If it was, a few pounds per acre would be sufficient. Its value consists in changing the chemical and physical character of the soil--in developing the latent mineral plant-food, and in decomposing and rendering available organic matter, and in forming compounds which attract ammonia from the atmosphere. It may be that we can purchase this ammonia and other plant-food cheaper than we can get it by using lime. It depends a good deal on the nature and composition of the soil. At present, this question can not be definitely settled, except by actual trial on the farm. In England, where lime was formerly used in large quantities, the tendency for some time has been towards a more liberal and direct use of ammonia and phosphates in manures, rather than to develop them out of the soil by the use of lime. A judicious combination of the two systems will probably be found the most profitable.

Making composts with old sods, lime, and barn-yard manure, is a time-honored practice in Europe. I have seen excellent results from the application of such a compost on meadow-land. The usual plan is, to select an old hedge-row or headland, which has lain waste for many years. Plow it up, and cart the soil, sods, etc., into a long, narrow heap. Mix lime with it, and let it lie six months or a year. Then turn it, and as soon as it is fine and mellow, draw it on to the land. I have assisted at making many a heap of this kind, but do not recollect the proportion of lime used; in fact, I question if we had any definite rule. If we wanted to use lime on the land, we put more in the heap; if not, less. The manure was usually put in when the heap was turned.

Dr. Vœlcker analyzed the dry earth used in the closets at the prison in Wakefield, England. He found that: Phosphoric Nitrogen. Acid. 10 tons of dry earth before using contained 63 lbs. 36 lbs. 10 tons of dry earth after being used once contained 74 ” 50 ” 10 tons of dry earth after being used twice contained 84 ” 88 ” 10 tons of dry earth after being used thrice contained 102 ” 102 ”

After looking at the above figures, the Deacon remarked: “You say 10 tons of dry earth before being used in the closet contained 62 lbs. of nitrogen. How much nitrogen does 10 tons of barn-yard manure contain?”

“That depends a good deal on what food the animals eat. Ten tons of average fresh manure would contain about 80 lbs. of nitrogen.”

“Great are the mysteries of chemistry!” exclaimed the Deacon. “Ten tons of dry earth contain almost as much nitrogen as 10 tons of barn-yard manure, and yet you think that nitrogen is the most valuable thing in manure. What shall we be told next?”

“You will be told, Deacon, that the nitrogen in the soil is in such a form that the plants can take up only a small portion of it. But if you will plow such land in the fall, and expose it to the disintegrating effects of the frost, and plow it again in the spring, and let the sun and air act upon it, more or less of the organic matter in the soil will be decomposed, and the nitrogen rendered soluble. And then if you sow this land to wheat after a good summer-fallow, you will stand a chance of having a great crop.”

This dry earth which Dr. Vœlcker analyzed appeared, he says, “to be ordinary garden soil, containing a considerable portion of clay.” After it had been passed once through the closet, one ton of it was spread on an acre of grass-land, which produced 2 tons 8 cwt. of hay. In a second experiment, one ton, once passed through the closet, produced 2 tons 7 cwt. of hay per acre. We are not told how much hay the land produced without any dressing at all. Still we may infer that this top-dressing did considerable good. Of one thing, however, there can be no doubt. This one ton of earth manure contained only 1¼ lb. more nitrogen and 1½ lb. more phosphoric acid than a ton of the dry earth itself. Why then did it prove so valuable as a top-dressing for grass? I will not say that it was due solely to the decomposition of the nitrogenous matter and other plant-food in the earth, caused by the working over and sifting and exposure to the air, and to the action of the night-soil. Still it would seem that, so far as the beneficial effect was due to the supply of plant-food, we must attribute it to the earth itself rather than to the small amount of night-soil which it contained.

It is a very common thing in England, as I have said before, for farmers to make a compost of the sods and earth from an old hedge-row, ditch, or fence, and mix with it some lime or barn-yard manure. Then, after turning it once or twice, and allowing it to remain in the heap for a few months, to spread it on meadow-land. I have seen great benefit apparently derived from such a top-dressing. The young grass in the spring assumed a rich, dark green color. I have observed the same effect where coal-ashes were spread on grass-land; and I have thought that the apparent benefit was due largely to the material acting as a kind of mulch, rather than to its supplying plant-food to the grass.

I doubt very much whether we can afford to make such a compost of earth with lime, ashes, or manure in this country. But I feel sure that those of us having rich clay land containing, in an inert form, as much nitrogen and phosphoric acid as Dr. Vœlcker found in the soil to be used in the earth-closet at Wakefield, can well afford to stir it freely, and expose it to the disintegrating and decomposing action of the atmosphere.

An acre of dry soil six inches deep weighs about 1,000 tons; and consequently an acre of such soil as we are talking about would contain 6,200 lbs. of nitrogen, and 3,600 lbs. of phosphoric acid. In other words, it contains to the depth of only six inches as much nitrogen as would be furnished by 775 tons of common barn-yard manure, and as much phosphoric acid as 900 tons of manure. With such facts as these before us, am I to blame for urging farmers to cultivate their land more thoroughly? I do not know that my land or the Deacon’s is as rich as this English soil; but, at any rate, I see no reason why such should not be the case.