The Story of the Soil; from the Basis of Absolute Science and Real Life

by Cyril G. Hopkins

CHAPTER XXX

"STONE SOUP"

THE next forenoon Percy and Mr. West spent some time making some further tests with hydrochloric acid and litmus paper in different places on the farm; but the result only confirmed the previous examinations.

"I never before saw any such light as now appears," said Mr. West. "It seems to me that for the first time in the history of Westover, covering about two centuries, a real plan can be intelligently made based upon definite information looking toward the positive improvement of the soil. While you have been away, I have been looking up the lime matter. I find that a lime is being advertised, and sold in small amounts, that is called hydrated lime, and it is especially prepared as an agricultural lime. It is recommended by some dealers as being fully equal to the ordinary commercial fertilizer which sells at about $25 a ton, while this hydrated agricultural lime can be bought for $8 a ton, and I think for a little less in larger amounts. You mentioned also that you had seen some one who had used hydrated lime, but it didn't seem to make much of a clover crop. Of course, I understand from what you said that his soil contained only one hundred and sixty pounds of phosphorus, and I take it that lime alone could not markedly improve his soil; but still I would like to know why, if he has one hundred and sixty pounds of phosphorus in his plowed soil, he could not produce a few good crops of clover. HOW much phosphorus does it require for a ton of clover?"

"One ton of clover contains only five pounds of phosphorus," Percy replied, "and of course the roots must also require some phosphorus, although after the crop is produced and removed, the phosphorus contained in the roots remains for the benefit of subsequent crops. Thus we might suppose the land which contains one hundred and sixty pounds of phosphorus ought to furnish the phosphorus needed for a three ton crop of clover every year for ten years; but in actual practice no such results are secured. The invoice of the plant food in the soil is a matter of very great importance, for it reveals the mathematical possibilities, but another matter of almost equal importance is the problem of liberating plant food from this supply sufficient for the crops to be produced year by year.

"Decaying or active organic matter is one of the great factors in the liberation of plant food, and undoubtedly the extension or distribution of the root system of the growing plant is another very potent factor. If the root surfaces come in contact with one per cent. of the total surface of the soil particles in the plowed soil, then we might conceive of a relationship whereby one per cent. of the phosphorus in that soil would be dissolved or liberated from the insoluble minerals and thus become available as food for the growing crop. We know that the rate of liberation varies greatly, with different soils and seasons, and crops also differ in their power to assist themselves in the extraction of mineral plant food from the soil. The presence of limestone encourages the development of certain soil organisms which tend to hasten some decomposition process. But, all things considered, it may be said, speaking very generally, that the equivalent of about one per cent. of the total phosphorus contained in the plowed soil does become available for the crops under average conditions. On this basis one hundred and sixty pounds of phosphorus would furnish about one and one-half pounds for the crops during one season. But in such a soil the phosphorus still remaining may be the most difficultly soluble, and the supply of decaying organic matter may be extremely low, so that possibly less than one pound per acre would become available, and this would meet the needs of less than four hundred pounds per acre of clover hay. Furthermore, the supply grows less and less with every crop removed.

"With your ordinary soil, carrying twelve hundred and seventy pounds of phosphorus, perhaps you may be able by a liberal use of decaying organic matter to liberate ten or fifteen pounds of phosphorus, or sufficient for a crop of forty to sixty bushels of corn; and, with a subsoil richer in phosphorus than the surface, and with more or less of the partially depleted surface removed by erosion year by year, the supply of phosphorus is thus permanently provided for unless the bed rock is brought too near the surface. It is doubtful if the direct addition of phosphorus to your sloping lands will ever be necessary or profitable. Certainly such addition is not advisable until you have brought the land to as high a state of fertility as is practicable by means of limestone, legumes, and manure."

"That seems clearly to be the case with most of the land now under cultivation on this farm," said Mr. West "Can you tell me anything about this hydrated lime?

"I can tell you it is correctly named," Percy replied. "Hydrated means watered, and an investment in hydrated lime is properly classed with other watered investments. If you prefer to use hydrated lime I would suggest that you buy fresh burned lump lime and do the hydrating yourself, which only requires that you add eighteen pounds of water to each fifty-six pounds of quick lime; in other words, that you slack the lime by adding water in the proper proportion. Both quick lime and hydrated lime are known as caustic lime. Webster says that the word caustic means 'capable of destroying the texture of anything or eating away its substance by chemical action.'

"This definition is correct for caustic lime, as you can easily determine by keeping your hand in a bucket of slacked lime a few minutes. Caustic lime eats away the organic matter of the soil. In an experiment conducted by the Pennsylvania Experiment Station, during a period of sixteen years, eight tons of hydrated lime destroyed organic matter equivalent to thirty-seven tons of farm manure, as compared with the use of equivalent applications of ground limestone; and, as an average of the sixteen years, every ton of caustic lime applied liberated seven dollars' worth of organic nitrogen, as compared with ground limestone. That this much liberated nitrogen was essentially wasted and lost is evidenced by the fact that larger crops were produced where ground limestone was used than where burned lime was applied.

"The limestone must be quarried whether used for grinding or for burning, and the grinding can be done for twenty-five cents a ton where a large equipment with powerful machinery is used and where cheap fuel is provided, as near the coal mining districts. It need not be very finely ground. If ground to pass a sieve with twelve meshes to the linear inch, it is very satisfactory, provided that all of the fine dust produced in the grinding is included in the product. You see the soil acids are slightly soluble and they attack the limestone particles and are thus themselves destroyed or neutralized. If, however, you ever wish to use raw rock phosphate, insist upon its being sufficiently fine-ground that at least ninety per cent. of it will pass through a sieve with ten thousand meshes to the square inch, this being no finer than is required for the basic slag phosphate, of which several million tons are now being used each year in the European countries. Like the raw rock phosphate, the slag gives the best results only when used in connection with plenty of decaying organic matter."

"That reminds me," said Mr. West, "of what one of the fertilizer agents said about raw phosphate. He said the use of raw phosphate with farm manure reminded him of 'stone soup,' which was made by putting a clean round stone in the kettle with some water. Pepper and salt were added, then some potatoes and other vegetables, a piece of butter and a few scraps of meat. 'Stone soup,' thus made, was a very satisfactory soup. He said that in practically all of the tests of raw phosphate conducted by the various State Experiment Stations, manure has been used as a means of supplying organic matter to liberate the phosphorus from the raw rock, but in such large quantity as to be entirely impracticable for the average farmer to use on his own fields; and his opinion was that the entire benefit was due to the manure. He had a little booklet entitled 'Available or Unavailable Plant Food—Which?' published by the National Fertilizer Association, and said I could get a copy by addressing the Secretary at Nashville, Tennessee."

"Fortunately," said Percy, "this is not a question of opinion but one of fact; and it has been discovered that the fertilizer agents who are long on opinions and short on facts prefer to sell four tons of complete fertilizer for $80, or even two tons of acid phosphate for $30, rather than to sell one ton of raw phosphate, containing the same amount of phosphorus, for $7.50. In the manufacture of acidulated fertilizers, one ton of raw phosphate, containing about two hundred and fifty pounds of the element phosphorus, is mixed with one ton of sulfuric acid to make two tons of acid phosphate; and, as a rule, these two tons of acid phosphate are mixed with two tons of filler to make four tons of complete fertilizer. A favorite filler is dried peat, which is taken from some of the peat bogs, as at Manito, Illinois, and shipped in train loads to the fertilizer factories. The peat is not considered worth hauling onto the land in Illinois, even where the farmers can get it for nothing; but it contains some organic nitrogen, and, by the addition of a little potassium salt, the agent is enabled to call the product a 'complete' fertilizer.

"Experiments with the use of raw rock phosphate have been conducted by the State Agricultural Experiment Stations over periods of twelve years in Maryland, eleven years in Rhode Island, twenty-one years (in two series) in Massachusetts, fourteen years (in two series) in Maine, twelve years in Pennsylvania, thirteen years in Ohio, four years in Indiana, and from four to six years on a dozen different experiment fields in different parts of Illinois.

"I have here some quotations taken from the directors of several of these experiment stations which fairly represent the opinions which they have expressed concerning their own investigations. Thus the Maryland director says:

"'The results obtained with the insoluble phosphates has cost usually less than one-half as much as that with the soluble phosphates. Insoluble South Carolina phosphate rock produced a higher total average yield than dissolved South Carolina rock.'

"The Rhode Island director comments as follows:

"' With the pea, oat, summer squash, crimson clover, Japanese millet, golden millet, white podded Adzuka bean, soy bean, and potato, raw phosphate gave very good results; but with the flat turnip, table beet, and cabbage it was relatively very inefficient.'

"The following statement is from the Massachusetts director:

"'It is possible to produce profitable crops of most kinds by liberal use of natural phosphates, and in a long series of years there might be a considerable money saving in depending at least in part upon these rather than upon the higher priced dissolved phosphates.'

"The director of the Maine State Experiment Station gives us the following:

"'For the first year the largest increase of crop was produced by soluble phosphate. For the second and third years without further addition of fertilizers, better results were obtained from the plots where stable manure and insoluble phosphates had been used.'

"The stable manure and insoluble phosphates here referred to were not applied together, but on separate plots. In deed, the raw phosphate was not used in connection with manure either in Maryland, Rhode Island, Massachusetts, Maine, Pennsylvania, or Indiana; and in the extensive experiments in progress in Illinois the raw phosphate has been used, as a rule, not with farm manure, but with green manures; and wherever manure has been used in connection with the raw phosphate, as in Ohio, the comparison is made with the same amounts of manure applied without phosphate.

"The Pennsylvania Report for 1895, page 210, contains the following statement:

"'The yearly average for the twelve years gives us a gain per acre of $2.83 from insoluble ground bone, $2.45 from insoluble South Caroline rock, $1.61 from reverted phosphate, and 48 cents from soluble phosphate, thus giving us considerably better results from the two forms of insoluble phosphate than from the reverted or soluble forms.'

"The Indiana director reports as follows:

"'It will be seen that during the first and second years the rock phosphate produced little effect, while the acid phosphate very materially increased the yields. During the third and fourth seasons, however, the rock produced very striking results, even forging ahead of the acid. This and very similar investigations in progress lead us to believe that rock phosphate is a cheap and effective source of phosphorus where immediate returns are not required.

"In the Ohio experiments eight tons of manure per acre were applied once every three years in a three-year rotation of corn, wheat, and clover, three different fields being used, so that every crop might be grown every year. The average yields for the thirteen years where manure alone was used were:

53.1 bushels of corn 20.6 bushels of wheat 1.63 tons of hay

"The average yields on the unfertilized land were:

32.2 bushels of corn 11.4 bushels of wheat 1.16 tons of hay

"If the corn is worth 35 cents a bushel, the wheat 70 cents, and the hay $6 a ton, in addition to the expense of harvesting and marketing, then the total value of the manure spread on the land is $2.07 a ton.

"Where $1.20 worth of raw phosphate (320 pounds) were added in connection with the manure the average yields were as follows:

61.4 bushels of corn 26.3 bushels of wheat 2.23 tons of hay

"And where $2.40 worth of acid phosphate (320 pounds) were used with the same amount and kind of manure the following average yields were secured:

60.4 bushels of corn 26.5 bushels of wheat 2.16 tons of hay

"These are the actual yield, and by any method of computation yet proposed, each dollar invested in raw phosphate has paid back much more than has a dollar invested in acid phosphate."

"And was the use of the raw phosphate really profitable?" asked Mr.
West.

"Well, you might figure that out for yourself," Percy replied, "preferably using the average prices for your own locality for corn, wheat and clover. As I figure it at prices below the ten-year average for Illinois, the raw phosphate paid about eight hundred per cent. net on the investment."

"Eight hundred per cent! You must mean eight per cent. net.

"No, Sir, I mean eight hundred per cent. net, but you had better take the data and make your own computations. But does it not seem strange that, with such positive knowledge as this available, many of the Illinois landowners who have managed to sell off enough of their original stock of fertility in grain or stock at good prices to enable them to more than pay for their lands, should continue to invest their surplus in more land with hope that it will pay them eight per cent. interest, when they could secure many times that much interest from investing in the permanent improvement of the land they already own?"

"Perhaps it is not so strange," replied Mr. West. "I fear that some of their ancestors did the same thing in Virginia and other Eastern States until the land became poor, and then of course they were 'land poor.' But, say, that 'stone soup' wouldn't be so bad for those Ohio landowners, would it? I should think they would avail themselves of the positive information from their experiment station. Speaking of soup, I wonder if it isn't time for lunch! But tell me; are the Illinois farmers doing anything with raw phosphate?"

"Yes, they are doing something, but by no means as much as they ought. About two months ago a group of the leading farmers from our section of the State went up to Urbana to look over the experiment fields, some of which have been carried on since 1870. The land is the typical corn belt prairie, and consequently the results should be of very wide application. Well, as a result of that day's inspection of the actual field results, an even twelve carloads of raw phosphate were ordered by those farmers upon their return home; and I learned of another community where ten carloads were ordered at once after a similar visit. As an average of the last three years the yield of corn on those old fields has been 23 bushels per acre where corn has been grown every year without fertilizing, 58 bushels where a three-year rotation of corn, oats and clover is followed, and in the same rotation where organic matter, limestone, and phosphorus have been applied the average yield has been 87 bushels in grain farming and 92 bushels in live-stock farming.

"I attended the State Farmers' Institute last February, and there I met many men who have had several years' experience with the raw rock. Usually they put on one ton per acre as an initial application and plow it under with a good growth of clover; and, afterward, about one thousand pounds per acre every four years will be ample to gradually increase the absolute total supply of phosphorus in the soil, even though large crops are removed.

"A good many of our thinking farmers are now using one or two cars of raw phosphate every year, and they are figuring hard to keep up the organic matter and nitrogen. The most encouraging thing is the very marked benefit of the phosphate to the clover crop, and of course more clover means more corn in grain farming, and more corn and clover means more manure in live-stock farming.

"On the Illinois fields advantage is taken of these relations in the developing of systems of permanent agriculture. You see, if the phosphate produces more clover, then more clover can be plowed under on that land; or, if the crops are fed, then more manure can be returned to the phosphated land than to the land not treated with phosphate and not producing so large crops. Really the phosphate is not given full credit for what it has accomplished in the Ohio experiments; because, while the land receiving phosphated manure has produced about one-fourth larger crops than the land receiving the untreated manure, the actual amounts of manure applied have been the same, whereas one-fourth more manure can be produced from the phosphated land and if this increased supply of manure were returned to the land it would increase the supply of nitrogen and thus make still larger crop yields possible."

"That is surely the way it would work out in practical farming," said Mr. West. "I think I did not tell that $4.80 a ton is the lowest quotation I have been able to get as yet for ground limestone delivered at Blue Mound Station."

"That would make its use prohibitive," said Percy. "You ought to get it for just one-fourth of that, or for $1.20 a ton. In Illinois we can get it delivered a hundred miles from the quarry for $1.20 a ton. It costs no more for a thirty-ton car of ground limestone than the farmer receives for a cow; and the cost of a car of fine-ground natural phosphate is about equal to the price of one horse."

"Of course, our limestone supplies are essentially inexhaustible," said Mr. West, "but is that also true of our natural phosphate deposits?"

"It is not true of the high-grade phosphate," replied Percy; "for, according to the information furnished by the United States Geological Survey, it is evident that the known supplies of our high-grade phosphate will be practically exhausted in fifty years if our exportation continues to increase at the prevailing rate. After that is gone we may then draw upon our low-grade phosphate deposits, which though probably not inexhaustible are known to be exceedingly extensive."