590 pounds of nitrogen 1,980 pounds of phosphorus 37,940 pounds of potassium 24,808 pounds of magnesium 31,320 pounds of calcium
"A splendid subsoil," Percy continued. "I know of none better in Illinois, except that we sometimes have more calcium in the form of carbonate, and even somewhat more potassium in places; but this must be a fine subsoil for alfalfa, where the bed rock is not too near the surface. Of course there is but little nitrogen in the subsoil, but that is true of all normal soils, because the nitrogen is contained only in the organic matter, and that decreases rapidly with depth and usually becomes insufficient to color the soil below 18 inches."
"Now," began Mr. West, "from these different analyses or invoices, and from your discussion of these results, I take it that you would not advise me to purchase any commercial fertilizer for use on the land we are still using in my rotation; but you think we should make large use of limestone and legume crops."
"Yes, Sir. Phosphorus is markedly deficient only in the very level upland which has been allowed to remain uncleared for fifty years or more, and nitrogen is certainly the limiting element on the land you are trying to keep in your rotation. While you cannot hope to put into your soil any such reserve of slow-acting organic matter as we still have in our comparatively new soils of the West, we may keep in mind that a small amount of quick-acting fresh organic matter is more effective than a large supply of what we might call embalmed material that decomposes very, very slowly unless assisted by the addition of more active organic matter. It frequently happens that one soil containing a large reserve of old humus, and hence showing more organic carbon and more nitrogen, by the ultimate invoice, than another soil, is, nevertheless, less productive, because the other soil contains a larger amount of fresh organic matter which decays quickly and thus furnishes more nitrogen and liberates more of the other elements from the insoluble minerals of the soil because of the greater abundance of the active products of organic decay.
"I think you should keep in mind, however, that, for every twenty-five bushels of corn you wish to produce, you should return to the soil one ton of clover or four tons of average farm manure, and that for one ton of produce hauled to the barns and fed, you will probably not return to the land more than one ton of manure."
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.