[ 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.”