“And yet,” said the Doctor, “you would probably not get more than half a ton of manure from the hens, while the liquid and solid excrements from the pigs, if the corn-meal was made into a thin slop, would weigh two or three tons.”
“More, too,” said the Deacon, “the way you feed your store pigs.”
“Very well; and yet you say that the half ton of hen-manure made from a ton of corn is worth more than the two or three tons of pig-manure made from a ton of corn. You do not seem to think, after all, that mere bulk or weight adds anything to the value of the manure. Why then should you say that the manure from a ton of corn-fodder is worth more than from a ton of straw, because it is more bulky?”
“You, yourself,” said the Deacon, “also say the manure from the ton of corn-fodder is worth more than from the ton of straw.” —“True,” said I “but not because it is more bulky. It is worth more because the ton of corn-fodder contains a greater quantity of valuable plant-food than the ton of straw. The clover is still richer in this valuable plant-food, and the manure is much more valuable; in fact, the manure from the ton of clover is worth as much as the manure from the ton of straw and the ton of corn-fodder together.”
“I would like to see you prove that,” said the Deacon, “for if it is true, I will sell no more clover-hay. I can’t get as much for clover-hay in the market as I can for rye-straw.”
“I will not attempt to prove it at present,” said the Doctor; “but the evidence is so strong and so conclusive that no rational man, who will study the subject, can fail to be thoroughly convinced of its truth.”
“The value of manure,” said I, “does not depend on the quantity of water which it contains, or on the quantity of sand, or silica, or on the amount of woody fibre or carbonaceous matter. These things add little or nothing to its fertilizing value, except in rare cases; and the sulphuric acid and lime are worth no more than the same quantity of sulphate of lime or gypsum, and the chlorine and soda are probably worth no more than so much common salt. The real chemical value of the manure, other things being equal, is in proportion to the nitrogen, phosphoric acid, and potash, that the manure contains.
“And the quantity of nitrogen, phosphoric acid, and potash found in the manure is determined, other things being equal, by the quantity of the nitrogen, phosphoric acid, and potash contained in the food consumed by the animals making the manure.”