of farm manure, 600 bushels of whole cotton seed, 900 pounds of
cotton seed meal, 900 pounds of kainit, 1100 pounds of guano, 200
pounds of bone meal, 200 pounds of acid phosphate, and 400 pounds of
sodium nitrate."

"I would also like to know the facts about this nitrogen business,"
said Mr. Thornton. "I've understood that one could get some of it
from the air, and I would much rather get it that way than to buy it
from the fertilizer agent at twenty cents a pound. Cowpeas don't
seem to help much, and we don't have the cotton seed, and we never
have sufficient manure to cover much land."

"It is a remarkable fact," said Percy, "that of the ten essential
elements of plant food, nitrogen is the most abundant, measured by
crop requirements, and at the same time the most expensive. The air
above an acre of land contains enough carbon for a hundred bushels
of corn per acre for two years, and enough nitrogen for five hundred
thousand years; and yet the nitrogen in commercial fertilizers costs
from fifteen to twenty cents a pound. At commercial prices for
nitrogen, every man who owns an acre of land is a millionaire.

"You mean he has millions in the air," amended Mr. Thornton.

"Yes, that is the better way to put it," Percy admitted, "but the
fact is he can not only get this nitrogen for nothing by means of
legume crops, but he is paid for getting it, because those crops are
profitable to raise for their own value. Clover, alfalfa, cowpeas,
and soy beans are all profitable crops, and they all have power to
use the free nitrogen of the air.