Page:Popular Science Monthly Volume 84.djvu/63

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fertilizer manufacturers and advertising agencies to use, would cost about $75.

Illinois Experiments.—As an average of 318 tests conducted in southern Illinois during a period of eight years, two tons of ground limestone, applied once in four years at a cost of about $2.50 per acre, has produced an increase of 5 bushels of corn, 6$1⁄2$ bushels of oats, 4 bushels of wheat and $1⁄2$ ton of hay; and where one ton per acre of fine ground rock phosphate was applied on the common corn-belt land in a rotation of wheat, corn, oats and clover, the value of the increase produce paid back more than 100 per cent, for the first crop rotation and nearly 200 per cent, for the second four-year period.

On one of our oldest soil experiment fields on typical Illinois prairie