on the steeper slopes and one thousand pounds on the more gently undulating areas, ours contains five thousand pounds in the brown silt loam and eight thousand pounds in the heavier black clay loam.  This means that our Illinois prairie soil contains from five to ten times as much humus, or organic matter, as your best upland soil.  To supply this difference in humus would require the addition of from four hundred to eight hundred tons per acre of average farm manure, or the plowing under of one hundred to two hundred tons of air-dry clover.  This represents the great reserve of the Illinois prairie soils above the total supplies remaining in your soils.

“Our farmers are still producing crops very largely by drawing on this reserve.  Of course most of this great supply of humus is very old.  It represents the organic residues most resistant to decomposition; and, where corn and oats are grown exclusively, the soil has reached a condition on many farms under which the decomposition of the reserve organic matter is so slow that the nitrogen liberated from its own decay and the minerals liberated from the soil by the action of the decomposition products are not sufficient to meet the requirements of large crops, and for this reason alone some of our lands that are still rich are said to be run down; but they only require a moderate use of clover or farm manure or other fresh and active organic matter to at once restore their productiveness to a point almost equal to the yields from the virgin soil.  Some Illinois farmers who have discovered this apparent restoration have jumped to the conclusion that they have solved the problem of permanently maintaining the fertility of the soil; and I judge from a remark made by the Secretary of Agriculture that some Iowa farmers have the same mistaken notions.

“These fresh supplies of active organic matter serve primarily as soil stimulants, hastening the liberation of nitrogen from the organic reserve and of minerals from the inorganic soil materials.

“Where one of the Eastern farmers has managed a farm under the rotation system with the occasional use of clover or light applications of farm manure,—­where this has been continued until the great reserve is largely gone, and the phosphorus supply greatly depleted, then the land is truly run down, but not until then.

“Finally, land-plaster and quick-lime, still more powerful soil stimulants, are often brought into the system to bring about a more complete exhaustion of the soil reserves, and lastly the use of small amounts of high-priced commercial fertilizers serves to put the land in suitable condition for ultimate abandonment.”

“Do you mean that commercial fertilizers injure the soil?” asked Mr. West.