"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. "Well, to some extent they injure the soil because they tend to destroy the limestone and increase the acidity of the soil, and also because they contain more or less manufactured land-plaster and thus serve as soil stimulants; but the chief point to keep in mind concerning the use of the common so-called complete commercial fertilizer is that they are too expensive to permit their use in sufficient quantities to positively enrich the soil. Thus the farmer may apply two hundred pounds of such a fertilizer at a cost of $3.00 an acre, and then harvest a crop of wheat, two crops of hay, pasture for another year or two, plow up the grounds for corn, apply another two hundred pounds for the corn crop, follow with a crop of oats, and then repeat. He thus harvests five crops and pastures a year or two and applies perhaps four hundred pounds of fertilizer at a cost of $6.00.