Soils and fertilizers . ater-soluble matter to productiveness.— It might be expected that there would be a direct relationbetween the productive capacity of a soil and the quantitiesof plant nutrients in its water extract, and that this relationwould hold between different soils. This would imply that,as between two or more soils, the plant-food materials dis-solved by water would, in general, be proportional to thequantities of the readily available constituents in the has been demonstrated that such relations do obtainbetween certain soils, but it has not been proven that thisis inva
Soils and fertilizers . ater-soluble matter to productiveness.— It might be expected that there would be a direct relationbetween the productive capacity of a soil and the quantitiesof plant nutrients in its water extract, and that this relationwould hold between different soils. This would imply that,as between two or more soils, the plant-food materials dis-solved by water would, in general, be proportional to thequantities of the readily available constituents in the has been demonstrated that such relations do obtainbetween certain soils, but it has not been proven that thisis invariably the case. Indeed it is probable that soils whichdiffer little in their productivity would not, in every instance,show such a direct proportional relationship. Experimentswith four good and four poor soils showed the followingaverages for their crop yields and water extracts. PLANT-FOOD MATERIALS IN SOILS 97 Table 19.—Average Yields and Composition of Water Ex-tracts OF Four Good and Four Poor Soils Good Soils. Crop Yields per Acre Corn, bushels Potatoes, bushels Water soluble salts in pounds per acre of surfacefour feet Nitrogen Phosphoric acid Potash Lime Magnesia A somewhat similar result was obtained with two soilscontained in large -tanks from which drainage water wascollected, and that have been under experiment for a num-ber of years. Each tank holds about three and one-halftons of soil. In 1915 tanks filled with soils of different typeswere planted to corn. The yields of grain and stalks com-bined are given in Table 20 and also the number of poundsto the acre of plant nutrients in drainage water collectedduring seven months from the same soil types kept bareof vegetation. As only a trace of phosphoric acid was foundin the drainage that ingredient is not included in the table. Table 20. — Yields of Crop and Plant-Pood Material inDrainage Water prom Two Soil Types Soil Type DunkirkClay Loam VolusiaSitt Loam Yield of com silage (tons per acre) ....Sub
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