Yields of crops are dependent in a large measure on the supply of plant food in the soil. Although many of our soils had a high virgin fertility, past soil management practices have not included adequate provisions for the return to the soil of a substantial portion of the plant food removed by crops. Specific knowledge concerning the rate of depletion of our soils with respect to soil organic matter, nitrogen, and phosphorus is imperative to sound recommendations regarding crop rotations, fertilizer application, and other soil-building practices. This investigation is concerned with soil fertility changes which are the result of cropping practices and fertilizer treatment on plots at the Agronomy Farm of the South Dakota Agricultural Experiment Station.
South Dakota State University
Puhr, Leo F., "Soil Changes as Influenced by Cropping and Fertilizer Treatment" (1945). Agricultural Experiment Station Technical Bulletins (1939-2011). 16.