Effect of Crop Rotation and Fertilizer Treatment on the Nitrogen and Organic Carbon Contents of a Prairie Soil

Abstract

AbstractThe effects of cropping systems and soil treatments on the nitrogen and organic carbon contents of Geary silt loam were studied in 1915, 1923, 1934, 1946, and in 1956 on the Agronomy Farm at Manhattan, Kansas.Losses of nitrogen and organic carbon were largest where the original contents of these constituents were highest. Losses were most rapid in the earlier years of the study. Largest losses occurred under a 3‐year rotation of corn, soybeans (for hay), wheat. Losses tended to be lower in the continuous wheat plots than in plots under rotations including row crops and legumes in addition to wheat.Differences between losses of nitrogen and organic carbon under the different fertility treatments were small. However, losses were greatest under phosphate, and phosphate and potash treatments, and were smallest under the complete fertilizer treatment.Although alfalfa increased the nitrogen content of the subsoil slightly, the other crops in the rotation reduced it so that the rotation studied did not appreciably change the subsoil nitrogen content.