Effect of Cultivation on the Nitrogen and Organic Carbon Contents of a Kansas Argiustoll (Chernozem)
1971
Hobbs, J. A. | Thompson, C. A.
As a continuation of a Kansas dryland-soil study, started in 1916, samples from 44 plots and 2 uncultivated areas at the Ft. Hays Experiment Station were analyzed to determine the effects of a single cropping system (fallowwheat-sorghum) from 1956(58) to 1966 on soil organic-matter content. Surface soils containing more than 0.100% nitrogen in l958 generally lost nitrogen between 1958 and 1966; those containing less than 0.100% generally gained nitrogen. A regression equation developed from the relationship between 1958 nitrogen content and 1958-to-1966 loss (or gain) predicted an equilibrium-nitrogen content of 0.103%. Nitrogen losses from surface soils followed a curvilinear tiend, as in earlier phases of this study. Relation between soil-nitrogen content and duration of cultivation, developed from a knowledge of nitrogen contents of unbroken sod and of cultivated plots from 1915 through 1966 predicted that, with the fallow-wheat-sorghum cropping system and no additional organic matter or commercial fertilizer, the soil-nitrogen content should stabilize eventually at 0.103%. Subsoils (18 to 51 cm) lost nitrogen between 1958 and 1966, which contrasted with results from earlier samplings.
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