Carbon‐nitrogen relationships in soil. IV.—Mineralization of Carbon and Nitrogen

Abstract Production of carbon dioxide and accumulation of inorganic nitrogen have been studied in a group of 27 soils differing widely in origin. Samples of each soil were incubated for 28 days at 23.5° and 30°. Further batches of soil were incubated at 23.5° after partial sterilization by steaming, and others after air‐drying and re‐moistening. Significant relationships were found between the carbon and nitrogen mineralized under each of the experimental conditions tested. Steaming and air‐drying the soils generally increased the mineralization of both carbon and nitrogen, as compared with untreated soils incubated at the same temperature, and resulted in a lower ratio of carbon to nitrogen mineralized. The amounts of nitrogen and carbon mineralized were significantly correlated with the total nitrogen and organic carbon contents of the soils. Evidence was obtained that the organic matter of intensively cultivated soils is more resistant than that of maiden soils to further microbiological decomposition.