Laboratory and Field Mineralization of Nitrogen from Fermentation Residues

The proper disposal of organic wastes is one of our most pressing problems. Applications of these materials to agricultural land are becoming increasingly popular and information concerning nitrogen mineralization rates is necessary to ensure sufficient nitrogen for optimum plant growth and to prevent ground water contamination. The objectives of this study were to determine the nitrogen mineralization rate of an industrial fermentation waste and to relate rate of land application to potential leaching of mineralized nitrogen. Mineralization rates were determined by incubating soil‐waste mixtures at 35°C in leaching tubes and periodically extracting the mineralized nitrogen with 0.01 M CaCl 2 . Fermentation wastes, obtained from the production of various antibiotics and organic acids, were also applied to field plots at rates of 0, 112, and 224 dry metric tons/ha. Soil samples were obtained periodically at predetermined depths and extracted with 2 N KCl for the determination of mineral‐N. Under optimum conditions in the laboratory between 55 and 95% of the organic nitrogen added was mineralized in a 24‐week period. Approximately 50% of the mineralization occurred during the first 2 weeks of incubation. Available nitrogen concentrations in field plots exceeded 100 ppm at the 45‐cm depth for both the 112‐ and 224‐metric ton/ha rates during the late summer of the year of application. Levels of available nitrogen in treated plots were not appreciably different from the check during the second year.