Mineralization of Nitrogen from Cattle Slurry Decomposing in Soil

An incubation experiment was conducted over a period of one year to find gross and net mineralization of N from cattle slurry decomposing in soil at 25°C and 50 per cent water holding capacity moisture. Labelled ammonium sulphate and fresh cattle slurry with its inorganic fraction labelled with ammonium sulphate were used to follow the transformations of N. Measurements were made at different intervals for NH,-N, NO,-N, organic-N, clay fixed-N and gross mineralization and immobilization of N were calculated. There was extensive mineralizatrion and immobilization of N in a slurry-amended soil and there was no net mineralization of N over about 30 days because rates of both the reactions were equal. Steady net mineralization of slurry organic N started after the rapid phase of turnover at about 1–2 months. The amount of N mineralized from the organic fraction of slurry in one year was 49.1 per cent of the organic N in slurry and net mineralization was 26.3 per cent of the organic N in slurry.