Effect of nitrogen and sulphur on manure decomposition in a savanna soil of Nigeria

The rate of decomposition of manure and nutrients release pattern have been the concern of many workers. The ability of manure to provide essential plant nutrients depends on its quality. Due to variation in composition, availability of nutrients in manure is critical to its use in addressing soil fertility constraints. The objective of this study was to determine the effect of mineral N and S fertilizers on CO 2 evolution and nitrogen mineralization during manure incubation. Three rates of N and S (0, 60 and 120 kg N ha -1; 0, 15 and 30 kg S ha -1 ) and 0, 5 and 10 t ha -1 manure (CD) were mixed with100 g of soil and incubated at 25 0 C and sampled weekly for CO 2 flux for six weeks. Ammonium- N and nitrate-N were determined at the end of the incubation. The amount of CO 2 flux increased in the first 2 wk of incubation where 10 t ha -1 CD significantly increased CO 2 flux than half its rate. The interaction of 120 kg N ha -1 x 0 kg S ha -1 x 5 t ha -1 CD had the highest amount of CO 2 flux (9.7 g kg -1 ) in wk 2. Ammonium-N increased significantly from the control (0.42 g kg -1 ) to 0.70 g kg -1 at 120 kg N ha -1 or 40 % difference, while nitrate-N was highest with 10 t ha -1 CD (0.25 g kg -1 ) compared to control (0.02 g kg -1 ) or 86 % difference. The decline in the amount of CO 2 flux in wk 6 revealed that the biodegradable carbon pool in the substrate decreased with time. Our findings suggest that mineral nitrogen fertilizer is required for manure decomposition whereas, mineral S fertilizer is not a major requirement for manure decomposition.