Effect of Water Logging and Weeds as Green Manures and their Composts and Subsequent Drainage of Paddy Soil on Release of Nitrogen and Phosphorus

A laboratory incubation experiment was carried out to study the changes in the ammonical extractable nitrogen and phosphorus under submerged and well drained conditions of paddy soil with the use of Parthenium and Chromolaena as green manure and their compost. Based on the content of total C of plant material organic material applied at the rate of 0.5, 1.0 and 2.0 per cent level of organic carbon. In general NH⁺ ₄-N and brays – P increased with the period of submergence, among different treatments maximum NH⁺ ₄-N (138.67mg/kg) was noticed in T₁₀: Mandya soil + Chromolaena compost @ 2.0 % C whereas least (92.23mg/kg) in T₁: Mudigere soil alone and brays –P recorded highest (23.83 mg kg^-1) in T₁₀: Mudigere soil + Chromolaena as green manure @2.0% and least (11.84 mg kg^-1) in T₁:. Mudigere soil alone on 120^th day of flooding. Increasing the level of organic carbon application increase the NH⁺ ₄-N and brays –P. Under well drained conditions the ammonical nitrogen contents of all the treatments decreases rapidly and nitrate content increases whereas brays phosphorus also increases.