Microbial biomass as an indicator of nutrient status of soil as influenced by parthenium and chromolaena as green manures and their compost under submerged condition

Laboratory incubation was conducted to study the changes in the microbial biomass nitrogen and microbial biomass carbon under waterlogged condition of paddy soil with the use of parthenium and chromolaena as green manures and their compost. Based on the content of total C of plant material organic material was applied at the rate of 0.5, 1.0 and 2.0 per cent of organic carbon. The increase in extractable C in soil alone treatment was 24.53 mg/kg soil at 60^th day of flooding. On 120^th day of flooding it was 30.12 mg/kg. The E_N values also increased with time. Addition of organic C through different sources at 0.5, 1.0 and 2.0 per cent levels increased the E_C and E_N values. Biomass C content (B_C) across different treatments at 60^th day of flooding ranged from 65 to 286 mg/kg in soil. Lowest microbial biomass content was noticed in T₅ (Parthenium green manure @ 0.5% C) among treatments which received organic carbon inputs.