Effect of Weeds and their Compost on Microbial Biomass and Nutrient Status Under Waterlogged Condition

Laboratory incubation experiment was carried out 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 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. The increase in extractable C and N in Mudigere soil alone was 30.81 mg kg^-1, at 60th day of flooding. On 120^th day of flooding the EC values of Mudigere soil alone was 32.47 mg kg^-1. Similarly with time, the EN values also increased. The highest EC value was recorded in T10: Mudigere soil+Chromolaena compost @ 2.0% C at day 60 and 90 was 112.11 and 153.52 mg kg^-1 soil, respectively. The EC: EN ratio in control was 7.91 in Mudigere soil whereas on 120th day of flooding the value was 7. On 120 day, it ranged from 85 to 381 mg kg-1 soil. On 120th day lowest biomass nitrogen (BN) (215 mg kg^-1) was recorded in T5:Mudigere soil+Parthenium green manure @ 0.5% C. Increasing the C level resulted in increasing BN and BC, but to different degrees, depending on the native of C sources. Addition of different levels of organic manures to soils showed highly significant changes in nutrient content of soil over control at 60 and 120 days after flooding.