Spatial distribution of microbial biomass in relation to land-use in subtropical systems of north-east India

Spatial distribution of microbial biomass in relation to major land-use (grassland and agroecosystem) in subtropical region of north-east India was studied from April 2000 to March 2001. The mean microbial biomass C, N and P across the study sites at 0-10 cm soil depth ranged from 168 to 395, 20 to 68 and 8 to 30 mu g g super(-1) soil month super(-1) respectively. The microbial biomass exhibited seasonal peak in May and consistently decrease in both systems to the minimum in September and thereafter increase in later months. The microbial biomass in soil was characterized by a mean C:N:P ratio of 15:2:1 in grassland and 14:2:1 in agroecosystem. The microbial biomass was positively correlated to soil organic carbon, total nitrogen, phosphorous and soil pH. Higher soil microbial biomass was recorded in grassland than in agroecosystem indicating its decline on conversion of grassland into agroecosystem.