ESTIMATION OF MICROBIAL BIOMASS CARBON AND NITROGEN IN BANGLADESH SOILS

In order to estimate the microbial biomass content and to quantify the amount of available plant nutrients derived from microbial biomass in Bangladesh soils, biomass-C, -N, and available-N contents using samples from 8 soils were measured by applying the chloroform fumigation and drying-rewetting methods, respectively. 1) Contents of organic carbon and total nitrogen were 0.36-1.06 (av. 0.74) and 0.04-0.11 (av. 0.07)% in samples from eight soils collected in the central and north-eastern region of Bangladesh. 2) The contribution of biomass-C to soil organic carbon was about 2%, ranging from 1.35 to 3.32. The contribution was higher in grassland soil than in cropped arable soil with similar organic C contents. 3) The contribution of biomass-N to total soil nitrogen ranged from 1.15 to 2.95 (av. 2.11). 4) The average ratio of flush-C to flush-N for a 10 day period of incubation was 7.02. 5) The contents of organic C, microbial biomass and available plant nutrients in the Bangladesh soils were significantly lower than those in the temperate region soils where intensive agriculture is practiced.