DefinePK

Abstract

A laboratory study was conducted at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh during 1997. The changes in microbial biomass carbon due to incorporation of different organic materials in soil were studied to determine the contribution of microbial biomass C to carbon pool of soil. The organic materials incorporated into the soil were: rice straw. wheat straw. napier. azolla. water hyacinth and town refuse. Individual organic materials were incorporated n the soil immediately after soil moisture adjustment (50% of maximum water holding capacity) @ 150 mg/20 g aw dried soil and were incubated for 98 days. The C account in the form of CO; (CO,-C) was measured upto 98 days at different time intervals. All the soil samples incorporated with different sources of organic matter showed higher biomass C as compared to untreated soils. At 98 days of incubation, wheat straw treated so1! gave higher CO,-C (133.93 mg/100 g air dry soil) and biomass C (215.31 mg/100 g air dry soil) followed by town refuse treated soil (CO-C 123/61 mg/100 g air dry and biomass C 192.37 mg/100 g air dry soil). The amounts of CO,-C and biomass C recorded at 7 days of incubation gradually increased in soil treated with all the organic materials upto 98 days of incubation but the amounts varied with respect to different organic materials. Maximum CO,-C and biomass C were produced at the primary stage of incubation (7 w0 21 days), With the increase of incubation period, CO,-C and biomass C production rates were decreased. Contribution of biomass C to organic C was higher in the soil treated with napier (1.81%) followed by the soil treated with town refuse (1.58%). It was concluded that among organic matter sources wheat straw had greater ability 1o increase CO,-C and biomass C.