Microbial biomass and enzyme activities in submerged rice soil amended with municipal solid waste compost and decomposed cow manure

We studied the suitability of municipal solid waste compost (MSWC) application to submerged rice paddies in the perspective of metal pollution hazards associated with such materials. Experiments were conducted during the wet seasons of 1997, 1998 and 1999 on rice grown under submerged condition, at the Agriculture Experimental Farm, Calcutta University at Baruipur, West Bengal, India. The treatments consisted of control, no input; MSWC, at 60 kgNha(-1); well decomposed cow manure (DCM), at 60 kgNha(-1); MSWC (30 kgNha(-1)) +Urea (30 kgNha(-1)); DCM (30 kgNha(-1)) +U (30 kgNha(-1)) and Fertilizer, (at 60:30:30 NPK kgha(-1) through urea, single superphosphate and muriate of potash respectively). Soil microbial biomass-C (MBC), MBC as percentage of organic-C (ratio index value, RIV), urease and acid phosphatase activities were higher in DCM than MSWC-treated soils, due to higher amount of biogenic organic materials like water soluble organic carbon, carbohydrate and mineralizable nitrogen in the former. The studied parameters were higher when urea was integrated with DCM or MSWC, compared to their single applications. Soil MBC, urease and acid phosphatase activities periodically declined up to 60 day after transplanting (DAT) and then increased after crop harvest. The heavy metals in MSWC did not detrimentally influence MBC, urease and acid phosphatase activities of soil. In the event of long term MSWC application, changes in soil quality parameters should be monitored regularly, since heavy metals once entering into soil persist over a long period.