INFLUENCE OF CADMIUM ON CARBON AND NITROGEN MINERALIZATION IN SEWAGE-SLUDGE AMENDED SOILS

The effect of cadmium on C and N mineralization in sewage sludge amend ed and unamended sandy loam, loam and clay loam soils was studied duri ng 2 months incubation at 30 +/- 1-degrees-C The sludge amendment caus ed 15-39% increase in microbial respiration, with the maximum C minera lization in sandy loam and the minimum in loam soil. The addition of 1 0 mug Cd g-1 soil had no remarkable effect on C and N mineralization a nd microbial biomass; whereas significant decreases in the above param eters were observed at 25 and 50 mug Cd g-1 soil, irrespective of the sludge addition. Less NO3--N accumulated at higher Cd concentration. C d recovery was high in sandy loam and low in clay loam soil. DTPA extr actable Cd exhibited a significant negative correlation with microbial biomass (r = -0.58 to -0.86*; p < 0.05).