Effect of heavy metal contaminated sewage sludge on soil microbiological properties and growth of Indian mustard

Abstract

A laboratory incubation and pot experiment were carried out to study the effect of amendment of uncontaminated and metal contaminated sewage sludge on soil microbial biomass carbon (C), soil enzyme activities and growth of Indian mustard in a sandy loam soil. The application of metal contaminated sewage sludge containing chromium (Cr) (2400 mg kg−1), nickel (Ni) (400 mg kg−1) and lead (Pb) (2400 mg kg−1) had a detrimental effect on soil microbial biomass C and soil enzyme activities at different levels. Metals present in sewage sludge inhibited the microbial biomass carbon by 5.6–19.0% at different levels after 90 days of incubation. Dry matter yield, uptake of nitrogen (N), phosphorus (P) and potassium (K) increased significantly with the increasing levels of uncontaminated sewage sludge, whereas, amendment of metal contaminated sewage sludge at the levels of 40 and 80 t ha−1 decreased the growth of Indian mustard. The accumulation of Cr, cadmium (Cd), Ni and Pb was 997, 36, 793 and 620 mg kg−1, respectively, in the shoots of Indian mustard. Sewage sludge contaminated with metals Cr, Ni, and Pb at double the EU limits showed adverse effect on soil microbiological activities and growth of Indian mustard.