Cobalt and nickel uptake by rice and accumulation in soil amended with municipal solid waste compost

Effect of addition of municipal solid waste compost (MSWC) on cobalt (Co) and nickel (Ni) contents of submerged rice paddies were studied. A sequential extraction method was used to determine the metal (Co and Ni) fractions in MSWC and cow dung manure (CDM). Both metals were significantly bound to the organic matter and Fe and Mn oxides in MSWC and CDM. Metal content in rice straw was higher than in rice grain. Metal bound with Fe and Mn oxides in MSWC and CDM best correlated with straw and grain metal followed by water soluble and exchangeable fractions. Carbonate, organic matter bound and residual fractions in MSWC and CDM did not significantly correlate with rice straw and grain metal. MSWC would be a valuable resource for agriculture, but long-term field experiments with MSWC are needed to assess by regular monitoring of the metal loads and accumulation in soil and plants.