Effect of vermicomposted municipal solid wastes on growth, yield and heavy metal contents of rice (Oryza sativa)

The commercial organic manure formulation of a processed organic municipal solid waste (MSW) was used in field experiments with rice (Oryza sativa), and MSW being composted by an earthworm (Lampito mauritii) was also added to the soil to assess growth, yield and heavy metal contents of soil and plants. MSW incorporated in soil caused significant increase of many growth parameters, germination of seeds, and chlorophyll contents of rice. Vermicomposted (VC) MSW (0, 50, 100, 150, 200, 250 kg/ha) caused further increases in growth. At the highest level of MSW, rice yield was also the highest, and VC+MSW amendments had additive effects. Physicochemical properties of soil were progressively improved with increasing MSW levels. Heavy metals (Cr, Ni, Cu, Zn, Cd and Pb) increased in soil and plant parts with MSW addition, analyzed by atomic absorption spectrophotometry. Maximum uptake of these heavy metals was observed in rice roots, and decreased in leaves and seeds. But the amounts of Cu, Zn, and Pb remained in one range in roots, leaves or seeds of rice grown in MSW-treated soils. Vermicomposting of MSW caused ameliorations of heavy metal contents in plant parts.