Heavy Metal Dynamics in Crops Grown on Municipal Solid Waste Compost Amended Soils

Abstract

Growing interest in using compost derived from municipal solid waste (MSW) in agriculture raises critical questions about its ecological safety, particularly the accumulation pattern of potentially toxic heavy metals in food and fodder crops. This study assessed the effects of a single application of MSW compost on soil heavy-metal dynamics and plant uptake in Napier grass (Pennisetum purpureum), ragi (Eleusine coracana), maize (Zea mays), and hyacinth bean (Lablab purpureus). The compost complied with the maximum permissible heavy-metal limits prescribed under the Fertilizer (Control) Order (FCO), 1985. Statistical analysis (Welch’s t-test with multiple-comparison correction) revealed significant cropspecific changes in soil metal concentrations following compost amendment, with reductions observed for certain metals such as Zn, Cu, Pb, and Cr. Bioconcentration and translocation factor results indicated elevated translocation (TF > 1) and accumulation in edible parts, particularly for Pb in maize and for Zn, Cu, Ni, and Cd in hyacinth bean. Essential metals (Zn and Cu) showed regulated uptake, while potentially toxic metals (Pb, Cd, and Cr) were variably immobilized or translocated depending on crop type. Overall, the findings demonstrate that the impact of MSW compost on heavy-metal mobility and plant uptake is crop-dependent. Although compost application may reduce the bioavailability of certain metals, it does not universally prevent their transfer to edible plant parts. These results highlight the need for crop-specific risk assessment and monitoring to ensure the safe and sustainable use of MSW compost in agricultural systems.