Reduction of Lead Bioavailability and Phytotoxicity in Pb-Slag Contaminated Soil Using Soil Mixing and Compost-Modified Biochar

Abstract

Food security and human safety are being threatened by heavy metal contamination of agricultural lands. Several physical and biological methods have been employed separately for soil remediation. In this study, effects of combining soil mixing with compost (C) and cow-dung (CD) for reduction and immobilization of Pb in the soil as well as growth, Pb uptake and biochemical responses of maize grown on contaminated soil were investigated. Lead contaminated soil mixed with uncontaminated soil at different ratios to give 0%, 25%, 50%, 75% and 100% levels of contamination were further mixed with C and CD at four different levels (0, 10 20 and 30 t/ha) before planting of maize. Data were collected on maize growth and yield, Photosynthetic Pigments (PP), stress indicators (proline and glycine betaine) contents as well as Pb uptake by maize crop and post-cropping soil Pb concentrations. Pb concentration was reduced by 29-85% in soil mixtures while, C and CD further reduced Pb by 69-77% and 42-66%, respectively. Combined treatments reduced Pb uptake, enhanced maize tolerance and growth as no germination was recorded in 100% Pb contaminated soil. Dry matter accumulation and PP were more in maize crop grown on compost treated soils compared with those grown on soil mixtures only. Proline and glycine betaine contents in maize leaf were reduced in treated plants than untreated plants. Combination of soil mixing with organic amendments could be a better approach for reducing Pb uptake by maize crop and enhanced maize growth on contaminated soil.