Organic Amendments and Biochar Alleviate Chromium Stress in Mungbean (Vigna radiata)

Abstract

Chromium (Cr) contamination poses severe risks to crop productivity and food safety due to its toxicity and persistence. This study assessed the effectiveness of organic amendments cow dung manure, poultry manure, farmyard manure, biochar and lignite in mitigating Cr stress (25 ppm) in mungbean (Vigna radiata) under controlled pot conditions. Soil Cr fractionation, plant growth, and yield responses were evaluated. Cow dung manure emerged as the most effective treatment, reducing exchangeable Cr by 33.5% and increasing residual (immobilized) Cr by 147%, thereby limiting Cr mobility. Physiological and agronomic improvements were substantial, with increases in shoot length (45.8%), shoot biomass (315%) and seed yield (6,842%) over Cr-stressed controls. Poultry and farmyard manures provided moderate benefits, whereas biochar and lignite showed minimal impact. The superior performance of cow dung manure is attributed to its nutrient richness, enhancement of soil organic matter, and stimulation of microbial Cr(VI) reduction to less toxic Cr(III). Overall, results demonstrate that nutrient-rich organic amendments, particularly cow dung, offer a sustainable, low-cost solution for Cr remediation, improving both soil health and crop productivity. Field-scale validation is recommended to confirm long-term stability and optimize application strategies for managing Cr-contaminated agricultural soils.