Utilizing spent mushroom substrate biochar to improve Zea mays L. growth and biochemical resilience against cadmium and chromium toxicity.

Heavy metal contamination in agricultural soils is a growing environmental concern, particularly due to the increasing accumulation of cadmium (Cd) and chromium (Cr) from industrial discharge, wastewater irrigation, and excessive fertilizer use. These toxic metals severely impact crop productivity by disrupting nutrient uptake, damaging root structures, and inducing oxidative stress, which collectively inhibit plant growth and development. Maize (Zea mays L.), a globally important cereal crop, is highly susceptible to heavy metal toxicity, making it essential to develop cost-effective and sustainable mitigation strategies. Spent mushroom substrate (SMS) biochar has emerged as an effective and sustainable method due to its ability to absorb heavy metals. Spent mushroom substrate biochar improves compost quality, soil fertility, and health. Its high porosity and surface area immobilize toxic metals, reducing nutrient losses and oxidative stress in plants. Pyrolysis temperature affects its surface area, nutrient composition, and adsorption abilities. This study aims to address this gap by evaluating the effectiveness of SMS biochar at varying application rates in mitigating Cd and Cr toxicity in maize. By assessing key physiological and agronomic parameters, this research provides novel insights into the potential of SMS biochar as a sustainable soil amendment for heavy metal-contaminated soils. Five treatments, i.e., 0, 50, 100, 150 and 200B were applied under Cd and Cr toxicity in 3 replications following the completely randomized design (CRD). Results exhibited that 200B caused an increase in maize plant height (26.1%), root dry weight (99.7%), grain yield (98.2%), and chlorophyll contents (50%) over control under Cd and Cr stress. In conclusion, 200B can mitigate Cd and Cr stress in maize plants. More investigations are suggested to declare 200B as a promising amendment for mitigation of Cd and Cr stress in other crops.