Vermicompost and biogas slurry synergy attenuates Pb toxicity in maize by modulation of physio-biochemical traits and Pb sequestration

ABSTRACT Lead (Pb) contamination in soils poses a serious threat to crop plant productivity and human health by enabling the transfer of toxic metals into the food chain. Developing effective and sustainable remediation strategies is therefore essential. This study examined the combined effects of vermicompost (VC) and biogas slurry (BGS) in reducing Pb toxicity in maize, an area that has not been widely explored. Organic amendments can reduce Pb mobility by enhancing adsorption processes and increasing hydroxide (OH − ) concentration in the soil solution, which promotes Pb precipitation and immobilization. A factorial experiment was conducted using four Pb levels (0, 100, 200, and 300 mg kg -1 soil) and four VC–BGS application rates (0, 32, 48, and 64 g kg -1 soil), with both amendments applied in equal proportions. Their combined application of VC and BGS significantly improved maize performance, increasing 100-grain weight (88.54%) and biological yield (41.02%). It also enhanced antioxidant activity, as shown by reduced electrolyte leakage and lower levels of hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA), indicating improved membrane stability. In addition, VC–BGS application helped maintain ionic balance by reducing sodium (Na⁺) accumulation in roots (31.81%) and increasing potassium (K⁺) levels in shoots (52.94%). It also promoted the accumulation of osmolytes, including total soluble proteins (19.10%) and soluble sugars (46.40%). Importantly, Pb uptake was substantially reduced in roots (72.92%), shoots (75.64%), and grains (76.06%). Phytoaccumulation indices suggested that maize has potential for phytoremediation under Pb stress. Overall, the combined application of VC and BGS improved plant growth, reduced Pb availability, and enhanced plant tolerance to stress. These findings highlight a practical and environmentally sustainable approach for managing Pb-contaminated soils and supporting safer agricultural production.