Vermicompost-mediated regulation of soil Pb bioavailability, ionic homeostasis, and root morpho-functional traits...

Lead (Pb) contamination in agricultural soils presents substantial risks to soil health, crop productivity, and food safety. The use of vermicompost derived from agricultural crop residues offers a promising approach to reduce Pb bioavailability in soil and alleviate its toxicity in maize seedlings by improving soil properties. This study investigates how vermicompost use can counteract Pb toxicity in maize with varying Pb accumulation tendencies. A pot experiment was conducted using four vermicompost doses (0, 4, 6, and 8 tons ha^-1) applied through the soil route to assess the morpho-physiological and root structural-functional responses of maize plants under different Pb levels (0, 100, 200, and 300 mg kg^-1 soil) in the growth medium, a topic that remains underexplored in the existing literature. Results indicated that Pb toxicity markedly inhibited maize seedling growth, as revealed by decreases in shoot fresh weight, root characteristics, and inorganic ions uptake; greater Pb accumulation was noted in roots and shoots of Pb-stressed plants relative to vermicompost-untreated plants. The vermicompost treatment promoted maize growth more efficiently, with increments of shoot fresh weight (124.96%), root length (138.46%), root average density (103.44%), and root volume (321.87%), as well as improved root anatomical characteristics. Vermicompost decreased Pb deposition in shoots (50.89%) and roots (65.25%) relative to untreated Pb-stressed plants. VC enhanced Pb stress resistance in maize by modulating activities of phytoaccumulation indices, such as BAC (24.35% ↓), BCF (35.50% ↓), and TF (40.99% ↑), while concurrently maintaining ionic balance, root Na⁺ (38.61% ↓), and shoot K⁺ (68.75% ↑). The application of vermicompost in this study significantly reduced Pb-induced stress, improved nutrient uptake, and enhanced growth parameters of maize under controlled conditions. These results indicate that vermicompost has considerable potential as an organic amendment for mitigating Pb toxicity in maize.