Soil application of vermicompost modulates physiological and biochemical responses enhancing lead tolerance in hemp cultivated in lead-contaminated soils

This is the authors' abstract. We don't add key points for this paper.

• Hemp growth is negatively affected by Pb toxicity. • Pb mine stressed soil enhanced antioxidant enzymatic activities in leaves. • Soil applied vermicompost mitigate the phytotoxic effects of Pb. • Optimal usage of vermicompost is sustainable tool for alleviation of Pb stress. Industrial globalization has resulted in significant lead (Pb) contamination of agricultural soils, threatening crop productivity and necessitating sustainable, cost-effective strategies to improve crop tolerance. This study investigated the effects of soil-applied vermicompost (VC; applied at w/w concentrations of 0 %, 1 %, 3 %, 5 %, and 7 %) and different Pb contamination sources (control: un-contaminated soil; Pb_SS: artificially Pb-spiked soil; Pb_MS: naturally Pb-contaminated mine soil) on the growth, physiological attributes, and Pb accumulation of industrial hemp ( Cannabis sativa L.). Pb stress, particularly from the mine-contaminated soil (Pb_MS), significantly inhibited hemp growth, biomass accumulation, and physiological performance. The application of VC to the soil mitigated these adverse effects, promoting plant growth and biomass production during both the rapid-growth and harvesting phases. Vermicompost application at 5 % w/w was identified as the optimal rate for maximizing stress mitigation. This specific treatment reduced the accumulation of malondialdehyde, a key biomarker of oxidative stress, by 41.15 %, whilst increasing soluble protein and soluble sugar content by 51.77 % and 33.24 % respectively, compared to Pb-stressed controls. Application of VC significantly strengthened the plant's resistance mechanisms, resulting in reduced translocation and accumulation of Pb in the aboveground biomass. The study concludes that soil application of VC, particularly at the 5 % rate, effectively mitigates Pb toxicity in hemp. This mitigation is achieved by enhancing growth and biomass production, stimulating antioxidant defense systems and the synthesis of osmoprotectants, and restricting Pb translocation. Soil-applied VC thus represents a reliable, practical, and low-cost technique for enhancing the resilience of hemp cultivation in Pb-polluted environments.