Alleviation of lead toxicity and enhancement of wheat (Triticum aestivum L.) yield and antioxidant capacity using silicon and humic acid amendments in contaminated soil.

Lead (Pb) contaminates agricultural soils, endangering human health, plant life, and the global food supply. Several strategies have been explored to mitigate Pb toxicity. Silicon (Si) can be used to increase crop production and sustain crop growth under heavy-metal stress. A field trial was conducted to assess the influence of two Si fertilizer sources on wheat yield, Pb accumulation, and antioxidant activities in a Pb-contaminated field. Si was applied as Ca silicate and burnt rice husk at 75 and 150 kg ha-1, respectively, either individually or in combination with humic acid (10 mg kg-1 of soil), as compared with the control (Pb-contaminated soil only). The addition of both Si sources reduced Pb stress; however, Ca silicate at 75 kg ha-1 + humic acid increased the plant height (23.22%), total chlorophyll content (24.16%), and grain yield (32.20%) compared with the control. Notably, both Si sources reduced Pb accumulation in roots as well as Pb translocation to the shoots and grains. Both Si fertilizers also reduced oxidative stress in wheat and increased superoxide dismutase and peroxidase activities. However, the outcome of synthetic Si fertilizer (Ca silicate + humic acid) was more pronounced than that of natural Si fertilizer (burnt rice husk + humic acid). Significant reductions of 22.39%, 25.19%, and 46.55% in Pb concentrations were observed in the roots, shoots, and grains, respectively, in response to synthetic Si fertilizer. Thus, the use of Si fertilizer (Ca silicate at 75 kg ha-1 + humic acid) was a more viable strategy for enhancing wheat productivity by improving the antioxidant defense system and reducing Pb accumulation in food crops.