Regulating selenium nutrition-toxicity in cadmium stressed maize with date palm frond biochar

Cadmium (Cd) toxicity in maize possesses a significant threat to crop safety and productivity in developing countries. Selenium (Se), on the other hand is reported to have dose dependent nutritional as well as toxic roles in maize, which are not well explored under co-existence of Cd and date palm frond biochar (FB) and important residue available in Kingdom of Saudi Arabia. The present pot experiment explored effect of FB applications (@1%) on Maize growth, yield, physiology, biochemical and elemental (Cd/Se) attributes under Cd (0 and 50 mg kg⁻¹) and Se (0, 5, 10, and 20 mg kg⁻¹) soil applied treatments. The FB resulted in significant enhancement of maize growth and physiology while modulating antioxidants activity suggesting stress reversal and reduction in oxidative stress demand under Cd and Se co-stressed conditions. The FB application effectively reduced the maize root, shoot and grain Cd concentrations and associated targeted health quotient (THQ) from potential contaminated grain consumptions. Concurrently, FB influenced Se bioavailability and decreased its transfer to grain, thereby moderating Se accumulation and associated health risk at highest application dose (20 mg kg⁻¹), while Se showed beneficial effects at the lower applied concentrations, further enhanced by FB applications. Overall, the results showed that FB can be an effective soil conditioning amendment under controlled conditions for not only managing in Cd phytotoxicity but also regulating nutritional-toxicity balance of Se in maize plant, helping avoid its transition from a beneficial nutrient to toxic pollutant in maize grains intended for human consumption.