The Effect of Foliar Application of Humic Acid and Selenium on the Agrophysiological Traits of Corn Plants under Water Deficit Conditions

As freshwater resources have been reduced, drought stress is a significant challenge. This study aimed to investigate the effect of foliar application of humic acid and selenium on the agro-physiological traits of corn (type: SC704) under drought stress conditions. The experiments were conducted in Baghmolek, southwest Iran, during 2020 and 2021. The main factors included normal irrigation and irrigation interruption at the silking stage, while sub-factors were foliar spraying of humic acid (0, 100, 200, and 300 ppm) and selenium (0, 10, and 20 g/ha). Plant performance indicators, biological yield, relative water content (RWC), malondialdehyde (MDA), and di-tyrosine (DI-TY) were evaluated across treatments. The results showed that drought stress significantly reduced all agro-physiological traits. Foliar application of humic acid (300 ppm) and selenium (10 or 20 g/ha) mitigated the adverse effects of drought by improving key physiological indicators. The combined treatment increased RWC to 84.4% under normal irrigation, versus 55.5% in untreated drought-stressed plants. MDA decreased from 7.63 in untreated drought plants to about 5.1 with treatment, showing reduced lipid peroxidation. The-DI-TY was minimized by 300 ppm humic acid plus selenium, reaching 1.06 under normal irrigation and 2.54 under drought. The significant triple interaction of irrigation × humic acid × selenium highlights their synergistic role in improving water status and cellular protection under drought. These findings demonstrate that the combined application of humic acid and selenium can effectively mitigate the negative effects of drought stress on corn by enhancing physiological and biochemical traits.