Maize (Zea mays L.) is a vital grain crop cultivated globally, which ranks third after wheat and rice. Its consumption in Egypt is primarily for human food, livestock and poultry feed, and raw materials for industrial products, such as, oil and starch. The main environmental factors that limit crop productivity worldwide include salinity, drought, and nutrient imbalance. Plant Growth regulators (PGR), such as, gibberellic acid (GA3) and mepiquat chloride (M.C), reduce the dramatic impacts of salinity and drought on crop growth and yield. This experiment sought to verify the influence of foliar spray application of GA3 and M.C as growth regulators on the growth metrics, chemical components, and maize harvest cultivated in calcareous soil under salinity during the summer of 2021 and 2022, respectively. The following treatments comprised foliar applications of 50 ppm GA3, 100 ppm GA3, 100 ppm M.C, and 250 ppm M.C, applied three times every season. It is clear from the results that foliar application of gibberellic (GA3) and mepiquat chloride (M.C) enhanced growth metrics, biochemical parameters, nutritional content, yield and its components, and oil percentage. After treatment with 100 ppm GA3 and 250 ppm M.C foliar spray, the yield and its constituents and oil percentage achieved the highest shares, with substantial differences between the two treatments. Compared with the control, treatments with 100 ppm GA3 and 250 ppm M.C increased grain yield by 33% and 29.9%, respectively. The study concluded that the most effective therapy for improving maize growth, development, and output under salt stress was 100 ppm GA3 and 250 ppm M.C foliar application during the growth stages. Administering GA3 and M.C mitigated successfully the damage caused by salt stress. Under salinity, gibberellic acid and mepiquat chloride addition increased the growth of maize, chlorophyll content, soluble protein, proline, and the concentration of K⁺ ions while decreasing the oxidative stress and the accumulation of Na⁺ ions.

Keywords: maize, gibberellic acid (GA3), mepiquat chloride (M.C), salinity, biochemical parameters, yield, and oil content

Key findings: Administration of GA3 and M.C mitigated successfully the damage caused by salt stress. Under salinity stress, gibberellic acid (100 ppm) and mepiquat chloride (250 ppm) addition increased maize growth, chlorophyll content, soluble proteins, proline, and the concentration of K⁺ ions while decreasing the oxidative stress and the accumulation of Na⁺ ions.