Impact of Humic Acid and Cycocel Foliar Application on Wheat (Triticum aestivum L.) Yield and Nutrient Uptake under Late-Season Drought Stress

BACKGROUND: Drought stress, particularly when occurring in the late season, can significantly reduce crop yield. To mitigate its impact, it is essential to adopt appropriate strategies that optimize nutrient management. OBJECTIVES: This study aimed to investigate the potential effects of foliar applications of HA and cycocel on wheat yield and nutrient uptake during the 2018 and 2019 growing seasons in Ahvaz, Iran. METHODS: Current research was designed as a factorial split plot based on randomized complete block design with three replications. The main factor in the study was late-season drought stress, evaluated at two levels: conventional irrigation and irrigation cessation after pollination. The sub-factors included cycocel at three levels (control, 1.5 g.L-1, and 3 g.L-1) and humic acid (HA) at three levels (control, 2 L.ha-1, and 4 L.ha-1). RESULT: The results indicated that the interaction between late-season drought stress and cycocel application significantly affected grain yield, iron and zinc content, and grain protein content. Specifically, the interaction of 3 g.L-1 cycocel application with conventional irrigation conditions resulted in the highest grain yield, reaching 4840.5 kg.ha-1. Furthermore, HA application significantly influenced all experimental treatments. The highest grain yield and iron content (4810 kg.ha-1, 53.2 mg.kg-1) were achieved with 4 L.ha-1 of HA under conventional irrigation conditions. Overall, it can be concluded that the application of 4 L.ha-1 HA in combination with 3 g.L-1 cycocel under conventional irrigation conditions effectively enhances both the quality and quantity of the yield. CONCLUSION: These results can be utilized to inform agricultural policies aimed at improving crop productivity and resilience, especially in regions prone to drought.