Effect of leaf iron and zinc applications on soybean plantdevelopment in Diyarbakir conditions

This study was conducted to evaluate the effects of foliar applications of different doses of ferrous sulfate (FeSO₄) and zinc sulfate (ZnSO₄) on plant growth, yield, and quality parameters of the Sonya soybean cultivar grown as a second crop under the ecological conditions of Diyarbakır, Türkiye. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Foliar applications were performed during the V1 and V3–V4 phenological stages of the plants. Parameters such as plant height, number of branches, seed yield, protein content, and oil content were measured. According to the analysis of variance, there were statistically significant differences (P < 0.01) among the treatments in terms of plant height, number of branches, and seed yield. The highest plant height (89.33 cm), branch number (16.66), and seed yield (399.93 kg/da) were recorded in the 0.4% Fe treatment. No statistically significant differences were observed in oil and protein content, although the highest oil content (21.40%) was obtained from the 0.25% Zn treatment, and the highest protein content (36.26%) was observed in the 0.5% Zn application. The findings demonstrated that foliar applications of iron and zinc had positive effects on vegetative growth and yield, while their impact on quality traits was relatively limited. Optimizing application dose and timing can enhance soybean productivity under second cropping conditions. In this context, the 0.4% Fe foliar treatment was identified as a particularly effective practice. It is recommended that future studies explore the use of chelated micronutrients, alternative application timings, and different crop species to validate the general applicability of these results. KEYWORDS: Soybean, Foliar fertilization, Ferrous sulfate, Zinc sulfate, Second crop cultivation