Organomineral Fertilizer Effects on Sunflower (Helianthus annuus L.) Growth and Soil Enzyme Activity

This study investigated the effects of different doses of organomineral fertilizer on sunflower growth, soil enzyme activities, and nitrogen forms in soils with high pH and lime content. The experiment was conducted in 2024 in Şanlıurfa Province using a randomized complete block design with three replications. The Suomi sunflower cultivar was used as the plant material. Four organomineral fertilizer doses (0, 10, 20, and 30 Mg/ha) were applied. Plant growth parameters, yield components, soil enzyme activities, and nitrogen forms were measured throughout the experiment. Organomineral fertilizer applications had statistically significant effects (p < 0.01) on plant height, head diameter, number of seeds per head, 1000-seed weight, seed yield, soil enzyme activities (catalase, urease, and dehydrogenase), and nitrogen forms (ammonium [NH₄⁺] and nitrate [NO₃⁻]). In contrast, the effect on hectoliter weight was significant at the p < 0.05 level. These findings indicate that the controlled and optimal use of organomineral fertilizers can improve both crop yield and soil health.