Effect of foliar fertilization on the size and quality of oilseed sunflower achenes

Foliar fertilization is an agronomic practice commonly used in crop cultivation. The effectiveness of this treatment depends on many factors, including plant species, chemical composition of the preparation, dosage and date of application, and soil and weather conditions. Sunflower has moderate fertilization requirements, but certain elements are crucial for achieving high, good quality seed yield. The purpose of this study was to evaluate the response of oilseed sunflower (variety MAS 81K) to foliar application of micronutrients, zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), molybdenum (Mo), and boron (B), in comparison to the control. A one-factor field experiment was conducted in 2022 and 2023 in a randomized block design. The soil at the experimental site was classified as Haplic Cambisol (Eutric) formed from loess, with moderate levels of Zn, Fe, Cu, and Mn and low levels of B. The results of the present field experiment demonstrated a significant response of sunflower to foliar application of individual micronutrients (Zn, Fe, Cu, Mn, Mo, and B) compared to the control. The most favorable results were obtained following foliar B fertilization, but positive results were also achieved with the application of Mo and Cu. Weather conditions during the study years had a significant impact on the results of foliar fertilization. For these reasons, the results from the first year were not always reproducible in the second year. Seed quality (oil) was mainly affected by the application of Cu, followed by Mn, Fe, and Zn. The results of the current experiment demonstrated that the application of B was most beneficial, while the use of molybdenum (Mo) and copper (Cu) exerted a comparatively smaller effect. The application of the remaining micronutrients yielded results that were below expectations.