Optimisation of mineral nutrition norms for sunflowers to increase yield

The aim of the study was to determine the optimal mineral nutrition rates for sunflower that ensured maximum yield and stable seed quality indicators within the Forest-Steppe zone of Ukraine. The methodology involved a two-year field experiment with four fertilisation variants (control, N₁₂₀K₈₀, N₁₂₀P₈₀K₈₀ та N₁₅₀P₈₀K₈₀), the assessment of morphometric parameters and yield, as well as laboratory analysis of the chemical composition of seeds. Statistical processing of the results was carried out using a comparative analysis approach with an evaluation of the relative increase in indicators compared to the control. It was found that sunflower responded to the level of mineral supply already at the early stages of development, with a strengthening effect during the formation of reproductive organs. It was established that the diameter of the head served as a sensitive indicator of fertilisation efficiency, with the highest values recorded under the N₁₂₀P₈₀K₈₀ variant. The yield dynamics were examined and a clear advantage of complete mineral nutrition was identified, ensuring an 83.3% increase in yield compared to the control. The oil output per hectare was analysed and found to rise to 0.73 t/ha under optimal fertilisation, indicating the efficient realisation of the crop’s potential. It was summarised that excessive nitrogen supply did not always provide additional benefits, as it might lead to a redistribution of nutrients towards vegetative mass. It was confirmed that balanced NPK nutrition contributed not only to high yield formation but also to stable oil accumulation in seeds. The practical significance of the study lay in the possibility of applying the obtained recommendations by agricultural producers and agronomic services to optimise sunflower nutrition systems under conditions of climate change and resource constraints