Effect of mineral nutrition and nitrogen-fixing agent on maize yield in the Central Forest-Steppe of Ukraine

In modern agricultural production, there is an increasing demand for the use of biopreparations, particularly nitrogen-fixing agents, which can reduce the need for mineral fertilisers while enhancing maize yields. This study aimed to determine the effects of different fertilisation strategies and plant densities on the morphological characteristics and yield of maize under the agroecological conditions of the Central Forest-Steppe of Ukraine. Field experiments were conducted during 2023-2024 under the soil and climatic conditions of a farm in the Kyiv Region, using the maize hybrid P9255 (FAO 330). The area of each experimental plot was 33 m2, with four replications and a sequential multilevel arrangement. The application of a nitrogen-fixing biological agent in combination with mineral fertilisers had a positive effect on plant growth. In particular, plant height was 1.7%-5.1% greater than in the treatments where only mineral fertilisers were applied. An evaluation was carried out to determine the effectiveness and impact of optimising the fertilisation system on the morphological characteristics and productivity of maize plants through the use of a biological preparation in combination with mineral fertilisers at various application rates. Overall, the application of mineral fertilisers alone resulted in a 14.5%-22.5% increase in grain yield compared to the control. The highest yield, reaching 12.94 t/ha, was recorded under the N150P120K120 treatment at a plant density of 70,000 plants/ha. In treatments combining mineral fertilisers with the biological agent, grain yield was 12.2%‑21.2% higher than in the corresponding control variants. The highest average grain yield, amounting to 13.38 t/ha, was achieved with the N150P120K120 + nitrogen-fixing agent treatment at a plant density of 70,000 plants/ha. The application of the biological preparation in combination with mineral fertilisers produced a 3.6% (or 0.43 t/ha) higher grain yield compared to treatments without the biological agent