Influence of climate trends on the effect of nitrogen fertilizers, nitrapyrin and inoculates in soybean growing in Male Polissya

The objective of the research was to determine the effects of different forms of nitrogen fertilizers, applied at varying rates, the use of the nitrification inhibitor N-Lok™ and seed inoculants on soybean grain yield in Male Polissya, considering the mesoclimate dynamics in Western Ukraine. The experiments were conducted at the Lviv National University of Nature Management during 2022-2024, at an experimental field located at coordinates 50°12'07.8" N and 24°32'52.9" E. Weather statistics were obtained from the Meteopost website (https://meteopost.com/weather/climate). The experimental plot is characterized by deep gleyed soddy sandy-loam soil with 4% humus content in the arable layer, elevated levels of easily hydrolyzable nitrogen and available phosphorus, medium levels of exchangeable potassium, and a slightly acidic pH of 5.6-5.8. Traditional research methods were applied. Over 14 years of observations, the climatic norm for precipitation, set at 748 mm, was exceeded in 9 years and fell below the norm in 5 years, with record-low precipitation in 2022 and 2024. The average annual temperature over 14 years, as well as in the last three years, showed a tendency to increase. In the last three years, July recorded lower average monthly temperatures compared to August, with temperatures reaching 20-21°C in 2022 and 2023. Under these conditions, soybeans provided an average three-year yield range of 2.81-3.95 t/ha of grain. With the nitrogen fertilization system N30 (ammonium sulfate) on a P60K60 background and the use of a nitrogen-fixing inoculant, the highest three-year yield was achieved, with a maximum grain yield of 4.12 t/ha in 2023. This vegetative period was the most favorable for the crop, yielding 0.40 t/ha more than the average for 2022-2024. The use of nitrapyrin and inoculants under different systems of nitrogen fertilization of soybeans on the P60K60 phosphorus-potassium background had different effectiveness, depending on the hydrothermal conditions of vegetation in Male Polissya on sod deep clayey sandy-light loamy soil. The use of the nitrate stabilizer N-Lok™ (applied before sowing at 1.7 l/ha) on a N30+30P60K60 background resulted in a soybean yield of 3.90 t/ha, which was 0.36 t/ha higher than the N30 (ammonium sulfate) on a P60K60 background, considered the traditional production method.