SOYBEAN GRAIN YIELD DEPENDING ON VARIETY, NUTRIENT BACKGROUND AND SEEDING RATE UNDER THE CONDITIONS OF THE RIGHT-BANK FOREST-STEPPE ZONE

Abstract

Soybean is the most widespread and profitable legume crop, enjoying high demand both on the Ukrainian and global markets. This drives significant scientific and agricultural interest in improving technological practices that enhance grain yield, technological parameters, and chemical composition – particularly protein content. The research article presents an analysis of optimizing elements of soybean cultivation technology under the conditions of the Right-Bank Forest-Steppe of Ukraine. The experimental design included the following factors: variety (Factor A): Aratta (mediumearly) and Sofiia (medium-maturing); nutrient background (Factor B): without inoculation, inoculation, N30P40 + inoculation, and N60P40 + inoculation; seeding rate (Factor C): 400, 500, 600, 700, and 800 thousand seeds per hectare. According to the obtained yield data, the optimal seeding rate for the Aratta variety was 600 thousand seeds/ha, providing yields within 2.68–3.12 t/ha, while for Sofiia the optimal rate was 500 thousand seeds/ha, resulting in yields of 2.70–3.14 t/ha. Regarding the nutrient background, the most effective treatment for both varieties was N30P40 + inoculation with the Rhizoaktiv+ preparation, which increased grain yield by 0.44 t/ha for Aratta and 0.45 t/ha for Sofiia. Experimental data confirmed that nitrogen supply significantly affects soybean seed protein content, as nitrogen is the key element for protein synthesis. Adequate nitrogen availability, correlated with higher overall productivity, increases protein accumulation in seeds. However, excessive mineral nitrogen may suppress atmospheric nitrogen fixation, leading to reduced protein quality and quantity. The optimal protein content (39.8%) was recorded in the Sofiia variety under the N30P40 + inoculation treatment with a seeding rate of 600 thousand seeds/ha. For the Aratta variety, the same treatment produced slightly lower results, by 1.6%. Treatments without inoculation and fertilization showed significantly lower protein levels – 37.8–38.0% for Aratta and 38.1–38.3% for Sofiia.