The influence of plant density and doses of fertilizers on photosynthetic activity and yield of soybean of middle-ripening variety Sviatohor in conditions of irrigation

Abstract

Goal. To establish the optimal parameters of photosynthetic activity of crops of mid-season soybean variety Sviatogor in conditions of irrigation in the South of Ukraine depending on plant density and doses of nitrogen fertilizers. Methods. The field — for determination of yield; calculation — for optimization of doses of mineral fertilizers, plant density; measurement-weighe — for fixation of plant height, leaf area, and photosynthetic indices. Results. The density of sowing significantly influenced the leaf area of soybean plants, its indices varied in the range of 23.5–47.38 thousand m2/ha at the density of 300 thousand plants/ha; 26.19–52.42 thousand m2/ha at the density of 600 thousand plants/ha; 50.56–49.92 thousand m2/ha at the density of 900 thousand plants/ha. It was fixed that the leaf area of plants in the plots with the introduction of N30 and N60 was 50% and 49% more than in the variant without fertilizers. High yield was provided by the density of plants 600 t/ha on the background of fertilizers N30 and N60. Conclusions. For the first time for the South of Ukraine, features are determined of the formation of the photosynthetic activity of soybean crops of mid-season variety Sviatohor depending on plant density and doses of nitrogen fertilizers, providing the yield at the level of 4.32–4,47 t/ha. The best performance of interfacial photosynthetic capacity (beginning of flowering — beginning of seed ripening) — 1.38–1.23 million m2 of days/ha, and over the vegetation period — 3.45–3.19 million m2 of days/ha were formed in areas where the plant density was 600 thousand plants/ha on the background of N30 and N60 respectively. Correlation is determined between the yield level and the studied factors. It is found that the maximum leaf area in the ripening phase of the seeds is 52.42 thousand m2/ha at a plant density of 600 thousand plants/ha, and the rate application of nitrogen fertilizer involves a dose of N30.