IRRIGATION MODE, WATER CONSUMPTION AND AVERAGE DAILY EVAPORATION DEPENDING ON THE VARIETY COMPOSITION, FERTILIZER AND PROTECTION SYSTEM OF SOYBEAN PLANTS FOR CULTIVATION ON IRRIGATED LANDS OF THE SOUTH OF UKRAINE

Abstract

Goal. The goal was to describe the soybean irrigation regime, create a balance of total water consumption, calculate the water consumption coefficient depending on the studied factors and evapotranspiration of the studied soybean varieties from the soil layer 0–50 cm by months and decades of growing season. The results. The total water consumption in the soil layer 0–50 cm decreased to 4114 m3/ha in 2021 in the variant with the Ideal variety, and this indicator was the largest, within the range of 6463–6487 m3/ha, in the soil layer 0–200 cm in the variants with medium-ripening varieties Oleshshya and Pivdenna krasunya in 2019. The regularity of the growth of total water consumption by 57.1–57.8% according to the depth of the calculated soil layer, the increase in the aridity of weather conditions against the background of the lack of atmospheric precipitation, as well as the sowing of seeds of later ripening varieties (Oleshshya, Zorya Stepu) was revealed. The coefficient of water consumption for the cultivation of soybean seeds had minimal values in Zorya Stepu variety. The use of fertilizers and plant protection led to a steady decrease in the water consumption ratio for the cultivation of all investigated soybean varieties, on average by factors, by 7.3–49.9 and 7.9–21.3%, respectively. Plant protection had a direct positive effect on reducing the water consumption ratio in options with biological and chemical protection, on average, in 2019 by 17.8–21.3%; 2020 – 7.9–15.7; 2021 – by 17.3–17.5%. The average data of the water consumption coefficient for the years of research had similar patterns of this indicator, as well as in individual years of research. Average daily evaporation (evapotranspiration) from the 0–50 cm soil layer had the lowest values (9.9–13.9 m3/ha/day) at the beginning of the growing season. The highest value, at the level of 85.3 m3/ha/day, was recorded in the plots of Oleshsha variety in the second decade of July, the lowest value in Ideal variety was 36.1 m3/ha/day. Conclusions. In the course of this article, the irrigation regime of the investigated soybean varieties, the balance of total water consumption, the coefficient of water consumption and evapotranspiration were described. The data contain scientific and practical value, informing about these important indicators in all four varieties that can be grown in the South of Ukraine.