The influence of meteorological factors on the yield and grain quality of soybean varieties belonging to different groups of ripeness in the conditions of the Stavropolupland

Soy is a unique leguminous crop, the grain of which is used by the processing industry for the production of protein concentrate, vegetable fat, biofuels, and concentrated feed. The experiments were laid in 2008-2011 and 2017-2019, at the experimental station of the Stavropol State Agrarian University. Soybean varieties were sown: precocious - Lira (St1) and Selecta 101, early-ripening - Duar (St2) and Selecta 201, medium-ripe - Vilana (St3) and Selecta 302. In the conditions of the Stavropol upland, the duration of the growing season from germination to the ripening of soybeans in the precocious group was 106 days, early-ripening - 119, middle-ripening - 130 days. The greatest dependence of the grain harvest was in July, the yield by 71.6% was determined by the influence of meteorological conditions. In August, the yield dependence decreased, but is still very noticeable, the yield by 51.5% was determined by the influence of the amount of precipitation and the amount of active temperatures greater than 10 °C. The yield of soybean grain varied in: precocious varieties from 1.49 to 1.52 t/ha, early–ripening - from 1.70 to 1.78 t/ha, medium-ripened - from 1.64 to 1.77 t/ha. The highest quality grain was obtained by growing the early-ripening Duar variety (St2), the crude protein content was 41.3%, and vegetable fat - 22.3%. When growing this variety, 0.662 t/ha of vegetable protein and 0.357 t/ha of vegetable fat were obtained.