The productivity of agricultural crops is the most variable and integral indicator of their vital activity, which accumulates their genetic potential, soil fertility, weather conditions and components of agricultural technology. Soybean under optimal growing conditions (the reaction of the soil is close to neutral, sufficient phosphorus and potassium nutrition, the use of nitraginization) assimilates from the air about 70 % of the total nitrogen requirement. Therefore, it is believed that it is enough to apply only a starting dose of nitrogen fertilizers (20–40 kg/ha a. s.), to get a high yield with good indicators of grain quality. The results of studies of the influence of long-term (8 years) application of different doses and ratios of fertilizers in field crop rotation on podzolized chernozem in the conditions of the Right -Bank Forest-Steppe of Ukraine on the yield and quality of soybean seeds preceded by spring barley were presented. It was found that crop yields could be increased by 18–77 % owing to different doses, ratios and types of fertilizers. The highest indicators of seed yields for three years of the research (3,02 t/ha) were obtained under the application of mineral fertilizers at a dose of N110P60K80 per 1 ha of crop rotation area, including under soybean – N60P60K60. Exclusion of the nitrogen component from the complete fertilizer (N60P60K60) reduced its yield by 26 %, phosphorus – by 17, and potassium by 11 %. There was no significant decrease in soybean yield in the variant of the experiment with a decrease in the proportion of potassium in the composition of complete mineral fertilizer (N60P60K30) for three years of study. The largest mass of 1000 soybean seeds was formed at doses of N60К60 fertilizers, and their protein content — under the application of complete mineral fertilizer in doses of N60P60K60 and N60P60K30.
Lectin activity of soybean seeds
