FEATURES OF THE NUTRITIONAL REGIME OF THE SOIL DEPENDING ON MINERAL FERTILIZERS

Soy is a valuable food product, as well as a raw material for the production of concentrated feed, vegetable oil and dietary protein. It is grown in many countries of the world, different in agro-climatic conditions and economic situation. The role of fertilizers in increasing soil fertility, increasing crop yields and their impact on product quality is most fully revealed in long-term stationary experiments. As some researchers point out, in long-term experiments, it is possible to better and more reliably determine the conditions that allow you to get the greatest effect from fertilizers. Experimental studies were conducted on the experimental fields of the North Caucasus Research Institute of Mountain and Foothill Agriculture of the Vladikavkaz Scientific Center of the Russian Academy of Sciences. The dynamics of nitrates on soybean crops proceeded as follows: from the moment of awakening of biological activity in the soil in the spring, the amount of nitrates gradually increased until the middle of the growing season; then it fell sharply (as the crop consumed nitrogen) and increased again only by the time of harvesting, and after harvesting the soybean, the content of nitrates in the soil reached high values. So, in 2018 (the average indicator in the 0-30 cm soil layer) on the control variant during sowing was 0.26 mg/100 g a.s.n., in the branching phase – 0.23, in the flowering phase-0.11, seed filling-0.22 and in the maturation phase-0.37 mg/100 g a. s. n. It was found that when applying phosphorus-potassium fertilizers, the nitrate regime of the soils of the experimental site improved, as can be judged by the amount of accumulated nitrates in the 0-30 cm soil layer. In the fertilized variants, the nitrate content was noticeably higher during all the observation periods than in the control, despite the fact that soybean plants grew and developed better on these variants, formed a higher yield and, consequently, consumed more nitrogen from the soil. This trend was also observed for other phases of growth and development of the culture, except for the maturation phase, when the largest amount of nitrate nitrogen (0.37 mg/100 g a.s.n.) was detected in the control variant.