The justification of the use of various forms of nitrogen fertilizers for agricultural crops and their impact on the fertility of gray forest soil

The result of the research was the assessment of the effect of simple nitrogen fertilizers in the course of their longterm permanent use in crop rotation in the non-Chernozem zone of the Russian Federation on gray forest heavy loam soils with an average level of fertility. In addition, their influence on the content of total, mineral and easily hydrolyzed nitrogen in the crop rotation with alternating crops was studied: annual grasses on the green mass - spring wheat - potatoes - barley, taking into account the duration of the use of mineral fertilizers for rotation of the crop rotation. The complex of nutrition elements introduced with mineral fertilizers activating the mineralization of organic matter increased the degree of soil nitrogen assimilation and reduced the coefficient of nitrogen use from mineral fertilizers, which did not exceed 30.1 % when cultivating potatoes, the lowest value of this indicator (15.2 %) was noted when growing barley. With a low utilization rate, crop rotation crops could be divided into the following groups according to their responsiveness to the forms of nitrogen introduced with mineral fertilizers: ammonia-nitrate fertilizers and ammonia water - barley; nitrate-responsive forms - annual grasses; ammonia-nitrate and nitrate-responsive forms of fertilizers - potatoes; amide-responsive and ammonia-nitrate forms of fertilizers - spring wheat. The dynamics of annual consumption of nitrogen fertilizer had nonlinear nature of the value of the index, stabilizing or increasing to the fifth rotation and decreasing in the subsequent rotation, i.e. a long-term permanent use of the same forms of nitrogen fertilizers on the same location significantly reduced the efficiency of nitrogen used for fertilizer, which in turn reduced the efficiency of the insertion of nitrogen fertilizer. The nitrogen balance in the soil-plant-fertilizer system through fifteen rotations of crop rotation was negative and depended on the form of the applied nitrogen fertilizer against the background of phosphorus and potash fertilizer.