NITROGEN AND ITS FRACTIONAL COMPOSITION IN ORDINARY CHERNOZEM IN ROSTOV REGION DURING FERTILIZATION

Purpose: to study in the field the effect of the systematic fertilizers application on the content of total nitrogen and its fraction composition in ordinary chernozem of Rostov region. Materials and Methods. Research was carried out over 10 years at Don Zonal Research Institute of Agriculture. The object of research is ordinary carbonate medium-power chernozem of varying degrees of erosion with a total nitrogen content of 0.228–0.131 %. The fertilizers influence on the content of total nitrogen and its fractional composition was studied in a grain-crop rotation: bare fallow, winter wheat, winter rye, corn for grain, spring barley, peas, winter wheat, corn for silage, winter wheat, sunflower. Soil is ordinary non-eroded chernozem (total nitrogen is 0.258 %). Fertilizer application system: 7.0 tons of manure + N43Р30K24 kg a. a./ha, the increased system of 11.2 tons of manure + N64Р42K42 kg a. a./ha. The nitrogen bulk was determined by two-stage acid hydrolysis, dividing the nitrogen bulk into various groups agronomically valuable for plant nutrition. Results: erosion processes, causing a total nitrogen loss, also worsened its fractional composition (the number of all fractions fell, the largest percentage of fall concerns the fraction of mineral nitrogen). The application of manure and mineral fertilizers in medium (7.0 tons of manure + N43Р30K24) and especially in higher doses (11.2 tons of manure + N64Р42K42) increases the fraction of non-hydrolyzable nitrogen, which is not involved in plant nutrition, other forms of nitrogen decreased. Conclusions: it was determined that the quantitative and qualitative composition of the soil nitrogen of ordinary chernozem changes as erosion processes increase. In the control (ordinary non-eroded chernozem), the total nitrogen content remained practically unchanged, but there was redistribution of various fractions in its composition. The application of fertilizers promotes the transformation of mobile forms of soil nitrogen and fertilizers over time into forms that are not digestible for plants.