NITROGEN BALANCE IN CROP ROTATIONS OF DIFFERENT DESIGN ON ORDINARY CHERNOZEMS OF ROSTOV REGION

Aim: the purpose of the work is to determine by means of balance calculations the possibility of preserving the nitrogen stock of ordinary chernozem in Rostov Region without fertilizers, and their introduction in crop rotation with bare fallow and without it, with a different number of perennial leguminous herbs and a slight fluctuation of number of other crops and their different productivity. Material and Method. Research was conducted at Don Zonal Research Institute of Agriculture (over 10 years). The object of research is ordinary medium-power light clayey chernozem. The nitrogen balance was calculated in a grain-fallow-raw crop rotation: bare fallow, winter wheat, winter rye, corn for grain, spring barley, peas, winter wheat, maize for silage, winter wheat, sunflower. Fertilizer application system is 7.0 tons of manure + N₄₃Р₃₀K₂₄ per 1 ha, increased system of 11.2 tons of manure + N₆₄Р₄₂K₄₂ per 1 ha. To solve this problem the nitrogen balance was determined taking into account its crop removal and crop rotation: with fertilizers, precipitation, seed grain due to non-symbiotic and symbiotic nitrogen fixation by legumes (alfalfa and peas). The amount of nitrogen fixed by free-living microorganisms was estimated taking into account the mass of crop-root residues by the equations compiled earlier. Results: as a result the use of manure and mineral fertilizers in medium doses (7.0 tons of manure + N₄₃Р₃₀K₂₄) did not compensate for the nitrogen removal. A negative balance was maintained (minus 3.4 kg per ha). Fertilizers in a dose of 11.2 tons of manure + N₆₄Р₄₂K₄₂ completely eliminated the lack of nitrogen, the excess of the incoming part of the balance over the expenditure was 16.0 kg per ha. Conclusion: it was found that to replenish the removal of nitrogen from the soil within 50–109.5 kg per ha and to prevent environmental pollution, it is necessary to apply 27–45 kg per ha of nitrogen fertilizers depending on the design of crop rotation against the background of manure.