Environmental aspects of long-term use of mineral fertilizers on leached blacksoil of the Western Ciscaucasia

The research purpose consists in studying the effect of long-term use of mineral fertilizers on changes in the fertility of leached blacksoil (Grey-Luvic Chernozems) of the Western Ciscaucasia. The studies were conducted in the framework of the stationary field experiment of the Department of Agrochemistry of the Kuban State Agrarian University, founded in 1981 and occupied by crops of 11-field grain-grass-row crop rotation. Over the period of 1981-2019 years, N950P910K670, N1900P1820K1340 and N2850P2730K2010 were applied on contrasting variants with single, double and triple norms of mineral fertilizers, respectively. Comparison backgrounds are represented with initial indicators prior to the station establishment and with the control variant without fertilizers. The fertilizer system used in crop rotation supports optimal parameters of leached blacksoil fertility (PHH2O = 6.41-6.50; humus content - 3.50-3.58%; nitrogen content - 21.8-27.7 mg NO3/kg and 13.0-16.0 mg NH4/kg; mobile phosphorus - 155-170 mg P2O5/kg; exchange potassium - 255-266 mg K2O/kg) and improves the physical properties of soil. At the same time, during the 38-year period of annual application of mineral fertilizers, soil acidification was recorded (hydrolytic acidity increased by 0.51-0.93 mg-eq/100 g; pH(KCl) values decreased by 0.30-0.38 units; pH(H2O) - by 1.20-1.33 units), while the amount of absorbed bases decreased by 10.27-12.27 mg-eq/100 g, cation exchange capacity - by 9.76-11.34 mg-eq/100 g, and the degree of soil saturation with bases - by 2.66-4.00%. Periodic monitoring of changes in agrochemical and agrophysical indicators is necessary to reduce the risks of degradation and preserve the fertility of leached blacksoil.