FEATURES OF HUMUS AND NITROGEN ECOLOGICAL STATUS FOR STEPPE ZONE CHERNOZEMS OF THE NORTH CAUCASUS

The purpose of the paper presented is to determine tendency and intensity for quantitative and qualitative changes in humus and nitrogen status of chernozems. The system approach to study natural objects is assumed as the basis for research methodology of humus and nitrogen status of soils. It is established that the depth typical values of chernozem humus horizons in the North Caucasus are 120-180 cm for South European facies of leached chernozems, 100-170 cm for modal chernozems, 70-160 cm for common chernozems, 70-120 cm for southern chernozems; for East European facies of southern chernozems the value is 55-70 cm. A distinctive ecological feature of the soils is thought to be a low humus content in the arable layer, its deep distribution along the profile and slight variability among each subtype. Nitrogen quantity in chernozems of the region variates within a comparatively wide range: 0.20-0.35 % in South European facies of leached, modal and common chernozems, 0.22-0.30 % in East European facies of southern chernozems. Southern chernozems of South European facies contain least of all nitrogen, i.e., 0.18-0.22 %. Total nitrogen composition is mainly presented by non-hydrolysable facies, making 74.2-78.9 %. The research materials are intended to design farming systems on the landscape basis for specialists dealing with the issues of soil preservation, increasing soil fertility as well as environment protection. The results of the research may contribute to making a purposeful impact on decision making to control humus and nitrogen status of soils, thus serving as the basis for preservation of bioecological potential of chernozems