By results of statistical data, biological degradation of soils is observed in all regions and native zones of Ukraine. It is proved that after ploughing virgin soil and paleocrystic long fallow, irrespective of fertilizer system of crops, in grain crop rotations the general content of humus in arable layer of typical black earth is diminished by 20 -25%. Accumulation of humus will be justified only in that event when it is more effective than other agrotechnical means and methods which improve soil characteristics limiting productivity of cultivated crops.