Influence if soil treatment on its agricultural and physical qualities, sowings infestation and soybean yield on leached chernozem of the Western Ciscaucasus

There was studied dependence of the agricultural and physical qualities of soil, weeds infestation and soybean yield on the systems of the primary soil treatment (intensive, tillage on different depths, minimal and surface). The research was conducted in stationary plot of VNIIMK in four rotations of ten-field crop rotation with cereals on leached chernozem of the Western Ciscaucasus in 1971-2007. The different systems of primary soil treatment were used under unstable moistening for a long period of time. Minimal and surface treatments did not promote significant tighten of tilled soil layer compared to moldboard, nevertheless, in these variants density of soil layer 10-30 от was increased (on 0.07 g per сm3) up to 1.35 g per cm3. It certifies a negative aftereffect any soil treatment. Inroduction of soil herbicides treflan and nitran (active ingredient trifluralin) to control weeds in soybean sowings for three rotations caused a wide spreading of weeds resistant to these herbicides, especially if soil treatment did not involve soil overturning. Usage of highly effective herbicides on soybean seedlings in forth rotation promoted lowering of these weeds number. The highest productivity of soybean sowings was reached under moldboard treatments on the depths 20-22 or 30-32 cm; it proved the highest and most stable crop yield (1.89 t per ha). In variants with surface and minimal soil treatments yield was decreased on 0.07-0.27 t per ha, respectively. Soybean production under minimal soil treatments, especially without herbicides application, promotes decreasing of its yield on 15% and more. If perennial soboliferous weeds are absent and highly effective herbicides are applied, moldboard on leached chernozen can be changed for nonmoldboard loosing or smaller moldboard treatment on the depth 12-14 cm.