INFLUENCE OF PRE-CROPS ON WEEDY COMPONENT OF AGROPHYTOCENOSIS IN CULTIVATION OF WINTER WHEAT UNDER NO-TILLAGE TECHNOLOGY

The exclusion of mechanical tillage leads to the concentration of seeds on the surface under plant residues and in the upper soil layer. In the period of full ripeness of pre-crops, before their harvesting, the potential of weed seeds in the 0-5 cm layer after winter rape is 36. 9 % lower than after corn for grain and 44.3 % compared to sunflower. A longer post-harvest period after winter rape helps clear the top layer of the soil from weed seeds to sowing winter wheat by 30.8 %. The lack of a time interval from harvesting of sunflower and corn before sowing of winter wheat leads to the accumulation of weed seeds in the 0-5 cm layer.At this time the culture is marked by negative dynamics of infestation of the top layer. This process takes place more intensively after winter rape and is 47.2 %. With deepening in the soil to 10 cm, the number of weed seeds is reduced. Use of no-tillage technology changes the formation of agrophytocenosis of winter wheat. After the predecessor of winter rape in the tillering phase, the number of weeds is reduced by 34.1 % compared to sunflower and by 47.1 % - to corn. Different efficiency of pre-crops in the reduction of weed populations can be traced in the future during the growing season of winter wheat. In the period ofwinter wheat earing, the contamination of crops is significantly reduced for all pre-crops.But it is not only the result of chemical weeding carried out in the tillering phase, but also real competition of the culture itself, as there is an increase in its vegetative mass. Weeds in this period have a small mass, little different in pre-crops, located in the range from 9.3 to 12.2 g m(-2). To the full ripeness of winter wheat, the contamination of crops increases and this is due to the "clarification" of crops, when the culture no longer competes with weeds. During this period, the pattern established bythe pre-crops in the previous phase remains.