The effect of differentiated fertilization on weed infestation of winter wheat and decrease of grain yield

Great differences in weed infestation in different years and in dependence on nutrition intensity were shown in three-year investigation of weed infestation of winter wheat stands in the field stationary trial conducted in experimental basis of the Regional Research Institute of Agroecology. Michalovee on East-Slovakian Lowlands. Intensity of secondary weed infestation was studied on ten models of five-plot crop rotations. Winter wheat, the Hana variety, at the seeding rate of 5 mil, germinating seeds per 1 ha and row spacing of 125 mm, was used in the trial. Five variants with differentiated nutrition intensity was evaluated in total. The occurrence of weeds was finding a week before harvest. The dominance. of weeds was evaluated by nine-point scale EWRS. The occurrence of the following weeds was recorded: quackgrass. barnyard-grass, wild oat, common hair-grass, common dungweed, field thistle, field horsetail, black bindweed, corn chamomile, and willow weed. Total weed infestation of stands was evaluated separately - all species of vegetating weeds. Good competitiveness of winter wheat has been confirmed in the trial. Average weed infestation of studied stands was on relatively low level in the evaluated three-year period, whereas higher weed infestation was recorded in the year with earlier start of spring when the period of lower temperatures occurred. A marked differentiation in weed infestation and competitiveness of cultivated crops in conditions of different level of nutrition of stands was found in the trial. General increase of stand weed infestation in dependence on the decrease of nutrition intensity of variants was confirmed whereas the variant with rationalizing nutrition is considered as favouring in view of competitiveness of cultural crop. The decrease of not only competitiveness of stands was found with falling nutrition intensity but also the yields of cultivated crop. The occurrence of weeds participated statistically significantly in decrease of winter wheat yields in most cases. Our results confirm the fact that a serious role in crop production is played by appropriate nutrition and fertilization of stands what can damp as well as support competitiveness of cultural and weed plants.