The aim of this study was to estimate the quantitative indexes of stand weed infestation and yields of three cultivars of spring wheat sown in sowing densities 500 and 800 grains per 1 m². The study was conducted in 2006-2009 in the gray-brown podsolic soil formed from loess. The experimental factors were three cultivars of spring wheat different in respect of morphology: Nawra, Zadra and Korynta, as well as their two sowing densities: 500 and 800 grains per 1 m². Assessment of the effect of research factors on weeds occurring in stand was carried out on treatments without herbicides. State of weed infestation of stand was assessed with the quantitative-gravimetric method before spring wheat harvest. Quantitative weed infestation indexes were significantly modified by the sowing density of spring wheat. Increasing sowing density from 500 to 800 grains per 1 m² resulted in a decrease by 22% in the number of weeds and by 27% in their air-dry weight. Of the assessed cultivars, Korynta and Zadra showed a satisfactory competitiveness against weeds, particularly in conditions of increased sowing density (800 grains·m^-2). No differences in yield were statistically indicated either between cultivars or depending on sowing density.

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