Field studies were conducted in the district Dobrzyniewo Duże. A. vulgaris appears in a similar percentage in winter cereals (52.6%) and spring cereals (47.4%). The highest share occurred in winter rye and in a mixture of oat and spring barley. The highest frequency of Avena fatua (100%) in spring cereals was stated. In winter cereals A. fatua occurred sporadically in subsequent years (0 to 20% of phytosociological evaluations). A. fatua preferred a mixture of oat and spring barley, oats and a mixture of oat with spring barley and spring wheat. To increase of participation of A. fatua affected by: the system of cultivation, rarely renewed seed, reducing mechanical and chemical treatments and technology (contributing to the spread and preservation of a significant quantity of weed seeds in cultivated fields).