The objective of the study was to analyse the variability of the weed infestation of several winter wheat cultivars in relation to the soil tillage system applied and to the height of preceding crop stubble. The study was conducted in the years 2008-2010 in Lower Silesia, Poland. The following factors were studied in the experiment: factor I - stubble height a/ short stubble (10 cm) b/ tall stubble (40 cm); factor II - soil tillage systems a/ no-till b/ reduced tillage c/ conventional tillage - ploughing; factor III - winter wheat cultivars a/ Mewa, b/ Rapsodia, c/ Legenda. After the harvest of the preceding crop, glyphosate was sprayed on plots with short and tall stubble, in the first 10-days of August. The number of weeds on each analysed plot was estimated at random, with the frame method. For statistical analysis, the 8 most frequent weed species were selected: Viola arvensis, Sinapsis arvensis, Lamium purpureum, Veronica persica, Apera spica-venti, Capsella bursa-pastoris, Anthemis arvensis and Geranium pusillum. Based on the log-linear analysis, it was determined that V. arvensis and S. arvensis w ere the dominant weed species, whereas A. spica-venti and C. bursa-pastoris were characterised by significantly smaller numbers per 1 m 2. Significantly greater weed infestation was observed on plots with tall stubble. Increased weed infestation of winter wheat was noted in the reduced tillage treatments compared to those with conventional tillage. Only the numbers of S. arvensis were considerably lower under the conditions of no-till than in the conventional or reduced tillage systems. Cultivar Mewa limited the number of weeds per unit of area to a significant degree, while cv. Legenda increased weed infestation.
