The effect of soil compaction and four soil tillage systems (conventional, combined, U-1 reduced and U-2 reduced tillage) on vernal weed infestation of winter oilseed rape, winter wheat and spring barley was assessed experimentally. When plants began to grow in the spring, winter oilseed rape was more significantly infested with weeds on plots where soil packing had been performed than on plots where no such treatment had been carried out. Significantly more weeds grew on plots after combined and U-2 reduced soil tillage than on a conventional plantation (control) or on a field subjected to U-1 reduced soil tillage. In both treatments (with and without soil compaction), conventional and U-1 reduced soil tillage significantly reduced the density of weeds per surface area unit compared to U-2 reduced tillage, an effect which was particularly evident on plots with soil packing. In both treatments (with and without soil packing), Thlaspi arvense, Polygonum aviculare, Viola arvensis andStellaria media dominated. The degree of pre-sowing soil compaction significantly differentiated the number of weeds at the tillering phase of winter wheat. Significantly more weeds were found on plots with soil packing. In both treatments (with and without soil packing), weed communities were formed by approximately the same number of species, with the dominant Thlaspi arvense, Lamium amplexicuale, Stellaria media and Viola arvensis. The extent of soil packing did not differentiate significantly the abundance of weeds during the tillering phase of spring barley. However, the analysed trait was significantly modified by the soil tillage method. After U-2 reduced soil cultivation (plots without soil packing), the extent of weed infestation was significantly higher than after conventional or combined soil tillage technologies. On compacted soil, U-2 reduced soil tillage significantly increased weed infestation of a plantation compared to the other soil tillage variants, and significantly more taxa were found than in the conventional tillage variant (control). The following weeds prevailed on plots without soil compaction: Thlaspi arvense, Capsella bursa pastoris, Stellaria media and  Chenopodium album. On plots with soil packing, the following weeds were numerous: Thlaspi arvense, Polygonum aviculare andViola arvensis.