A 4-year-field experiment (2000–2003) carried out on loessial soil in the central Lublin Region evaluated the influence of four systems of soil tillage (conventional, simplified with intercrop, simplified and direct sowing) and plant cultivation on the infestation of two forms of spring barley (hoed and naked). The floristic composition, number and dry weed weight were analyzed prior to spring barley harvest. It was proved that direct sowing and simplified soil tillage induced the highest increase of the studied barley forms infestation. It manifested itself with an elevated weed number (by 55.5%) and their biomass (85.9%) as well as flora infestating by 9 weed species additionally. The chemical cultivation of plants at the objects with the soil tillage systems under study contributed to a reduction of infestation of the evaluated spring barley (hoed and naked) canopies from 20 to 40%. It, however, did not affect the infestating flora composition. The studied barley forms did not vary in respect of canopy infestation, i.e. weed association, their number and biomass. The dominant weed species in the evaluated spring barley canopies were shown to be: Chenopo dium album, Galinsoga parviflora, Galeopsis tetrahit, Polygonum convol -vulus and Apera spica -venti.