The response of weeds to simplified tillage systems and the nature of changes in the weed community are presented in the paper. The paper is based on the results of strict field experiments with two experimental factors applied in three-year winter wheat monoculture over 1997/98-1999/2000. The factors included: soil tillage systems (traditional (A), and three simplified systems: B) disking, C) cultivating with cultivator, D) direct sowing) and two weed control systems (harrowing by toothed harrow and harrowing + herbicides). Fundamental parameters of wheat canopy weed infestation, collected in spring and prior to wheat harvest, were used to calculate some ecological indices: relative weed abundance (Ra), Shannon’s biodiversity index (H’), and dominance index (C). Weed communities did not get significantly modified under different tillage methods, however they differed depending on the weed control method and on the years. With time under each tillage method, the dominance index increased and the biodiversity index decreased. Weed infestation was mostly caused by 6-7 weed species only, which accounted for over 4/5 of Ra index value. Apera spica-venti (L.) P. Beauv. was the most important dominant.

47-59