In field experiments, the grain yield, grain quality and weed infestation of winter durum wheat were evaluated in conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) systems. The C/N ratio in the soil was also assessed on all plots. In the CT system, shallow ploughing and pre-sowing ploughing were performed after harvest; in RT – the shallow ploughing and pre-sowing ploughing were replaced by cultivating; and in NT – glyphosate spraying was performed on the stubble field. The grain yield of winter durum wheat was higher in CT than in RT and NT systems. Also, more spikes per m2 were found on the CT than on the RT and NT plots. Furthermore, the grain weight per spike and the 1000 grain weight were higher in the crops from the CT than from the RT and NT systems. Higher contents of total protein, wet gluten and starch were determined in wheat grains harvested from the CT plots than from the RT and NT plots. Also, the crop from the CT system had higher values of grain density and grain uniformity compared to the crop from the RT and NT systems. The tillage systems differentiated the number of weeds per m2. On the RT and NT plots, the number of weeds and their air-dry weight were higher compared to the CT plots. The RT and NT plots were dominated by weeds of the upper level (they accounted for 51.3-54.2% of the weed number), whereas the CT plots were most densely infested by the weeds of the upper (31.9%) and the middle (35.5% of the weed number) levels. The most favorable C/N ratio occurred on the NT plots, and the least beneficial one on the CT ones.