SUMMARY
A pot experiment was conducted to evaluate the allelopathic potential of Nigella sativa L. on seedling emergence and first growth of the serious weed rigid ryegrass (Lolium rigidum L.). The results revealed significant weed suppressive effects of N. sativa residues incorporated into the soil. The lowest seedling emergence rate (38%) was observed in pots treated with 20 g leaf residues. Regarding height, the lowest value (26.7 cm) was found in 20 g root residues. The highest quantity of shoot residues reduced leaf number, tiller number, fresh and dry aerial biomass up to 58, 51, 64 and 59%, respectively. It can be concluded that the effect of incorporation of plant residues depended on the type and amount of residue. N. sativa could be utilized as an allelopathic crop to control weeds and future studies should focus on isolating and identifying allelochemicals in roots, shoots and leaves of this species.