LABORATORY STUDIES ON GERMINABILITY AND SEEDLING GROWTH OF COTTON CROP UNDER THE ALLELOPATHIC INFLUENCE OF PURPLE NUTSEDGE

Weeds interfere with crop plants not only through competition but also with allelopathy. Purple nutsedge (Cyperus rotundus L.) is considered as a highly allelopathic weed causing considerable yield losses to crops. A pot study to evaluate the allelopathic effects of purple nutsedge on cotton crop was undertaken at Wire House, Sindh Agriculture University, Tandojam, Pakistan during Kharif (summer) 2013. The experiment was laid out under completely randomized design with three replications. The seeds of cotton variety Sadori were used in the experiment. The analysis of data indicated that application of C. rotundus in both forms (powder and water extract) caused significant (P≤0.05) adverse effects on germination and growth of cotton seedling when compared with control. The integrated application of C. rotundus powder and water extract at higher rates (30 g + 30 ml kg^-1 soil..) exerted greater phytotoxic effects in comparison with combined application of powder or water at lower rates and sole application in both forms at higher rates. The results showed that integration of C. rotundus powder @ 30 g kg^-1 soil + C. rotundus water extract @ 30 ml kg^-1 soil resulted in lowest seed germination, root length, shoot length, fresh weight seedling^-1 and dry weight seedling^-1. The combination of C. rotundus powder @ 15 g kg^-1 soil + C. rotundus water extract @ 15 ml kg^-1 soil was found equal in allelopathic action with C. rotundus powder @ 15 g kg^-1 soil + C. rotundus water extract @ 15 ml kg^-1 soil due to having non-significant (P≥0.05) statistical differences with each other. Hence, it is concluded that C. rotundus possesses allelopathic compounds with inhibitory effects and the presence of this weed in the field may negatively affect growth and yield of cotton.