Evaluation of Competition Potential in Rice Varieties (Oryza sativa L.) against Yellow Nutsedge (Cyperus esculentus L.)

An experiment was conducted to evaluate yellow nutsedge (Cyperus esculentus L.) density effects on some rice physiological, morphological characteristics and its paddy yield at Sari Agricultual Sciences and Natural Resources University. This experiment was performed as factorial based randomized complete blocks design with three replications. Weed density in four levels (0, 60, 120 and 180 plants m-2) and rice varieties in three levels (Tarom as traditional cultivar, Shirodi and Ghaem as improved cultivars) were the treatments. Results of ANOVA revealed significant difference of weed numbers, rice cultivars and their interactions on shoot length, flag leaf area, leaf number, leaf wet and dry weight, chlorophyll content, SPAD value, harvest index and paddy yield. Mean comparisons showed that the highest levels of all characteristics were recorded in the control plots, while their lowest levels were observed in weed density of 180 plant m-2.The response of different rice varieties to nutsedge densities varied. Among rice cultivars, Tarom had the lowest slope in flag leaf area equation (y= 33.22 - 0.04x), stem length (y= 105.33 - 0.20x), fertile tiller number (y= 22.5 - 0.03x), harvest index (y= 24.98 - 0.3x) and paddy yield (y= 366.6 - 0.57x). Therefore, this traditional cultivar is recommended as the strongest competitor compared to Shirodi and Ghaem improved cultivars which were shown to be as weak competitors to yellow nutsedge weed.