Evaluation of oxadiargyl and thiobencarb herbicides efficacy on rice (Oryza sativa L.) yield and yield components

To investigate the effect of various levels of Oxadiargyl and Thiobencarb herbicides on yield and yield components of rice (Oryza sativa cv. Hashemi), an experiment was carried out as a randomized complete block design with 8 treatments in 4 replications, in Rice Research Farm of Agriculture Faculty of Guilan University in 2011 growing season. In this experiment, the effects of Oxadiargyl (450, 900 and 1350 g.a.i ha-1) and Thiobencarb (1500, 3000 and 4500 g.a.i ha-1) herbicides were investigated. The two untreated control and hand weeding twice was also considered. Rice plant height, number of filled and unfilled grains per spike, grain yield and biological yield were significantly affected by treatments. But, there was no significant effecton 1000- grain weight and harvest index. The more than recommended concentration of Thiobencarb and Oxadiargyl increased 61/7 and 54/3 % the grain yield in comparison with untreated control that was not significantly different from each other. The Most plant height (134.6 cm), number of tillers (16.6), number of grains per spike (76.4) obtained at high concentration of Thiobencarb that 10 to 44 percent higher than untreated control. The lowest number of tillers, grains per spike and plant height obtained at untreated control and the lower than recommended concentration of two herbicides. In general, the high levelsof Thiobencarb and Oxadiargyl herbicides with control 75 and 69% of the total dry weight of weeds and 69 and 71% of the total density of weeds in comparing with untreated control showed higher efficiency in weeds control and performance better in comparing with low levels of self.