Yield loss and economic thresholds of yellow nutsedge in irrigated rice in function of cultivars

Resumo

Weeds cause reduction in the rice yield. Little is known about the competitive ability of yellow nutsedge (Cyperus esculentus) with rice and the extent of the economic threshold (ET). The aim of this study was to determine the fit of the regression model to estimate hyperbolic yield losses and ET of yellow nutsedge in rice due to the cycle of cultivars (BRS Querência - Early cycle and IRGA 424 - mid cycle). For this, a field study of competition in the agricultural year 2010/11 was conducted. Yield losses and ET of yellow nutsedge in rice crop is function on the competitive ability of rice cultivar used. The use of rice cultivar with early cycle, BRS Querência, increases the ETs of weed in rice crops compared to the use of IRGA 424, mid-cycle. The hyperbola satisfactorily estimated yield losses that yellow nutsedge causes in rice crops. The explanatory variable, population of yellow nutsedge, was the best fitted to the model. Increases in yield, price paid for rice and control efficiency promoted by the herbicide and decreased cost of weed control, promote ET reduction in yellow nutsedge in rice crops, justifying the adoption of control measures of smaller populations of the weed.