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

Dirceu Agostinetto,André Da Rosa Ulguim,Nixon Da Rosa Westendorff,Luis Antonio De Avila,Marcos André Nohatto

doi:10.14393/bj-v32n3a2016-26128

Abstract

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 Querencia - 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 Querencia, 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.

Highlights

Rice is the most consumed cereal worldwide, and the second most cultivated after corn, occupying an average area of 153.4 million hectares over the last decade
The variables analyzed in the study, presumably associated with loss of yield experienced by rice cultivars at 25 days after crop emergence (DAE) were weed population (WP), shoot dry weight of the weed (SDW), and ground cover by the weed (GC)
The results showed that the estimated values for the parameter i were lower for BRS Querência compared to IRGA 424

Summary

Introduction

Rice is the most consumed cereal worldwide, and the second most cultivated after corn, occupying an average area of 153.4 million hectares over the last decade. One way to reduce losses caused by yellow nutsedge in rice crops includes the use of cultivars with greater competitive ability and differentiated management practices (BALBINOT JUNIOR et al 2003; FLECK et al 2004). Features such as early emergence and establishment, plant vigor, increased leaf expansion rate, rapid canopy development, greater plant height, early cycle and increase in root size, have shown a direct influence on the competitive ability of cultivars (TIRONI et al 2009)

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Conclusion