Integration of Molinate use with Water Management for Red Rice (Oryza sativa) Control in Water-seeded Rice (Oryza sativa)

Abstract

Integration of preplant-incorporated molinate (S-ethyl hexahydro-1H-azepine-1-carbothioate) at 4.5 kg ai/ha and a brief postseeding drainage period in water-seeded rice (Oryza sativaL.) gave the best red rice (Oryza sativaL. # ORYSA) control without a significant reduction in cultivar stand density. This combination of practices provided higher cultivar grain yield and lower red rice grain yield than any water management practice alone. Continuous-flood water management provided a substantial reduction in red rice stand density, but it also caused a significant reduction in the cultivar stand density. Under the reduced stand density conditions, the red rice was very competitive and yielded more than the cultivar. Although brief drainage alone gave a significantly lower level of red rice control, it had no significant effect on the cultivar stand density, and the red rice and cultivar yields were not significantly different from the continuous-flood yields. Prolonged drainage had the highest red rice and cultivar stand densities and the highest red rice grain yield, but the cultivar yield was not significantly different from the other plots that were not treated with herbicide. Although this treatment gave the highest total grain yield, its composition had the highest percentage of red rice. Puddling the seedbed did not alter the stands or yields of red rice or cultivar compared to the nonpuddled plots with the same water management and herbicide rate. The application of molinate as a preplant-incorporated treatment or as a preplant postflood treatment before or after puddling gave results that were not significantly different from each other. The superior performance of preplant application of molinate in water-seeded rice in conjunction with a brief postseeding drainage period provides an excellent tool for red rice suppresion.