Bentazon mixtures to control weeds in rice

Three herbicide trials on rice (Oryza sativa L.) were conducted on Coloso clay (Entisols) and on Toa clay loam (Mollisols) from 1981 to 1983 with bentazon [3(1-methyl)-(1 H)-2, 1,3-benzothiadiazin-4-(3H)-one 2,2- dioxide] mixed with propanil [N-(3,4-dichlorophenyl) propanamide] or with bifenox [methyl 5-(2,4-dichlorophenoxy) 2-nitrobenzoate] for early postemergence weed control. Good to excellent weed control was obtained by the above-mentioned bentazon mixtures. These mixtures were particularly effective against rice flatsedge (Cyperus iria L.), a weed not previously controlled by other herbicides. Marginal herbicide phytotoxicity to rice plants was noted in one trial when bentazon at a higher rate was mixed with propanil. All bentazon mixtures resulted in higher yields than standard treatment of propanil alone or thiobencarb [S-(4-dichlorophenyl methyl diethylcarbamothioate] alone by a margin of 8.7 to 26.9%.