Preharvest Desiccation of Rice With Paraquat1

Abstract

Studies to determine the suitability of paraquat (1,1′dimethyl‐4,4′‐bipyridinium ion) as a preharvest desiccant were conducted on rice (Oryza sativa L.) cultivars ‘Brazos’ and ‘Labelle’. Under hot, clear weather conditions, paraquat rates of 0.14 kg/ha or above desiccated the leaves within 1 day. Under cool, cloudy conditions 2 to 3 days were required for desiccation. Paraquat applied to rice after the grains were fully developed at rates up to 0.56 kg/ha up to 10 days before harvest (DBH) did not reduce grain yields. Grain moisture, however, was reduced when a minimum of 0.14 kg/ha paraquat was applied at least 4 DBH. Percent whole kernels after milling was not lowered, or lowered only slightly, by application of up to 0.56 kg/ha paraquat up to 10 DBH. These results suggest that paraquat could be a valuable preharvest desiccant for rice if toxic residues are not found in the grain.