Residual Effect of Herbicides on the Succeeding Crop of Rice

Abstract

The residual effects of herbicides applied in the second crop of 1971 on the infestation of weeds and the growth performance of rice in the first crop of 1972 are summarized. The treatments of 2,4-D IPE, Benthiocarb, and C-288+2,4-D IPE were infested with smaller number of weeds while those of CP 53619, Benthiocarb+2, 4-D IPE, and C-290+2,4-D IPE were more heavily infested. However, the correlation between average weed control rating in the second crop of 1971 and average number of weeds per m2 in the first crop of 1972 gave r value of -0.0389 which was too small to attain significance. This indicates that application of herbicides does not affect appreciably the infestation of weeds in the succeeding crop of rice. Plant height and number of tillers per hill at 60 days after transplanting, plant height and number of panicles per hill at maturity stage, days to heading, and grain yield per ha did not differ significantly among treatments. Thus, residues from the application of herbicides in the second crop of 1971 may not persist in amounts toxic to the growth of rice in the following first crop of 1972.