Direct and Residual Effects of Herbicides in a Soybean (Glycine max)-Wheat (Triticum aestivum) Cropping System

Field years experimentation in soybean-wheat cropping sequence revealed that in soybean the effective weed control and higher yield were noted under oxadiazon 1.0 kg/ha (1689 kg/ha) followed by fluchloralin 1.0 kg/ha (1392), butachlor 2.0 kg/ha (1334) and oxyfluorfen 0.2 kg/ha (1330) and all these were at par with hand weeding (1756) but significantly superior to weedy check (743). The herbicides used in wheat did not show residual effect on either weed control or crop growth and seed yield. The population of Echinochloa crusgalli (L.) P. Beauv. and Cyperus rotundus L. remained almost unchanged, whereas the population of Commelina communis L. increased but Phyllanthus fraternus Webster, and Cyperus iria L. decreased. In wheat, the residual effect of soybean herbicides was not found on crop growth but reduction in weeds was noted by 14.5, 44.4, 22.8 and 32.3%, respectively compared to weedy check. The direct application of isoproturon and oxadiazon each 1.0 kg/ha preemergence continuously for four years in sub-plots to wheat did not show phytotoxicity to wheat.