Standardization of Rate and Time of Application of Imazethapyr Weedicide in Soybean

A field experiment comprised of imazethapyr, a post-emergence herbicide application at 15 and 25 days after sowing (DAS) with three doses (i.e. 50, 75 and 100 g/ha), pendimethalin 0.45 kg/ha (pre-emergence) + hand weeding (40 DAS), two hand weedings (20 + 40 DAS) and unweeded control was conducted at Punjab Agricultural University (PAU), Ludhiana in 2008 and 2009 and at PAU Regional Station, Kapurthala and Bathinda in 2009. Application of imazethapyr at 75 or 100 g/ha applied at 15 or 25 DAS recorded almost similar weed density, weed dry matter and seed yield of soybean as recorded in two hand weedings irrespective of locations and years. No doses of herbicides could cause any phtyotoxicity on the crop as the plant height was similar. On mean basis, the highest net returns were recorded in imazethapyr @ 75 g/ha applied at 25 DAS, which was statistically on par with imazethapyr @ 75 g/ha applied at 15 DAS and in imazethapyr @ 100 g/ha applied at 15 or 25 DAS and Pendimethalin 0.45 kg/ha + hand weeding (40 DAS) but significantly higher than imazethapyr @ 50 g/ha applied at 15 or 25 DAS, two hand weeding and unweeded check.