Effect of weed management with post emergence herbicides on seed yield, net return and oil quality of linseed (Linum usitatissimum L.)

An experiment was conducted during three consecutive rabi seasons (2005–06 to 2007–08) at Kanpur to study the effect of post emergence herbicides on seed yield, economics and oil yield as well as its quality of linseed. The experimental fields during all the three years were infested mainly with Phalaris minor and Chenopodium album, whereas the share of Phalaris minor was observedmorethan Chenopodium album. Besides, Cyperus rotundus, Asphodelues tennufolius and Melelotus indica during 2005–06, Partulaca oleracea, Convolvulus arvensis and Anagalis arvensis during 2006–07 and only Convolvulus arvensis during 2007–08 were also recoded. Results revealed that no weeding throughout the crop season reduced the yield by 51.66% over weeding twice at 20–25 and 40–45 days after sowing (DAS). Among the herbicides, weed control efficiency was recorded higher with sulfosulfuon but its phyto toxic effect on linseed variety ‘Shekhar’ could not record lowest weeds competition index “crop yield loss in comparison to hand weeding twice”, which was observed maximum with clodinafop 80 gha−1 (3.60%) and minimum with sufosulfur on 30 gha−1 (50.48%). Post emergence application of clodinafop 80 gha−1, clodinafop 60 gha−1, isoproturon1 kgha−1 andisoproturon1 kgha−1 +2, 4-D0.5kgha1 at 30–35 DAS could be an alternative of hand weeding twice for weed management in irrigated linseed to fetch higher return per rupee investment, but it would be better to spray clodinafop 80 g ha−1 at 30–35 DAS for higher net return per unit area. Clodinafop either 60 g ha−1 or 80 g ha−1 could be an alternative of isoproturon where Phalaris minor have shown resistance for isoproturon. The oil yield of linseed was recorded maximum when weeds were managed with two hand weeding but clodinafop @ 80 g ha−1 also produced almost equal oil yield. The application of herbicides increased the saturated fatty acids and decreased the unsaturated fatty acids as compared to hand weeding twice and weedy check. The reduction in synthesis of the iodine value, w-3/w-ratio, PUFA/MUFA ratio and nutritional quality index (NQI) value were also reduced with the application of herbicides.