Gidnavar, V SHanumanthappa, D C2019-08-082019-08-082002No. of references 108http://krishikosh.egranth.ac.in/handle/1/5810120117"A field experiment was conducted at Main Research Station, University of Agricultiiral Sciences, Dharwad on vertisols during kJiarif 2001 to study the bio-efficacy of clomazone herbicide for weed management in soybean. The experiment was laid out in randomized block design with 12 treatments comprising of pre-emergence (PE) application of clomazone @ 625, 750, 875 and 1000 g ai.ha""', clomazone @ 500 g a.i.ha'' + chlorimuron @ 9 g a.i.ha'', clomazone @ 500 g a.i.ha""' + metribuzin @ 250 g a.i.ha""', alachlor @ 2500 g a.i.ha""', pendimethalin @ 1000 g a.i.ha""', chlorimuron @ 9 g a.i.ha""', one hand weeding + one intercuhivation, weed free and weedy checks. The treatments were replicated thrice. Clomazone did not cause any phytotoxicity on soybean. Clomazone @ 750 to 1000 g a.i.ha""' applied as PE were found effective in reducing both population and dry weight of weeds. These treatments also recorded higher weed control efficiencies. There was an improvement in growth and yield components of soybean with the application of clomazone. Clomazone @ 750 to 1000 g a.i.ha""' recorded significantly higher seed yield as compared to clomazone @ 625 g a.i.ha''. Weedy check recorded significantly lower seed yield. Application of clomazone @ 750 to 1000 g a.i.ha""' also recorded significantly higher nutrients uptake by crop compared to clomazone @ 625g a.i.ha""' and pendimethalin @ 1000 g a.i.ha"" and vice-versa with uptake of nutrients by weeds. Significantly higher net return and B:C ratios were realized with clomazone @ 750 g a.i.ha""' compared to clomazone @ 625 g ai.ha""', alachlor @ 2500 g a.i.ha""', pendimethalin @ 1000 g a.i.ha'' and clorimuron @ 9 g a.i.ha""'. Application of clomazone @ 625 to 1000 g a.i.ha""' had no adverse effect on urease, dehydrogenase and phosphatase acti^'ities at 20 days after sowing and also on succeeding crops. Based on the results, it could be concluded that clomazone @ 750 g a.i.ha""' applied as PE was economically feasible for effective weed control in soybean."ennullThesis