Efficacy and economics of imidazolinone herbicides in cluster bean and their residual effect on mustard

A field experiment was carried out at two different locations, research area of CCS HAU Hisar and farmer's field (Kheri Batter) to study efficacy and economics of imidazolinone herbicides in cluster bean during Kharif 2013 and their carryover effect on mustard was observed during Rabi 2014. Significantly higher herbicide efficiency index (HEI) was observed under PE application of pendimethalin + imazethapyr 1000 g/ha and tank mixture 500 g + imazethapyr 50 g/ha at 30 DAS and these two treatments also provided better control of weeds at 60 DAS without any phytotoxic effect on cluster bean at both the locations. At 30 DAS, less dry weight of weeds was recorded under pendimethalin 1000 g/ha as PE, but at 60 DAS, due to new emergence of weeds, percent weed control reduced due to more dry weight of weeds, thus HEI was lower under pendimethalin 1000 g/ha PE. At 60 DAS, PoE application of imazethapyr 100 g/ha fb propaquizafop 62.5 g/ha provided the highest HEI which was at par with pendimethalin + imazethapyr (ready and tank mixture), but at Hisar, HEI of imazethapyr + imazamox at all the doses was lower due to heavy infestation of T. portulacastrum as compared to other herbicidal treatments. The lowest weed index (WI) was observed under pendimethalin 500 g + imazethapyr 50 g/ha (tank mixture) as PE which was significantly at par with pendimethalin + imazethapyr (RM) 1000 g/ha as PE and imazethapyr 75 and 100 g/ha fb propaquizafop 62.5 g/ha, but significantly higher WI was recorded under imazethapyr + imazamox due to lower efficacy against T. portulacastrum. The highest biological yield, seed yield, maximum net returns and increase over weedy check were obtained under pendimethalin 500 g + imazethapyr 50 g/ha (tank mixture) as PE and pendimethalin + imazethapyr (RM) 1000 g/ha as PE, but both were statistically similar to each other and similar to PoE imazethapyr 100 g/ha fb propaquizafop 62.5 g/ha at both the locations. No injury was visible at 2 WAS, 4 WAS and later stages on mustard.