A preliminary study on the time of application of imazethapyr and its ready mix combination with pendimethalin and imazamox against weeds in blackgram

The bio-efficiency of imazethapyr and its ready mix combination products with pendimethalin and imazamox against weeds, their effect on growth, yield and phytotoxic effects on black gram and residual effect on succeeding mustard crop were studied during ۲۰۱۳-۱۴. Significantly lower weed count and dry weight was recorded with application of imazethapyr + pendimethalin (pre-mix) at ۸۰۰ g/ha, pendimethalin at ۱۰۰۰ g/ha and imazethapyr + pendimethalin (pre-mix) at ۹۰۰ g/ha. Imazethapyr + pendimethalin (pre-mix) ۱۰۰۰ g/ha and ۸۰۰ g/ha, pendemethlin ۱۰۰۰ g/ha and imazethapyr ۵۰ and ۷۰ g/ha (pre emergence) behaving statistically similar with pendimethalin ۱۰۰۰ g/ha (pre emergence) and hand weeding at ۲۰ and ۴۰ days after sowing resulted in significantly higher seed yield of black gram. Seed yield of blackgram was negatively associated with total weed count and weed dry weight (P≤۰.۰۱). With every one weed increase per square meter, the blackgram seed yield was expected to reduce by ۱۶.۸ kg/ha. Net returns, B:C and net returns over weedy check were highest under imazethapyr + pendimethalin ۹۰۰ g/ha. The economic threshold levels i.e. No m-۲ and g m-۲ with the weed management practices studied varied between ۱.۷ – ۱۸.۰ m-۲ and ۱.۰-۱۰.۰ g m-۲. Imezethapyr + pendimethalin ۱۰۰۰ g/ha and imazethapyr + imazamox ۵۰ g/ha had lowest weed persistence index (WPI). Imazethapyr + pendimethalin ۹۰۰ g/ha resulted in highest crop resistance index. Weed management index (WMI), Agronomic management index (AMI), and Integrated weed management index (IWMI) were highest following imazethapyr ۴۰ g/ha. Overall impact index (Ii) was highest under imazethapyr ۵۰ g/ha followed by imazethapyr + pendimethalin ۹۰۰ g/ha, imazethapyr + pendimethalin ۱۰۰۰ g/ha and pendimethalin ۱۰۰۰ g/ha. Weed index (WI) indicated ۷۰.۸% loss in yield of blackgram. The residual effects of herbicide treatments on succeeding mustard crop were not observed.

Keywords:

Blackgram , Imazamox , Imazethapyr , Pendimathalin , Weeds