Herbicides tank-mixes effects on weeds and productivity and profitability of chilli (Capsicum annuum L.) under conventional and zero tillage

Abstract

Weeds heavily infest chilli and cause significant yield losses. Herbicide mixtures control diverse weeds better and prevent/delay weed shift and resistance. They have been hardly studied in chilli under conservation agriculture. Pendimethalin is the prevalent herbicide used in chilli, but not effective against nutsedge. Oxyfluorfen and quizalofop-p-ethyl also have negligible/no effect on nutsedge. Imazethapyr is a post-emergence herbicide and more effective against nutsedge, but its pre-emergence activity against nutsedge/weeds and selectivity to chilli have not been studied. In this study, these herbicides were tank-mixed or sequentially applied to expand the weed spectrum being currently controlled. Our objective was to compare herbicide mixes to improve weed control, especially with nutsedge. We observed that the pre-emergence tank-mix application of pendimethalin 0.75kgha−1+imazethapyr 0.075kgha−1 resulted in significantly higher weed control efficacy (∼86%) and leaf chlorophyll, but lower ascorbate peroxidase activity, suggesting that imazethapyr was selective to chilli. In this treatment, the yield and gross returns were 2% lower, but the net returns and net returns:cost were higher by 3% and 20%, respectively compared to weed-free check that included the costs of hand weeding. The zero tillage with residue (ZT+R) did not affect herbicide activity. The pendimethalin+imazethapyr tank-mix treatment with ZT+R would provide higher yield and income through better weed management and less/no chances for nutsedge insurgence, which usually occurs due to continuous use of herbicides with limited efficacy on nutsedge. It would reduce application cost by 50%, and doses and residues of these herbicides by 25% in agro-ecosystems.