Impacts of sequential herbicides and residue mulching on weeds and productivity and profitability of vegetable pea in North-western Indo-Gangetic Plains

Abstract

Vegetable pea (hereafter referred to as pea) is heavily infested with weeds, which can cause yield losses up to 39%. Only pre-emergence herbicide is not enough to control diverse weeds. Its efficacy is greatly affected by soil surface dryness during winter. Integration of other options with herbicides may provide effective weed management. Therefore, this experiment was designed to evaluate the effects of combinations of pre- and/or post-emergence herbicides, residue retention, mechanical weeding on weeds in pea. Results showed that the applications of pendimethalin 0.5 kg a.i. (active ingredient) ha-1 as pre-emergence + residue 2 t ha-1 followed by imazethapyr 0.075 kg a.i. ha-1 as post-emergence gave comparable pea yield with weed-free control, which was 79.6% and 77.3% higher, respectively in first and second year than that in unweeded control. This treatment resulted in higher weed control efficiency (68% and 70%), leaf area index (4.90 and 5.52) and biomass (5.38 and 5.72 g plant-1) of pea, net returns and net benefit:cost than most other treatments. Contrast analysis revealed that crop residue mulch was superior to no residue and cono-weeding, by giving 41.9-55.5% and 25.5-29.6% higher pea yield, respectively. The residues of pendimethalin, imazethapyr, and quizalofop in pea and soil were below detectable level (0.05 mg kg-1) in all treatments, except two treatments, which, otherwise, had pendimethalin residue below maximum residue limit (0.1 mg kg-1). Thus, the combination of pendimethalin, crop residue, and imazethapyr could lead to better weed management and higher pea productivity and profitability without risks of herbicide residue in pea and soil. It would reduce the use and intake of residues into environment of pendimethalin by 50% and imazethapyr by 25%.