Herbicidal efficacy and selectivity of pendimethalin, oxadiazon and their tank mixtures to direct seeded onion

Abstract

Production of direct seeded onion is constrained by weeds and complete loss of crop yield is not uncommon. Field trials were undertaken to study the influence of sequential applications of the herbicides pendimethalin, oxadiazon and their tank mixtures on efficacy and selectivity to direct seeded onion. Experiments were undertaken at the Gezira and Shendi Research Stations. Onion (cv Saggai) seeds were planted on ridges. Grassy weeds were predominant at the Gezira Research Farm (62 and 69%), while at Shendi Research Farm broad-leaved weeds were the most common (71%). Pendimethalin at 1.19 and 1.79 kg a. i. ha-1, applied at planting, effected excellent and persistent control (85-100%) of grassy weeds. The herbicide at the low rate displayed inconsistent performance on broad-leaved weeds across seasons and sites, while at the high rate it was toxic to the crop. Unrestricted weed growth reduced the onion bulb diameter by 55- 61% and bulb yield by 86-93%. Pendimethalin at 1.19 kg a. i. ha-1, applied at planting, followed by oxadiazon and/or their tank mixtures 2 or 4 weeks after crop emergence provided adequate weed control and significantly increased bulb size and yield. The bulb diameter and yield, obtained, were often comparable to those of the weeded control. Keywords: Direct seeded onion, weed, oxadiazon, pendimethalin, broad-leaved weeds, grasses