Abstract

To assess the integrated effect of planting pattern and low dose herbicide mixtures on weeds and growth, yield attributes and yields of cowpea, and to determine the economic feasibility of different weed management practices in cowpea, a field experiment was conducted at Sirinka Agricultural Research Center experimental sites at Jari and Sirinka in Northern Ethiopia during the 2014 main cropping season. There were 16 treatments comprising the combinations of two planting patterns (60 cm × 10 cm, 45 cm × 15 cm) and eight weed management practices (s-metolachlor 2.0 kg ha^-1, s-metolachlor at 1.0 kg ha^-1+hand weeding and hoeing 35 weeks after crop emergence (WAE), pendimethalin at 1.0 kg ha^-1+hand weeding and hoeing 5 WAE, s-metolachlor at 1.0 kg ha^-1+pendimethalin at 1.0 kg ha^-1, s-metolachlor at 1.0 kg ha^-1+pendimethalin at 0.75 kg ha^-1, s-metolachlor at 0.75 kg ha^-1+pendimethalin at 1.0 kg ha^-1, hand weeding and hoeing 3 WAE and weedy check. The treatments were laid out in factorial combination in a randomized complete block design with three replications. The highest number of pods per plant, number of seeds per pod, and hundred seed weight were obtained from the combination of s-metolachlor at 1.0 kg ha^-1+hand weeding 5 WAE along with 60 cm × 10 cm at Sirinka. Higher (3092 kg ha^-1) grain yield was recorded at Sirinka than at Jari (2714 kg ha^-1). The highest (53460 ETB ha^-1) gross benefit was obtained from s-metolachlor at 1.0 kg ha^-1+hand weeding and hoeing 5 WAE, followed by pendimethalin at 1.0 kg ha^-1+hand weeding and hoeing 5 WAE (46737 ETB ha^-1). Therefore, managing the weeds with the application of 1.0 kg ha^-1 of s- metolachlor+hand weeding and hoeing 5 WAE along with 60 cm × 10 cm proved to be the most feasible practice. Alternate herbicides for the control of X. strumarium infested fields in the study area needs to be explored.

Keywords: Broadleaved and grass weeds; Cowpea; Grain yield; Herbicide mixtures; Integrated management; Pendimethalin; s-metolachlor; Vigna unguiculata; Weed