Management of Weeds in Common Bean (Phaseolus vulgaris L.) through Herbicide Combinations in Eastern Ethiopia

Weeds cause significant yield and quality loss in common bean. Therefore, the effects of low dose herbicidecombinations were evaluated for broad spectrum weed management in common bean at Haramaya and Hirna,eastern Ethiopia in 2013 main cropping season. The study comprised 14 treatments: s-metolachlor and pendimethalineach at 1.0 kg ha -1 supplemented with one hand hoeing and weeding at 4 weeks after crop emergence (WAE),combinations of s-metolachlor + pendimethalin (1.0 + 1.0, 0.75 + 1.0, 1.0 + 0.75, 0.75 + 0.75, 0.5 + 1.0, 1.0 + 0.5, 0.5 +0.5, 0.5 + 0.75 and 0.75 + 0.5 kg ha -1 ), one hand hoeing and weeding 2 WAE, weed-free and weedy check arranged ina randomized complete block design with three replications. Weed flora in the experimental fields consisted ofbroadleaved and sedge with the respective relative densities of 95.6 and 4.4% at Haramaya, and 23.4 and 76.6% atHirna. S-metolachlor at 1.0 kg ha -1 supplemented with one hand hoeing and weeding 4 WAE significantly reducedthe weed dry weight by 50.0% compared to the weedy check plots. S-metolachlor 1.0 kg ha -1 supplemented with onehand hoeing and weeding 4 WAE had significantly higher number of pods plant -1 , number of seeds pod -1 , hundredseed weight, grain yield (4045.3 kg ha -1 ) and aboveground dry biomass than the weedy check plots. Significantlyhigher grain yield (3878.6 kg ha -1 ) was recorded at Hirna than at Haramaya. The highest net benefit of ETB 33601 ha -1was obtained by application of s-metolachlor at 1.0 kg ha -1 + one hand hoeing and weeding 4 WAE.