Influence of Weed Dynamics on the Productivity of Common Bean (Phaseolus vulgaris L.) in Eastern Ethiopia

Common bean is an important cash crop for smallholder farmers in Ethiopia. However, its yield is constrained by weed infestations. Therefore, a study was conducted in 2012 cropping season at Haramaya and Hirna research fields eastern Ethiopia, to determine the critical periods of weed-crop competition and yield losses in common bean at the two sites. The experiment consisted of sixteen treatments in two sets, i.e one weed-free and one weedy set each comprising weed competition durations up to 10, 20, 30, 40, 50, 60 and 70 days after crop emergence and up to harvest). The experiment was laid out as a randomized complete block design with three replications for each set. The dominant weed species were Galinsoga parviflora and Parthenium hysterophorus with the highest relative densities of 26.7 and 39.8% at Haramaya and Hirna, respectively. With increasing duration of weed interference, weed dry weight, and the number of days of common bean plant required to reach physiological maturity were increased whereas the pods per plant, seeds per pod, hundred seed weight, grain yield, aboveground biomass, and harvest index of the common bean crop were reduced. At Haramaya and Hirna, uncontrolled weed growth significantly reduced common bean grain yield by 70 and 48%, respectively compared to the grain yield obtained from the weed-free check plots. In conclusion, the results of the study revealed that, to reduce the loss in the grain yield of common been by more than 10%, it is important to keep the crop weed-free between 140 to 608 growing degree days (24 to 70 days after crop emergence) at Haramaya and from 140 to 707 growing degree days (14 to 70 days after crop emergence) at Hirna