Estimation of critical period for weed control in sesame (Sesamum indicum L.) in northern Ethiopia

A field experiment was conducted for three consecutive cropping seasons (2006, 2007 and2008) to estimate the critical period of weed control and yield loss in sesame at HumeraAgricultural Research Center, Northwestern Ethiopia. Quantitative series of both increasingduration of weedy and weed free periods were compared with complete weed free andweedy check. The experimental design used was RCBD with three replications. The resultsindicated that the experimental field was infested both with broadleaved (90.1%) and grassy(9.9%) weeds. Three years pooled data revealed that, Ocimum basilicum, Corchorus trilocularis,Corchorus orinocensis and Hibiscus trionum were among the dominant broadleaved weedswhere as Digitaria abyssinica and Digitaria ternata, were the dominant grassy weeds. Significantdifference in dry weed biomass was observed both under early and late competition periodsin all the three years. Uninterrupted weed growth caused a reduction of 82.9%, 82.5% and86.3% in 2006, 2007 and 2008 respectively, in yield as compared to complete weed free. On theother hand, the yield loss from weedy up to 14 and weed free up to 28 or more days after cropemergence were less than 10% and hence, the critical period of weed control in sesame atHumera area was found to be between 14 and 28 days after crop emergence with duration of14 days.