Determination of Critical Period of Weed-Crop Competition in Malt <i>Barley</i> (Hordeum <i>vulgare </i>L.) in North Showa Zone, Central Ethiopia

Weeds are the principal limiting biological factor in national barley production, with losses that vary from region to region, depending on the cultivation system, predominant weed communities and weed control methods employed by the farmers. Therefore, field experiment was conducted under rain fed conditions in 2017 cropping season to determine the critical period of Weed-Crop Competition in malt barely (Hordeum vulgareL.) at Debre Birhan University in North Showa Zone, Central highlands of Ethiopia. A total of eighteen treatments were laid out in a randomized complete block design (RCBD) with three replications. The treatments consisted of increasing duration of weedy and weed-free set each consisted weed competition and weed-free durations up to 20, 30, 40, 50, 60, 70, 80 and 90 days after crop emergence (DAE) were compared with two checks namely completely weedy and weed free up to harvest. The major weed families competing vigorously with barley were Compositae and Gramineae and Cyperaceae. According to the current study, the weed density and weed dry weight were decreased, whereas crop parameters like the number of days required to reach heading of barely, the number of days required to reach physiological maturity, number of seed per spike, spike length, thousand seed weight, aboveground dry biomass, grain yield and harvesting index of crop were highly increased, with increasing duration of weed-free periods. The highest yield loss due to weed competition from the weedy check treatment of barely as compared to weed free check. Uncontrolled weed growth significantly reduced barely grain yield by 70.38% compared to the grain yield obtained from the weed-free check plots. The beginning and the end of critical period of weed crop competition were based on 5 and 10 % acceptable yield loss levels, which were determined by fitting logistic and Gompertz equations to relative yield data, representing increasing duration of weed-interference and weed-free periods. In conclusion, the results of the study revealed that, to reduce the loss in the grain yield of barley by more than 10% and higher economic return, it is important to keep the crop weed-free between 33 to 49 days after crop emergence (639 to 1049 GDD) at Debre Berhan.