Determination of Optimal Irrigation Scheduling for Durum Wheat in the Central Highland Vertosol of Ethiopia

The field trial was conducted for three years from 2014/15 to 2016/17 to determine optimal irrigation scheduling. There were five levels of irrigation water application; 60%, 80%, 100%, 120%, and 140% of the allowable soil moisture depletion levels (ASMDL) for each of the treatments laid out in a randomized complete block design with three replications. In the study, the combined year analysis result showed that there is a significant yield difference among the irrigation water applications at a P < 0.05 level of significance. The highest yield (5.269 tone ha^-1) was obtained by applying irrigation water of 80% ASMDL followed by 120% ASMDL (4.734 tone ha^-1) however the least yield (4.165 tone ha^-1) was observed at irrigation water application of 60% ASMDL of the recommended level which means the application of 40% less water than the FAO recommended level. There is no significant difference in water use efficiency between the treatments, but the highest water use efficiency has been observed at 80% ASMDL. The overall result of this experiment suggests that the application of irrigation water using 20% less than the FAO recommendation (100% ASMDL) can sufficiently be used for irrigation scheduling of irrigated durum wheat under central highland vertosol conditions. Therefore, to have a higher yield of irrigated durum wheat it was recommended to flush frequently before critical depletion occurred.