Measured and estimated crop et and kc for wheat and barley in central Saudi Arabia

A field experiment was conducted at the educational farm. King Saud University (central region of Saudi Arabia) to measure crop evapotranspiration (ETC\ for wheat and barley crops. The measurements of alfalfa reference ET were coupled with the measured crop ET(ETC) to obtain the crop coefficients (A'r). Also, three models for estimation of reference ET (ETnf) were examined to assess their suitability for prediction of ETC under local climate conditions The measurements were accomplished using nine non-weighting lysimeicrs constructed with reinforced concrete. The lysimetcrs were randomly and evenly planted with the selected crops, wheat and barley, and with alfalfa reference crop. The research outputs revealed that the seasonal E7\ for wheat and barley are 898 and 930 mm, respectively. The maximum daily ETC rates never exceeded 11 mm/day for both crops. The average maximum daily ET, was 10.34 and 10.21 mm/day for wheat and barley, respectively. For wheat crop, the A',, values for initial, mid-season, and late-season stages have been found to equal 0.63, 1.38, and 0.41 for the three stages, respectively On the other hand, the Kt values for barley were 0 60, 1.39, and 0.29, for the initial, mid and late-season stages, respectively, The tested models for predicting ET, gave almost identical estimates. The standard errors of estimates (SEE) lor the three models were in the vicinity of 1.7 mm/day