Assessment of different methods for simulating actual evapotranspiration in a semi-arid environment

Field experiment was carried out to examine the effects of full and deficit irrigation treatments on yield and irrigation water productivity of potato crop conducted under semi-arid conditions of Tunisia. In addition, the accuracy of different models for computing daily ET0 have been assessed against the standardized FAO 56-Penman Monteith estimations. An application of the FAO-56 dual approach to calculate actual evapotranspiration (ETa) is reported, implemented by means of the FAO-56 model. The obtained daily values of ET0, were used as input in the FAO-56 model, in order to assess their impact on simulated actual evapotranspiration of potato crop. The obtained results indicate that potato yield decrease significantly with decreasing irrigation amount. However, no significant difference was obtained in term of WPirrig. Comparison between the different ET0 methods against the FAO-56 PM, revealed that the Makkink and Priestley-Taylor models might be considered as efficient alternatives for estimating ET0. Furthermore, the simulated actual evapotranspiration are compared with their corresponding obtained by the water balance method. The statistical results of comparison highlighted that the best performances are accorded to the FAO-56 PM. More detailed analysis, evidenced also that the Hargreaves-Samani, Pristley-Taylor and Makkink approaches can be used as valid alternatives for estimating ETa.