This study compares the performance of four models to estimate the daily evapotranspiration (ET) under greenhouse. The first, De Villele model (ETDV), Penman-Monteith model (ETPM), Stanghellini model (ETST) and finally the transpiration model based on the heat balance equation at the cover, Takakura (ETTK). The work was conducted during two tomato production seasons 2012 and 2013 under two greenhouses types; Monospan and Canarian, located at Experimental Station of Melk Zhar in Balfae (INRA Agadir, Morocco). ST models and PM correctly simulate tomato transpiration for both measured values ??for daily gain of the tomato stem (MC / DG) Monospan greenhouse (r² = 0,55 and 0,62). Similarly, we have reached a satisfactory relationship between the Eff-TR (the efficiency of plant transpiration) and the report MC / DG using the ST model under Monospan and Canarian greenhouses (r² = 0,67 ; 0,58) respectively. Consequently, we identified critical thresholds or baselines water status of tomato; water comfort (0,40 <MC / DG <0,50 and 70 <Eff-TR <90%); overestimation of irrigation (MC / DG <0,42 and Eff-TR <70% and water stress (MC / DG > 0,46 and Eff-TR > 90%). In addition, the comparing means depending on the yield level has identified three groups of ET models ; STa (318T / ha)> TKb (272t / ha)> ~ DVc PMc (236-249t / ha).

Keywords: Evapotranspiration Model, greenhouse Tomato, Daily gain of stem, transpiration efficiency, plant water status, yield.