Résumé
To improve the irrigation water management in oasian context, evapotranspiration assessment is required. In Tunisian oases, date palm (Phoenix dactylifera L.) is the main crop and its water use is an essential evapotranspiration element. In this research, sap flow measurement was implemented to assess the date palm transpiration inside an irrigated-drained field within which the shallow-groundwater level and the water balance elements were continuously monitored. The site is a Tunisian Saharan oasis, stamped by waterlogging and salinity manifestation and by low-frequency and irregular flooding irrigation. The cropping system is two-storey palm/grass layered system. This paper focuses on one-year period sap flow measurements using a recalibrated Granier's TDP-method. Results showed that the instantly transpiration varied with the air temperature and was high related to the shallow water table nycthemeral fluctuation. The daily transpiration ranged between 0.5 and 3.5 mm d-1 with a clear seasonal variation. A water stress appearance according to water delivery frequency during the summer season was also revealed. The one-year-cumulated date palm transpiration was about 730 mm and represented almost 60% of the overall oasis deduced evapotranspiration. From this experiment case, it was noted that the date palm tree transpiration reflect a modest water consumption (35 to 45%) relatively to the surrounding high evaporative demand and it can be deduced that date palm tree, in itself, isn't a great water consumer in such cropping conditions. After more validation, these elucidations should be considered to rethink the date palm irrigation scheduling and the water management practices inside oasis schemes.