Is it true that the date palm tree consumes a lot of water? Evaluation of the date palm tree transpiration using Granier's sap flow method in a Tunisian Saharan oasis

Abstract

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