Estimating transpiration in an intercropping system: measuring sap flow inside the oasis

The quantity of water transpired by a plant is an important factor in investigating irrigation control, biomass production, and, in studies of plant–water relations. Measuring sap flow in plant stems provides a method for estimating transpiration. Sap flow within the xylem of date palm and apricot, inside an oasis in the south of Tunisia, was monitored continuously using the Granier’s method. We have been able to calculate transpiration of the date palm and fruit canopies alone and both combined. The daily average values of transpiration are about 1.91 and 1.2 mm per day for date palm and fruit trees, respectively. We have also established the relationship between transpiration and global and net radiation inside the oasis. These relationships are important for control irrigation on an hourly and daily scale. We can show that transpiration for date palms represents 32% from global radiation received above the oasis and 53% from net radiation. Transpiration in the fruit trees canopy represents 21% from global radiation above the oasis and 33% from net radiation.