Contribution of groundwater to date palm (Phoenix dactylifera) water use in the oases

In arid regions, water resources are extremely limited. The contribution of groundwater to satisfy crop water requirements can be very high, but is often not known. This contribution depends on the root zone environment and the water table depth. Understanding the interaction between groundwater tables and plant development is fundamental to improve water use efficiency. The objectives of this paper are to study the effect of shallow water tables on date palm root distribution, and to determine the contribution of groundwater to date palm water consumption. Experimental research was conducted in a farm located in the Tafilalet oasis (Morocco) with Mejhoul palm tree variety. The groundwater depth fluctuated from 4 to 5m with an average salinity of 5 g.L-1. Many measurements were undertaken to determine soil moisture, roots characterization and transpiration. The results show that during the dry season (June, July and August), and without irrigation supply, 50% of date palm transpiration is satisfied by groundwater. The results also revealed that the root system of date palm tree can reach very important depth (up to 9m) to withdraw water from the aquifer. Therefore, the determination of palm tree water requirements has to take into account the interaction of its root system with the phreatic water table.