Evaluation contribution of ground shallow water table to irrigation of date palm trees under irrigation reduction in Saudi Arabia

Contribution of shallow water table to irrigation water requirement (IWR) of crops depends on capillary rise that develops within root zone. This capillary rise is function of root zone environment and depth of shallow water table. In this study impacts of drying the root zone of a date palm tree with 50% irrigation reduction combined with changing depth of water table on IWR of date palm trees at Al-Hassa oasis were investigated. Five drainage ysimeters (1.3 m in diameter and 2m in depth) were setup for growing three years old uniform date palm trees (Phoenix dactylifera.). In each lysimeter soil moisture tensions, i.e., at varied depths 25, 50, 65 and 85 cm, were monitored using Granule matrix sensors and watermarks. In addition to that, water table depth, drained outflow water, and upward flow soil water by capillary rise were determined in each lysimeter. Using the interpretation of soil moisture tension under 50% irrigation reduction, the contribution of ground water with average depths of 133 and 145 cm to the IWR estimated to be 50% and 22% respectively during the month of August. Besides, when soil water balance was used, the contribution with the average depths 144, 141 and 133 were 17%, 20% and 21% respectively during month of October.