Assessment of Water Requirements by Several Methods and Impact of Deficit Irrigation on the Date Palm Productivity and Water use Efficiency

This study was conducted on (Khalas) date palm, which is well-known for its cultivation in the regions of the Kingdom of Saudi Arabia (KSA) to estimate the monthly, annual irrigation water requirements and effect of different deficit irrigation levels on yield, soil moisture distribution and water use efficiency. The experiment consisted of four levels of deficit irrigation: 60%, 80%, 100% and 120% of crop evapotranspiration (ETc) compared with traditional irrigation. Two different water qualities: well 4.79 dS/m and treated electrical conductivity 1.86 dS/m. Several methods of estimating water requirements were used, such as the Penman Monteith method, the evaporation pan, and the water balance. The results indicated that the traditional irrigation (farm method) gave the highest amount of productivity with the most water consumption. The results showed that the water requirements of the Khalas date at the 100% of crop evapotranspiration (ETc) were 53.57, 37.67, 58.89 m3/year/tree, calculated using water balance, the evaporation pan and Penman Monteith equations, respectively. The results indicated that an increase in the amount of well water added by the traditional irrigation compared to the deficit irrigation, whereas the increase % at 100% ETc ranged from 38.71% to 195.59% using well water, while the increase % ranged from 22.63% to 280.37 % in March and November, respectively. While in the case of comparing the quantities of water added by the traditional method with 60% ETc of the water requirements, the increase% ranged from 78.71% to 235.59% in the case of well water and 62.63% to 320.37% using treated water of March and November months, respectively.