Irrigation management with saline groundwater of a date palm cultivar in the hyper-arid United Arab Emirates

Irrigation is essential for dates (Phoenix dactylifera L.), an important crop economically and culturally. Groundwater is relied on, yet it is a non-renewable resource at the rate it is being used. Furthermore, as the water-table drops, it is becoming more saline. Law no. 5 has been passed in Abu Dhabi to regulate the use of groundwater and set allocation limits for agriculture. Over four years the hourly pattern of Lulu date-palm water use, ETc, at two levels of irrigation-water salinity: Treatment S1 at 5 dSm−1, and S3 at 15 dSm−1, were measured. The mid-summer ETc for the S1 Lulu trees is up to 190 L d−1, on average, whereas for the S3 trees ETc is lower at 130 L d−1 (68% of S1) because of the salt. Current practice is to irrigate trees with 275 L d−1, irrespective of salinity. Our recommendation for Law 5 is to tailor irrigation to the seasonal demand in the reference evapotranspiration of ETo, and allow for a 25% factor-of-safety and a 25% salt leaching fraction. For S1 date palms this would mean an annual average of 210 L d−1, and for S3 just 137 L d−1. This represents savings of 25–50% from current practice.