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

The United Arab Emirates has a hyper-arid climate.‎ 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.‎ For assessing the allocation of irrigation water to date farms under Law 5, we carried out measurements of tree water-use by the compensation heat-pulse method, complemented by measurements of the changing soil-water dynamics using time domain reflectometry and bulk soil electrical conductivity.‎ Over four years we measured the hourly pattern of Lulu date-palm water use, ETc, at two levels of irrigation-water salinity: Treatment S1 at 5 dSm−۱, and S3 at 15 dSm−۱. The mid-summer ETc for the S1 Lulu trees is up to 190 L d−۱, on average, whereas for the S3 trees ETc is lower at 130 L d−1 (68% of S1) because of the salt.‎ Measurements of canopy radiation interception using a ‘light stick’ showed the S1 trees intercepted 26% of the incident radiation, whereas the S3 trees only intercepted 20% (ratio S3/S1=76%).‎ The date yield of the S1 trees was 68 kg tree۱, but was 46 kg tree−۱ for the S3 trees (ratio 68%).‎ Current practice is to irrigate trees with 275 L d−۱, 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 d۱, and for S3 just 137 L d−۱. This represents savings of 25–50% from current practice.‎

Authors: 
Ahmed Al-Muaini, Steve Green, Abdullah Dakheel, Al-Hareth Abdullah, Wasel Abdelwahid Abou Dahr, Steve Dixon, Peter Kemp, Brent Clothier
Year: 
۲۰۱۹
Publication type: 
Scientific Paper
Publication Source: 
Agricultural Water Management
Volume/Chapter/Issue: 
۲۱۱
Page Number: 
۱۲۳ - ۱۳۱