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Water requirements for irrigation with saline groundwater of three datepalm cultivars with different salt-tolerances in the hyper-arid United Arab Emirates

Direct measurement of sap flow enabled determination of the seasonal pattern of water use, ETc, of three date (Phoenix dactylifera L.‎) varieties irrigated with groundwater at different salinities: S1 at 5 dS m−۱ and S3 at 15 dS m−۱. The ETc at the higher salinity was 43–46% lower across all varieties.‎ The crop factor, Kc, was computed from ETc ‎/ ETo, where ETo is the reference evapotranspiration.‎ By proximal sensing using a light stick, we measured the fraction of light intercepted, LI, by the trees’ canopies.‎ For all varieties and salinities, we found the ratio Kc LI−1 to be about 0.‎95, which enables proximal sensing to be used to predict ETc for all varieties and across salinities.‎ These predictions can then be used to schedule irrigation the recommended rate of 1.‎5 ETc, which accounts for a 25% factor-of-safety and a 25% salt leaching fraction.‎ For S1, the salt-tolerant ‘Lulu’ used 50 kL tree−۱ y−۱, the moderately tolerant ‘Khalas’ consumed 43.‎1 kL tree−۱ y−۱, and the salt-intolerant ‘Shahlah’ transpired 57.‎3 kL tree−۱ y−۱. Whereas the drop in ETc across all varieties was similar between S1 and S3, there were large differences in the drop in date production.‎ Date production between S1 and S3 dropped 29% for ‘Lulu’, 43% for ‘Khalas’, and 52% for ‘Shahlah’.‎ Analysis of the consumed water productivity, CWP (kg-dates kL−۱) provides insight into the impacts of salinity on date yield.‎ For the tolerant ‘Lulu’ the CWP for S3 was higher (2.‎21 kg-dates kL−۱) than that for S1 (1.‎78 kg-dates kL−۱), although production was higher with S1 (89.‎1 kg tree−۱) than S3 (62.‎9 kg tree−۱). The CWP for ‘Khalas’ was the same for both treatments (≈ 1 kg-dates kL−۱). For the salt intolerant ‘Shahlah’, CWP dropped between S1 (1.‎5 kg-dates kL−۱) and S3 (1.‎34 kg-dates kL−۱). Based on the price of dates, the CWP can also be used to assess the economic value of irrigation water by variety and salinity.‎

Authors: 
Ahmed Al-Muaini, Steve Green, Abdullah Dakheel, Al-Hareth Abdullah, Osama Sallam, Wasel Abdelwahid Abou Dahr, Steve Dixon, Peter Kemp, Brent Clothier
Year: 
۲۰۱۹
Publication type: 
Scientific Paper
Publication Source: 
Agricultural Water Management
Volume/Chapter/Issue: 
۲۲۲
Page Number: 
۲۱۳–۲۲۰