Irrigation water management in date palm (Phoenix dactylifera L.) under arid environment

Date palm (Phoenix dactylifera L.), a traditional crop closely linked to Arab culture, is well adapted to the hyper-arid environment of Kuwait. Nevertheless, the present irrigation practice in Kuwait which relies on applying large quantities of water (>200 m³ tree^‑1 year^‑1) using inefficient delivery systems has enormous economic and environmental consequences. Recognizing the need for developing sustainable irrigation practices, a series of studies were conducted at Kuwait Institute for Scientific Research between 2009 and 2017 to determine real-time irrigation needs of selected date palms cultivars and evaluate their response to saline irrigation water (1.6, 5, 10 or 20 dS m^‑1), deficit irrigation (50, 75 or 100% of water ET_c), irrigation systems (subsurface drip, basin flooding, and surface drip), surface mulch, and soil application of hydrophilic polymer. Under the hyper-arid conditions of Kuwait, the lowest (3.22 mm day^‑1) and the highest (12.73 mm day^‑1) ET_c were recorded in February and June, respectively. The annual ET_c varied between 2,307.16 mm year^‑1 in cultivar ‘Nabusaif’ and 2,725.08 mm year^‑1 in cultivar ‘Siwi’ and consequently, the net irrigation requirements of these cultivars varied between 23,392 and 27,251 m³ ha^‑1 year^‑1, respectively. Results also indicated that irrigating the palms using the surface drip system at 50% of their ET_c improved water use efficiency without adversely affecting tree performance. Similarly, the combination of soil application of hydrophilic polymer (Agrichope^®) and date palm leaf mulch significantly improved irrigation water use efficiency and reduced water consumption by up to 35% without affecting their growth.