A three-year experiment (2015–2017) was conducted under the semiarid conditions of the Hydrogeological Unit Eastern Mancha (HUEM) (Spain), using the optimized regulated deficit irrigation for a limited amount of irrigation water (ORDIL) methodology on barley. Five irrigation treatments were performed during the experiment: no deficit (ND), 100% (T100), 90% (T90), 80% (T80), and 70% (T70) of barley net typical irrigation requirements (2500 m3 ha-1) in the area. The aim was to determine the effect of ORDIL: 1) on the quality of grain and malt; 2) on the profitability and use of water at farm scale; and 3) on the profitability and sustainability of the HUEM. Despite using less water, ORDIL treatments showed no significant differences in grain quality with respect to ND, while T80 achieved the highest economic water productivity (average 0.17 € m-3). Thus, by using T80 instead of ND and increasing the irrigated area of barley on the farm by 14%, it is possible to save up to 31% of water with the same profitability. This amount of water could be used for more profitable crops, increasing the profitability of the farm. The use of ORDIL at basin scale, using T80 instead of ND and increasing the cultivated area by 9%, could have saved up to 55.9 hm3 over the 3 experimental years (16% of annual extractions in the HUEM). Supplying this water to more profitable crops, the profitability of the basin could have increased by up to 44.4 M€. In the case of saving this amount of groundwater, piezometric levels would have risen, decreasing the pumping costs and improving the environmental conditions in the area. Consequently, applying ORDIL in lowprofit crops, such as barley, and in water scarce areas, could improve the profitability and/or the sustainability of agricultural systems, maintaining the production.
Keywords: Hordeum vulgare L. MOPECO model ORDIL Malting process Semiarid