Effect of the optimized regulated deficit irrigation methodology on water use in barley under semiarid conditions

In areas with low availability of irrigation water, it is necessary to improve water-use efficiency in crops, especially if their profitability is low. This is the case of barley in the Castilla-La Mancha region (Spain), where farmers are demanding methods to achieve adequate harvests with a supply of low amounts of irrigation water to this particular crop. The optimized regulated deficit irrigation (ORDI) methodology was developed to maximize the yield of annual crops under water-scarce conditions. The objective of this study was to determine the effect of ORDI for a limited amount of available irrigation water on yield, water productivity and water footprint of a barley crop (Shakira cv.) under semiarid conditions. To this end, five irrigation treatments were performed over three years (2015-2017) on an experimental farm located in Albacete province: no deficit (ND) (control), and four with different volumes of available irrigation water, corresponding to 100 % (T100), 90 % (T90), 80 % (T80), and 70 % (T70) of barley net irrigation requirements (2500 m(3) ha(-1)) for the weather conditions of the intermediate typical meteorological year. As expected, yield decreased with deficit and ND was the treatment that achieved the highest average yield (9049 kg ha(-1)). While the average yield decreased by 19.4 % and 29.9 % with regard to ND, the highest average irrigation water productivity was for T80 and T70 (average 3.63 kg m(-3)), as these treatments reduced the average amount of irrigation water by 39.1 % and 46.7 %, respectively. Nevertheless, in terms of water-use sustainability, the most interesting treatment was T80, which achieved the lowest average water footprint (531 m(3) Mg-1) while ND showed the highest (9.5 % greater). Consequently, ORDI yielded barley harvests with more efficient water use under limited volumes of available irrigation water and unknown climatic conditions, which were drier than typical in the three experimental years.