Evaluating the differences in irrigation methods for winter wheat under limited irrigation quotas in the water-food-economy nexus in the North China Plain

Quantitatively evaluating the effects of multiple factors on the performance levels of different irrigation methods under a limited water supply in the water-food-economy nexus at the regional scale is of great significance; such evaluations can facilitate the selection of appropriate irrigation methods and schemes to reduce the contradiction between the water shortage and grain production circumstances. In this study, the distributed SWAP-WOFOST (Soil-Water-Atmosphere-Plant-WOrld FOod STudy) model was applied to a typical area of severe deep groundwater overexploitation in the North China Plain. This model was used to simulate various scenarios of sprinkler irrigation (SI) and limited surface irrigation (LSI) under the three limited irrigation quotas (i.e., 75 mm, 150 mm and 225 mm) and to further quantify the differences in crop yield, evapotranspiration and water productivity (WP) between the two irrigation methods by considering three rainfall levels and 66 soil texture profile (STP) types. Then, the impacts of irrigation methods on farmers’ net income were analyzed; the increasing extents of SI implementation scale and workday wage to improve farmers’ net income were estimated according to irrigation, rainfall and soil conditions. Under a specific limited irrigation quota, the yield and WP of winter wheat under LSI were greater than those under SI without fertigation in more than 92% of the 66 STP types under the three rainfall levels, with yield differences mainly in the range of 200–1600 kg hm−2 and WP differences mainly in the range of 0–0.5 kg m−3. In no more than five STP types (e.g., sandy or loamy sandy soil in the five layers), the yield and WP under LSI were lower than those under SI. Relative to the evapotranspiration under LSI, the evapotranspiration under SI did not show the same trend, while the ratio of transpiration to evapotranspiration under SI decreased in more than 98% of the STP types. For different irrigation quotas and rainfall levels, the farmers’ net incomes under SI were 374–1517 yuan hm−2 greater than those under LSI for up to five STP types, and they were 0–3000 yuan hm−2 lower than those under LSI for the other 92% of the STP types. When labor could be saved by more than 8 d hm−2 by improving the implementation scale of SI and the workday wage could increase to more than 100 yuan d−1, SI was recommended to obtain higher farmers’ net income in more STP types in the study area.