Limited-irrigation improves water use efficiency and soil reservoir capacity through regulating root and canopy growth of winter wheat

The North China Plain (NCP) is a remarkable region with serious water shortages, especially during the winter wheat growing season. Developing water-saving irrigation is an important strategy to thoroughly resolving water scarcity in this region. Field experiments were conducted at Wuqiao Experiment Station of China Agricultural University, Hebei, China, in 2013-2014 and 2014-2015 using “Jimai22”, a winter wheat cultivar planted widely across China. The three irrigation regimes used were no-irrigation (no water applied after sowing), limited-irrigation (60 mm of water applied at elongation), and sufficient-irrigation (a total of 180 mm of water applied, with 60 mm at regreening, elongation, and anthesis stages, respectively). Soil water storage, soil reservoir capacity, root length density, leaf expansion, water use efficiency (WUE), and grain yield of winter wheat were measured. The highest WUE was observed in the limited-irrigation treatment, achieving a relatively high grain yield. With increases in water (i.e., sufficient-irrigation), winter wheat grain yield increased, but water WUE decreased. Limited-irrigation hampered leaf expansion, which can reduce transpiration, and slightly reduced grain yield compared to the sufficient-irrigation treatment. Moreover, limited-irrigation stimulated roots to grow into deeper soil layers and thus enhanced the uptake of soil-stored water from the subsoil layer, developing a large soil reservoir capacity to store rain-water in summer. Overall, this study demonstrates that regulating soil water depletion moderately in the non-critical period and supplementary water in the critical period (through limited-irrigation, i.e., 60 mm of water applied at elongation) in winter wheat results in high WUE with relatively high grain yield and enlarges soil reservoir capacity. Therefore, in years with typical climate conditions, irrigation of 60 mm applied at elongation is the best irrigation scheme for efficient water use and relatively high yield in winter wheat in NCP.