Effect of supplemental irrigation on nitrogen translation and high-yield wheat yield in drylands

The effects of different supplemental irrigation schemes on nitrogen translation and high-yield wheat yield in the drylands of Qingdao were investigated via field experiments. The results reveal that increasing supplemental irrigation negatively influences grain protein content, while grain protein content is highest under CK (dry land treatment). Grain protein accumulation under CK is lower than those under treatments with only one or two irrigations, however, obviously higher than those with four or five irrigations. Appropriate supplemental irrigation enhances grain yield and nitrogen utilization efficiency, while nitrogen transfer rates and amounts reduce under excessive irrigation. There is an insignificant yield difference between W4 (a three-time irrigation treatment at wintering, jointing and filling stages) and W3 (a two-time irrigation treatment at jointing and filling stages). With increasing frequency and volume of irrigation, wheat yield, 1000-grain weight and per-spike grain decrease accordingly. Based on yield, water use efficiency and grain protein accumulation under W2 at 120 mm irrigation at jointing and filling stages are optimum.