Water and Nitrogen Coupling Effects on Grain Yield, Water and Nitrogen use Efficiency of Oilseed Flax in Semiarid Area of China

Abstract Irrigation and nitrogen management are essential for sustainable agricultural development in arid and semi-arid regions. Lower water availability and fertilizer utilization are two major factors of constrainting agricultural production in the semi-arid regions. Therefore, improving the utilization efficiency of water and fertilizer has become an important research goal. A two-year field experiment was laid out in a split-plot design with no irrigation (I0), 1200 m3 ha−1 (I1200) and 1800 m3 ha−1 (I1800) as the main factor and 0 (N0), 60 (N60) and 120 (N120) kg N ha−1 nitrogen rate as a sub-factor to investigate the effects of irrigation and nitrogen rates on precipitation storage efficiency (PSE), soil water storage, grain yield, and water and nitrogen use efficiency of oilseed flax in the Loess Plateau of China. The result showed that irrigation and nitrogen significantly increased PSE, soil water storage during the fallow period (ΔSWCf), dry matter accumulation and grain yeild of oilseed flax. However, the change of soil-water storage during the growing season (ΔSWCg) and the change of soil-water storage in the whole year (ΔSWCy) decreased. Soil water storage in irrigation supply treatment at after harvest in each growing season was higher than that in non-irrigation. PSE was highest under I1800N120 treatment. I1800 increased SWSs, SWSh and ETg at 2018 and improved above-ground biomass (anthesis and maturity stage), while decreased WUE and WUEI. Grain yield under 60 and 120 kg N ha−1 with 1800 m3 ha−1 increased by 69.12, 68.07 (2017) and 22.77, 15.23% (2018), respectively, when compared to the I0N0 treatment. Considering flax grain yield, water and nitrogen productivity, 60 or 120 kg/ha N and irrigation of 1800 m3/ha are recommended for water and nitrogen management of oilseed flax in Loess Plateau of China.