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Ridge-furrow planting, supplementary irrigation and density regulation are effective measures to improve crop yields in (semi-)arid and drought-prone regions around the world, but their interactive effects on crop evapotranspiration, plant nitrogen uptake, grain yield and its components, water productivity, nitrogen use efficiency and economic benefit of winter wheat are not fully understood. Field experiments were carried out on winter wheat in a semi-humid but drought-prone region of northwest China during 2020 − 2021 and 2021 − 2022. There were two planting patterns (P): ridge-furrow planting with plastic film mulching on ridges (RF) and conventional flat planting (F), two supplementary irrigation amounts (I): 30 mm supplementary irrigation at both overwintering and returning-green stages (I60) and no supplementary irrigation (I0), and three planting densities (D): 240 × 104 plants ha−1 (LD), 360 × 104 plants ha−1 (MD) and 480 × 104 plants ha−1 (HD). The results showed that significant interactive effects of P × I, P × D, I × D and P × I × D on grain yield and water productivity of grain yield (WPg) were obtained, and the interactive effects of P × I, I × D and P × I × D on partial factor productivity of nitrogen (NPFP) and net income (NI) were significant. Compared with F, RF increased grain yield by 10.4%, WPg by 11.9%, water productivity of biomass yield (WPb) by 6.2%, precipitation and irrigation water use efficiency (PIUE) by 10.4%, irrigation water use efficiency (IUE) by 12.0%, agronomic nitrogen use efficiency (ANUE) by 5.3%, NPFP by 10.6% and NI by 17.1%. Compared with I0, I60 increased grain yield by 13.5%, WPg by 7.8%, ANUE by 5.7%, NPFP by 13.7% and NI by 27.9%. Increasing planting density improved soil water consumption, population nitrogen uptake, effective number of panicles per unit area, WPb, PIUE, ANUE, NUtE and total income. Grain yield, WPg, NPFP and NI reached the maximum values at MD under RF, because the presence of plastic film in RF reduced the number of planting rows and resulted in excessive planting density in the plant row at HD compared to F. In summary, the optimized planting density (360 ×104 plants ha−1) combined with ridge-furrow planting and supplementary irrigation is more desirable for balancing grain yield, water productivity, nitrogen use efficiency and economic benefit of winter wheat in the semi-humid and drought-prone region of northwest China.
Dai et al. (Tue,) studied this question.