Productivity and economic benefits of winter wheat in Northwest China by optimizing irrigation and planting density

Winter wheat is a key staple crop in Northwest China, yet optimizing its productivity and economic returns remains a challenge due to water constraints and suboptimal planting densities. This study evaluates the combined effects of irrigation strategies and planting density (PD) on winter wheat yield, resource-use efficiency, and net economic benefits (NEB). A two-year field experiment was conducted under four irrigation treatments (I1, no irrigation; I2, before winter and jointing; I3, jointing; I4, jointing and anthesis) and three PD treatments (PD1, 562.5×10⁴ plants ha^–1; PD2, 375 ×10⁴ plants ha^–1; PD3, 187.5×10⁴ plants ha^–1). Through field trials, we identified optimal water-saving irrigation regimes and planting densities that maximize grain yield while enhancing water productivity. Our results demonstrated that lower PD (187.5×10⁴ plants ha^–1) under reduced irrigation significantly improved dry matter accumulation (DMA), SPAD, and leaf area index (LAI), leading to higher grain yield. Moderate irrigation at the jointing stage (I3) enhanced grain yield in higher planting densities by up to 18.42% compared to other irrigation regimes, while the highest overall yield (6,310 kg ha^–1) was achieved in medium PD under the I3 irrigation. Water-use efficiency (WUE) was significantly improved by reducing irrigation at specific growth stages, mitigating excessive evapotranspiration. PD3–I3 achieved the highest NEB, exceeding I1, I2, and I4 by 11.9, 18.4, and 16.4%, respectively, in 2022–2023 and by 15.1, 14.0, and 8.4%, respectively, in 2023–2024. The findings provide practical insights for sustainable wheat production, ensuring higher profitability while conserving water resources. Implementing optimized irrigation and PD strategies offers a strategic pathway to improving food security and farm income in the semi-arid regions of Northwest China.