Enhancing water productivity and yield of spring wheat through irrigation and planting density optimization under...

Improving spring wheat production in oasis irrigation districts requires management strategies that reconcile high grain yield with efficient irrigation water use.

A two-year field experiment was conducted in the Hexi Oasis, Northwest China, during 2024-2025 to evaluate the coupled effects of three planting densities (PD1, 10.0 million seeds ha^-1; PD2, 10.8 million seeds ha^-1; and PD3, 11.6 million seeds ha-1) and three irrigation levels (I1, 360 mm; I2, 315 mm; and I3, 270 mm) on grain yield, soil water use, crop water productivity (WP_C), irrigation water productivity (WP_I), dry matter translocation, and grain filling under shallow-buried drip irrigation.

Grain yield was consistently maximized under PD3I1, reaching 8455 and 8796 kg ha-1 in 2024 and 2025, respectively, whereas PD2I2 achieved a more favorable balance between yield and water productivity. Compared with I1, I2 reduced grain yield by only 5.3% and 6.0% in 2024 and 2025, respectively, but increased WP_C and WP_I by 5.5% on average. Across planting densities, PD2 increased WPC and WPI by 6.4% and 7.1% relative to PD1, respectively. Soil water profiles showed that reduced irrigation increased reliance on stored water in the 40-100 cm profile, particularly under high density. Grain filling followed a sigmoidal trajectory, with irrigation primarily regulating grain-filling rate, grain weight, and active filling duration, while excessive density restricted individual grain filling under water deficit.

Overall, moderate planting density combined with moderate irrigation provided a practical strategy for sustaining yield while enhancing irrigation water productivity in arid oasis wheat systems, with the benefits being primarily attributable to improved management coordination rather than to novel physiological mechanisms.