Reduced nitrogen (N) inputs inevitably limit maize yield and its components, while increased planting density can potentially boost productivity per unit area. This study investigated the compensatory interplay between reduced N application and elevated planting density on grain yield and photosynthetic performance under water-limited conditions. Reducing N decreased grain yield, kernel number per spike, and 1000-kernel weight. Higher planting densities similarly reduced kernel number and weight, yet increased grain yield through a greater spike number per area. Under a 20% irrigation reduction with traditional N, a medium-density treatment (N180D2) increased grain yield by 19.1–41.6% and spike number by 28.0–28.2% compared to a treatment combining the same water reduction with 25% less N at traditional density (N90D1). This compensation was driven by a 23.9–25.7% increase in spike number, which offset a 9.1–11.7% reduction in kernel number per spike. Physiologically, moderate density elevation under reduced irrigation and traditional N maintained superior late-season photosynthetic capacity, with increases of 6.2–7.7% in leaf greenness, 64.4–83.1% in leaf area index, and 19.8–80.7% in crop growth rate relative to low-density, resource-reduced treatments. We conclude that a strategic increase in planting density effectively compensates for yield losses from concurrent water and N reductions by sustaining photosynthetic source strength and dry matter accumulation during critical late-growth stages. These findings provide a practical agronomic framework for maintaining maize productivity in resource-constrained environments.
Heying et al. (Tue,) studied this question.