Optimized planting density and organic fertilizer substitution improve maize yield by enhancing dry matter...

Increasing planting density and partial substitution of chemical fertilizer with organic fertilizer are important strategies for improving maize yield. However, how their interaction regulates dry matter accumulation, translocation, and grain-filling characteristics to affect yield formation remains unclear.

A three-year field experiment (2023-2025) was conducted with three planting densities (70,000, 100,000, and 130,000 plants ha^-1) and four fertilization treatments (no fertilization, chemical fertilizer only, and 17% and 34% organic fertilizer substitution) to evaluate canopy light interception, dry matter accumulation and translocation, grain -filling characteristics, and yield formation.

The results showed that 17% organic fertilizer substitution improved radiation use efficiency at silking by 7.76%-20.42%. Although increasing planting density reduced per-plant dry matter accumulation by 20.29%-36.53%, 17% organic fertilizer substitution improved dry matter partitioning and partly alleviated the reductions in grain-filling duration and grain weight. Random forest analysis identified aboveground biomass accumulation as the primary predictor of yield and showed that maximum and mean grain-filling rates contributed more strongly to yield prediction than the active grain-filling period. Partial least squares path modeling further revealed that yield reduction under high density was mainly attributed to suppressed post-silking dry matter accumulation, while fertilization promoted dry matter accumulation and translocation, thereby strengthening their positive contributions to grain filling and yield formation. Across three growing seasons, 100,000 plants ha^-1 with 17% organic fertilizer substitution (D2F2) increased yield by 7.46%-23.83% compared with conventional management (D1F1). Therefore, D2F2 may serve as a promising management option for improving dry matter translocation, grain filling, and maize yield. These results provide valuable references for optimizing density-fertilization management in semi-arid maize production systems.