The impact of varying straw return rates and nitrogen application timings on winter wheat performance and soil nutrient availability

Optimizing straw return and nitrogen (N) fertilizer management is critical for enhancing sustainable wheat production. A two-season field study investigated the synergistic effects of varying rice straw return rates (s₁ = full straw return, s₂ = 50% straw return, s₃ = no straw return) and split nitrogen fertilizer strategies (n₁ = conventional N, n₂ = 126 kg ha-1basal + 54 kg ha-1overwinter, n₃ = three-split N application; ck = control, no N fertilizer) on wheat yield, yield components, soil fertility, biomass accumulation, and photosynthetic efficiency. The results consistently demonstrated that the combined strategy had a significant impact on all measured parameters. The optimal treatment, 50% straw return (s₂) coupled with a two-split nitrogen application (n₂), maximized wheat grain yield at approximately 7,384±173 kg ha-1, representing a 15−19% increase over conventional practices (s₃-n₁). This yield advantage was primarily attributed to enhanced spike formation. Furthermore, full straw return (s₁) combined with a three-split nitrogen application (n₃) significantly improved soil fertility, achieving the highest soil organic carbon (SOC) content (22.1 g kg-1), which was 55.1−81.5% higher than conventional methods, alongside substantial increases in soil N, P, and K. The s₂-n₂ treatment also led to peak dry matter accumulation (31,604 kg ha-1 at maturity), a 158% increase over the control (ck). For photosynthetic performance, 50% straw return (s₂) with three-split nitrogen (n₃) consistently produced superior SPAD values (83.1) and LAI (4.65) at 14 days after flowering, sustaining active photosynthesis 50−100% longer than conventional practices. These research findings underscore that moderate straw retention combined with strategic split nitrogen application provides a balanced approach, enhancing both wheat productivity and soil health by optimizing nutrient availability and prolonged photosynthetic activity, while avoiding the yield penalties associated with excessive incorporation.