Organic fertilizer substitution delays leaf senescence and improves source-sink balance in winter wheat under different precipitation types.

BACKGROUND: To elucidate the regulatory effects of organic fertilizer substitution on leaf senescence and source-sink relationships in dryland winter wheat under different precipitation types, a long-term fertilization experiment was conducted in Heyang County, Shaanxi Province, with three consecutive seasons of field trials analyzed from 2022 to 2025 (based on a trial initiated in 2017). The experiment included two fertilization types: conventional chemical nitrogen fertilizer (CN) and 25% organic nitrogen substitution (MN). Each type comprised four N application rates (60, 120, 180, and 240 kg N ha-1), along with a blank control (N0, no nitrogen applied). RESULTS: Results demonstrated that precipitation types exerted a stronger regulatory effect than N fertilization. The MN treatment significantly prolonged the grain-filling period, delaying its cessation by 0.12-1.48 days relative to chlorophyll senescence. While the N180 treatment achieved the optimal source-sink ratio, differences among the N120 and N240 treatments were not significant. Grain yield responses varied with precipitation types: the CN240 treatment maximized grain yield in wet years, while the MN180 and MN120 treatments were optimal in normal and dry years, respectively. CONCLUSION: Consequently, 25% organic fertilizer substitution combined with 180 kg N ha-1 may serve as a relatively robust baseline N management strategy for dryland winter wheat under the rainfed agroecological conditions of Heyang County on the Loess Plateau, as it effectively coordinated leaf senescence with grain filling. © 2026 Society of Chemical Industry.