Enhancing Wheat Yield and Quality Through Late-Season Foliar Nitrogen Application: A Global Meta-Analysis

Late-season foliar nitrogen (N) application is widely employed to improve wheat grain yield and protein concentration, particularly during later growth stages when root activity declines and N uptake becomes less efficient. However, the reported effects of foliar N application on grain yield and the quality of wheat remain inconsistent. This meta-analysis, based on 51 field trials encompassing 1498 observations, quantitatively evaluates the impact of late-season foliar N application on wheat yield and protein concentration. The results demonstrate that late-season foliar N application significantly enhances both grain yield (+4.1%) and protein concentration (+5.9%) compared to control treatments. Notably, split foliar N application primarily increased protein concentration (+6.3%), whereas late-season N supplementation enhanced both yield (+3.4%) and protein concentration (+6.0%). Subgroup analyses reveal that the effectiveness of foliar N application is influenced by N management practices. Split foliar N application significantly increased both yield and protein concentration at N rates of 101–200 kg N/ha, whereas late-season N supplementation was beneficial only at higher N rates (≥200 kg N/ha). Moreover, the timing of foliar N application played a crucial role: application at anthesis resulted in the greatest increases in both yield (+5.3%) and protein concentration (+5.8%), while applications at booting or post-anthesis stages primarily increased protein concentration with minimal yield effects. Additionally, late-season foliar N application mitigated the conventional negative correlation between wheat yield and protein concentration, particularly when applied as a split N strategy, allowing for improved grain quality without reducing yield potential. This study highlights the importance of optimizing foliar N timing, the method, and N rate to maximize both wheat yield and quality while improving N use efficiency.