Booting stage is the key timing for split nitrogen application in improving grain yield and quality of wheat – A global meta-analysis

Abstract

Wheat is one of the most important staple crops and is mainly consumed as baked goods. Late nitrogen (N) application following a previous basic fertilization is commonly conducted to increase grain protein concentration and to improve the bread-making quality of wheat. However, the effect of late N application on the yield and quality of wheat highly varied among studies and, therefore, was questioned recently. This global meta-analysis, based on reported field experiments, aimed to clarify whether, and if so under what conditions, a late N (split from the overall N fertilization rate) application that follows an earlier N application is effective in high-protein bread-wheat production. The results showed that split N application enhanced the grain protein concentration by 5.8 %, wet gluten content by 7.9 %, and dough stability time by 10.8 %, while it decreased the grain yield of wheat by 3.5 % compared to that without split N application. However, the results varied, depending on the N application methods and environmental factors. At the fertilization level of 151–200 kg N/ha which is generally recognized as the rational N recommendation rate, split N application could increase the grain protein concentration by 6.9 %, stability time by 14.0 % and wet gluten content by 7.7 % without reducing the grain yield of wheat. More importantly, both the grain yield and quality of wheat were enhanced by split N application only when late N was applied at the booting stage. Moreover, the widely observed negative correlation between grain yield and grain protein concentration was weakened by split N application at the booting stage.