Impact of nitrogen and irrigation on the dynamic pattern of protein and starch concentration in the developing grains of winter wheat

Abstract BACKGROUND Unprecedented spikes of drought and nitrogen (N) deficiency restrict crop performance, particularly in dry areas. The quality formation of wheat grain under different irrigation‐N cropping systems provides important insights for determining its end‐use types. The present study was conducted for two consecutive years aiming to investigate the impact of irrigation, N and their interaction on the dynamic pattern of grain proteins and starch concentration in the developing grains of winter wheat under four levels of N (0, 90, 180 and 270 kg ha −1 ) and two water regimes (rainfed and irrigation at jointing and anthesis stages). RESULTS The results showed irrigation and N greatly influenced grain proteins and starch concentration during both cropping seasons. The general dynamic pattern of grain protein and starch concentration exhibits opposite trends. Moreover, the concentrations of protein and protein components were higher, when the crop was exposed to water stress conditions under high N applications. However, water scarcity considerably decreased the concentration of starch and starch components during all phases of grain development. Furthermore, the interaction of irrigation and N was non‐significant during both years. CONCLUSION Grain protein and its components were positively associated with N applications but negatively affected by irrigation, whereas starch and its components benefited from both irrigation and N. These results highlight the contrasting responses of protein and starch formation to water and N inputs, providing a scientific basis for optimizing wheat grain composition according to specific functional and processing demands. © 2025 Society of Chemical Industry.