Abstract:Application of nitrogen fertilizer (N) is one of the most important measures to increase grain yield and protein quality of winter wheat. To evaluate the effects of nitrogen fertilizer rates on grain yield, protein quality and flour color of winter wheat, the experiment was conducted in Zhengzhou of Henan province during cropping seasons of 2009-2010 and 2010-2011 Stronggluten wheat cultivar, Zhengmai 366, and medium strong gluten cultivar, Aikang 58 were planted. The results indicate that the increase of N-fertilizer could significantly increase the grain and protein yields, and protein contents of winter wheat in two cropping seasons. Both the highest grain yield and protein yield of Zhengmai 366 are got in the treatment of nitrogen application of 225 kg/ha. For Aikang 58, under the N-fertilizer rates from 150 kg/ha to 225 kg/ha the highest value of grain yield and protein yield are obtained. All protein compositions in grains are increased with the increase of N-fertilizer application, but the extent varies between two cultivars. N-fertilizer rates affect flour a*values of the two cultivars and b*value of Zhengmai366 significantly. With N-fertilizer increase, flour L*values of the two cultivars are declined, while the a*values are increased. The correlation analysis between protein compositions and flour color parameters show that the flour L*value is significant negatively correlated with the protein content and gliadin (P≤0.05), the a*value is significant positively correlated with the protein content and its compositions (P≤0.01), and the b*value is negatively correlated with the globulin content (P≤0.01). From the results we conclude that nitrogen application rate significantly influences the grain yield and protein content, and changes flour color parameters of winter wheat, but the response might vary between wheat cultivars and different years.