Effects of different nitrogen sources and rates on the yield and processing quality of winter wheat

Objectives  This study employed a multivariate statistical method to investigate the effects of 12 years long-term application and rate of soil amendment (organic N-fertilizer vs. chemical N-fertilizer) on wheat grain yield and quality. The study aims to provide a scientific basis for improving wheat quality through appropriate fertilization regimes.

Methods  Jimai 22 winter wheat was used in the study. The two N sources were organic N fertilizer and chemical N fertilizer. The fertilizers were applied at 0, 60, 120, 180, 240, 300, 360, 420, 500, and 600 kg/hm² respectively.

Results  We found no difference (P > 0.05) in grain volume weight and flour rate under the influence of N sources and application rate. However, the N application rate (P < 0.05) affected the grain volume weight and wheat flour rate. Both N source and application rate (P < 0.05) influenced the nutrient and processing quality of winter wheat. When N application rate was lower than 300 kg/hm², crude protein content, sedimentation value, wet gluten content, and water absorption were significantly higher in chemical fertilizer than those in organic fertilizer treatment. Above N 300 kg/hm² application rate, there was no difference in winter wheat grain quality indexes between two nitrogen fertilizer types. Crude protein content, wet gluten content, and sedimentation value were significantly correlated with most of the quality indicators. Principal component analysis showed that protein content had the highest contribution of 57% in PC1 compared to other factors. Cluster analysis showed that the fertilization treatments could be divided into four groups. The first was no fertilization and organic N at 60 kg/hm² categorized as low yield and quality; the second included organic N at 120 kg/hm² and chemical N at 60 kg/hm² categorized as low yield and medium quality; the third category included organic N at 180 kg/hm² and 240 kg/hm² and chemical N at 120 kg/hm² designated as medium yield and medium quality; the fourth category included organic N at ≥ 300 kg/hm² and chemical N at ≥ 180 kg/hm² designated as high yield and high quality.

Conclusions  The source and application rate of N fertilizer influence the grain yield and quality of winter wheat. When the application rate of organic fertilizer N is < 300 kg/hm² or chemical fertilizer N is < 180 kg/hm², wheat yield and quality are higher in chemical fertilizer treatment than those in organic fertilizer treatment. When the application rate of organic fertilizer N is ≥ 300 kg/hm² or chemical fertilizer N is ≥ 180 kg/hm², both wheat yield and quality are high. We conclude that these treatments can potentially improve wheat yield and quality.