Combination of high organic and low nitrogen fertilizers improvesgrain nutrition and grinding quality of strong gluten wheat

Objectives We analyzed the nutrition and grinding qualities of high gluten wheat under different organic and chemical fertilizer combinations, to provide suitable fertilizer measurement for high-quality wheat production.

Methods The research was based on a long-term organic-chemical combined fertilization experiment, that was located in Qingdao City of Shandong Province, and started since 1978. Nine treatments were set up, namely, no fertilizer control (CK), chemical N 138 kg/hm² (N1), organic fertilizer (manure) 30000 kg/hm² (M1), manure 30000 kg/hm²+ N 138 kg/hm² (M1N1), N 276 kg/hm² (N2), manure 60000 kg/hm² (M2), manure 30000 kg/hm² + N 276 kg/hm² (M1N2), manure 60000 kg/hm² + N 138 kg/hm² (M2N1), manure 60000 kg/hm² +N 276 kg/hm² (M2N2). The same amount of N was applied in N1 and M1 treatments, and in N2 and M2 treatments. At maturity in 2021, wheat grain samples were taken for the determination of the nutritional and processing quality indexes.

Results N1 treatment significantly increased the Fe, crude protein, dry and wet gluten content of wheat kernels, and improved flour yield, and the effect of chemical fertilizer was better than that of organic fertilizer. While N2 significantly reduced the starch content of wheat, which affected the pasting characteristics; M2 treatment had higher quality indexes than M1, and the pasting characteristics in M2 were improved accordingly. M2N1 significantly increased grain Fe content by 34.26%, Zn content by 19.77%, flour yield by 7.98%, crude protein content by 30.75%, starch content by 12.82%, peak viscosity by 24.93%, disintegration value by 14.81%, and repatriation value by 27.64%, compared to CK, and all the above indicator values were higher than those of the single chemical fertilizer (N1, N2) and organic fertilizer (M1, M2) treatments. Compared to M2N1, M2N2 reduced Zn content, flour yield, capacity, crude protein, amylose content, and pasting characteristics. The correlation analysis indicates that branched-chain amylose, total amylose, and branched/straight ratio of flour were positively (P<0.01) correlated with peak viscosity, valley viscosity, and final viscosity, while capacity and hardness were negatively (P<0.01) correlated with peak viscosity and valley viscosity, and straight-chain amylose was negatively correlated with peak viscosity, valley viscosity, and final viscosity.

Conclusions Single application of nitrogen fertilizer can significantly improve wheat flour yield, and protein and gluten content, single application of organic fertilizer has better promotion effect on the starch content and pasting characteristics of wheat flour, organic fertilizer and nitrogen fertilizer combination shares both the beneficial effect in wheat nutrition and processing quality. Comprehensively, combining application of 60000 kg/hm² organic fertilizer and chemical fertilizer N 138 kg/hm² is recommended for the high quality wheat production.