Combined Effects of Starch Sucrose Content and Planting Density on Grain Protein Content of Winter Wheat (<i>Triticum aestivum</i> L.)

Wheat (Triticum aestivum L.) is a staple crop worldwide, and yield improvement since the green revolution was attributed to chemical nitrogen (N) fertilizer application. We conducted field experiments in Yuncheng County, Shanxi Province, under planting density (2 million plants ha–1, 2.25 million plants ha–1, 2.5 million plants ha–1) and topdressing nitrogen (12 kg ha–1, 22 kg ha–1, 32 kg ha–1). The results shown that the starch content of grains with a density of 2.5 million plants ha–1 increased by 1.9%-7.5%, which improved the water absorption of flour and the processing quality of flour, but decreased the protein content, and gluten properties of grains. The nitrogen topdressing amount of 22 kg ha–1 wheat tiller increased by 6.3%-33.3%, and the dry matter accumulation increased by 1.0%-9.5%. The number of spikes increased by 3.7%-19.2%, and the yield increased by 3.7%-17.8% with the nitrogen topping amount of 22 kg ha–1 the protein content increased by 2.0%-4.2% with the nitrogen topping amount of 22 kg ha–1, the starch content increased by 1.2%-7.2%, and the gluten index increased by 4.3%-21.5%.