Integrating crop and soil nutrient management for higher wheat grain yield and protein concentration in dryland areas

Wheat grain protein concentration (GPC) is a key parameter related to processing quality and amino acid intake. However, synchronously enhancing grain yield (GY) and GPC is still challenging due to the physiological competition between carbon and nitrogen. This study determined plant and soil nutrients and surveyed yield and management data from 304 wheat fields at three locations on the Loess Plateau of China to explore limitations and design practices for producing high-yielding and high-protein wheat sustainably. Based on the overall average GY (4732 kg ha–1) and GPC (13.1%), the surveyed fields were grouped into low yield & low protein (LyLp), low yield & high protein (LyHp), high yield & low protein (HyLp), and high yield & high protein (HyHp), with average GYs of 3625, 3653, 5912, and 5962 kg ha–1 and GPCs of 11.2%, 15.2%, 11.7%, and 14.9%, respectively. The GY has significant positive correlations with cultivar release year (r = 0.192), plant density (r = 0.204), and soil total nitrogen (r = 0.131), a negative correlation with sowing date (r = –0.257), but no correlations with fertilizer rates and soil available nutrients of nitrogen, phosphorus, and potassium. Nitrogen and potassium requirements in HyHp fields were 25.1% and 16.4% higher than that in HyLp fields. Accordingly, HyHp fields had significant higher nitrogen and potassium fertilizer rates and soil nitrogen and potassium supplies than HyLp fields. Structural equation modelling showed that cultivar release year contributed the most to the GY variations, while soil available potassium has the largest effect on the GPC. In addition, soil nitrogen surplus was approximately 50% decreased from low- to high-yielding fields, but did not differ between HyLp and HyHp fields. These findings indicate that the integrated crop and soil management strategies, including improved newer cultivar, timely sowing date, advisable plant density and fertilizer rates, and adequate soil nutrients supply, are applicable for the complicated and changeable wheat production environments to improve GY and GPC synchronously.