Long-term nitrogen addition impact on agronomic traits, nitrogen uptake and nitrogen resorption efficiency of wheat in a rainfed region

Nitrogen (N) fertilizer management is one of the most important issues in wheat (Triticum aestivum L.) production. To explore the mechanism of N uptake efficiency (NupE) and N resorption efficiency (NRE) in wheat, this study examined the effects of different N fertilizer application rates (0, 52.5, 105, 157.5, 157.5, and 210 kg N ha⁻¹ yr⁻¹) on crop growth parameters, NupE, NRE, and N use efficiency (NUE). The results of the 2-yr (2018 and 2019) study showed that the growth of crops was enhanced in high-N treatments, resulting in higher N concentration in wheat tissues. The 105 kg N ha⁻¹ treatment (N105) was the best rate for improving spring wheat yield and NUE, ensuring the highest values of N uptake, evapotranspiration, and leaf NRE. Compared with the non-N-fertilized control, N105 increased grain yield and N uptake by 46.90 and 90.54%, respectively; thus, N105 had 16.40% higher NUE, 28.33% higher N utilization efficiency (NutE), and 0.58 kg kg⁻¹ greater NupE. Therefore, N uptake and N resorption are of great importance for increasing NUE of wheat, and for improving the sustainability of wheat production in the semi-arid Loess Plateau of China.