Wheat yield and nitrogen use efficiency enhancement through poly(aspartic acid)-coated urea in clay loam soil based on a 5-year field trial

The innovation of N fertilizer and N management practices is essential to maximize crop yield with fewer N inputs. A long-term field fertilization experiment was established in 2015 on the North China Plain (NCP) to determine the effects of a control treatment (CN) and the eco-friendly material poly(aspartic acid)-coated urea (PN), applied as a one-time basal application method, on winter wheat yield and N use efficiency at four N application rates: 0 (N0), 63 (N63), 125 (N125), and 188 (N188) kg N ha(–1). The results indicated that compared to CN, PN resulted in a significant increase in wheat yield by 9.6% and 9.2% at N63 and N125, respectively, across the three experimental years, whereas no significant (p < 0.05) difference was detected at N188. Leaf area duration (LAD), crop growth rate (CGR), and dry matter accumulation (DMA) increased with increasing N rates, while PN significantly increased LAD and CGR by 5.1%–16.4% and 5.4%–64.3%, respectively, during the anthesis-ripening growth stage and DMA by 13.7% and 10.1% at N63 and N125, respectively, after the anthesis stage compared to CN. During the grain-filling stage, PN significantly increased the kernel maximum grain-filling rate (Gmax) by 21.7% and the kernel weight at the maximum grain-filling rate (Wmax) by 6.7% at N125 compared to CN. Additionally, compared to CN, PN significantly improved the stover and grain N content at harvest and increased NUT, NPFP, and NAE by 5.7%–40.1%, 2.5%–23.3%, and 3.9%–42.8%, respectively, at N63–N125. Therefore, PN applied using a single basal nitrogen fertilizer application method showed promising potential in maintaining a stable wheat yield and increasing N use efficiency with a 33% urea cut (approximately 63 kg N ha(–1)) compared to CN at the current wheat yield level on the NCP.