Availability and technology of using urea-ammonium fertilizer to realize nitrogen reduction and simplified fertilization in wheat production of North China Plain

Objectives Ammonium-urea fertilizer (AUF) is produced for the utilization of allied alkali industry by-products. We conducted field trials in the main winter wheat production regions of North China to explore the availability and technology of UAF in nitrogen reduction and simplified fertilization in these regions.

Methods From 2021 to 2023, field trials were conducted over two years at five locations: Shunyi in Beijing, Luannan and Quzhou in Hebei, Jinan in Shandong, and Yuzhou in Henan. Field experiments contained six treatments, including urea at conventional rate (U), urea with 30% less N input (70%U), AUF with 30% less N input (70%AU), 70%AU with N-(n-butyl) thiophosphoric triamide (70%AU+NBPT), 70%AU with 3, 4-dimethyl-pyrazole phosphate (70%AU+DMPP), and 70%U combined with optimal topdressing time (70%U+Opt). At harvesting period, wheat yield and yield components, partial factor productivity of nitrogen fertilizer (PFP_N) and nitrogen uptake efficiency by wheat (NUE), and soil inorganic nitrogen concentrations were investigated.

Results Compared to U treatment, nitrogen reduction treatments (70%U and 70%AU) decreased wheat yields in one experimental site in 2022, and three sites in 2023; 70%AU+NBPT and 70%AU+DMPP treatments decreased yield in two sites in both 2022 and 2023, respectively; and 70%U+Opt treatment did not cause yield decrease over the two years. Compared to the U treatment, the majority of all the other treatments at the five sites increased PFP_N and NUE over the two years, with PFP_N increment from 19% to 77% in 2022 and 23% to 67% in 2023, and the NUE increment from 25% to 77% in 2022 and 21% to 71% in 2023. After wheat harvest, 70%AU+NBPT and 70%AU+DMPP treatments were tested higher soil NH₄⁺-N content and lower NO₃⁻-N content than U treatment in five sites in 2022 and four sites in 2023, the gap in NH₄⁺-N content was 19%−69% in 2022 and 30%−90% in 2023, and the gap in NO₃⁻-N content was 19%−59% in 2022 and 34%−60% in 2023.

Conclusions Under 30% of nitrogen reduction condition, the topdressing of ammonium-urea fertilizer or combination of NBPT or DMPP can maintain wheat yield and increase fertilizer nitrogen use efficiency.