Postponing nitrogen application under nitrogen reduction increased the yield of Tartary buckwheat

Clarifying the effect of postponing nitrogen application on yield under nitrogen reduction is of great importance for increasing yield and optimizing the nitrogen application system of Tartary buckwheat. A two-year field experiment with six nitrogen treatments, including a conventional fertilizer application pattern (CK) and five treatments under 20% nitrogen reduction, with 0% (NP1), 10% (NP2), 20% (NP3), 30% (NP4), and 40% (NP5) postponed of nitrogen amounts, topdressing at the flowering stage, was conducted on the high-yielding Tartary buckwheat variety ‘Daku 1’. Compared with CK, the NP4 treatment significantly increased osmotic adjustment substance content, antioxidant enzyme– and nitrogen metabolism–related activities, dry matter accumulation, and yield. Compared with CK, the NP2, NP3, NP4, and NP5 treatments increased yield by 8.09%, 22.06%, 66.91%, and 31.62%, respectively, whereas the NP1 treatment decreased yield by 33.09%. In summary, appropriately postponing nitrogen application can improve the yield of Tartary buckwheat by improving root activity, delaying leaf senescence, and coordinating nitrogen metabolism balance. Under the conditions of this two-year single-site field study, the NP4 treatment showed promise as a nitrogen-saving strategy for improving Tartary buckwheat yield; however, further validation across different environments, soil types, and cultivars is needed before broad production recommendations can be made.