关键词: 大气NH₃浓度, 小麦, 施氮, 光合特征, 株高, 产量

Abstract: To evaluate the effects of nitrogen (N) application rates on the growth, photosynthetic traits and yield of winter wheat under elevated atmospheric ammonia (NH₃) concentrations could provide guidance for N management under high NH₃ environment. We conducted a split-plot experiment for two consecutive years (2020-2021 and 2021-2022) with top-open chambers. The treatments included two NH₃ concentrations [elevated ambient NH₃ concentration at 0.30-0.60 mg·m^-3 (EAM) and air NH₃ concentration at 0.01-0.03 mg·m^-3 (AM)] and two N application rates [recommended N dose (+N) and no N application (-N)]. We analyzed the effects of aforementioned treatments on net photosynthetic rate (P_n), stomatal conductance (g_s), chlorophyll content (SPAD value), plant height, and grain yield. The results showed that averaged across the two years, EAM significantly increased P_n, g_s, and SPAD values at the jointing and booting stages at the -N level by 24.6%, 16.3%, 21.9% and 20.9%, 37.1%, 5.7%, respectively, compared with AM. However, EAM significantly decreased P_n, g_s, and SPAD values at jointing and booting stages at +N level by 10.8%, 5.9%, 3.6% and 6.8%, 18.9%, 9.3%, respectively, over AM treatment. There was a significant effect of NH₃ treatment, N application rates and their interaction on plant height and grain yield. Compared with AM, EAM increased the average plant height and grain yield by 4.5% and 32.1% at -N level and decreased by 1.1% and 8.5% at +N level, respectively. In a nutshell, the eleva-ted ambient NH₃ concentration had positive effect on photosynthetic characteristics, plant height, and grain yield under ambient N condition, but a inhibitory effect under N application.

Key words: atmospheric NH₃ concentration, wheat, nitrogen application, photosynthetic trait, plant height, grain yield