Organically fertilized tea plantation stimulates N2O emissions and lowers NO fluxes in subtropical China

[摘要] Tea plantations are rapidly expanding in China and other countries in thetropical and subtropical zones, but so far there are very few studiesincluding direct measurements of nitrogenous gas fluxes from teaplantations. On the basis of 2-year field measurements from 2012 to 2014, weprovided an insight into the assessment of annual nitrous oxide (N₂O)and nitric oxide (NO) fluxes from Chinese subtropical tea plantations underthree practices of conventional urea application, alternative oilcakeincorporation and no nitrogen fertilization. Clearly, the N₂O and NOfluxes exhibited large intra- and inter-annual variations, and furthermore,their temporal variability could be well described by a combination of soilenvironmental factors including soil mineral N, water-filled pore space andtemperature, based on a revised "hole-in-the-pipe" model. Averaged over a2-year study, annual background N₂O and NO emissions were approximately4.0 and 1.6 kg N ha⁻¹ yr⁻¹, respectively. Compared to no nitrogenfertilization, both urea and oilcake application significantly stimulatedannual N₂O and NO emissions, amounting to 14.4–32.7 kg N₂O–N ha⁻¹ yr⁻¹and at least 12.3–19.4 kg NO–N ha⁻¹ yr⁻¹,respectively. In comparison with conventional urea treatment, on average,the application of organic fertilizer significantly increased N₂Oemission by 71 % but decreased NO emission by 22 %. Although themagnitude of N₂O and NO fluxes was substantially influenced by thesource of N, the annual direct emission factors of N fertilizer were estimated tobe 2.8–5.9, 2.7–4.0 and 6.8–9.1 % for N₂O, NO andN₂O+NO, respectively, which are significantly higher than thosedefaults for global upland croplands. This indicated that the rarelydetermined N₂O and NO formation appeared to be a significant pathway inthe nitrogen cycle of tea plantations, which are a potential source ofnational nitrogenous gases inventory.

[学科分类] 地球化学与岩石