Effects of fertilization and stand age on N<sub>2</sub>O and NO emissions from tea plantations: a site-scale study in a subtropical region using a modified biogeochemical model
<p>To meet increasing demands, tea plantations are rapidly expanding in China. Although the emissions of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) and nitric oxide (NO) from tea plantations may be substantially influenced by soil pH re...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/6903/2020/acp-20-6903-2020.pdf |
| Summary: | <p>To meet increasing demands, tea plantations are rapidly
expanding in China. Although the emissions of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) and
nitric oxide (NO) from tea plantations may be substantially influenced by
soil pH reduction and intensive nitrogen fertilization, process model-based
studies on this issue are still rare. In this study, the process-oriented
biogeochemical model, Catchment Nutrient Management Model –
DeNitrification-DeComposition (CNMM-DNDC), was modified by adding tea-growth-related processes that may induce a soil pH reduction. Using a
dataset for intensively managed tea plantations at a subtropical site, the
performances of the original and modified models for simulating the
emissions of both gases subject to different fertilization alternatives and
stand ages were evaluated. Compared with the observations in the early stage of
a tea plantation, the original and modified models showed comparable
performances for simulating the daily gas fluxes (with a Nash–Sutcliffe index
(NSI) of 0.10 versus 0.18 for <span class="inline-formula">N<sub>2</sub>O</span> and 0.32 versus 0.33 for NO), annual
emissions (with an NSI of 0.81 versus 0.94 for <span class="inline-formula">N<sub>2</sub>O</span> and 0.92 versus 0.94
for NO) and annual direct emission factors (EF<span class="inline-formula"><sub>d</sub></span>s). For the modified
model, the observations and simulations demonstrated that the short-term
replacement of urea with oil cake stimulated <span class="inline-formula">N<sub>2</sub>O</span> emissions by
<span class="inline-formula">∼62</span> % and <span class="inline-formula">∼36</span> % and mitigated NO emissions
by <span class="inline-formula">∼25</span> % and <span class="inline-formula">∼14</span> %, respectively. The
model simulations resulted in a positive dependence of EF<span class="inline-formula"><sub>d</sub></span>s of either
gas on nitrogen doses, implicating the importance of model-based
quantification of this key parameter for inventory purposes. In addition, the
modified model with pH-related scientific processes showed overall
inhibitory effects on the gases' emissions in the middle to late stages during a
full tea plant lifetime. In conclusion, the modified CNMM-DNDC exhibits the
potential for quantifying <span class="inline-formula">N<sub>2</sub>O</span> and NO emissions from tea plantations
under various conditions. Nevertheless, wider validation is still required
for simulation of long-term soil pH variations and emissions of both gases
from tea plantations.</p> |
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| ISSN: | 1680-7316 1680-7324 |