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https://doi.org/10.5194/bg-2019-14
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-14
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Feb 2019

Research article | 14 Feb 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

Regulation of N2O emissions from acid organic soil drained for agriculture: Effects of land use and season

Arezoo Taghizadeh-Toosi1, Lars Elsgaard1, Tim J. Clough2, Rodrigo Labouriau3, Vibeke Ernstsen4, and Søren O. Petersen1 Arezoo Taghizadeh-Toosi et al.
  • 1Department of Agroecology, Aarhus University, Tjele, Denmark
  • 2Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand
  • 3Applied Statistics Laboratory, Department of Mathematics, Aarhus University, Aarhus, Denmark
  • 4Geological Survey of Denmark and Greenland, Copenhagen, Denmark

Abstract. Drained organic soils are extensively used for cereal and high-value cash crop production or as grazing land, but emissions of nitrous oxide (N2O) are enhanced by the drainage and cultivation. A study was conducted to investigate the regulation of N2O emissions in a raised bog area drained for agriculture. The area has been classified as potentially acid sulfate soil, and we hypothesised that pyrite oxidation was a potential driver of N2O emissions. Two sites with rotational grass, and two sites with a potato crop, were equipped for monitoring of N2O emissions, as well as sub-soil N2O concentrations at 5, 10, 20, 50 and 100 cm depth, during spring and autumn 2015. Precipitation, air and soil temperature, soil moisture, water table (WT) depth, and soil mineral N were recorded during weekly field campaigns. In late April and early September, intact cores were collected to 1 m depth at adjacent grassland and potato sites for analysis of soil properties, which included acid volatile sulfide (AVS) and chromium-reducible sulfur (CRS) to quantify, respectively, iron monosulfide (FeS) and pyrite (FeS2), as well as total reactive iron (TRFe) and nitrite (NO2). Soil organic matter composition and total reduction capacity was also determined. The soil pH varied between 4.7 and 5.4. Equivalent soil gas phase concentrations of N2O ranged from around 10 µL L−1 at grassland sites to several hundred µL L−1 at potato sites, in accordance with lower soil mineral N concentrations at grassland sites. Total N2O emissions during 152–174 days were 3–6 kg N2O-N ha−1 for rotational grass, and 19–21 kg N2O-N ha−1 for potato sites. Statistical analyses by graphical models showed that soil N2O concentration in the capillary fringe was the strongest predictor for N2O emissions in spring, and for grassland sites also in the autumn. For potato sites in the autumn, nitrate (NO3) availability in the top soil, together with temperature, were the main controls on N2O emissions. Pyrite oxidation coupled with NO3 reduction could not be dismissed as a source of N2O, but the total reduction capacity of the peat soil was much higher than explained by the FeS2 concentration. The concentrations of TRFe were also much higher than pyrite concentrations, and potentially chemodenitrification could have been a source of N2O during WT drawdown in spring. The N2O emissions associated with rapid soil wetting and WT rise in autumn were consistent with biological denitrification. Soil N availability and seasonal WT changes were important controls of N2O emissions.

Arezoo Taghizadeh-Toosi et al.
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Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Arezoo Taghizadeh-Toosi et al.
Arezoo Taghizadeh-Toosi et al.
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