Nitrous oxide emissions from drained peat soil beneath pasture

ABSTRACT

Nitrous oxide (N₂O) emissions (E_N2O) from drained peat soils used for pastoral agriculture have not been measured throughout the year in New Zealand. In response to this research gap, E_N2O was measured fortnightly for 1 year in the Waikato region in a plot that was not grazed or nitrogen (N) fertilised. The time series was variable, the frequency distribution skewed and the fortnightly means correlated. To account for these factors, the data were log_e transformed and an order 2 autoregressive model used to estimate a mean E_N2O of 4.3 g N ha⁻¹ d⁻¹ and 95% confidence limits of 0.6–29.1 g N ha⁻¹ d⁻¹. There was a statistically significant, inverse relationship between E_N2O and the depth to groundwater. In winter, when rainfall totalled 393 mm, E_N2O and soil N content were significantly greater under a rain shelter designed to minimise N loss by leaching, than in an uncovered plot.

KEYWORDS:

• Drained soil
• groundwater
• nitrogen
• nitrous oxide
• peat

Acknowledgements

We are grateful to Brendon van Vugt for allowing us to work on his farm, Teresa Parayil-Symon and Manjula Premartne for the gas chromatography measurements, Jiafa Luo and Mike Rollo for valuable discussions and Cecile de Klein, Diana Selbie and three anonymous reviewers for helpful comments on the manuscript. Daily rainfall and hourly soil temperature data from the CliFlo web site were provided free of charge by the National Institute of Water and Atmosphere.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by the Ministry for Primary Industries.