Denitrification losses from an intensively managed sub-tropical pasture: Impact of soil moisture on the partitioning of N2 and N2O emissions

Friedl, Johannes, Scheer, Clemens, Rowlings, David W., McIntosh, Heather V., Strazzabosco, Alice, Warner, Daniel L., & Grace, Peter R. (2016) Denitrification losses from an intensively managed sub-tropical pasture: Impact of soil moisture on the partitioning of N2 and N2O emissions. Soil Biology and Biochemistry, 92, pp. 58-66.

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Abstract

Intensively managed pastures in subtropical Australia under dairy production are nitrogen (N) loaded agro-ecosystems, with an increased pool of N available for denitrification. The magnitude of denitrification losses and N2:N2O partitioning in these agro-ecosystems is largely unknown, representing a major uncertainty when estimating total N loss and replacement. This study investigated the influence of different soil moisture contents on N2 and N2O emissions from a subtropical dairy pasture in Queensland, Australia. Intact soil cores were incubated over 15 days at 80% and 100% water-filled pore space (WFPS), after the application of 15N labelled nitrate, equivalent to 50 kg N ha−1. This setup enabled the direct quantification of N2 and N2O emissions following fertilisation using the 15N gas flux method. The main product of denitrification in both treatments was N2. N2 emissions exceeded N2O emissions by a factor of 8 ± 1 at 80% WFPS and a factor of 17 ± 2 at 100% WFPS. The total amount of N-N2 lost over the incubation period was 21.27 kg ± 2.10 N2-N ha−1 at 80% WFPS and 25.26 kg ± 2.79 kg ha−1 at 100% WFPS respectively. N2 emissions remained high at 100% WFPS, while related N2O emissions decreased. At 80% WFPS, N2 emissions increased constantly over time while N2O fluxes declined. Consequently, N2/(N2 + N2O) product ratios increased over the incubation period in both treatments. N2/(N2 + N2O) product ratios responded significantly to soil moisture, confirming WFPS as a key driver of denitrification. The substantial amount of fertiliser lost as N2 reveals the agronomic significance of denitrification as a major pathway of N loss for sub-tropical pastures at high WFPS and may explain the low fertiliser N use efficiency observed for these agro-ecosystems.

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3 citations in Web of Science®

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ID Code: 93886
Item Type: Journal Article
Refereed: Yes
Additional Information: Unmapped bibliographic data:
PY - 2016/1// [EPrints field already has value set]
JO - Soil Biology and Biochemistry [Field not mapped to EPrints]
Keywords: N2-emissions, N2O emissions, N2/(N2 + N2O) ratio, 15N gas flux method, Denitrification, Pastures
DOI: 10.1016/j.soilbio.2015.09.016
ISSN: 0038-0717
Subjects: Australian and New Zealand Standard Research Classification > ENVIRONMENTAL SCIENCES (050000) > SOIL SCIENCES (050300) > Carbon Sequestration Science (050301)
Australian and New Zealand Standard Research Classification > ENVIRONMENTAL SCIENCES (050000) > SOIL SCIENCES (050300) > Soil Biology (050303)
Divisions: Current > Institutes > Institute for Future Environments
Funding:
  • AUSTRALIAN GOVERNMEN/1202.030
Facilities: Science and Engineering Centre, Central Analytical Research Facility
Deposited On: 17 Mar 2016 23:12
Last Modified: 20 Mar 2016 22:35

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