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Nitrification represents the bottle-neck of sheep urine patch N 2 O emissions from extensively grazed organic soils.
- Source :
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The Science of the total environment [Sci Total Environ] 2019 Dec 10; Vol. 695, pp. 133786. Date of Electronic Publication: 2019 Aug 06. - Publication Year :
- 2019
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Abstract
- Extensively grazed grasslands are understudied in terms of their contribution to greenhouse gas (GHG) emissions from livestock production. Mountains, moorlands and heath occupy 18% of the UK land area, however, in situ studies providing high frequency N <subscript>2</subscript> O emissions from sheep urine deposited to such areas are lacking. Organic soils typical of these regions may provide substrates for denitrification-related N <subscript>2</subscript> O emissions, however, acidic and anoxic conditions may inhibit nitrification (and associated emissions from nitrification and denitrification). We hypothesised urine N <subscript>2</subscript> O-N emission factors (EFs) would be lower than the UK country-specific and IPCC default value for urine, which is based on lowland measurements. Using automated GHG sampling chambers, N <subscript>2</subscript> O emissions were determined from real sheep urine (930 kg N ha <superscript>-1</superscript> ) and artificial urine (920 kg N ha <superscript>-1</superscript> ) applied in summer, and from an artificial urine treatment (1120 kg N ha <superscript>-1</superscript> ) and a combined NO <subscript>3</subscript> <superscript>-</superscript> and glucose treatment (106 kg N ha <superscript>-1</superscript> ; 213 kg C ha <superscript>-1</superscript> ) in autumn. The latter treatment provided an assessment of the soils capacity for denitrification under non-substrate limiting conditions. The artificial urine-N <subscript>2</subscript> O EF was 0.01 ± 0.00% of the N applied in summer and 0.00 ± 0.00% of the N applied in autumn. The N <subscript>2</subscript> O EF for real sheep urine applied in summer was 0.01 ± 0.02%. A higher flux was observed in only one replicate of the real urine treatment, relating to one chamber where an increase in soil solution NO <subscript>3</subscript> <superscript>-</superscript> was observed. No lag phase in N <subscript>2</subscript> O emission was evident following application of the NO <subscript>3</subscript> <superscript>-</superscript> and glucose treatment, which emitted 0.69 ± 0.15% of the N applied. This indicates nitrification rates are the bottle-neck for N <subscript>2</subscript> O emissions in upland organic soils. We calculated the potential impact of using hill-grazing specific urine N <subscript>2</subscript> O EFs on the UK inventory of N <subscript>2</subscript> O emissions from sheep excreta, and found a reduction of ca. 43% in comparison to the use of a country-specific excretal EF.<br /> (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)
Details
- Language :
- English
- ISSN :
- 1879-1026
- Volume :
- 695
- Database :
- MEDLINE
- Journal :
- The Science of the total environment
- Publication Type :
- Academic Journal
- Accession number :
- 31422321
- Full Text :
- https://doi.org/10.1016/j.scitotenv.2019.133786