Biochar suppresses N2O emissions while maintaining N availability in a sandy loam soil

Case, Sean D.C.; McNamara, Niall P. ORCID: https://orcid.org/0000-0002-5143-5819; Reay, David S.; Stott, Andy W.; Grant, Helen K.; Whitaker, Jeanette ORCID: https://orcid.org/0000-0001-8824-471X. 2015 Biochar suppresses N2O emissions while maintaining N availability in a sandy loam soil. Soil Biology and Biochemistry, 81. 178-185. 10.1016/j.soilbio.2014.11.012

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Abstract/Summary

Nitrous oxide (N2O) from agricultural soil is a significant source of greenhouse gas emissions. Biochar amendment can contribute to climate change mitigation by suppressing emissions of N2O from soil, although the mechanisms underlying this effect are poorly understood. We investigated the effect of biochar on soil N2O emissions and N cycling processes by quantifying soil N immobilisation, denitrification, nitrification and mineralisation rates using 15N pool dilution techniques and the FLUAZ numerical calculation model. We then examined whether biochar amendment affected N2O emissions and the availability and transformations of N in soils. Our results show that biochar suppressed cumulative soil N2O production by 91% in near-saturated, fertilised soils. Cumulative denitrification was reduced by 37%, which accounted for 85–95 % of soil N2O emissions. We also found that physical/chemical and biological ammonium (NH4+) immobilisation increased with biochar amendment but that nitrate (NO3−) immobilisation decreased. We concluded that this immobilisation was insignificant compared to total soil inorganic N content. In contrast, soil N mineralisation significantly increased by 269% and nitrification by 34% in biochar-amended soil. These findings demonstrate that biochar amendment did not limit inorganic N availability to nitrifiers and denitrifiers, therefore limitations in soil NH4+ and NO3− supply cannot explain the suppression of N2O emissions. These results support the concept that biochar application to soil could significantly mitigate agricultural N2O emissions through altering N transformations, and underpin efforts to develop climate-friendly agricultural management techniques.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.soilbio.2014.11.012
UKCEH and CEH Sections/Science Areas:	Shore
ISSN:	0038-0717
Additional Keywords:	biochar, nitrous oxide, immobilisation, denitrification, mineralisation, nitrification, ammonium, nitrate
NORA Subject Terms:	Ecology and Environment Agriculture and Soil Science
Date made live:	08 Dec 2014 10:36 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/509004

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