Separating N2O production and consumption in intact agricultural soil cores at different moisture contents and depths

A - Papers appearing in refereed journals

Button, E. S., Marsden, K. A., Nightingale, P. D., Dixon, E. R., Chadwick, D. R., Jones, D. L. and Cardenas, L. M. 2023. Separating N2O production and consumption in intact agricultural soil cores at different moisture contents and depths. European Journal of Soil Science. 74 (2), p. e13363. https://doi.org/10.1111/ejss.13363

AuthorsButton, E. S., Marsden, K. A., Nightingale, P. D., Dixon, E. R., Chadwick, D. R., Jones, D. L. and Cardenas, L. M.
Abstract

Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N2O. To implement management practices that minimise microbial N2O production and maximise its consumption (i.e. complete denitrification) we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling these processes is challenging and typical N2O flux measurement techniques provide little insight into subsurface mechanisms. Additionally, denitrification studies are often conducted on sieved soil in altered O2 environments which relate poorly to in situ field conditions. Here, we use a novel dual headspace system with field-relevant O2 concentrations to incubate intact sandy clay loam textured agricultural topsoil (0-10 cm) and subsoil (50-60 cm) cores for 3-4 d at 50 and 70% water filled pore space (WFPS), respectively. 15N-N2O pool dilution and an SF6 tracer were used to determine the relative diffusivity (Ds/D0) and the net N2O emission and gross N2O emission and consumption rates. The relationship between calculated fluxes from the below- and above- soil core headspaces confirmed that the system performed well. We found no difference in Ds/D0 between soil depth fractions, which was probably because of the preservation of preferential flow pathways in intact cores. Both gross N2O emissions and uptake were not different with depth but were higher in the 50% WFPS, contrary to expectation. We attribute this to aerobic denitrification and simultaneously occurring denitrification and nitrification for the gross consumption and emission of N2O, respectively. Here, we developed a novel system that allows careful control of conditions and, with a headspace below and above a soil core, a more realistic reconstruction of in situ gas dynamics. We provide further evidence of substantial N2O consumption in drier soil and without net negative N2O emissions. The results from this study are important for the future application of the 15N-N2O pool dilution method and N budgeting and modelling, as required for improving management to minimise N2O losses.

KeywordsDiffusion coefficient ; Denitrification; Sulphur hexafluoride; Isotope pool dilution; Nitrogen cycling
Year of Publication2023
JournalEuropean Journal of Soil Science
Journal citation74 (2), p. e13363
Digital Object Identifier (DOI)https://doi.org/10.1111/ejss.13363
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
S2N - Soil to Nutrition - Work package 2 (WP2) - Adaptive management systems for improved efficiency and nutritional quality
Publisher's version
Accepted author manuscript
Output statusPublished
Publication dates
Online04 Apr 2023
Publication process dates
Accepted01 Apr 2023
PublisherWiley
ISSN1351-0754

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