# Impact of soil type on nitrifiers and denitrifiers communities and subsequent gaseous N losses following sheep urine application

Aude Mancia, David R Chadwick, Sinéad M Waters, Dominika J Krol

► To cite this version:

Aude Mancia, David R Chadwick, Sinéad M Waters, Dominika J Krol. Impact of soil type on nitrifiers and denitrifiers communities and subsequent gaseous N losses following sheep urine application. Agricultural greenhouse gas and ammonia mitigation: Solutions, challenges, and opportunities, Association of applied biologists, Mar 2022, Edinburgh (United Kingdom), United Kingdom. hal-05384017

HAL Id: hal-05384017

https://hal.inrae.fr/hal-05384017v1

Submitted on 26 Nov 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Impact of soil type on nitrifiers and denitrifiers communities and subsequent gaseous N losses following sheep urine application

Aude Mancia¹,²,³*, David R. Chadwick², Sinéad M. Waters³, Dominika J. Krol¹

¹Teagasc, Crops, Environment, Soils and Land Use Department, Johnstown Castle, Co. Wexford, Ireland, ²School of Natural Sciences, Bangor University, Bangor, Wales, UK,³Teagasc, Animal and Grassland Research and Innovation Centre, Athenry, Co. Galway, Ireland

## ABSTRACT

Grazing ruminants deposit excreta patches onto pasture soils, which represent hotspots for the emission of a potent greenhouse gas, nitrous oxide (N₂O). IPCC provides default (Tier 1) emission factors (EF; proportion of deposited nitrogen emitted as N₂O) associated with ruminant excreta deposition. However, due to great spatial and temporal variation, development of country-specific (Tier 2) EFs is encouraged. Ireland has already generated a Tier 2 EF for cattle excreta deposition but no experimental data are available for sheep. Along with N₂O, other nitrogen gases can be produced such as nitrogen oxide (NO) and dinitrogen (N₂) but the quantification of these gases after ruminant excreta deposition and the mechanisms responsible for the production of these various N gases require more understanding. Therefore, the first aim of this project was to generate Tier 2 EFs for N₂O emissions from sheep excreta deposition in Irish grasslands, and to assess the effects of excreta type, grassland type and season of deposition on emissions. The second aim was to establish relationships between soil chemical variables, nitrification/denitrification genes and gaseous N losses (N₂O, N₂, NO). For the first objective, a field experiment was carried out on two sites with contrasting soils in the west of Ireland: a well-managed lowland grassland on mineral soil and a rough-grazed hill-land pasture on acid peat soil. For each season, four treatments were applied to the soil in a fully randomized block design: control (C), sheep urine (U), sheep dung (D), and artificial urine (AU). Static chambers were used to measure N₂O fluxes for one year after each application. Soil from the two sites were then incubated in the DENIS laboratory system to measure N₂O, NO and N₂ emissions for two weeks following synthetic urine or water control application. A parallel soil incubation was simultaneously established for destructive sampling to assess soil chemical variables and nitrification/denitrification genes abundance. The field study showed that on the lowland site, a peak of N₂O flux was observed within the first days after each application of U and AU, and N₂O emissions were significantly higher in autumn compared to summer. Average EFs were close to zero: -0.04, -0.05 and 0.08% for aggregated excreta in spring, summer and autumn respectively, thus lower than the 2019 IPCC Tier 1 EF (0.3% for aggregated excreta of sheep). On
the hill-land site, no peak of N₂O and no effect of season was observed following treatments application and emissions were significantly lower compared to lowland with negligible EFs. Initial results from the incubation experiment are supporting field observations, with low N₂O fluxes after urine application and higher emissions from lowland site compared to hill-land. These findings suggest low and soil type-specific N₂O emissions from sheep excreta deposited in Irish grasslands and highlight the importance to develop Tier 2 EFs.