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Understanding nitrous oxide “hot-spot” dynamics in upland soils

Project Description

Nitrous oxide (N2O) is a powerful greenhouse gas. It is important, therefore, to understand the factors controlling its emission – particularly from agricultural systems. Urine patches are believed to represent important N2O emission “hot spots” and “hot moments” in pastures grazed by cattle and sheep. Whilst much is known about emissions from sheep-grazed lowland pastures, emissions from extensive upland systems are uncertain.

Emission estimates currently employ assumptions based on measurements made in lowland systems which may not be valid in sheep grazed upland environments. Limited reports of emission rates from upland soils suggest that they are variable and may be controlled by interactions between fluid movement and the properties of near surface soil horizons – particularly if thick litter and organic layers are present (where nitrification may be limited). In this project, interactions between fluid movement, urea hydrolysis, nitrification and denitrification in upland soils will be investigated via a combination of field measurements, laboratory experiments and numerical modelling. This work will link closely with an ongoing NERC project which aims to quantify the spatial and temporal dynamics of N2O emissions from sheep-grazed upland pastures.

Laboratory incubation assays will be conducted to determine potential rates of urea hydrolysis, nitrification and denitrification in material sampled from upland soil litter and organic horizons. Experiments will also be conducted to quantify rates of N transformation in materials receiving artificial and real sheep urine in realistic ratios. Nitrification may be limited by pH and dissolved oxygen concentrations in the pore water which will, in turn, limit denitrification (due to a shortage of nitrate). There is also some uncertainty about the composition and functional competence of the microbial communities in upland soils which may be adapted to using alternative electron acceptors to nitrate under anaerobic conditions. The dynamics of solute transport and transformation in different materials in upland soils will be explored using state-of-the-art solute transport models such as HYDRUS-2D.

Dr Mick Whelan and Dr Joerg Kaduk will supervise this project. The group have interests in understanding the fate and transport of environmental contaminants and trace gas emissions from terrestrial systems, including applications of the biosphere exchange model JULES.

The Leicester team will be supported by Dr Laura Cardenas from Rothamsted Research (North Wyke) and Prof. Dave Chadwick from the University of Bangor. They have a wealth of experience in understanding soil nitrogen dynamics and regularly contribute to the refinement of emission factors for national and international Greenhouse gas inventories.

Entry requirements

Applicants are required to hold/or expect to obtain a UK Bachelor Degree 2:1 or better in a relevant subject. The University of Leicester English language requirements apply where applicable.

How to apply

Please refer to the CENTA Studentship application information on our website for details of how to apply
As part of the application process you will need to:
• Complete a CENTA Funding form – to be uploaded to your PhD application
• Complete and submit your PhD application online. Indicate project CENTA2-GGE14-WHEL in the funding section.
• Complete an online project selection form Apply for CENTA2-GGE14-WHEL

Funding Notes

This studentship is one of a number of fully funded studentships available to the best UK and EU candidates available as part of the NERC DTP CENTA consortium. The award will provide tuition fees as the UK/EU rate and a stipend at the RCUK rates for a period of 3.5 years.

For more details of the CENTA consortium please see the CENTA website: View Website.

Applicants must meet requirements for both academic qualifications and residential eligibility: View Website

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