Validating portable gamma spectrometry as a tool for mapping spatial patterns in soil organic carbon

Director of Studies: Professor Will Blake
2nd Supervisor: Dr Jennifer Rowntree
3rd Supervisor: Dr Lauren Ansell
4th Supervisor: Dr Gonzalo Irisirri /Dr Martin Blackwell (Rothamsted Research)

Applications are invited for a 3.5 years PhD studentship within the Environmental Intelligence doctoral training programme at the University of Plymouth. The studentship will start on 01 October 2024. 

This project aims to integrate new advances in portable gamma spectrometry technology with emerging and urgent environmental land management needs regarding measurement of soil organic carbon (SOC) (Black et al., 2023). Enhancing SOC stocks is an important step toward meeting climate change adaptation and mitigation needs as well as enhancing soil productivity.

Processes behind building SOC and soil response are complex and quantifying changes in SOC patterns from field to farm scale is an essential step for developing knowledge of optimum management interventions. Convention sampling at scale, however, is expensive and time consuming. Innovation in gamma sensors (Van der Veek, 2021) offers opportunity to deliver rapid, on farm assessment of soil organic carbon (Taylor et al., 2023) but there is dearth of evidence to validate the efficacy of the sensor in range of conditions (different soil types, variability in soil moisture etc).

This project will close this gap by (1) developing passive sensor protocols that can be applied at farm and landscape scale, (2) creating new open-source libraries of conversion data to validate spectrometer data in a range of contexts and (3) derive data and evidence on soil health status to both evaluate SOC model outputs and inform management decisions. 

Working in demonstration farms in South Devon and the Rothamsted Farm Platform (Orr et al., 2016), the student will (i) undertake preliminary scoping studies with the Medusa Radiometrics passive gamma sensor and ground truth results through laboratory analysis for environmental radionuclides and cross reference to SOC and moisture data derived from sampling; (ii) derive conversion algorithms for radioactivity as a proxy for soil SOC, soil texture and moisture; (iii) compare sensor data to modelled SOC using Roth-C modelling tool; (iv) work with University of Plymouth (UoP) technical specialists in the AGRI-ELL project to optimise deployment of the scanner via UoP autonomous agricultural robot platforms to develop field and farm scale evidence of SOC.

The student will be trained in advanced catchment survey and sampling approaches, deployment of sensors and data management to include development of multivariate conversion models, state-of-the-art analytical and diagnostic methodologies under ISO9001 (gamma spectrometry and soil health/composition), use of the Roth-C model to develop a sound understanding of complexity SOC processes, setting up and running controlled experiments.

The successful candidate will have a degree in environmental sciences, geography or related discipline with experience in soil science, land and water processes, environmental diagnostic tools, and /or Geographical Information Systems (GIS). They will be keen and willing to undertake substantial amounts of field and laboratory work. They will have an adaptable and flexible approach to problem solving and be willing to learn new skills.

Black, HIJ., Reed, MSR., Kendall, H., Parkhurst, R., Cannon, N., Chapman, PJ., Orman, M., Phelps, J., Rudman, H., Whaley, S., Yeluripati, J. B. & Ziv, G. (2022), What makes an operational Farm Soil Carbon Code? Insights from a global comparison of existing soil carbon codes using a structured analytical framework. Carbon Management. 13:554-580

Orr, R. J., Murray, P. J., Eyles, C. J., Blackwell, M. S. A., Cardenas, L. M., Collins, A. L., Dungait, J. A. J., Goulding, K. W. T., Griffith, B. A., Gurr, S. J., Harris, P., Hawkins, J. M. B., Misselbrook, T. H., Rawlings, C. J., Shepherd, A., Sint, H. M., Takahashi, T., Tozer, K. N., Whitmore, A. P., Wu, L. and Lee, M. R. F. 2016. The North Wyke Farm Platform: effect of temperate grassland farming systems on soil moisture contents, runoff and associated water quality dynamics. European Journal of Soil Science. 67: 374-385. 

Taylor A, Kalnins A, Koot M, Jackson R, Toloza A, Ahmed HS, Goddard R & Blake WH (2023) 'Portable gamma spectrometry for rapid assessment of soil texture, organic carbon and total nitrogen in agricultural soils' Journal of Soils and Sediments 23, (6) 2556-2563 

van der Veeke, S., Limburg, J., Koomans, R.L., Söderström, M., de Waal, S.N., van der Graaf, E.R., 2021. Footprint and height corrections for UAV-borne gamma-ray spectrometry studies. J. Environ. Radioact. 231. 

Applicants should have a first or upper second class honours degree in geography, environmental science or a relevant masters qualification. 

If your first language is not English, you will need to meet the minimum English requirements for the programme, IELTS Academic score of 6.5 (with no less than 5.5 in each component test area) or equivalent. 

The studentship is supported for 3.5 years and includes full home tuition fees plus a stipend of £19,088 2024/25 rate (TBC). The studentship will only fully fund those applicants who are eligible for home fees with relevant qualifications. Applicants normally required to cover international fees will have to cover the difference between the home and the international tuition fee rates approximately £12,697 per annum 2023/24 rate (2024/25 rate TBC).

NB: The studentship is supported for 3.5 years of the four-year registration period. The subsequent 6 months of registration is a self-funded ‘writing-up’ period.

If you wish to discuss this project further informally, please contact Professor Will Blake.

Please see our how to apply for a research degree page for a list of supporting documents to upload with your application.

For more information on the admissions process generally, please visit our how to apply for a research degree webpage or contact The Doctoral College at research.degree.admissions@plymouth.ac.uk.

Shortlisted candidates will be invited for interview after the deadline. We regret that we may not be able to respond to all applications. Applicants who have not received a response within six weeks of the closing date should consider their application has been unsuccessful on this occasion.