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QUADRAT DTP CASE: Waste to Land - Differential priming of soil carbon driven by additions of organic wastes

Project Description

The application of organic wastes (from food and agricultural residues) to land is becoming an increasingly popular method of waste management, on both national and international scale. The practice reduces the amount of landfilled waste and greenhouse gas emissions, while benefiting the soils by improving their physico-chemical characteristics. It is anticipated that the added organic wastes are also going to benefit the multitude of other ecosystem services that soils provide, such as nutrient cycling, food production and habitat provision. The empirical evidence behind this claim, however, is sparse.

In contrast to traditionally applied materials, such as manure, the modern organic wastes are composed of so-called fresh carbon, i.e. organic components at various phases of decomposition that are predominantly labile in nature. The additions of fresh carbon to soils have been acknowledged to cause a priming effect. Priming is defined as the stimulation of microbial activity and overall decomposition rates of labile carbon. The fresh carbon is a preferred energy source for soil microorganisms and stimulates decomposition processes, including the decomposition of native soil organic matter. Consequently, the application of organic wastes can result in an overall loss of soil organic matter. In addition, the higher carbon to nitrogen ratios of organic wastes have a potential to immobilise nitrogen in soils, causing nitrogen deficiency in plants. The exact mechanisms behind these processes, however, are uncertain.

This study will evaluate the magnitude of the priming effect associated with organic wastes added to soils. A particular attention will be paid to the factors, such as the quantity and quality of fresh carbon added to soils, its availability and effects on active microbial communities. The quality of fresh carbon will be appraised by the physical fractionation of soil organic matter. The effects on microbial communities will be addressed by a suite of enzymatic assays that target the main nutrient cycles and facilitate the identification of constraints imposed on nutrients turnover by environmental conditions.

The suitable candidate will engage with the disciplines of environmental science, soil ecology and soil science, and have opportunity to chart a project of wholly novel provenance. Training will be provided in research design and the assessment of soil physical, chemical and biological properties. The student will gain a first-hand experience of techniques used to assess soil nutrients and biological functioning of soils.

This project is supported by Keenan Recycling Ltd as a CASE partner.


Candidates should have (or expect to achieve) a minimum of a 2.1 Honours degree in a relevant subject. Applicants with a minimum of a 2.2 Honours degree may be considered providing they have a Distinction at Master’s level.


• Apply for Degree of Doctor of Philosophy in Biological Sciences
• State name of the lead supervisor as ‘Name of Proposed Supervisor’ on application
• State ‘QUADRAT DTP’ as Intended Source of Funding
• Select the ‘Visit Website’ to apply now

Funding Notes

This project is funded by the NERC QUADRAT-DTP and is available to UK/EU nationals who meet the UKRI eligibility criteria. Please visit View Website for more information.

The studentship provides funding for tuition fees, stipend and a research training and support grant subject to eligibility.


Bongiorno, G., Bünemann, E.K., Oguejiofor, C.U., Meier, J., Gort, G., Comans, R., Mäder, P., Brussaard, L., de Goede, R., 2019. Sensitivity of labile carbon fractions to tillage and organic matter management and their potential as comprehensive soil quality indicators across pedoclimatic conditions in Europe. Ecological Indicators 99, 38-50.

De Graaff, M.-A., Jastrow, J.D., Gillette, S., Johns, A., Wullschleger, S.D., 2014. Differential priming of soil carbon driven by soil depth and root impacts on carbon availability. Soil Biology and Biochemistry 69, 147-156.

Brown, S. and Cotton, M., 2011. Changes in soil properties and carbon content following compost application: results of on-farm sampling. Compost Science & Utilization 19(2), 87-96.

How good is research at Aberdeen University in Biological Sciences?

FTE Category A staff submitted: 89.42

Research output data provided by the Research Excellence Framework (REF)

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