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Project Highlights:

  • Testing and evaluating alternative soil husbandry practices for restoring soil fertility and reducing greenhouse gas emissions to sustain global agriculture.
  • Utilization of cutting-edge isotope, nutrient sensing and greenhouse gas flux technologies for developing and informing sustainable soil management practices
  • Part of a multidisciplinary and multi-institutional experimental soil research network with active support of partners and farm owners, thus offering diverse training opportunities.


Soil is fundamental to life and is vulnerable to losses in stored carbon (C) and productivity, particularly under intensive agriculture.1 For example, 133 billion tons of soil C has been lost due to agriculture, which alone represents between 10-20% of the total anthropogenic CO2 emission into air.1 Among others, loss in soil C reduces fertility and thus to sustain productivity, application of synthetic fertilizers including nitrogen (N) has intensified. The use of fertilizers has led to increases in production;2 however, at the same time excessive fertilization has been linked to deterioration of environmental quality, and emission of greenhouse gases (GHG) particularly nitrous oxide, which is 300 times more potent in inducing global warming than CO23, 4, 5. Thus there is an urgent need for the identification of soil management practices that can help sustain soil fertility and productivity whilst reducing GHG emissions.6 Arable agriculture in the UK like the global seriously suffers from the soil exhaustion challenge, and there is a current impetus on improving soil health to ensure food security.

One way is to introduce rotations in agriculture such that leys (as soil’s resting phase in between cultivation) can be optimized for enhancing fertility whilst sustaining income. A new multi-institutional project in the UK on ‘Restoring Soil Health through Integration of Leys and Sheep Grazing in Arable Rotations’ is now establishing farm-scale experimental fields (2019-2022) to evaluate the broader agro-environmental effectiveness of rotations with grass and herb rich leys with and without grazing and tillage, respectively (Fig1). It is hypothesized that herbaceous leys with N fixing plants will enhance soil fertility that will reduce reliance on fertilizers in subsequent cultivations and to this effect the project is focused on measuring soil nutrients and productivity. Since the planned rotations will affect the emission of GHG through its impact on soil N and C transformation processes, which is not included in the consortium project, therefore, the proposed PhD research will evaluate the impacts of traditional (grass-clover) and herbal leys rotations on biological N fixation, N mineralization and greenhouse gas emission rates to identify efficient soil management strategies for incorporation into agricultural practices.


The project will encompass selected experimental farm trail sites, namely Allerton Farm in Loddington, NIAB farm in Duxford and Davies Farm in Great Dunmove. Within each site, access to a split-farm design integrating ley types, grazing, mowing and tillage types (Fig1 above at NIAB) will thus enable a robust evaluation of the rotational treatments on N transformation processes and GHG emission rates. N fixation and transformation processes will be measured using cutting-edge isotope tracing techniques, while greenhouse gas emission rates will be determined using static chambers and a 15N-N2O Piccaro analyser available at the Centre for Ecology and Hydrology, Lancaster. Laboratory incubation of soil samples will be undertaken to isolate the role of individual environmental and soil management factors in affecting soil fertility, nutrient availability and GHG emission potentials. The data will be analysed to identify the most efficient management system delivering multiple benefits and services.

Training and Skills

The student will become part of the PhD student’s community within in the University of Birmingham where transferable skills trainings are in place to benefit from. Training will be provided in the operation of analytical instruments (Birmingham), spectrometry (CEH-Lancaster); and will attend the soil analysis practicals module, which is led by S. Ullah for hands-on experience in support of the project plans. A placement at the National Trust in year 1 of the project will enable contextualization of the research plan within the UK farm policy needs. In addition, interactions with project members and international partners will enable knowledge exchange and lasting linkages.


The project is flexible to accommodate the student’s training, networking and site visit needs before field work across the sites to match up experimental timelines more efficiently.

Year 1:

  • Literature review and training in analytical instruments (Chromatography, colorimetry, isotopes) and experimental designs at Birmingham and CEH-Lancaster. Introductory visits of the experimental sites in England.
  • Placement (2 weeks) at the National Trust office to learn about farms management on the National Trust Estate and contemporary challenges and opportunities in sustainable agriculture.
  • Research plan finalization, installation of chambers for GHG emission and publication of a literature review paper.

Year 2:

  • Seasonal measurement of GHG fluxes from the experimental plots with associated relevant environmental characterization of soils using in situ sensor technology.
  • Seasonal sampling of soils in the experimental plots for in situ incubation for N mineralization and N fixation rates.
  • Data analysis and compilation of results for publication.

Year 3:

  • Continuation of GHG flux and net N mineralization measurement in the field and analysis of selected samples on the 15N-N2O Picarro analyser at CEH Lancaster for source portioning.
  • Collection of soil samples for incubation in the laboratory for gross N mineralization and nitrous oxide emission using 15N tracers to elucidate controls on microbial pathways of nitrous oxide production, N immobilization and availability in response to the rotational treatment.
  • Data analysis and completion of experimental work.

Year 4:

  • Thesis write up, defence and publications.
  • Involvement with project partners in this large project will offer further opportunities for pooling data within multidisciplinary data pool for the publication of large synthesis papers and methodologies.

Partners and collaboration (including CASE)

This studentship benefits directly from access to farm-scale experimental network sites currently being established under a multi-intuitional project (> £ 0.9 million) funded by the UKRI-Sustainable Agriculture Research and Innovation Club program. Thus this studentship leverages the very high experimental establishment costs of the project, which would be beyond the funding capacity of any single PhD studentship. The involvement of National Trust, and CEH-Lancaster offers significant in-kind value: access to 15N2O Picarro (>£100k) at CEH and student placement at National Trust (£3000) for the contextualization of the proposed research provides a broad-based training environment in addition to the collaboration potential across the institutions.


Further Details

For further information and specific questions, contact  (s.ullah@bham.ac.uk). Relevant PhD studentship and Research information available on the departmental web page: https://www.birmingham.ac.uk/research/activity/physical-geography/index.aspx