Soil Steps

Research

Soil Steps

Linking soil food web ecology to carbon modelling in grazed grasslands.

Soil Steps tests whether soil biology, not just bulk carbon measurement, explains why grazing based carbon claims vary so widely, then builds that biology into better carbon and risk models.
A block of soil showing root structure and clover growth
~33%of land worldwide is grassland
Mostgrassland carbon sits below ground
3+journal papers planned from this PhD

Why current carbon claims fall short

Grasslands are increasingly promoted as a nature based climate solution, particularly through regenerative grazing and soil carbon credit markets. But the evidence on how grazing affects soil carbon is mixed. Moderate grazing can stimulate plant productivity and carbon inputs, while heavy grazing can strip carbon out through compaction and biomass removal, and the outcome depends heavily on context.

Current carbon accounting frameworks mostly rely on bulk soil carbon measurements and simplified turnover models. They rarely capture the biological processes, particularly soil microbial and faunal communities, that actually determine whether carbon is stabilised in soil or lost again through respiration. That gap is what Soil Steps addresses.

The research questions

How Soil Steps links grazing to carbon and nitrogen cycling A flow diagram showing grazing intensity affecting plant and soil inputs, which shape nematode trophic structure, which in turn regulates carbon and nitrogen cycling. Three research questions label the connections between each stage. RESEARCH QUESTION 2 How does grazing intensity alter productivity & carbon inputs? RESEARCH QUESTION 1 How do soil physical & chemical properties shape nematode structure? RESEARCH QUESTION 3 How does trophic structure regulate C & N turnover? Grazing intensity The starting variable: how hard and how often livestock graze each field. Low stocking Moderate / rotational Intensive / set stocking Plant & soil inputs What grazing changes on the ground and in the soil. Productivity (NPP), root & litter carbon Organic matter, pH, compaction, structure Nematode trophic structure The soil food web at the centre of this project: five feeding groups, each a bioindicator. Bacterivores Fungivores Herbivores Omnivores Predators Measured via enrichment, structure, channel & maturity indices Carbon & nitrogen cycling The outcome: whether carbon is stored or lost, and how fast nitrogen becomes available. Carbon turnover vs. retention (POXC, MAOM) Nitrogen mineralisation rate Basis for more accurate carbon claims Structural equation modelling tests all four stages together, as one connected system, not isolated pairwise links.
How Soil Steps links grazing management to soil carbon and nitrogen outcomes, via the soil food web.

What Soil Steps measures

Soil, vegetation, microbial, and faunal data are collected seasonally across grassland sites spanning low, moderate, and intensive grazing management. Soil sampling covers physical properties (texture, bulk density, moisture, aggregate stability), chemical properties (pH, CEC, total and inorganic nitrogen, phosphorus, C:N ratio), and carbon fractionation that distinguishes labile from stabilised pools: permanganate oxidisable carbon (POXC), particulate organic matter, and mineral associated organic matter (MAOM).

Vegetation productivity is estimated from aboveground biomass, litter, and root biomass. Microbial activity is assessed through microbial biomass carbon and nitrogen, CO2 respiration, and potentially mineralizable nitrogen. Soil food web structure is assessed by extracting nematodes (the Baermann funnel method) and classifying them into functional trophic groups: bacterivores, fungivores, herbivores, omnivores, and predators, using established faunal indices and metabolic footprints to estimate carbon and energy flow through trophic pathways.

A nematode under the microscope, extracted from a soil sample
A nematode, extracted and viewed under the microscope.
Fungal hyphae under the microscope in a soil sample
Fungal hyphae, part of the microbial community nematodes feed on.
An amoeba under the microscope in a soil sample
An amoeba, another key player in the soil microbial food web.
Soil fauna under the microscope in a soil sample
Soil fauna, part of the wider community assessed alongside nematodes.

Analysis uses linear mixed effects models and redundancy analysis in R to relate grazing intensity to soil and biological variables, and structural equation modelling to test the full mechanistic cascade from grazing, through vegetation inputs and soil chemistry, to microbial activity, nematode trophic structure, and carbon and nitrogen cycling, as one connected system rather than isolated pairwise relationships.

Why it matters beyond academia

This research sits close to my day job. As investment in regenerative grazing and soil carbon credit projects accelerates, carbon claims are often made without mechanistic biological validation, a real source of both scientific and financial risk.

A microbial and food web informed carbon model can flag where projected carbon gains are likely overstated (transition risk), where microbial metabolism is vulnerable to drought or warming (physical climate risk), and where declining soil biological complexity signals reduced ecosystem resilience. That is directly relevant to nature related financial disclosure requirements, including TNFD, that companies are now expected to report against.

Dissemination

Findings are intended for academic, policy, and farmer facing audiences. At least three peer reviewed journal articles are planned across the project, targeting journals including Soil Biology & Biochemistry and Global Change Biology, alongside conference presentations, annual summaries for participating farms and industry partners, and a final policy facing report on grazing management and soil carbon.

Publications & outputs

Sunset over a grazed pasture field

In progress

Forthcoming

Peer reviewed articles from my Soil Steps PhD research, covering soil carbon dynamics, nitrogen cycling, and soil food web structure under grazing intensity gradients.

Peer reviewed & policy publications

Peart, G.; Vousough-Ahmadi, B.; Barratt, A.

"Farmer Responses to Brexit: Intentions to engage in public good provision." Published for the Scottish Government's Brexit preparation policy planning division. First author.

Peart, G.

"Conserving Farm Animal Genetic Resources in the UK: The Future Post Brexit." Livestock policy paper, presented at the 30th International Congress of Agricultural Economists, Vancouver, 2018.

Dissertation

Peart, G.

"Breeder Motives and Values in UK Native Cattle Conservation." MSc dissertation, Scottish Rural College. Analysed farmers' views on the value of rare and native breed cattle compared with globalised breeds, and produced a cost optimisation model of livestock biotechnology integration in modern cattle farming systems.

Supervision and funding

I'm supervised by William Stiles and Sarah Watson-Jones, IBERS, Aberystwyth University. This research is supported by Regeno, with additional external sponsorship from Soil Steps Ltd.