Early indicators to monitor changes in soil health: evidence to update guidance for UK farmers

The project’s aim was to identify ‘early indicators of soil health.’ These were indicators that a farmer might be able to use soon after they had introduced some change in management to find out if it was having a positive impact on soil health. AHDB’s current suite of soil health indicators are meant to be measured every 3 to 5 years to get a feeling for the long-term trajectory of changes in soil health. Early indicators of soil health would ideally detect a change in soil health as early as six months following a change in soil management. The challenge with finding these indicators was to identify a test that was sensitive to management, but not so sensitive that it would be affected by recent weather or land operations.

Project Leaders and Partners

ORC (project leader)
SRUC
Eurofins
Frontier Agriculture
Hill Court Farm Research
Verdant Carbon

Project Description

Building on previous and current national-scale initiatives, including the AHDB Soil Health Scorecard (SHSC) and the Defra Healthy Soils Indicator, this project engages a multidisciplinary team of soil scientists and agronomists to propose and evaluate ten candidate soil health indicators. A combination of project team expertise, industry input and stakeholder feedback is utilised from Verdant Carbon, Hill Court Farm Research, Frontier Agriculture and Eurofins to give perspectives on soil health analysis and help select the most appropriate early indicators of soil health (EISH). To refine the list of indicators proposed, a logical sieve will be used to score each shortlisted indicator against six criteria: data robustness, links to ecosystem services, sensitivity to agricultural management, ease of sampling, cost-effectiveness, and interpretability. Results will draw on careful review of impactful soil health literature, utilisation of open-data repositories, expert consultation, and engagement with the commercial laboratories, agronomists and farm advisors. The project team will develop an interpretation framework for the top three ranked indicators. They will utilise the project findings to establish meaningful thresholds and rates of change, adapting for soil texture, climate, and cropping system to produce a traffic-light scorecard which is complementary to the current Soil Health Scorecard. Throughout the project, any knowledge gaps identified where UK-relevant evidence is lacking, will be compiled into a matrix to indicate the specifics of missing knowledge. This will result in a comprehensive summary of the state of evidence for all indicators considered in the project.

Project aims

The project aims to improve land manager confidence in the measuring and monitoring of soil health by improving our understanding of which soil metrics are most suitable to evaluate as early indicators of soil health changes. There will be 2 key outcomes to this work:

a list of early indicators of soil health that have been found to be the most useful and practicable on-farm in terms of contribution to both agricultural productivity and environmental function.
A farmer-friendly interpretation framework to sit alongside the list of early indicators of soil health. We will also be submitting a final report to AHDB which summarizes our selection process, the creation of the interpretation framework and any avenues for future research.

ORC’s role

ORC researchers are leading the management, knowledge exchange, and delivery of the shortlist of early indicators of soil health in the project, while our colleagues at SRUC are leading on the interpretation framework.

Current progress highlights

Project Kick Off October 2025

The official launch of the research project: “Early indicators to monitor changes in soil health: evidence to update guidance for UK farmers”, funded by the Agriculture and Horticulture Development Board (AHDB) took place on October 20th.

AHDB Agronomy Conference Project Update December 2025

Dr Amanda Bennett, Senior Environment Manager, AHDB presents some early results from the project in her talk on soil health metrics.

Deliverables

AHDB project webpage, including report:

Early indicators to monitor changes in soil health: evidence to update guidance for UK farmers | AHDB

New webpages:

Measure aggregate stability to detect changes in soil health early | AHDB

Measure active carbon to detect early changes in soil health | AHDB

Using potentially mineralisable nitrogen to measure soil health | AHDB

Project output

We identified three indicators with potential as ‘early indicators of soil health.’

The slake test is a farmer-led measure of aggregate stability that appealed to our stakeholders. However, there is still a lack of UK-relevant data for interpretation of slake scores i.e. what is a ‘good’ slake score versus a ‘poor’ score.
Potentially mineralisable nitrogen (PMN) is already included in the soil health scorecard and is sensitive to recent additions of organic nitrogen, so it shows potential as an early indicator of one aspect of soil health: the ability of the soil microbial community to decompose organic matter and release nutrients. However, we were unable to update the traffic light scores for this indicator due to a lack of UK-relevant data on how PMN links to soil health and function in different soil types and cropping systems
Potassium permanganate oxidisable carbon (POXC), is a measure of one component of the soil’s organic matter pool. There is some evidence that links POXC to the quality and accessibility of soil organic matter to soil microorganisms; however, other studies have shown a high correlation with good old-fashioned organic matter by loss on ignition, suggesting it doesn’t really provide additional information. So this one also requires further investigation.

The project therefore successfully screened a range of indicators and identified those with potential as early indicators of soil health. Further research is still required to verify the links between these tests and soil health, how sensitive they are to recent changes in management, and to build a database of results for development of interpretation systems e.g. a traffic light system similar to the existing AHDB soil health score card.

How to monitor soil health more frequently within the rotation is the subject of AHDB’s new evidence-based web pages, resulting from the project. AHDB’s Senior Environment Manager Amanda Bennett describes the approaches and how the results can support management decisions. New guidance to make sense of soil health indicators | AHDB