Restoring agricultural soils
Changes to the management of agricultural soil could contribute to improving the ability of soils to produce crops, as well as to wider benefits including mitigating future climate change. This POSTnote summarises the state of England’s agricultural soils and evaluates soil stewardship opportunities. Soil indicators that could be used for monitoring in policy frameworks and incentives relating to soil restoration are explored.
DOI: https://doi.org/10.58248/PN662
Soils underpin the food system, providing nutrients and water for plants to grow, as well as other benefits including carbon storage and water regulation. The components of soil are minerals, organic matter, organisms, water and gases. Soil Organic Matter (SOM) is the organic material leftover from decomposing plants and animals, whereas Soil Organic Carbon (SOC) is the measurable carbon concentration of SOM. A productive soil for agriculture has a balance of nutrients (such as carbon, nitrogen and phosphorous) and minerals, for example, calcium and zinc, as well as appropriate SOM content. Intensive agriculture has put pressure on the soil, resulting in erosion, compaction, carbon loss, nutrient imbalances and contamination. Many arable soils have lost 40-60% of their organic carbon, almost 4 million hectares of agricultural land in England and Wales are at risk of compaction and there are concerns about the largely unknown risk of microplastic contamination in farmland soils.
Restoration of soils using principles from regenerative, organic and conservation agriculture could reverse soil degradation. Practices such as biochar additions, cover cropping and reduced reliance on synthetic fertilisers could promote soil carbon storage and reduced greenhouse gas emissions. Reduced and zero tillage methods may also be beneficial for soil carbon storage, although evidence for the effectiveness of no-till in the UK is mixed and may be limited to heavier clay soils. Policy initiatives around soil health and management are mentioned in the UK Government’s 25 Year Environment Plan and more recently the Soil Health Action Plan for England. A key ambition is to manage soils sustainably by 2030. The Sustainable Farming Incentive, part of the new Environmental Land Management schemes, will pay farmers to protect and restore soil health through SOM testing and soil assessments. Key soil indicators, such as organic carbon and soil biology, can be measured and monitored through national assessments with the help of remote sensing and modelling techniques. Advances in technology and understanding of soil biological interactions could help buffer soils against climate change, increasing their resilience.
Key points
- Intensive agricultural practices have caused soil degradation in the UK, leading to loss of carbon, nutrient imbalances, erosion, compaction, and contamination.
- Key soil indicators, such as soil organic carbon, have decreased. This is affecting the benefits soils provide, such as food production.
- Research provides evidence for practices that could be used to reverse soil degradation in different contexts. Examples of practices include cover cropping and biochar additions.
- The 2022 Sustainable Farming Incentive scheme will pay farmers to manage soils, but it is not clear that the level of payment is great enough to incentivise change.
- Innovations in soil monitoring technology could simplify national and farm scale soil monitoring, reporting and verification.
Acknowledgements
POST Board members*
Professor Gideon Henderson, Defra*
Brendan Freeman, Committee on Climate Change
Dr David Smedley, Defra*
Professor Pete Smith, University of Aberdeen*
Dr Marcelo Galdos, University of Leeds
Dr Maria Hernandez-Soriano, John Innes Centre
Dr Kate Schofield, University of Plymouth
Dr Maud van Soest, Loughborough University
Dr Sara Abad Guaman, University College London*
Dr Stephan Haefele, Rothamsted Research*
Professor Steve McGrath, Rothamsted Research*
Professor Mark Fitzsimons, University of Plymouth*
Dr Carla Washbourne, University College London
Dr Lisa Norton, UK Centre for Ecology and Hydrology*
Professor Richard Bardgett, University of Manchester
Dr Simon Jeffery, Harper Adams University
Dr Felicity Crotty, Royal Agricultural University
Professor Jim Harris, Cranfield University
Professor Colin Snape & Professor Helen West, University of Nottingham
Dr Miranda Prendergast-Miller, Northumbria University*
Philippa Arnold, NFU
Helen Browning, Soil Association
* denotes people and organisations who acted as external reviewers of the POSTnote.