SoilBioHedge: harnessing hedgerow soil biodiversity for restoration of arable soil quality and resilience to climatic extremes and land use changes

Lead Research Organisation: University of Leeds
Department Name: Sch of Geography


Only 30% of Earth's surface is land, only 9% is cultivated, and there is little scope for future expansion. The supply of water and nutrients from soil to crops in approximately 7800 km3 of topsoil (to 0.5 m) currently sustains 7 billion humans. This soil resource is the essential foundation of arable farming on which plant production for food, fiber and biofuels, and ultimately the entire global economy depends. How we manage this vital, life sustaining, resource will determine the quality of life and Earth's carrying capacity for future generations.

SoilBioHedge addresses the central problem for soil security: continuous conventional arable cultivation depletes soil organic matter, degrades soil structure, reduces water drainage and water holding capacity, and increases the susceptibility of soil and crops to the impacts of climatic stress through decreased resilience to flood and drought conditions.

We will test our central hypothesis: grass-clover leys sown into arable fields and connected to hedgerows and unploughed grassy margins enable key ecosystem-engineers (earthworms and mycorrhizal fungi) to recolonize the fields, restoring and improving soil quality compared to leys unconnected to field margins.

We will determine for the first time the importance of connectivity from biodiversity refugia under hedgerows to arable fields via grass-clover leys in restoring functional biodiversity. We will quantify soil quality as functional benefits from soil-organism interactions: increases in soil organic matter, water-stable macroaggregates, water holding capacity, infiltration rates, drought and flood resilience, and resulting crop yields. We will quantify the operational temporal and spatial scales for ecosystem engineers (grass-clover roots, AM fungi, and earthworms) and soil functions to synergistically develop with land use and management change. We will transform mechanistic understanding of soil structure dynamics by combined metabolomics and metagenomic analyses tracking soil aggregate formation over 3 growing seasons.

Our research design includes three nested scales of observation.
1) Hedge-to-Field Experiments at Leeds U. farm to quantify spatial/temporal changes in soil functions and biodiversity, arising from arable-to-ley conversion strips that are disconnected or connected to the field margin, and across a whole field converted to arable in 2012, and ley-to-arable conversion using conventional vs. minimal tillage strips and a field that converted to ley in 2009. Monolith mesocosm studies will use turf blocks removed from the experimental plots, treated with herbicide and direct drilled with wheat. We will compare crop yields between the field and monoliths maintained at near-ambient conditions, under simulated drought and excess rainfall causing flooding. The results will quantify soil quality and the resilience of the crop and soil organisms and functions to these stresses.
2) Landscape-Scale Hedge-to-Field Transects will quantify soil functional changes on long-term arable fields and pairs of arable fields converted to ley over 2 differing time scales. We will utilize our network of >100 farms that provide a range of soil types, and management (conventional, organic, and minimal tillage).
3) Field-to-Landscape Scale mathematical modelling to establish an integrative and predictive spatiotemporal model of soil quality change at field-to-landscape-scale, including the role of dispersal of hedgerow and field margin biodiversity into arable land resulting from land use and management change involving leys. We will integrate mechanistic understanding of soil aggregation and carbon accumulation through the synergistic actions of roots, AM, and earthworms from our experiments and landscape-scale transect observations with existing Countryside Survey data and national digital soil map, to deliver a step-change in understanding for sustainable soil management policy and practice.

Planned Impact

Who will benefit and how?
Results from SoilBioHedge, and their practical applications in sustainable soil management by UK and international farmers have potential to deliver far-reaching benefits across a wide range of sectors, from individuals and organizations, to societal benefits from long-term potential gains in soil and food security.
Pre- and post-farmgate stakeholders and policymakers. The core outcomes of the project will directly influence a) Farmers, farm managers: benefit through understanding benefits of leys and the spatiotemporal scales over which they restore soil quality under different management practices and soil types, b) Statutory agencies involved in water and soil conservation (e.g. Natural England, Environment Agency), c) Utility companies involved in water supply, nitrate pollution and management of stormwater and associated sediment discharges, d) households in flood-risk areas where the risks have been increased by loss of arable soil water infiltration and storage capacity, e) Game and Wildlife Conservation, (f) Government policy makers (DEFRA) and via the SoilTrEC project network EC and member state agencies tasked with policy innovation for EU soil security, g) The wider UK and international public via the SCOPE Soil Carbon project network including dissemination activities of the UN Environment Programme, European Soil Bureau web portal, and UN FAO (via the Global Soils Partnership) - all specifically aimed at improved soil and food security and environmental sustainability, consistent with the aims and vision of the global food security (GFS) programme

We will employ 4 major mechanisms of communication and engagement:
1. National and international conference presentations, including: International Conference on Mycorrhiza, British Soil Science Society, British Ecological Society, International Earthworm Ecology Symposium, The European and American Geophysical Union, US and European Goldschmidt Conferences.
2. Publications in high impact and / or open access peer reviewed journals. We plan to submit at least 6 major journal articles over the course of the project. These publications will reach academic audiences, and via press releases and open access publication enable wide impact.
3. Knowledge and information transfer to national databases on earthworms, AM fungi and tipulid biodiversity and distributions.
4. Stakeholder and Outreach Events. We will have 4 major stakeholder engagement activities: a) Our steering group stakeholders (see letters of support) will meet with us annually (see Workflow Plan and Project Management document) for all three years of the project, guiding our strategies for effective engagement with the stakeholder groups they represent. b) We will hold a 3-day public engagement event "Hedge-to-Field: What's hiding under your hedge and why is it important for our soil?" at the Great Yorkshire Show 2017 which typically has >130,000 visitors over 3 days). c) Host a 1 day outreach/engagement meeting in the project's final year to demonstrate research outcomes and communicate findings to farmers and key policy makers, following the successful model we used in a meeting co-hosted with the Organic Growers Alliance and facilitated by the Technology Strategy Board Environmental Sustainability Knowledge Transfer. d) Contribute to a meeting with a wider stakeholder group with interests in wheat breeding and sustainable cultivation methods, hosted at the Allerton Project Visitor's Center and drawing on their extensive network of contacts (see Dr AR Leake letter of support).

Dissemination materials for the above series of events will be distilled into 2-page Fact Sheets/Policy briefs that summarize key findings and provide advice for farmers and soil management practitioners and the agritech commercial supply chain, and provide key science evidence to support policy innovation for government agencies and NGOs working at the science-policy interface.
Description Strong differences in soil properties in ley strips compared to cropped land. Hydrological function is different which will have implications for water storage and response to rainfall events, flood resilience etc. Major differences in soil function between hedgerow, field margins and grassland or arable fields. Mean bulk density was significantly lower while organic matter content and porewater dissolved organic carbon concentrations were significantly greater in hedgerow soils, than the margins or fields. Infiltration and soil permeability were significantly greater under hedgerows where it took an average of 2 hours longer for soils to reach maximum moisture content following rainfall, than adjacent arable or grassland fields. While macropore flow played a significantly greater role in percolation for the field margin soils, compared to the arable fields, macropore flow was more limited under hedges. Their high permeability yet low potential for bypass flow means hedge soils are likely to be important in trapping sediments and other mobile chemicals. Earthworm abundance was 3 times greater in grassland fields compared to hedge, margin and arable soils. Earthworm diversity was higher in hedge, margin and grassland soils compared to arable soils, which consisted mainly of juvenile endogeic species. Earthworms under hedgerows tended to be dominated by epigeic litter-feeding species, and the overall low hedgerow abundance was probably due to drier hedgerow soil moisture. Hedgerow soils contained arbuscular mycorrhizal (AM) communities that were distinct from those in arable fields, and the field margins are intermediate, revealing a gradient in composition from hedge to the centre of arable fields. Permanent grassland AM communities were distinct from arable fields suggesting a significant impact of management history on development of soil microbial communities. Our findings demonstrate that soils under typical hedges can provide important functions on farmland including storing organic carbon, intercepting rainfall and runoff, storing water, increasing earthworm diversity and hosting distinct AM communities.

Through a three-year field-scale experiment we examined the impacts of conversion from long term arable to ley and pasture to arable on soil physical and hydrological functions. We used 70 m long ley and crop strips within arable rotations and pasture fields, respectively. While there was little evidence of significant changes in soil physical properties in the first three years following conversion of arable to ley, we did find significant differences in hydrological function. We observed an increase in water holding capacity in the upper 10 cm of ley soils. In contrast, water holding capacity was reduced by conversion from pasture to arable in the upper 10 cm. Conversion of arable to ley had a positive impact on the proportion of flow through macropores >1 mm and overall permeability (saturated hydraulic conductivity) was significantly greater for ley soils compared to arable soils. While permeability increased upon conversion from pasture to arable there was a reduced proportion of flow through macropores >1 mm, this impact was largest for conventional tillage which may reflect impacts of tillage on earthworm abundance.

Using monoliths of soil taken from four intensively cropped arable fields, 19 month-old grass-clover ley strips in these fields, and from 3 adjacent permanent grasslands, effects on soil properties, and wheat yield in response to four-weeks of flood, drought, or ambient rain, during the stem elongation period were evaluated. Compared to arable soil, leys increased earthworm numbers, infiltration rates, macropore flow and saturated hydraulic conductivity, and reduced compaction (bulk density) resulting in improved
wheat yields by 42-95% under flood and ambient conditions. The leys showed incomplete recovery compared to permanent grassland soil, with modest gains in soil organic carbon, total nitrogen, water-holding capacity, and grain yield under drought that were not significantly different ( P > 0.05) to the arable controls. Overall, grassclover
leys regenerate earthworm populations and reverse structural degradation of intensively cultivated arable soil, facilitating adoption of no-tillage arable cropping to break out of the cycle of tillage-driven soil degradation.The substantial improvements in hydrological functioning by leys will help to deliver reduced flood and water pollution risks, potentially justifying payments for these ecosystem services, especially as over longer periods, leys increase soil carbon sequestration.
Exploitation Route We will run events with farmers and policy-makers via iCASP to help maximize impacts. Essentially, the results show how crucial hedgerows are and that they need further enhancement and protection to support soil systems and agricultural resilience. Leys are also highly beneficial and we need enhanced upscaling of effort to use leys in arable farming.
Sectors Agriculture, Food and Drink,Environment

Description The results are informing the debates on rural payments and public goods from agriculture. The research contributed to our response to government consultations on soil health and soil health metrics. It also contributed to an evidence review of the impacts of land management on soil health for public goods.
First Year Of Impact 2018
Sector Agriculture, Food and Drink,Environment
Impact Types Policy & public services

Description Improving the evidence-base for hedgerow planting to contribute to UK net zero target
Amount £27,870 (GBP)
Organisation United Kingdom Research and Innovation 
Department Research England
Sector Public
Country United Kingdom
Start 12/2021 
End 03/2022
Description Collaboration with NIAB 
Organisation National Institute of Agronomy and Botany (NIAB)
Country United Kingdom 
Sector Academic/University 
PI Contribution Use of the NERC-funded specialist plot harvester and research collaboration
Collaborator Contribution Partners signed an agreement over 2 years with a further 2 year extension in 2021. Some elements are commercially confidential.
Impact Funding, shared resource use, shared use of land/field plots.
Start Year 2018
Description BBC Radio York, Yorkshire Farming Science Special, October 2016 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact One hour BBC radio broadcast focused on the project, outlining the research aims, methods, teams, and findings and its regional and wider importance. The broadcast was recorded at the field site with different project team members.
Year(s) Of Engagement Activity 2016
Description Defra strategy advisor visited study site (University of Leeds farm) to discuss research results 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Direct engagement with senior policy advisor from Defra to discuss project results and potential policy implications
Year(s) Of Engagement Activity 2018
Description Field meeting with company 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Meeting with company directors - 'Environment and Business' interested in developing a carbon market for enhancing soil carbon. In particular we discussed how our research could influence the business model and how CSR schemes and carbon offsetting schemes could be used to fund soil carbon initiatives.
Year(s) Of Engagement Activity 2018
Description Soil security programme final conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation, poster and discussions at an event aimed at policy and practice community interested in soils and farming.
Year(s) Of Engagement Activity 2020
Description Stakeholder advsiory meeting, May 2016 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Day long stakeholder advisory meeting with site visits. Involved industry and farm practitioners
Year(s) Of Engagement Activity 2016
Description Workshop with stakeholders 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Workshop with stakeholders to discuss project, show them the site, get feedback on the science and potential impacts
Year(s) Of Engagement Activity 2015