Devon and Cornwall Soils Alliance Colebrooke – Business Case
John Morgan
December 2021
©Lewis Clarke (CC BY-SA 2.0)1. Introduction
The following report provides a brief business case overview of the findings from the feasibility study area, which is one of nine across the Devon and Cornwall region funded by the Water Environment Grant (WEG). These waterbodies fail the WFD for sediment related issues and these business cases provide evidence as to type and location of soil and sediment issues, degree of farm advice and grant required to support business, regulatory issues/failings and whether current farming practices within the catchment are aligned with inherent land capability.
2. Colebrooke
2.1 Background
The Colebrooke catchment is a mixed farmed catchment in central Mid Devon, to the north east of Exeter, it is approximately 2210ha (Figure 1) and feeds into the River Creedy. The catchment has two distinct soil types both of which are vulnerable to soil erosion and or soil wash if soil structure is damaged and infiltration rates compromised
2.2 Deskbased study
A comprehensive data pack was provided as reference material from the project managers. Content included information on soil type and hydrology, geology, geography, recent crop use, habitats, Natural Capital assumptions, landownership, water condition plus more.
Usefulness in terms of valuable area specific detail, of what was a very comprehensive pack, varied between sections. Soil type, soil area composition, soil area hydrology and catchment geology proved very accurate and very useful.
The CEH Natural Capital maps, being generated by modelling based on limited sampling, and for 1 km squares, were of too large a scale to be of significant use.
The Land Ownership map, via RPA CLAD database, proved particularly interesting and accurate when combined with local knowledge. The land cover and crops maps lacked sufficient detail, being too blocky and pixelated to be of specific field/ farm reference.
River Condition data provided by the Environment Agency (EA) was useful in that it allowed targeting of wet weather walk overs. Key farmer land use changes have taken place since this (2016) river condition data set was completed, which meant this was not as useful as it could have been if it were more up to date.
Key soil pressures identified by the desk research include the growing of risky arable crops on relatively high risk (soil type, soil hydrology & degree of slope) land.
2.3 Literature summary
Desk based research, and local knowledge of the physical catchment and land managers plays an important role at the start of any catchment focused project. Having exhausted the potential of desk-based research, on the ground field work of the current land use and management is the next, and vitally important, step in the process to get a full and current picture.
In addition to the data pack provided by project managers additional literature was referenced to learn as much about the catchment as possible pre commencement of wet weather walkovers.
Data considered included:
- Magic Maps for:
- Environmental priority status;
- Stewardship scheme target areas and existing agreements;
- Ordnance survey maps:
- Contour maps, water course mapping, national footpath/rights of way network routes;
- Soils Scape – Online app providing soil series information alongside physical soil, drainage and cropping information.
2.4 Fieldwork findings
Several farms are thought to be impacting the whole catchment, but these were evenly distributed across the area. Soil erosion and to a lesser extent soil wash, resulting from overland flow from autumn cultivated winter cereal crops, is the originating land use for most issues. Poaching of grassland and run off from infrastructural tracks, both public and private, also resulted in soil entering the surface water.
One hundred percent of the maize stubbles in the catchment had been actively managed to reduce the loss of sediment to the water environment. Post-harvest management of maize stubbles ranged from cross field cultivation strips to post harvest new crop establishment.
Walkovers during January identified infrastructure soil loss issues where machinery, field tipping organic manure and or collecting round bales from field heaps, was causing gateway and country lane verge soil structure damage. The Soil Mentor estimated that 70% of the observed issues were the result of sediment laden runoff leaving arable fields as a result of limited ground cover and large field sizes. While 15% of the issues were observed were associated with grassland poaching and the remaining 15% were associated with private and public infrastructure including tracks and country lanes.
2.5 Regulation
The Soil Mentor was asked a series of questions that related to the issues and failings they observed in the catchment. These questions and the Soil Mentor’s responses are outlined in (Table 1).
In the Colebrooke catchment the Soil Mentor estimated that between 51-75% of the observed issues were classed as regulatory failings, this was similar in the majority of the catchments. The Soil Mentor suggested that all of the issues could be improved with better enforcement of the current regulations (Table 1).
Of the issues highlighted in the feasibility report, what percentage of these issues would be classed as regulatory failings? E.g. SSAFO, FRFW, X compliance. Please note, this is for the % of issues highlighted, not the % of the whole catchment?
Would better enforcement of current regulations such as FRFW, X-compliance, NVZ work towards improving the issues highlighted?
2.6 Land capability and landuse type
According to the Soil Mentor there was some evidence that the farming practices were not aligned with the land capability. There are probably four farms that are overstocked and whose business model has little room for change. Maize cultivation although greatly reduced still continues to impact on soil loss.
2.7 Solutions and recommendations
In addition to improved regulation, the Soil Mentor also suggested the following land management measures:
- Reduce the area of autumn established winter cereal cropping – Less bare soil in vulnerable high rainfall autumn months;
- Reduced levels of soil structure ‘busting’, cultivation when establishing autumn sown crops;
- Reduced machinery instigated, compaction associated with infield tractor movement in high-risk autumn months;
- Reduced field size, either via permanently or temporary barriers both in arable and grassland fields;
- Increasing the physical, permanent, distance between cultivated soil and surface water;
- Stop the infield movement of tractors during high-risk winter months.
2.8 Estimated cost of remediation
The approximate costs of addressing the pollution issues in the catchment are shown in Table 2
Recommendation
Within catchment soil management advice should be provided by a local, experienced, known/respected advisor
Within catchment farm business advice should be provided by a local experienced, known/respected advisor.
Estimated cost
£10,000 per year
£10,000
Capital infrastructure Hedge creation – up to £120,000
Field Stores for manure
Up to £108,000
Total cost approx £288k (Medium) based on a 3 year project
2.9 Risks and barriers associated with solutions
No risks associated with the approach outlined above identified were listed by the Soil Mentor.
2.10 Benefits of change
Reducing the volumes of sediment entering the stream would deliver several and significant benefits including:
- Increased levels of, in field, agricultural top soil retention will maintain and possibly improve land crop/grass output. Improve output per unit of land is seen as a key performance indicator for land managers keen to dilute the relatively fixed/sunk costs (seed, cultivations etc) associated with managing agricultural land;
- Reduced sedimentation of stream and river beds is likely to result in improved waterway bed fauna biodiversity;
- Less agricultural, field derived sediment, will reduce the levels of nutrient (particularly phosphorus) entering the water way. Less phosphorus means lower risk of eutrophication and a more ‘natural’ biodiverse surface water ecosystem;
- Less agricultural field derived sediment and overland flow will reduce the risk of agrochemicals including herbicides, pesticides and fungicides entering the watercourse. Less agrochemical within the water course is likely to result in a diverse flora and fauna ecosystem;
- Improved water quality and increased biodiversity is likely to increase local fish populations. Improved fish populations deliver the benefit of improved fishing both in terms of recreational activity and financial enterprise.
Specific, direct and objectively identified payback for water quality improvement is a challenge to financially quantify however the reduced cost of water treatment and impact on an improved fishery could both be costed. Increased water course biodiversity can also be quantified via pre- and post-improvement program assessment. Improved watercourse biodiversity could/should be viewed as a public good and as such could/should be rewarded in future central support funding.
2.11 Lessons learnt
The feasibility study highlighted the stark reality that commercial, food producing agriculture, is likely to be harmful to the environment. The challenge for land mangers is to limit negative impacts on the environment to a level that is within the law and does not impact on environmental sustainability.
The more intrusive the land management the greater the risk of soil erosion and or overland flow the greater the risk of significant surface water economic and environmental damage.
More grass and less arable cropping in this relatively high-risk catchment would reduce the sedimentation issues in the catchment.
Increased uptake of grass-based livestock systems should be encouraged particularly in the higher risk areas of the catchment.