Appendix 3. Workshop Report on Diffuse Agricultural Pollution Mitigation Methods

Appendix 3. Workshop Report on Diffuse Agricultural Pollution Mitigation Methods:

Multi-pollutant treatment of agricultural runoff by buffer zones, bioreactors, ditches and ponds. 25th -26th September 2012

Context of workshop

In order to reach the target ecological status for EU waters as outlined in the Water Framework Directive (WFD) (2000/60/EC), a major requirement is the reduction or mitigation of diffuse water pollution from agriculture (DWPA).Measures to mitigate DWPA can be broadly divided into four groups:

Measures to improve facilities and infrastructure to reduce the risk of pollutant losses from sources to the environment: e.g. separating clean and dirty water, increasing slurry storage capacity
Measures to reduce the mobilisation and transport of pollutants e.g. improving soil structure.
Measures that reduce the intensity of farming in high risk areas: range from reducing fertiliser application to changing land use e.g. arable reversion to grassland.
Measures to trap or process/transform pollutants at the edge of field: buffer strips, sediment traps, ponds and wetlands.

The DWPA measures have been identified in a User Manual (Newell-Price, J. P., D. Harris, et al. (2011) which is adatabase of 83 mitigation options that have been divided into 7 main categories based on land use, soil management, crop and livestock breeding, fertiliser management, livestock management, manure management and infrastructure. Assessment of the effectiveness of the methods has been determined from evidence, output from models and expert opinion.

In September 2012 Rothamsted Research, North Wyke hosted a 2 day Defra sponsored workshop (supporting project WQ1026), with the aim of addressing methods of mitigating diffuse pollution from agriculture. The main objective of the workshop was to bring together leading scientists, policy makers, advisors and catchment practitioners from the UK and overseas to further our understanding of a range of diffuse water pollution mitigation techniques, different methods of implementation and different policy approaches with a particular emphasis on edge-of-field methods.

The workshop was split into 3 main, themed sessions:

1.Reviewing the current evidence base for mitigation methods.

2.Putting mitigation measures into practice.

3.Wider implications of mitigation strategies for multiple pollutants.

Each session began with presentations from keynote speakers who set the scene for the rest of the session which consisted of a series of presentations on detailed studies followed by a general discussion.

On day two, the delegates were asked to attend one of two chaired breakout sessions titled:

1.Approaches to catchment management and tools – CSF, SuDS, Rivers Trusts, Farmscoper – what else is required and how can it be developed?

2.Evidence base/empirical studies – assessment of approaches to reviews, and what more is required?

Dan McGonigle (Defra) set the background to the workshop with an outline of ministerial priorities that are: to improve productivity and competitiveness of food and farming businesses with better environmental performance, to negotiate a smaller, simpler, greener Common Agricultural Policy, and to adopt a proportionate approach to regulation..

At present 27% of water bodies are at good ecological status.However, ~40% are at risk due to agriculture which occupies 70% of the UK land area. This contributes ~55% of nitrate, 20% of phosphorusand 75% of sediments in water bodies and has an impact on ecology and public water supply. In addition, microbes cause bathing and shellfish water failure in some parts of the country leading to health risk and economic impact. Agriculture is also a significant source of ammonia and greenhouse gases. The challenge is to be able to reduce the impact of diffuse pollution to achieve WFD goals by 2015 (and 2021/ 2027)whilst increasing food production and competitiveness of farming.

Some key issues on edge-of-field mitigation that wereaddressedduring the workshop include:

How couldagri-environment schemes be better designed to get more out of measures?

Which measures are best/appropriate and where should they be used?

What steps should a farmer or advisor take in designing and targeting these types of measure?

Can they be designed and managed to provide multi-functional/ecosystem service benefits?

What maintenance of the measures is required for pollutant control and for other ecosystem services?

What are the knowledge gaps and what are the potential areas for future development?

Session 1:Reviewing the current evidence base for mitigation methods

The objectives for Session 1 were to explore evidence on:

How effective are edge-of-field measures and what works well?

What are the gaps in our knowledge?

What needs to be done to address these gaps?

Emerging technologies and approaches?

Keynote Speakers:

Phil Haygarth (Lancaster University). Overview of diffuse pollution to surface waters and the range of edge of field mitigation measures.

Take home message: Important to be mindful of mitigation across transfer continuum: Source –Mobilisation – Transport – Impact.

Marc Stutter (James Hutton Institute). Riparian buffers: Realising their multiple benefits in managed landscapes.

Take home message: Multiple benefits of buffers – requires design and management input.

Adrian Collins (ADAS). Sediment trapping by riparian buffer strips: field, landscape and aquatic biology perspectives.

Take home message: Sediment trapping efficacy should be considered alongside relationship with ecological impact e.g. what is trapped, not how much – quality not quantity.

Detailed Studies

Jane Hawkins (Rothamsted Research). Modular approaches to the control of diffuse agricultural pollution: buffer zones, subsurface permeable reactive barriers, ditches and ponds.

Tegan Darch and Alison Carswell (Rothamsted Research, Lancaster University, Reading University). Retention of nitrogen and phosphorus forms in buffer strip soils: Impact of slope and hydrological pathways.

Joshua Thompson (Agri-Food and Biosciences Institute). Dynamics of hydrological connectivity and nutrient loss – implications for mitigation measures.

Will Roberts (Lancaster University). Phosphorus retention and remobilisation in riparian vegetated buffer strip soils.

Martin Blackwell (Rothamsted Research). Phosphorus saturation in riparian buffer strips.

MaryOckenden (Lancaster University). Sediment and nutrient trapping in field wetlands.

Tristan Ibrahim (Teagasc). Achievement of an N blockade in denitrifying bioreactors.

Key points raised during discussion on evidence base gaps and opportunities.

Should edge-of-field mitigation be a last resort or a standard requirement? It was agreed that they shouldn’t be the last resort and that they should be considered as part of a suite of methods that includes methods aimed at pollutant source and mobilisation such as in-field mitigation.

Targeted approach versus blanket approach?Edge-of-field mitigation methods need to be site specific.

There is still uncertainty over buffer performance, and so need to ‘sell’ them as multi-functional measures within a wider suite of mitigation measures.

Buffers require management – more flexible approaches e.g. varying width depending upon crops.

Role of plough furrows at leading edge of buffers – these can be efficient for removal of sediment but will only be effective in arable situations.

Evidence base is good so need to start implementing edge-of-field mitigation methods more widely.

Although, there is a wide range in reported performance efficiencies on mitigation methods, as long as the methods are removing pollutants then we should accept these differences and shouldn’t become obsessive about disagreement in efficiency values.

Sessions 2 and 3: Putting Mitigation Methods into Practice and Wider Implications of Mitigation Strategies for Multiple Pollutants.

Objectives

The objective of sessions 2 and 3 was to demonstrate examples and case studies of mitigation approaches.

Keynote Speakers:

Dylan Bright (Westcountry Rivers Trust). The WRT approach to water quality improvement.

Take home message: Recognise the point on the diminishing return curve at which uncertainty over environmental response prevents wholesale action. Could we agree some no-regrets regulations? Could we agree some no regrets incentives?

Brian Chambers (ADAS).Mitigation Methods – User Guide

Take home message: Mitigation Methods User guide is the Science-evidence base underpinning the FARMSCOPER tool. It’s a living and evolving document (production efficiency). New methods added/existing ones enhanced in light of ongoing R&D.

Detailed Studies Presented:

Jamie Letts (Environment Agency). Sustainable rural drainage systems – slow, store and filter.

James Grischieff (Natural England). Targeting and delivery of DWPA projects through Catchment Sensitive Farming across 74 catchments (and counting) in England.

Juliette Hall (Environment Agency). How do we know that the Catchment Sensitive Farming project actually works? Evidence for success.

Richard Gooday. Application of Farmscoper for the assessment of Environment Stewardship options.

Martyn Silgram (ADAS). In-field mitigation methods.

Report from breakout sessions

Session 1: Approaches to catchment management and tools – CSF, SuDS, Rivers Trusts, Farmscoper – what else is required and how can it be developed?

Contributors:

McGonigle (Lead facilitator), Blackwell, Hawkins, Young, Doody, Bryburgh,Carson, Gönczi,Grischeff, Stoate, Habibiandehkordi, Freer, Thomas, Gooday, Ibrahim, Ockenden, Vargas, Jones, Williams, Allingham, Greipsland, Darch, Stutter, Payne.

The breakout session began with chair Dan McGonigle (Defra) expressing an interest in developing as an output a ‘rules of thumb-quick guide’ to edge-of-field approaches to mitigating DWPA. Below is the output of the breakout session and a possible outline for an edge-of-field quick guide. The outline is amended using comments from session participants.

1. Context

The edge-of-field quick guide should be placed in the broader context of:

Providing a clear message on the role of edge-of-field measures for control of either DWPA or habitat creation.
Being part of a broader suite of methods (e.g. In-field methods, reduced inputs, etc.) Not last resort.
The multiple benefits of edge-of-field measures (e.g. water temperature, water storage, stream habitat, connectivity, wildlife habitat).
The ‘equivalent effectiveness’ concept of edge-of-field methods e.g. an Xm wide buffer strip is equivalent to the implementation of other user manual methods aimed at source, mobilisation and transport points in the continuum. This approach could provide an incentive to choose more ‘upstream’ measures instead of ‘losing land’ to buffer strip creation.
Many measures will constitute ‘no regrets’ actions justified by the precautionary approach in the face of uncertainty.
The suite of relevant legislative drivers within both EU and UK directives.

2. Targeting

Edge-of-field methods should consider a number of site specific factors and draw upon information from a range of tools.

Key factors (examples):

The pressure/impact context i.e. Pollutant pressure/impact/other objectives e.g.biodiversity
Slope
Soil type
Land use
Field-level drainage patterns, soil moisture
Functional (event driven) versus structural (intrinsic) connectivity at relevant scales
Macro (watershed) versus micro (field) scale processes

Tools (examples):

SCIMAP
Google earth
Cost 869 – useful info
Existing Natural England guidance
Hydrology models
Farmscoper

3. Measure selection and design

The selection of measures should consider the pressure(s) to be mitigated.

Pressure-measure combinations (suggested examples):

Sediment-edge-of-field buffer strips (width site specific, accommodate ‘mower run width’).
Nutrients - edge-of-field wetlands, SUDS, wetlands, ponds (buffer strips may be ineffective in drained fields).
Pesticides (there was no consensus on the best measure(s) though woodlands, wetland and bio-beds all mentioned).
Biodiversity – depends on location, consider ecological networks.

Complementary measures (examples):

Aim for win:win situation.
Filter fences.
In-field strips/hedgerows.
Tree planting <=50% of riverbank.
Ditches (for both in and edge-of-field ditches there is a need to consider cleaning costs).
3-D structure.

4. Edge-of-field measure management

A number of technical issues need to be considered during the establishment and maintenance of edge-of-field mitigation measures:

Need to be site specific.

Need to define exact purpose of the feature especially in the case of buffer strips.i.e. pollutant mitigation or habitat creation.
Best practice for establishment of different measure(s).
The measure may need to be crop specific (i.e. different buffer widths for different crop types).
The timing of establishment and maintenance activities.
Grazing/mowing schedules (‘product’ can be used as ‘green fertilizer’ and return nutrients to production chain). Cut only 50% buffer width (front or back) per annum. Encourages tillering and control of injurious weeds whilst leaving habitat areas. Use off-take for bioenergy.
Species selection (rough stalk grasses, wild flowers, tussock species). See NE guidance documents.Need more info on use of trees, willow etc.
Periodic trampling of buffer herbage to create vertical habitat heterogeneity. Though need to be mindful of not causing compaction and addition of nutrients from animal excreta which could be detrimental to pollutant mitigation.

Session 2: Evidence base/empirical studies – assessment of approaches to reviews, and what more is required?

Contributors:

Chambers (Lead facilitator), Chadwick, Granger, Boye, Letts, Ramwell, Thompson, Norton, Hall, Roberts, Pilbeam, Hayes, Aller, Harris, Barry, Carswell, Peukert, Collins, Silgram.

A number of interesting topics were discussed in the session which also constituted evidence gaps. Initially, buffer strips were discussed and there was a discussion about more general aspects of mitigation.

Buffer strips

Targeted or blanket use? The group decided that targeted may be the best approach.
One aspect of an overall plan (how do they fit in with source and mobilisation mitigation methods?).
How do they interact with other mitigation methods? For example, would minimum tillage also improve buffer strip effectiveness?
Wording important of what we are trying to achieve.
How effective are buffer strips on grassland?Also how to deal with compaction problems and other grassland specific problems.
Failures e.g. concentrated flow paths etc. Fact sheet requiredto help farmers identify potential problems?
Buffer management.It is clear that buffer strips will require some sort of management to maximise the benefits they are intended to provide. Yet there is minimal evidence on the effectiveness of management practices. Management may come under general up-keep practices, for example, maintenance of perimeter fences and/or management practices that are more targeted, for example removal of vegetation to reduce nutrient status (general management/upkeepand specific management).
Multi-functionality. If a buffer strip is likely to function poorly for diffuse pollution mitigation it may still be justified to implement a buffer strip based on perceived biodiversity benefits (may imply a blanket approach). It is also not clear whether buffer strips can simultaneously provide both diffuse pollution mitigation and biodiversity benefits and whether targeted management practices for each would go hand-in-hand (is poor mitigation function offset by biodiversity benefits?).
Vegetation types. It is not clear what vegetation types can be used to alter the physical and biochemical soil properties that help to maximise diffuse pollution mitigation. For example, can plants with a certainroot structure that increases soil porosity be used to encourage infiltration?

General

Linking pollutant reduction to stream ecological quality? There is currently evidence from plot scale studies that incorporate source, mobilisation and delivery processes that mitigation measures can be effective. There is an evidence gap as these studies end at delivery and don’t incorporate impacts. Would a nutrient load reduction to stream actually result in an improvement in aquatic ecological quality and if so would there be a lag time associated with it?
Reducing diffuse pollution whilst increasing crop yields? There is little evidence that the two are compatible. Very important as maintaining or even increasing crops yields is a key aim of the farmer and shouldn’t be compromised.
Evidence for local pollution problems required. This would help us to gain a more integrated view of the contribution of local scale problems to catchment scale water quality and also to demonstrate to farmers that their practices can impact water quality.
Mitigation options need to be customised to specific areas/problems. Links to the above and the point about targeted approach.
Increase focus on in-field options?

Where are pollutants coming from?Source apportionment and fingerprinting techniques required.
Cost for complex measures?
FIO’s – on steep slopes use of sheep?
Fencing/access to watercourse? Management.
ELS:- Spreading techniques?
- Grassland compaction alleviation?
Mapping against WFD failure – CSF doing some work.

Overall Discussion –what more is needed?

The multi-disciplined nature of the workshop has been useful for developing communication between ecologists and water scientists and this needs encouraging and developing further in order to identify and improve multi-benefits from mitigation methods.
It was agreed that more workshops that focus on other areas of the pollutant transfer continuum such as source, mobilisation and transport would be beneficial.

It would be beneficial to link the User Guide to an Integrated Action Plan (IAP).

Advisors and 1 to1 advice for farmers/land managers.
Simple advice for implementation using appropriate language.
Access to risk based information for land managers and decision makers.

Possible Outputs from the workshop

We propose to:

Develop evidence based guidance for the selection and targeting of appropriate edge-of-field mitigation measures e.g. A Step-by-step guide for farmers, land managers, CSF officers, Rivers Trusts and catchment managers.

Provide a technical advice note on the use and management of buffers in standard format.

Delegate List

Delegate / Organisation / e-mail
Mr Paul Allen / Natural England /
Dr Kate Allingham / Natural England /
Miss Maria-Fernanda Aller / Promar International Ltd /
Mr Chris Barry / Agri-Food & Biosciences Institute /
Dr Martin Blackwell / Rothamsted Research /
Dr Kristin Boye / Swedish University of Agriculture /
Dr Dylan Bright / Westcountry Rivers Trust /
Mr Cliff Carson / Middle Level Commissioners /
Miss Alison Carswell / Rothamsted Research/University of Reading /
Dr Dave Chadwick / Rothamsted Research /
Prof Brian Chambers / ADAS /
Prof Adrian Collins / ADAS /
Mr Paul Cottington / National Farmers Union /
Miss Tegan Darch / Rothamsted Research /
Dr Donnacha Doody / Agri-Food & Biosciences Institute /
Mr Will Dryburgh / Scottish Environment Protection Agency /
Ms Deborah Elton / Forestry Commission /
Mr Adam Freer / Lancaster Environment Centre /
Ms Mikaela Gönczi / Swedish University of Agricultural Sciences /
Dr Richard Gooday / ADAS /
Dr Steven Granger / Rothamsted Research /
Miss Inga Greipsland / Bioforsk /
Mr James Grischeff / Natural England /
Mr Reza Habibiandehkordi / Lancaster University /
Mrs Juliette Hall / Environment Agency /
Prof Bob Harris / Defra /
Dr Jane Hawkins / Rothamsted Research /
Mr Roy Hayes / Natural England /
Prof Phil Haygarth / Lancaster University /
Mr Tristan Ibrahim / Teagasc Environment Research Centre /
Ms Sarah Jones / Natural England /
Mr James Letts / Environment Agency /
Mr Dan McGonigle / Defra /
Dr Lisa Norton / CEH /
Dr Mary Ockenden / Lancaster University /
Mr Michael Payne / rep National Farmers Union /
Mrs LizbePilbeam / Natural England /
Dr Carmel Ramwell / FERA /
Mr Will Roberts / Lancaster University and James Hutton Institute /
Dr Stephen Roderick / Rural Business School Duchy College /
Dr Martyn Silgram / ADAS /
Dr Chris Stoate / Game & Wildlife Conservation Trust /
Dr Marc Stutter / James Hutton Institute /
Mr Bryn Thomas / Natural England /
Mr Joshua Thompson / Agri-Food and Biosciences Institute /
Mr Frank Vargas / RSPB /
Miss Jodene Williams / Natural England /
Mr Kyle A Young / Environment Agency Wales /

References