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Department for Environment, Food and Rural Affairs CSG 15
Research and Development
Final Project Report
(Not to be used for LINK projects)
Two hard copies of this form should be returned to:Research Policy and International Division, Final Reports Unit
DEFRA, Area 301
Cromwell House, Dean Stanley Street, London, SW1P 3JH.
An electronic version should be e-mailed to
Project title / Reviewing the Potential for Reductions of Nitrogen and Phosphorus Inputs in Current Farm Systems
DEFRA project code / ES0201
Contractor organisation and location / Soil Science and Environmental Quality Team
Institute of Grassland and Environmental Research
North Wyke Research Station
Okehampton
Devon
Total DEFRA project costs / £ 77,000
Project start date / 01/07/04 / Project end date / 1 Oct 2004
Executive summary (maximum 2 sides A4)
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CSG 15 (Rev. 6/02) 3
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/ DEFRA
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This project was commissioned to support the Defra/HMT consultation ‘Developing Measures to Promote Catchment Sensitive Farming’, which considers whether achieving water quality targets will require action to address farm inputs. The specific purpose of the project was to review existing knowledge of:
1. the scope for reductions of nitrogen and phosphorus inputs within existing farm systems;
2. the potential role of reducing inputs in relation to other mitigation measures;
3. the extent to which measures to reduce nutrient emissions from agriculture are required in different areas of the UK.
It can be concluded that long-term monitoring records, export coefficient modelling and palaeolimnological studies all indicate that nutrient concentrations in UK freshwaters are greatly elevated above natural levels and this has had a considerable effect on their ecology, particularly in the last 50 years. Less impacted sites predominate in less agriculturally intensive (and less populated) landscapes, particularly Cumbria and the Scottish Highlands and Islands. Central/Southern England, Northern Ireland, lowland Wales and Central and Eastern Scotland are generally impacted much more severely.
The main N and P farm inputs are as feed and fertiliser. Farm surveys show that there is a wide range of feed and fertiliser management practices on farms so that it is impossible to generalise. Statistical and anecdotal evidence shows that many farms are adopting best practice (e.g. managing manure effectively, planning fertiliser recommendations, etc.), but a significant proportion of land managers need to improve practices and how these are targeted is the challenge.
Measures for decreasing N and P loss to water are generally well understood in concept, although there remains need for more controlled demonstration of these methods in action to support technology transfer activities. This review has demonstrated that:
1. There is scope for decreasing N and P inputs into some farming systems, but varies between systems.
2. The size of required reductions of N and P loss varies regionally and by farming system.
3. Source control is one method, but we also need to combine this with methods that control mobilisation and transport from soil to water. Nitrogen will probably respond quicker to source control whereas mobilisation and transport options may appear more feasible for P in the shorter term.
4. Required reductions may not always be achieved by changed management practices alone.
The time lag between changed practices and impacts on chemical water quality, and then on ecological quality could be tens or hundreds of years. Both input reduction and mobilisation and transport options should be implemented as soon as is practicable and politically acceptable in order to begin the process of water quality improvement.
CSG 15 (Rev. 6/02) 3
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Scientific report (maximum 20 sides A4)
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CSG 15 (Rev. 6/02) 3
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Reviewing the Potential for Reductions of Nitrogen and Phosphorus Inputs in Current Farm Systems
List of contributors
Phil Haygarth, David Scholefield, David Chadwick, Laura Cardenas and Patricia Butler
Institute of Grassland and Environmental Research, North Wyke Research Station, Okehampton, Devon, EX20 2SB, UK
Mark Shepherd, Gillian Goodlass, Paul Withers and Brian Chambers,
ADAS, Gleadthorpe Research Centre, Meden Vale, Mansfield, Notts., NG20 9PF
Eunice Lord, Bruce Cottrill, Ken Smith and David Harris,
ADAS, Woodthorne, Wergs Rd, Wolverhampton, WV6 8TQ
Robert Ferrier and Marc Stutter,
The Macaulay Institute, Craigiebuckler, Aberdeen, Scotland AB15 8QH
Laurence Carvalho
Centre for Ecology and Hydrology (Edinburgh), Bush Estate, Penicuik, EH26 0QB
John Anderson
Department of Geography, Loughborough University, Loughborough LE11 3TU.
Philip White
Warwick HRI, Wellesbourne, Warwick CV35 9EF
Steve Cuttle and Richard Dewhurst
Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion, SY23 3EB
Louise Heathwaite
Department of Geography, University of Sheffield, Sheffield, S10 2TN
Penny Johnes
Aquatic Environments Research Centre, School of Human and Environmental Sciences, University of Reading, Whiteknights, Reading, RG6 6AB
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A full version of this report has already been provided to Defra and approved (see Annex A for the full version) but here follows the executive summary.
Context and aims
The June 17th 2004 Defra/HMT consultation ‘Developing Measures to Promote Catchment Sensitive Farming’ is an output of Defra’s Strategic Review of Diffuse Water Pollution from Agriculture. It fulfils part of the commitment to consult formally on detailed proposals for action to control diffuse pollution. The consultation included consideration of whether achieving water quality targets will require action to address farm inputs as well as management practices, farm infrastructure and, possibly, land use. This is an important issue within the consultation. If a decision is made to address inputs, possible policy instruments for doing so could include: voluntary action by farmers and their suppliers; awareness raising, information and skills training; regulation; and economic instruments. Measures to address inputs would almost certainly be additional to instruments to address land management practices and farm infrastructure. They would probably be targeted at addressing inputs to the extent that this is more cost-effective than other approaches or is likely to provide additional benefits to water quality and aquatic ecologies.
This report was therefore commissioned to inform consideration of responses to issues within the consultation. Against this background, the review report was prepared during July-September 2004 and the specific purpose was to review existing knowledge of:
a) the scope for reductions of nitrogen and phosphorus inputs within existing farm systems;
b) the potential role of reducing inputs in relation to other mitigation measures;
c) the extent to which measures to reduce nutrient emissions from agriculture are required in different areas of the UK.
A way forward on where further research is needed is also provided.
The review was split into five aims and this executive summary is arranged according to those aims, plus a separate final conclusion section. Much of this executive summary is derived directly from the conclusions of the various sections from the main report.
Objective 1 To set the context and define the broad degree to which surface waters in different areas of the UK have nutrient levels which are above ‘natural’/’background’ levels likely to be consistent with healthy indigenous ecosystems.
1. Long-term monitoring records, export coefficient modelling and palaeolimnological studies all indicate that nutrient concentrations in UK freshwaters are greatly elevated above natural levels and this has had a considerable effect on their ecology, particularly in the last 50 years.
2. There are large regional differences in the degree to which lakes and rivers deviate from a ‘natural/background’ level, with less impacted sites predominating in less agriculturally-intensive (and less populated) landscapes, particularly Cumbria and the Scottish Highlands and Islands. Central/Southern England, Northern Ireland, lowland Wales and Central Scotland are generally impacted much more severely. Groundwater nutrient concentrations and their variability by region and over time are less well documented and this needs further work.
3. There are clear ecological effects of raised nutrient concentrations in both lakes and rivers, including:
· Increases in planktonic algae in lakes and slow-moving rivers
· Increases in filamentous algae e.g. Cladophora (blanket weed) in streams
· Changes in macrophyte communities to fast-growing, competitive (weedy) species particular impact on species or habitats of high conservation value e.g. mesotrophic lakes and water crowfoot (Ranunculus) cSAC rivers
· Impacts on fisheries, particularly economically important salmon rivers
4. The quantitative ecological response of individual waters to raised nutrient concentrations is, however, more uncertain and is partly mediated by their geoclimatic setting and land–use history as well as sensitivity factors such as flushing/flow regime. Much greater understanding of these sensitivity factors is required to enable more reliable predictions of likely ecological responses to and increase or decrease in nutrient loadings from the catchment.
5. The general regional pattern in ecological response does, however, reflect a broad regional split between the present day total phosphorus concentrations typically observed in upland and lowland waters. The greatest ecological change is observed in lowland regions in Northern Ireland and England where present-day nutrient concentrations are often well in excess of background or reference concentrations. Studies indicate that 36% (79) of the study lakes showed low floristic change, with the majority of these located in the uplands of Scotland (with a few sites in upland Wales and the English Lake District).
6. In these severely impacted regions, the extent of nutrient changes may be so great, that large reductions in nutrient loadings from catchments are likely to be needed before any ecological response is observed.
Objective 2 To describe and review nitrogen and phosphorus inputs into farming systems
1. The main inputs of N and P onto farms are as fertiliser and feedstuffs. Efficient management of both of these inputs needs skill and careful planning. Farm practice surveys suggest that there is scope for improvement.
2. Nationally, N & P surpluses have declined, suggesting a general reduction in N & P inputs. However, the average does not take account of regional/local situations, for example where there is a high density of livestock in a catchment.
3. Many of the problems of N and P surplus are associated with manure inputs. Therefore, the problem starts with feed imports on to farms, because feeding regimes are such that much of the N and P is not used by the animal and is excreted as manure. Improvements in efficiency of feed use are technically feasible but are not yet fully deployed, for a range of reasons.
4. Fertiliser statistics show that, on average, applications are in line with, or below, the recommended fertiliser rates. Clearly, this does not square with the increased losses observed over time. The average hides a lot of detail and it seems that in a significant proportion of farms:
· There is insufficient allowance made for nutrients supplied in manure.
· Crops are over fertilised.
· Autumn N is applied when not needed.
5. Further explanations of this are considered by Task 4 of this report. However, it should be noted that the above practices still continue despite technology transfer efforts over tens of years.
6. Intensive livestock units may have insufficient land to apply manure at acceptable rates, further compounding problems. On other farms, manure applications are often made to a limited number of fields (due to difficulty of access, proximity to houses etc.), thus some individual fields may receive excessive quantities.
7. Currently, legumes have a minor role. However, it may be that if restrictions are placed on other N & P sources, these will become more widely used in rotations. There is a nitrate leaching risk associated with their use.
Objective 3 To determine the list and describe options to reduce nitrogen and phosphorus inputs and determine if current recommendations for nitrogen and phosphorus inputs are too high
1. From the review, there would appear to be a growing mass of information showing the potential to reduce fertiliser and feed inputs of N and P, as well as utilising manure nutrients more effectively. However, it is also clear that uptake of some these measures will require a sustained campaign of knowledge transfer in order to convince land users that changes in management practice will maintain productivity, potentially reduce costs and ultimately benefit the environment.
2. Proof of effectiveness is even more important for the acceptance of measures that could have a negative impact on productivity or profit. For example, reducing N in the diet is an area where there is good research evidence showing its effectiveness at reducing N excretion without reducing milk output when reductions are balanced by other nutritional improvements (e.g. provision of sugar, starch or protected amino acids, as appropriate). However, the effectiveness of this approach could be much lower in real farm situations as a result of uncertainties about composition of concentrates and silage and differences in feed requirements of individual animals. There is, therefore, a need for on-farm trials and demonstration of effect.
3. Options to reduce nitrogen inputs include:
· Fertiliser management
· Nitrogen applications could be reduced by 20 kg ha-1 without influencing profitability on a range of crops.
· For grass, fertiliser inputs should be kept below 400 kg N ha-1 to minimise the relative increase in N leaching. However, most dairy, beef and sheep farmers do not use such high rates.
· On grass, N fertiliser inputs can be reduced by tactical approaches to fertilising, i.e. taking into account the soil mineral N supply throughout the growing season. This has been used to reduce N inputs by >25% and not influence productivity but decrease N leaching by >35%. There is a question over practicality of this approach on some soils.
· Use of ammonium based fertilisers in the spring will lead to a lower risk of fertiliser N transfers to water courses. Therefore, less fertiliser N is required to counter this risk. Also, there is evidence that ammonium-based fertilisers are used more efficiently by crops than nitrate-based fertilisers in cooler conditions, so again less would be required – but this will increase lime requirements in the long term.