The Environmental Impact of Livestock Production Review of Research and Literature February 2008

www.defra.gov.uk

Department for Environment, Food and Rural Affairs Nobel House 17 Smith Square London SW1P 3JR Telephone 020 7238 6000 Website: www.defra.gov.uk © Queen's Printer and Controller of HMSO 2007 This publication is value added. If you wish to re-use this material, please apply for a Click-Use Licence for value added material at: http://www.opsi.gov.uk/click-use/value-added-licence-information/index.htm. Alternatively applications can be sent to Office of Public Sector Information, Information Policy Team, St Clements House, 2-16 Colegate, Norwich NR3 1BQ; Fax: +44 (0)1603 723000; email: hmsolicensing@cabinet-office.x.gsi.gov.uk Information about this publication and copies are available from: Livestock and Livestock Products Hub Defra Area 5B, 9 Millbank c/o Nobel House 17 Smith Square London SW1P 3JR This document is available on the Defra website and has been produced for Defra by ADAS UK Ltd. Published by the Department for Environment, Food and Rural Affairs

Suggested citation for this report:

ADAS 2007: The Environmental Impact of Livestock Production. Report for Defra FFG.

The ADAS Team:

Kate PhillipsMartyn SilgramPaul Newell-PriceMichelle WerrettGill PoveyBruce CottrillJohn Newton.

With additional assistance from:

Mark ShepherdKen SmithNigel CritchleyBrian Chambers

Abbreviations used:

AONB – Area of Outstanding Natural BeautyBAP – Biodiversity Action PlanBOD – Biological Oxygen DemandCH4 – methaneCO2 – carbon dioxideEA – Environment AgencyFIO – faecal indicator organismFYM – farm yard manureGHG – greenhouse gasIPPC – Integrated Pollution Prevention and ControlN – nitrogenN2O – nitrous oxideNH3 – ammoniaNVZ – Nitrate Vulnerable ZoneSCOPS – Sustainable Control of Parasites in SheepTAN – Total ammoniacal nitrogen

Contents

Executive Summary 1

1. Introduction 51.1 Project Methodology 61.2 Background 61.3 Potential Impacts on Soil and Water 91.4 Potential Impacts on Air 101.5 Biodiversity and the Countryside 121.6 Valuing the Environment and Livestock Farming 14

2. Summary of Impacts – Dairy Farming Systems 152.1 Public Goods Delivered 152.2 Environmental Impacts of Dairy Farming Systems 152.3 Gaps in Knowledge and Future Research Needs (Dairy Farming) 20

3. Summary of Impacts – Beef Farming Systems 223.1 Public Goods Delivered 223.2 Environmental Impacts of Beef Farming Systems 233.3 Gaps in Knowledge and Future Research Needs (Beef Farming) 24

4. Summary of Impacts – Sheep Farming Systems 264.1 Public Goods Delivered 264.2 Environmental Impacts of Sheep Farming Systems 264.3 Gaps in Knowledge and Areas for Future Research 27

5. Summary of Impacts – Pig Farming Systems 295.1 Public Goods Delivered 295.2 Environmental Impacts of Pig Farming Systems 295.3 Gaps in Knowledge and Future Research Needs (Pig Farming) 32

6. Summary of Impacts – Poultry Farming Systems 336.1 Public Goods Delivered 336.2 Environmental Impacts of Poultry Farming Systems 336.3 Gaps in Knowledge and Future Research Needs (Poultry) 34

7. Overall Gaps in Knowledge Common to all Livestock Sectors 36

Contents – cont’d

8. Current Defra Funded Projects 37Dairy and Beef Cattle 37Pigs 37Sheep 37Poultry 38Livestock Manure 38Soil Erosion 38Veterinary Medicines 38Integrated Farm Management 38

Review of the Scientific Literature 40Appendix 1 – Environmental Impact of Dairy and Beef Farming 40

1.1 Soil 401.2 Water 451.3 Air 491.4 Biodiversity 53

Appendix 2 – Environmental Impact of Sheep Farming 592.1 Soil 592.2 Water 612.3 Air 612.4 Biodiversity 62

Appendix 3 – Environmental Impact of Pig Farming 663.1 Soil 663.2 Water 683.3 Air 693.4 Biodiversity 72

Appendix 4 – Environmental Impact of Poultry Farming 744.1 Soil 744.2 Water 764.3 Air 774.4 Strategies to Reduce Pollution From Poultry Systems 784.5 Biodiversity 79

References 80-96

TABLES

Table 1.1 – UK Agricultural Land by Use 5Table 1.2 – Population of Livestock in the UK, 2000 to 2006 7Table 1.3 – Output from the UK Livestock Industry (2006) 9Table 1.4 – Summary of 2005 Agricultural Methane Emissions 11Table 1.5 – Summary of 2005 Agricultural Nitrous Oxide Emissions 11

FIGURES

Figure 1.1 – UK Livestock Numbers per 100 km² for Poultry, Sheep, Cattleand Pigs.

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Figure A1.1 – The Probability of Grassland Poaching in Relation to theGrowing and Grazing Seasons, and Potential Transpiration

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Figure A1.2 – Typical N Content in Cattle Slurry and Potential NitrateLeaching Risk from Dairy Slurry and Old Cattle Farmyard Manure applied toa Sandy Soil in Different Months under Contrasting Annual RainfallConditions.

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Figure A3.1 – Typical Content of Pig Slurry; The Relative Risk of NitrateLeaching from Pig Slurry and Other Materials Applied to Two Clay Sites andthe Potential Nitrate Leaching Risk from Pig Slurry Applied to a Sandy Soilin Different Months under Contrasting Annual Rainfall Conditions.

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Figure A3.2 – Conventional Applications of Pig Slurry Using a Raingun andVia Broadcasting and Top dressing using a Boom. Strategies to ReduceAmmonia Volatilisation From Slurry Applications Include Open Slot ShallowInjection, Trailing Shoes and Trailing Hoses

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Figure A4.1 – Effect of Broiler Litter Application Rate on Topsoil AvailableWater Capacity (AWC) at Gleadthorpe (Spring 2001).

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Figure A4.2 – Nitrogen Leaching – Comparison Between Poultry Manureand FYM by Land Type and Time of Application. Data Collected Over 10Site Years.

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Executive Summary

The main domestic livestock sectors produce a wide range of products (food, leather, wooletc) and public services, such as employment, landscape and cultural heritage. Howeverlivestock production impacts on the environment in a variety of ways, both positive andnegative, but there are some systems where there is greater potential for the environment tobe compromised in order to achieve efficient production. The key is to minimise negativeimpacts in the most cost-effective way.

This work reviewed the scientific literature (and other unpublished research data) on theimpacts of livestock production on the environment and has highlighted gaps in knowledgeand areas for future research. The ‘back catalogue’ (King et al (2005) ES0127) was usedextensively to review relevant work undertaken between 1990 and 2005 and more recentwork was identified with help from Defra, ADAS specialists and other researchers. Thereview is divided into five sectors, dairy, beef, sheep, pigs and poultry and then by impact:soil, water, air and biodiversity. Sections 2 to 6 summarise the findings of the detailedliterature review in the appendices.

A workshop was held to consider gaps in knowledge and areas for future research, andrepresentatives from Defra, EBLEX, BPEX and ADAS were present.

The key findings of the review included:

1. The impacts of livestock on the environment are wide ranging. Extensive researchhas been dedicated to identifying the issues and developing techniques to limitnegative impacts. The majority of this research has been funded by GovernmentDepartments with responsibility for resource protection (particularly air and waterquality). More recently, there has been increased emphasis on assessing the cost-effectiveness and cost-benefit of mitigation methods for controlling diffuse pollutionfrom agriculture to support policy development (Cuttle et al 2006, Defra ProjectES0203, ES0121).

2. Many farmers are already managing their land in an environmentally beneficial waybut there are some considerable environmental challenges ahead, particularly inreducing air and water pollution (Nitrates Directive, Water Framework Directive).

3. The key issues identified for the more intensive sectors (dairy pigs and poultry)included loss of nutrients (nitrogen (N) and phosphorus (P)), sediment and microbialpathogens to water; gaseous emissions to air (especially ammonia, nitrous oxide andmethane); soil compaction and contamination. Most of the issues are associatedwith manure production, storage and handling. Mitigation methods are available toaddress many of the issues; however, the challenge remains to more effectivelyintegrate these into farm production systems with the capital costs of some mitigationmethods being a major barrier (AC0206).

4. Numbers of cattle, sheep and pigs in the UK have fallen in the last decade and thiswill have had a positive environmental benefit through reduced emissions to theenvironment. However If this decline continues, increased imports of meat and otheranimal products could simply export our environmental pollution elsewhere. The“environmental footprint” of home produced and imported animal products is currentlyan area of increased interest (Williams et al 2006).

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5. Reduced numbers of grazing animals will have a negative effect on many hill andupland areas with a high risk of undergrazing and loss of biodiversity (alreadyapparent in Scotland and hill areas of England) . The recent increase in the price ofcereals has persuaded farmers to plough up temporary grassland and cultivate theland for arable crops as this makes eminent economic sense where soil type andtopography is suitable. The loss of sheep and beef cattle in lowland areas will have adirect impact on the rural landscape close to many areas of dense population. Itremains to be seen how the public will react to these changes.

6. All livestock systems contribute positively to the environment by their addition ofnutrients to soils and indeed recycling of manures by well managed land spreading(as opposed to grazing animals) leads to better distribution of nutrients andpotentially a lower risk of nutrient leaching.

7. Systems of dairy production vary widely, but those that are able to effectively controlboth the level and quality of inputs would appear to be the most favourable from anenvironmental perspective. Zero grazing, where cows are housed all year (althoughnot always acceptable to the public from an animal welfare angle) gives significantcontrol, as opposed to ‘extended grazing’ systems that attempt to keep animalsoutside for much of the year and rely very heavily on grazed forage (Defra projectNT1902). However greater reliance on machinery has a negative impact.

8. Indoor pig and poultry systems provide good opportunity for control of inputs andoutputs and would seem to present lower risk than outdoor systems of production,whilst acknowledging public preference for ‘free-range’ eggs and pig meat. Outdoorpigs pose a significant challenge particularly in terms of soil erosion, but newresearch is already underway to develop mitigation methods (Defra project IS0215).

9. Little research has been conducted on the environmental impact of free range poultrywhere removal of vegetation and the creation of bare ground (close to the henhouse) lead to a higher risk of soil erosion and localised, heavy deposition of poultrymanure will increase the risk of leaching loss. The impact on biodiversity and localbird populations has not been studied.

10. For the less intensive sectors (beef cattle and sheep), manure handling andspreading is much less of an issue as farm yard manure, largely from straw beddedsystems, poses a much lower environmental risk than slurry. Grazing beef cattle andsheep are fundamental to the management of large areas of upland and hill land andcontribute significantly to the maintenance and enhancement of biodiversity, providedwinter grazing (where practised) is adequately managed (BD1228). Furtherdevelopment of integrated grazing systems, that deliver positive benefits to theenvironment, would seem to be the way forward with benefits to landscape,biodiversity and soil structure.

11. Extensive beef production, (when managed sympathetically with the environment)although generally inefficient in terms of nutrient use, has a very positiveenvironmental impact, both in terms of biodiversity and landscape. Intensive cerealbeef production in contrast, is very efficient in terms of nutrient use but adds little(apart from the recycling of nutrients in the form of farm yard manure) to theenvironment.

12. Sheep grazing is a key management tool for maintenance of many sensitive habitatsin upland and hill areas of the UK. Sheep are essential for the management andconservation of biodiversity (English Nature 2005). There are very few systems of

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sheep production that would have a significant negative impact on the environmentalthough winter grazing on forage crops can be high risk if poorly sited or in badweather conditions and high stocking rates on sensitive habitats can be detrimental(Milsom et al 2003)

13. Research across species needs to focus on more precise rationing of livestockaccording to age and sex and more accurate assessment of nutrient requirements.Better characterisation of feedstuffs and the use of feeds with higher levels ofavailable nutrients (or feed additives that help to achieve this) will help to improve theefficiency of conversion of feed into animal products. Excretion of surplus N, P andheavy metals (particularly zinc and copper) is then likely to be significantly reduced(e.g. Mateos et al 2005, Defra project SP0129).

14. Although many of the feed-related mitigation methods for reducing emissions bylivestock are well known, what is not known is the extent to which they have beenadopted by the livestock sector. Until we have this base-line information, we areunable to estimate possible reductions in emissions from known technologies(without having to rely on new research).

15. Mitigation strategies for the abatement of green house gas emissions and nutrientlosses to soil and water include management practices that are already accepted, butnot necessarily widely used. These methods require farmers to improve on currentpractice and usually should not require significant financial investment for example(see Defra project AC0206):

- Managing fertiliser (and manure) nutrient inputs to match crop requirements (usingRB209/PLANET), particularly relevant to intensive grassland systems (dairy andsome beef), poultry and pigs.

- Making full allowance of manure N supply (MANNER). - Good manure spreading practice, which includes selection of spreading rate,

machinery calibration (assessment of spreader load) and field application records;- Spreading manure at the appropriate time and under the right conditions.

Further mitigation might also be achieved by:

- Increasing the efficiency of nutrient use by livestock.- The adoption of anaerobic digestion technology for farm slurries has also been

proposed, but is a high cost approach and there is conflicting evidence about therisk of emissions of ammonia.

- Making use of improved genetic resources (e.g. more efficient animals and improvedplant breeding). Improved genetics across all species, but particularly cattle andsheep offers significant scope for improved efficiency in terms of nutrient use andperformance (fertility, longevity, resistance to disease etc) and reduced emissions.

16. Much progress has been made in developing new techniques of manure handling,better management of nutrients and improved handling and responsible use ofchemicals and veterinary medicines. However, it is not clear to what extent theindustry has taken up many of these techniques. There may also be difficulties intransferring the information to farmers in a relevant format that would encourageadoption of the most cost-effective techniques. There is a need to tailor knowledgetransfer to specific livestock sectors and a good example of this might be the ‘bestpractice guide for keeping pigs outdoors’ that will be the main outcome from the threeyear Defra project IS0215.

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17. The review has not taken into account the economic sustainability of the livestocksectors although it is acknowledged that many have severe financial constraints.Emphasis therefore needs to be placed on mitigation methods that are both simpleand cheap (and perhaps effective against several pollutants) if progress is to bemade in the short to medium term (Cuttle et al 2006, ES0121).

18. The public goods delivered by the livestock industry are difficult to value but ongoingresearch using the ‘Ecosystem services’ approach should help to resolve this in thefuture (MA).

19. The generic areas identified as gaps in existing knowledge can be grouped under thebroad titles of:

- More precise rationing and feeding – N and P supply in all species, feed additives(IS0208)

- Survey of feeding practices – to ascertain current base-line practices and guidefuture knowledge transfer

- Improved manure management systems – e.g. storage systems, applicationtechniques/timing

- Better use of improved crop and animal genetics- Integrated grazing systems – e.g. mixed grazing systems, wintering systems- Integrated nutrient management systems, taking an holistic approach (i.e.

considering feed inputs, storage and land spreading emissions to air and water) fromfeed through to the field.

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1. Introduction

UK farming contributed £5.6 billion to our economy in 2006, and employs about half a millionpeople. The total agricultural area in 2005 was 18.5 million hectares, some 77% of the totalland area of the UK. Agricultural land use in the UK is shown in Table 1.1.

Table 1.1 UK Agricultural Land by Use

Land Use Crops andbare fallow

Grass Roughgrazing

Set-aside Woodland andother land

Hectares (‘000) 4,490 7,204 5,732 513 874Percent 24% 38% 30% 3% 5%Defra:June 2006 Census.

Livestock production is an integral part of UK agriculture, and farming has shaped ourcountryside over centuries. It provides food in the form of basic commodities like milk, eggsand meat but also adds considerably to the landscape character and aesthetic value of ourcountryside. Farmers and their families form the backbone of many rural communities, andthe farmed landscape provides thousands of hectares of recreational land for people toenjoy. Domestic livestock play a fundamental part in many diverse ecosystems and providea rich genetic resource. The tourist industry for both UK and international visitors relies onthe landscape and diversity of the UK countryside.

The environmental impact of agriculture has been well documented over the years and muchresearch effort has been directed at minimising the negative impacts whilst trying to maintaina sustainable industry. The impacts are both positive and negative and vary from enhanced biodiversity andlandscape to potential for diffuse water pollution and greenhouse gas emissions. However, abalance needs to be struck between production of high quality, safe food, environmentalimpact and the public goods delivered by the industry in terms of agricultural produce and anenvironment for all to enjoy.

The strategic outcomes of the Sustainable Food and Farming Strategy include acommitment to improve the environmental performance of farming by:

• Reducing the environmental cost of the food chain,• Better use of natural resources,• Improved landscape and biodiversity.

The livestock sector has particular environmental challenges in dealing with manures (whichrepresent both valuable resources and potentially major sources of emissions to air andwater) and grazing to enhance biodiversity and maintain a desirable landscape.

The main aim of this report is to present the overall environmental impact of the livestocksectors on soil, air, water and biodiversity as evidenced by a wide variety of researchprojects carried out over the past two decades. The risk of potentially negative impacts tendsto increase with the intensity of production, while the positive impacts of livestock tend toincrease where inputs and stocking densities are in balance with outputs and with the abilityof soil and vegetation to support them. However a well managed, intensive system can have

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much less of an impact if the inputs and outputs are strictly controlled. For some systems oflivestock production, indoor operations offer greater opportunities for optimising the balancebetween inputs and outputs, thereby reducing waste. Also, increasing the intensity ofproduction means that inputs associated with the maintenance of livestock are spread overgreater output, and therefore emissions per unit of output (milk, meat or eggs) are reduced.

This project will support the Defra vision:

‘To develop a profitable and competitive domestic industry which enhances the biodiversityand rural landscape of England while minimising its impact on climate change, soil, waterand air quality. Such an industry will contribute to reducing the environmental footprint of ourfood production and consumption at home and abroad’.

This work will help to clarify the future role of the livestock industry in delivering public goods.

1.1 Project Methodology

The project has reviewed existing and on-going work that provides evidence on theenvironmental effects of the major sectors of the livestock industry (dairy, beef, sheep, pigs,eggs, and poultry meat). The reviewers concentrated on work carried out between 1990 and2007, and used the ‘back catalogue’ (King et al 2005 ES0127) extensively, as an initialsource of information.

The areas of environmental impact included in this work were:

• Soil - to include livestock manure recycling and heavy metal inputs.• Air - to include ammonia and greenhouse gas emissions.• Water - to include nutrient (i.e. nitrate, ammonium and phosphorus), oxygen depletion

and microbial pathogen pollution.• Biodiversity and landscape.

Once the scientific review was complete a seminar was organised (with representatives fromADAS, Defra, EBLEX and BPEX) to help identify the gaps in knowledge and areas for futureresearch.

The report is delivered in five sections by species, and by environmental impact. A summaryof the impacts, mitigation and gaps in knowledge is given in the main body of the text, insection 2, whilst the detailed scientific review is provided in the appendices (1-4).

1.2 Background

The population of the major livestock categories in the UK is shown in Table 1.2 and apictorial representation of livestock density across the UK is shown in Figure 1.

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Table 1.2 Population of Livestock in the UK, 2000 to 2006.

‘000 head 2000 2002 2004 2006Dairy Cows 2,336 2,227 2,129 2,066Beef Cows 1,842 1,657 1,739 1,733Breeding Ewes 20,448 17,630 17,664 16,637Breeding Sows 648 558 515 468Poultry Layers 29,895 28,778 29,662Poultry Broilers 105,689 105,137 119,912Defra June Census.

The drop in numbers of ruminants between 2000 and 2002 was mainly due to the 2001 Footand Mouth outbreak but for pigs this was due to swine fever in 2000, the outgoers schemeand then FMD. The table shows a steady decline in livestock numbers in the UK between2000 and 2006 (with the exception of poultry). As this decline continues there will be anincreasing impact on food supply and the landscape of the UK. The decline in pigs since2002 has been caused by wasting disease, increased costs of production (as a result ofdecreased output) and the influx of cheap imports.

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Figure 1.1 UK Livestock Numbers per 100 km2 for Poultry (top left), Sheep (top right),Cattle (bottom left) and Pigs (bottom right). Source: Government Census, 2004.

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The maps show clearly that pig production is now concentrated in the east of the country,whilst the density of sheep is particularly high in Wales and northern England. Cattle arewidespread but largely concentrated in the West. Poultry are more widely distributed acrossthe whole country but with relatively few in Wales and Scotland.

Areas of intense livestock production are associated with significant environmental risk (soilerosion, atmospheric emissions, diffuse water pollution etc) and farmers need to take everyprecaution to protect the local environment.

The UK livestock industry generated £7,351 m of output in 2006. Output by product isshown in Table 1.3.

Table 1.3 Output from the UK Livestock Industry (2006).

£m/year

MeatCattle 1,568Pigs 687Sheep 702Poultry 1,315Other animals 175

ProductsMilk 2,501Eggs 357Wool 16Other 30Total 7,351

1.3 Potential Impacts on Soil and Water

The forms of pollution of concern for livestock production systems include nitrogen (N),phosphorus (P) and organic nutrients as BOD; sediment; heavy metals used in feedsupplements; pathogens (measured as faecal indicator organisms - FIOs), and veterinarymedicines. It is estimated that agriculture accounts for around 60% of nitrate pollution and25% of phosphorus pollution in the water bodies of England. Pollution incidents aredeclining as farmers take on new legislation and adjust farming practices.

Environmental protection legislation includes the Nitrates Directive and Water FrameworkDirective, which limit nutrient enrichment of water bodies, in particular nitrate andphosphorus, the causes of eutrophication. Ecological thresholds of P in water bodies arevery low (ca. 100 µg/l) in relation to P application rates to land, and in comparison to the 50mg/l threshold for nitrate concentrations in drinking water, under the Nitrates Directive.Losses of N to water can be as much as 100 kg/ha from the most intensively managedgrassland systems, whereas losses of P are typically <2 kg/ha. Pathways of pollutant lossinclude surface runoff, and subsurface loss via drainage to groundwaters, and via lateralmovement (including tile and mole drains) to surface water systems. Specific aspects of the

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NVZ Action Programme are intended to reduce the risk of loss of N associated with livestockproduction.

Phosphorus (P) is predominantly associated with sediment, and the two should therefore beconsidered together in respect to their impacts on water quality (mean annual suspendedsediment concentrations of 25 µg/l are specified in the Freshwater Fish Directive). However,where soil phosphorus status is high, P may also be lost in solution.

FIOs include E. coli, viruses, and Cryptosporidium, and manure-borne pathogens can impacton bathing water quality and shellfish beds (EU Bathing Waters and Shellfish Directive E.colilimit 2000 cfu/100ml). Heavy metals (e.g. copper and zinc) in feed supplements, andveterinary medicines are associated with manures and slurries from grazing and housedanimals, and therefore the loss of these to the wider environment can have implications forsoil function and the chemical and ecological status of water bodies.

Nitrate leaching is governed by a combination of the magnitude of the nitrate pool originatingfrom all sources (i.e. fertiliser, atmospheric deposition, soil N reserves, and N deposited inapplied animal manures and slurries), and the risk of leaching (which is a function of soiltype, management, and weather conditions determining rainfall distribution and drainagevolumes). Research has shown clearly that nitrate leaching from grassland is related tolivestock N inputs (NT1902).

Around 90 million tonnes of manures (45% solid, 55% liquid) per year are generated as aresult of livestock production and require land application in the UK. Over 80% of thisoriginates from dairy and beef systems. Livestock manures are applied to 16% of UK tilledland and 48% of the UK grassland. The management of this manure therefore has a stronginfluence on the magnitude of the N, P and pathogens vulnerable to loss to water systemsvia drainage or surface runoff. In contrast, although grazing and outdoor animals alsorepresent potential sources of nitrate leaching, the risk of such transfers is generally smaller(e.g. concentrations of < 2.5 mg/l in drainage waters from grazed grass in Rowden (IGERexperimental site in Devon) receiving up to 400 kg N/ha (NT1902)) unless there are summerstorms or there is direct access of livestock to streams.

Although much of the research has focused on the risk of pollution from livestock manuresand slurries, it should be recognised that, with appropriate management, there is asubstantial positive benefit in applying livestock manures (and sewage sludge) to land. Thisis an energy-efficient approach, which recycles and utilises the available nutrients. Thisreduces dependency on chemical fertilisers and, hence, also reduces the emissions (C andN) associated with their manufacture. Moreover, alternative outlets or disposal options formanures are few (i.e. dumping of sewage sludge at sea is prohibited; landfill is expensiveand declining; incineration is only a practical option for certain manure types (e.g. poultry)).Manure processing options are very limited and although there is continued interest in thepotential for energy production from anaerobic digestion, the residue must still be applied toland.

1.4 Potential Impacts on Air

UK emissions of GHG include 554,200 kt of C02, 128 kt N20 and 2348 kt CH4 (Defra 2007).Agriculture accounts for 67% of the N20 emissions (62% from direct soil emissions and 32%from indirect emissions by N deposition and nitrate leaching) and 37% of CH4 emissions(86% from enteric fermentation in ruminants and 14% from decomposing waste manuresand slurries). The agriculture, forestry and land management sector contributes only 1% tototal UK CO2 emissions, including emissions and sequestration.

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As part of the Kyoto Protocol the UK has agreed a reduction of 12.5% in GHG by 2012.Defra project AC0206 has reviewed the research to identify best practice for reducing GHGfrom agriculture and land management. Table 1.4 shows the relative split of total agriculturalmethane emissions by livestock sector.

Table 1.4 Summary of 2005 Agricultural Methane Emissions (MtCO2e)

Sub-sector Waste Enteric TotalDairy 1.1 4.5 5.6Beef 0.7 7.5 8.2Sheep 0.1 3.5 3.6Pigs 0.3 0.1 0.4Poultry 0.3 0.0 0.3Total 2.5 15.6 18.1Source: IGER (2006)

Table 1.5 shows the total N20 emissions by livestock sector.

Table 1.5 Summary of 2005 Agricultural Nitrous Oxide Emissions (MtCO2e)

Sub-sector TotalDairy 4.4Beef 6.0Sheep 4.4Pigs 1.4Poultry 1.8Arable 7.9Total 18.1Source IGER calculations in (Defra 2007)

Emissions of ammonia and oxides of nitrogen increase acidification and nutrient enrichmentof ecologically sensitive habitats. An estimated 80% of the 320 tonnes of annual UKemissions of ammonia originate from agriculture, mainly from the production andmanagement of livestock manures and slurries, as well as the spreading of nitrogenfertilisers such as urea. Of the manure component, around 30% originates from spreadingmanures to land, 25% from animal housing, 9% from “hardstandings”, with the remainderfrom manure storage (11%) and outdoor grazing areas (10%) (Misselbrook et al, 2006).

Losses to air from livestock include ammonia (predominantly from dairy, beef, and pigslurries), methane (largely from cattle and sheep), and oxides of nitrogen resulting from thedenitrification process. Losses of ammonia and oxides of nitrogen tend to be greatest fromsurface applied materials (urine from grazing or housed livestock, surface-applied slurriesetc), with a 5% increase in ammonia emissions for each 1% increase in slurry dry mattercontent for surface applied slurries. Higher slurry dry matter contents limit infiltration, andincrease the risk of surface capping. Relevant regulations include the National EmissionsCeiling Directive, the Air Quality Daughter Directive, the UNECE Gothenburg protocol, andthe IPPC Directive (which affects large pig and poultry units only) and the need to introduceBest Available Technology (BAT) where possible. These directives specifically affectlivestock housing and attempt to minimise potential pollution whilst maintaining livestockwelfare. Mitigation options include low emission spreading techniques, covers for slurry and

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manure storage, and reducing the protein content in livestock feeds to improve the efficiencyof N utilisation..

The NARSES model (AM0101, AM0113, AM0133) is now used to estimate nationalammonia emissions from agriculture, and has been used to demonstrate the most cost-effective abatement measures (Webb et al,2006). These include covering poultry manurestores, replacing urea fertiliser with ammonium nitrate, the rapid incorporation of manure andslurry into arable land by discing and allowing cattle slurry storage to crust over.

The Air Pollution Information System (APIS) has been developed in partnership by the UKconservation agencies and regulatory agencies and the Centre for Ecology and Hydrology. APIS is a support tool for staff in the UK conservation and regulatory agencies, industry andlocal authorities for assessing the potential effects of air pollutants on habitats and species.As such, it aims to enable a consistent approach to air pollution assessment across the UK.Other potential users include non-governmental organisations, universities, students oranyone interested in finding out more about air pollution effects on wildlife.

1.5 Biodiversity and the Countryside

Grazing livestock are a crucial element of our landscape and about 80% of our countrysidehas been shaped by farming (National Trust 2001). 25% is semi natural habitat maintainedby grazing animals (Countryside Survey 2000).

8% of England’s land area is designated as National Parks and 15 % as Areas ofOutstanding Natural Beauty (AONB). These areas are protected by law, to ensureconservation and enhancement of their natural state and they are often referred to as"protected landscapes". Both National Parks and AONBs have their origins in the same postwar movements to protect the countryside and were given protective designation under theNational Parks and Access to the Countryside Act (1949) to conserve and enhance theirnatural beauty. AONB have been described as the jewels of the English landscape. Thereare 36 AONBs in all.

National Parks are extensive areas each with their own managing authority to conserve andenhance their environment, wildlife and cultural heritage and to promote opportunities for theunderstanding and enjoyment of their special qualities by the general public. National Parksprovide their 110 million annual visitors with the opportunity to explore some of England'smost dramatic and remote landscapes. The parks are living and working landscapes with anincreasing focus on supporting the communities and economic activities that underpin theirexistence. There are 8 National Parks in England plus the Norfolk and Suffolk Broads, whichhas equivalent status. Most National Parks and AONBs depend on livestock grazing fortheir maintenance.

Grazing livestock affect biodiversity in pastures through the creation and maintenance ofsward structural heterogeneity, particularly as a result of dietary choice. Differences betweendomestic grazing animal species and their impact on grazed communities can be related todifferences in dental and digestive anatomy and to differences in body size (see appendix forfurther details e.g. 1.4.2.1 and 2.4.1). Differences between breeds within species arerelatively minor and again largely relate to body size (Rook et al. 2004). One virtuallyubiquitous aspect of grazing is that it leads to increased plant diversity compared to nograzing (Hill et al., 1992; Bullock & Pakeman, 1997; Humphrey & Patterson, 2000).

Sheep and cattle are essential for recovering and maintaining favourable condition of a widerange of grazed habitats. For example, around half of the UK’s Biodiversity Action Plan

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(BAP) Habitats are considered dependent upon grazing by livestock for their conservation(Bullock & Armstrong 2000). However, the appropriate species, timing, density and relatedmanagement practices are crucial (English Nature 2001). In practice, these are seldom inplace by default (i.e. unless there is an explicit objective to conserve the habitat) and thewrong grazing management can be as damaging as no grazing management. EnglishNature state that undergrazing is now as much, if not more, of a problem than overgrazingwith 530 SSSIs covering 21,000 ha undergrazed and 190 SSSIs totalling 130,000haovergrazed (English Nature 2005), it can be difficult to strike the right balance.

Production from grassland is markedly improved by reseeding, regular fertilisation, limingand artificial drainage of wet sites and is often necessary for cost effective production fromgrazing livestock. Stocking rates and cutting frequency are higher and more homogeneousswards do not support a wide variety of wildlife. It could therefore be argued that intensiveproduction should be concentrated in certain areas (whilst abiding by all relevant legislation)and extensive production for conservation objectives should be supported in other areas.Certainly environmental stewardship schemes aim to enhance natural resources in theagricultural environment.

The preservation of species-rich grassland is a primary goal of nature conservation. Grazingat a low stocking rate has the potential to facilitate the restoration of diverse swards and tosupport reasonable individual performance of the grazing animals (Isselstein et al. 2005).Grazing by animals usually results in greater plant species richness; the sward is kept openallowing the establishment of forb species in the gaps (McCracken & Tallowin 2004).However, too little or too much grazing can both have an adverse effect on species diversity.

Heather moorland in Britain is a priority BAP habitat considered to be internationallyimportant and its retention a high conservation priority (Thompson et al. 1995). 75% of theworld’s remaining heather moorland is found in Britain, but the area has diminisheddramatically over the past 50 years (The Moorland Association). The current area ofmoorland in England and Wales is estimated at 7,790 and 6,360 km2 respectively. Heathermoorland was created by and for grazing and its retention is dependent upon grazing as amanagement tool.

Hedgerows are an integral part of a pastoral landscape and their creation and maintenancewas entirely due to the part they played in the management of livestock. England has lostmore than half its hedgerows since 1947, which is more than 200,000 miles of hedgerow.Between 1947 and 1985, over 4,300 miles of dry stone walls were lost, with 96% of theremaining walls in need of restoration at that time.

The majority of hedges today were planted during the enclosures of the 18th and 19thcenturies. Some 200,000 miles of hedges were planted between 1750 and 1850. As awildlife habitat, hedges occupy more land than all of our nature reserves put together. Theintroduction of Environmentally Sensitive Areas (ESAs) and Countryside Stewardship,together with legislation to prevent further removal of hedgerows have helped to halt thedecline in hedgerows and given farmers financial assistance to restore old hedges and plantnew.

As well as being valued landscape features, hedges offer feed, shelter and nesting sites to avariety of wildlife and their linear form renders them useful as wildlife corridors (Andrews &Rebane, 1994). The removal of hedgerows, and hence sources of pollen and nesting sitesreduces bee populations (Buchmann & Ascher, 2005) and butterflies (Hill et al. 1995).

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1.6 Valuing the Environment and Livestock Farming?

Those involved in managing and working the land believe inherently that our landscapeneeds to be farmed and maintained largely as it is now. The patchwork of fields with amosaic of different crops, the hedgerows, the animals and the buildings all create theEnglish landscape we all know. But is this landscape and the ‘services’ provided by it valuedby the general population? Haines-Young & Potschin (2007) suggest that ‘perhaps only indeveloped societies, where most people are no longer working directly with the resourcesprovided by the land, sea and air, do they need reminding of the importance of the benefitsthat nature provides’? The Curry Report (2002) previously highlighted the need for farmersto reconnect with their consumers, to tell people how their food is produced and to raise the‘value’ of locally grown food in the public perception.

The Millennium Ecosystem Assessment (MA) has stimulated widespread internationaldebate about the importance of the links between ecosystems and human well-being. TheEcosystem Approach is an evolving framework of ideas designed to help decision-makerstake full account of ecological systems and their associated biodiversity. ‘Ecosystemservices’ is an idea that is currently being widely promoted to emphasise the benefits thatecological systems provide to people, and the impact that systems based on biologicaldiversity have in maintaining the quality of peoples lives. Defra currently has a series ofprojects looking at developing an ecosystem approach for the UK.

The value of ‘landscape’ to the general population is very difficult to assess but researchersat MLURI have developed a ‘Virtual Landscape Theatre’ to test various landscapes onmembers of the public. If livestock numbers are to continue to decline then our landscapecould look entirely different over a number of years. Rank vegetation and scrub couldencroach in hill and upland areas with eventual return to forest. The changed environmentmay not appeal to UK taxpayers and public surveys have demonstrated the public’swillingness to subsidise farming to maintain the landscape in a desirable state. One studycarried out by Eftec for Defra (Johns et al 2006) attempted to estimate the value of changesin environmental features associated with the Severely Disadvantaged Areas of Englandwhich could arise from a change in policy for the LFA. The project used a choice experimentstated preference approach together with contingent valuation. The analysis revealed acertain ‘willingness to pay’ of £49 to £105 per household per annum for a worst to best casescenario.

We know from public attitude surveys that a high proportion of the population values therural environment. Most respondents say that they would support paying farmers toregenerate threatened landscapes or habitats.

The Northern Ireland Red Meat Industry Task Force: Strategy Review 2007 hasrevealed that the red meat industry in NI is currently generating a loss of over £200m per annum when full production costs are included. There are many, very smallproducers (80%) with beef herds of less than 30 cattle. The review has concludedthat there is no economic case for long-term Government financial support tosubsidise suckler-origin beef or hill sheep production: any case for Governmentsupport would therefore need to be based on other considerations. The hilllandscape of NI is therefore likely to deteriorate unless environmental schemepayments are sufficient to sustain it. Similar reports have been produced for areasof Scotland and England (e.g. Lewis & Beetham, 2006) where significant concernhas been expressed about the future of hill and upland areas of the country.

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2. Dairy Farming Systems

For further, more detailed information, refer to Appendix 1.

Key Issues Identified

• Improved handling and management of slurry and manures to minimise losses ofnitrogen, phosphorus and organic nutrients to water and ammonia and greenhouse gasemissions.

• Efficient use of fertiliser and manures to optimise grass/crop performance and minimiseunnecessary use of chemical fertiliser inputs.

• Efficient production (fertility etc) to maximise output and reduce non-productive stock.Increased focus on longevity and health to improve the efficiency of production overall.

• Improved rationing to optimise capture of nitrogen, phosphorus, and trace elements tohelp minimise losses to the environment

• Better planning of grass and maize production and grazing systems.

2.1 Public Goods Delivered

The dairy industry provides:

• Rural employment, directly on dairy farms, mainly west and south west of England andborders of Scotland.

• Rural /urban employment in milk processing and production plants, feed manufacturingfactories and abattoirs.

• Cattle grazing and slurry spreading sustains soil organic matter and enhances thephysical properties of soil, including fertility.

• Spreading of slurry and FYM is found to be beneficial to earthworms, which support alarge ecosystem of birds.

• Muck pats in fields provide food and shelter to a wide range of invertebrates and hencefood for birds.

• Dairy farms tend to incorporate hedges and dry stone walls as divisions of fields andhence contribute to the landscape character of the countryside. Hedges contain broad-leaved trees, plants, birds, insects and mammals.

• Dairy production supports dependent ecosystems - bacteria, fungi, insects, beetles, birdsand mammals

• Dairy cows make use of by-products from the food industry e.g. distillers products, wastebread, potatoes, rapeseed meal etc and will be a depository for by-products of biofuelproduction in the future.

2.2 Environmental Impacts of Dairy Farming Systems

2.2.1 Potential Negative Impacts

The factors listed below indicate possible negative effects of dairy farming activities but theextent to which these happen on farm is not well documented. The Defra Farm PracticesSurvey (2007) provides some information on manure management and on measures to helpmaintain water quality and limit soil erosion. The England Catchment Sensitive FarmingDelivery Initiative and the Environment Agency also provide limited evidence but moredetailed information is required to quantify the effects more accurately.

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Soil (see appendix 1.1 for detail)

• Grazing, slurry spreading, maize production and harvesting, and heavy traffic duringsilage making can cause soil erosion and compaction. When soil is compacted there isreduced infiltration of water that can lead to water run off and soil erosion. Yields are alsoreduced thus decreasing the efficiency of other inputs to the system.

• Maize growing for silage (see appendix 1.1.2.3) increases the risk of soil erosionespecially where harvested in wet conditions and if grown on slopes. Bare soil (lowvegetation covers) during the early part of the growing phase increases erosion risk.

Potential effects on soil ecology

• Microbial and invertebrate activity and hence degradation of cow pats can be reduced bythe presence of veterinary medicines e.g. avermectins.

• Veterinary medicines can potentially impact on insect and beetle populations, which inturn can impact on local bird and mammalian populations (e.g. Chough - Pyrrhocoraxpyrrhocorax and Greater Horseshoe Bat - Rhinolophus ferrumequinum).

• The cumulative increase in soil zinc levels arising from its inclusion in livestock diets or inveterinary medicines may ultimately lead to a small negative impact on rhizobial activity.

Water (see appendix 1.2 for detail)

• Potential for nitrogen, phosphorus and pathogen loss to water. • Potentially significant risk of pollution from manure produced at grazing and also slurry

spreading. The risk is related to stocking density and, in particular, to the timing and rateof slurry spreading.

• High (up to 250 – 300 kg/ha) fertiliser use on grassland in spring and summer monthscan potentially affect the balance of fungi and bacteria in soil, and can increase the riskof nitrate leaching if the nutrients applied in manure are not taken into account. However,the risk of nitrate leaching on grassland is normally lower than that on tillage land.

• Risk of contamination with pharmaceutical drugs and chemicals (e.g. strong cleaningagents used in dairies).

• Silage effluent is considered to be a small risk. It is categorised as a point sourcepollutant, which is associated with clearly defined discharges and will often be avoidable,with correct system design and good management practice.

• Dairy cattle have a huge demand for water, for drinking and parlour wash down. With anaverage consumption of >90 litres per day, the dairy herd in England is using in excessof 120 million m3 of water for livestock drinking and cleaning purposes alone.

Air(see appendix 1.3 for detail)

• Ammonia loss (from housing, from grazing and from manure spreading) and re-deposition can lead to the acidification and nutrient enrichment of sensitive habitats (e.g.lowland heath), leading to losses in biodiversity.

• Cattle farming accounts for the largest emission of ammonia, representing 53% of totalagricultural emissions. Following excretion by grazing cattle, or the application ofmanures to the soil surface, typically 10-60% of the readily available (i.e. ammonium) Nis lost to the atmosphere by ammonia volatilisation.

• The total ammoniacal nitrogen (TAN) content of fresh FYM is typically c. 25%, but only c.10% after it has been stored, as a result of emissions, N transformations and

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immobilisation in microbial protein during storage. As a consequence, ammoniaemissions are greater when fresh FYM is spread on land.

• Methane emission as a result of microbial fermentation in the rumen. Breeding dairycows produce about 15 kg CH4/head per year. CH4 is also lost from slurry storagethrough anaerobic decompostion. The dairy sector accounts for about 37 % of CH4 fromlivestock.

Biodiversity(see appendix 1.4 for detail)

• Ryegrass and ryegrass/clover swards lead to reduced biodiversity compared to moremixed swards.

• Intensive grazing leads to reduction in pollen and nectar, reducing food for insects andbirds and offers a poor nesting habitat.

• Silage cuts are taken 2 or 3 times per year from one field, which does not allow seedproduction and can potentially damage habitats.

2.2.2 Mitigation of Negative Impacts (Dairy farming)

A wide range of mitigation methods have been widely researched and put to the industry andmany have been adopted. However the number of dairy farmers using these methods andhence the size of the overall impact has not been adequately assessed. The Farm PracticesSurvey and the British Survey of Fertiliser Practice provide some information but this is notadequate to provide totally reliable evidence.

The Agricultural Industries Confederation (AIC) estimated that the amount of nitrogensupplied in compound feeds and concentrates to dairy cows in 2005 was 71,012 tonnes,which represented a 12.5% reduction since 1999. Over the same period, however, dairy cownumbers declined from 2.44 million to 2.065 million (a 15.4% reduction). At face value, thesedata would suggest that for dairy cows at least there was a slight increase in N intake/cowover this period, (which might be associated with the increase in productivity per cow).However, no information is available on the N content of the forages consumed, whichaccount for more than 50% of the total dry matter consumed by dairy cows, and therefore itis not possible to estimate changes in N intake by dairy cows.

The mitigation methods listed below are referenced where possible according to where theycurrently appear in the literature e.g. if a method appears in one of the Codes of GoodAgricultural Practice it is referred to as CoGAP. The uptake of the methods by farmers isvariable and no accurate assessment of uptake has been made.

Reducing soil compaction/erosion

• Minimise impact on soil by management of feeding and drinking points if possible (Cuttleet al., 2007).

• Reduce field stocking rates when soils are wet (Cuttle et al., 2007). Of those holdingsthat have taken livestock related steps to maintain water quality 65% would keep stockoff ground to avoid poaching – FPS 2007.

• Use of tracks to minimise compaction on walkways (Defra ES0121). • Spread slurry when dry and when, as a result of timing and crop growth stage, nutrient

recovery is most effective (CoGAP – Water; Chambers et al, 1999; Chambers et al,2001).

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• Avoid growing maize on steeply sloping land and on sensitive soils. Where practical (i.e.on simple, moderate slopes) (Defra 2006b), cultivate across the contours, not up anddown the slope (Defra 2006b, Defra ES0203).

• Use early maturing varieties of maize and avoid harvesting maize and grass in wetconditions (Defra 2006b).

• Undersow maize with a nurse crop or select an appropriate cultivation technique forcompacted soils post-harvest, under suitable conditions (Defra 2006b, Defra ES0203).

• Put in place controlled traffic systems to minimise damage (Jagoa et al., 2007).• Reduce the excretion of zinc and copper through lower levels of supplementation (and

possibly use chelated trace elements in animal diets). This is already controlled bylegislation and is likely to be reduced further in future.

Reducing nutrient/chemical/pathogen loss to water (see appendix 1.2.1)

• Restriction of timing and loading of applied manures and slurries with high available N toland (avoid applications in autumn/winter - NVZ Action Programme proposals August2007 extend this to cover all soils, not just freely draining soils; extended “closedperiods” where slurry cannot be spread). Many farms now have a nutrient managementplan and over 40% of holdings used the Entry Level Scheme to do this (FPS 2007).

• Transfers of N and P (and hence pathogens) following recent manure applications are amajor issue for wetter, grass-dominated areas such as Wales and SW England.Reducing the frequency of reseeding operations, careful management (rate and timing)of manure applications and the incorporation of manures into the soil as soon aspossible after application, will reduce the runoff risk and minimise ammonia losses(Chambers et al, 1999).

• Do not apply slurry to steep slopes etc, or when the soil is wet or frozen (of thoseholdings that have taken livestock related steps to maintain water quality 81% are notspreading slurry at high risk times, FPS 2007) (CoGAP – Water)

• Correct setting of slurry spreading bout widths (NT1415, NT2002) and increased use ofmanure analysis data, e.g. by sampling and analysis, or using on-farm estimates (slurryN meters, hydrometers). Also, assessment of manure spreader loads (ES0139). Thesemeasures would improve the targeting of manure N applications to land with the resultingreduced risks of pollution to both water and air (implied in CoGAP – Water).

• Limit slurry applications to reduce the risk of surface runoff (50 m3/ha) (CoGAP – Water).• There is evidence that cattle raised on organic farms produce manure with lower total N

contents compared to conventional farms (5.2 and 6.3 kg/t respectively (Anon, 2006:OBS03 report)), as no chemical fertilser is used, and hence reduce issues associatedwith N loadings from manures and the risk of pollution to water and air (Organic FarmingScheme and Organic Entry Level Scheme).

Collect all runoff from hard standing areas, woodchip pads etc, this will reduce the potentialrisk of pollution to water (CoGAP and Defra WA0804).

• Line all slurry stores to achieve compliance with IPPC legislation and reduce leakage towater (Beyond IPPC legislation).

• Reduce dietary nitrogen supply to dairy cows while improving dietary balance by usingimproved protein characterisation. There is some evidence that the diet can affect (a) thepartition of N between urine and faeces and (b) the solubility of P in the manure of dairycows. Changes in the source of both of these nutrients could have an effect on N and Plosses to water.

• Reducing the length of the grazing day and/or the grazing season; and adopting zerograzing can potentially mitigate the risk of water pollution arising from dairy and beefsystems (ES0203 and NT2511), provided that suitable precautions are taken to minimiselosses from the additional slurry produced.

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Prevent direct access of livestock to water courses, periodic movement of feeding troughs toreduce poaching risk. Fencing off river banks to prevent cattle access can substantiallyreduce bank erosion (sediment), and riverine inputs of nitrate (urine, faeces) andpathogens (Defra ES0121 and ES0203). This is now included within EnvironmentalStewardship options and capital grants within Catchment Sensitive Farming prioritycatchments.

• Establishment of ungrazed, unfertilised buffer strips at the edges of fields, and theconstruction of retention ponds/wetlands downstream of the agricultural area, are botheffective mitigation methods for reducing pollution from cattle systems reaching primaryriver systems (Environmental Stewardship). Of those agricultural holdings that havetaken measures to maintain water quality 38 % are using buffer strips (FPS 2007).

• Ploughing out grass in autumn releases up to 70 kg N/ha: reseeding should beundertaken early in spring so as to maximise the use of the N released by mineralisationand thereby reduce the potential for nitrate leaching (Defra NT0602 and NT1312). Re-seeding in the spring also reduces the risk of soil structural damage.

• Avoid routine use of wormers and other anti-parasitic medicines and target drugsappropriately.

• Plant breeding studies are underway to reduce the level of phosphorus in herbage hencereducing P intake by dairy cows.

Reducing gaseous emissions to air (see appendix 1.3)

• Use the appropriate crop N requirements as recommended in RB209/PLANET (CoGAP– Water)

• Make full allowance of manure N supply (MANNER) (CoGAP – Water)• Spread manure at appropriate times/conditions (CoGAP – Water)• Allow crusting of slurry stores, e.g. by bottom filling (there is evidence to suggest that

80% of cattle slurry stores are crusted) to reduce gaseous emissions (Smith et al, 2007),or fit lid or floating cover.

• Rapid incorporation of surface applied slurries and manures also substantially reducesammonia loss (WA0711) (CoGAP – Air).

• Spread slurry using direct injection or band application methods to minimise emissions(CoGAP – Air).

• Controlled anaerobic digestion of cattle and pig slurry enables the resulting methane tobe collected and used as fuel to produce electricity/heat, which has the added benefit ofreducing CO2 emissions by limiting the need for fossil fuels (Recommended in CoGAP –Air; encouraged in new NVZ Action Programme Rules).

• Improve the efficiency of nutrient use in cow diets• Make use of improved genetic resources – livestock and forages• Increasing the proportion of concentrates/reducing forage in ruminant diets results in

changes in rumen fermentation and reductions in methane emission. • Maintaining high levels of feed intake will increase the rate of passage through the

rumen, which reduces production of methane. • Incorporation of slurries with straw and bedding (FYM) can reduce leaching risk (by the

inclusion of a carbonaceous substrate) and can reduce ammonia emissions (CoGAPs). • For fertilised grass systems, move from using urea to alternative fertiliser types (such as

ammonium nitrate), as this reduces the potential loss from ammonia volatilisation (DefraNT26 projects).

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2.3 Gaps in Knowledge and Future Research Needs (Dairy Farming)

2.3.1 Nutrition (many of the research needs also apply to beef and sheep)

• The appropriate supply of rumen degradable protein is thought to be reflected in milkurea nitrogen (MUN) concentrations. Information on MUN is now available to almost allUK dairy farmers. Research methods for its use as an indicator of dietary nitrogenbalance could be developed in the UK (already used in the USA). Reducing excessnitrogen excretion could lead to potentially reduced ammonia emissions.

• Undertake a national survey of feeding practices – so that scope for further reduction innitrogen output (and other nutrients) may be ascertained.

• Reduce dietary P concentrations: This requires greater confidence in either estimates ofP requirements or in P supply, or both. This strategy can have a significant impact on Pexcretion, but needs to be undertaken with caution. Since inorganic P is not now widelyadded to ruminant rations, reductions in overall P content could necessitate changes inthe types of concentrate used. Further research is needed to assess the practicalimplementation of these strategies.

• Feed additives: Ruminants are ideally suited to consume and digest forages, yet CH4production is greatest on high forage diets. Because of this, considerable research effort– in the UK and world-wide - is being devoted to identifying feed additives that act asCH4 inhibitors for inclusion in high-forage diets. A number of additives have beendeveloped which have reduced CH4 emissions in the short term, but rumen adaptationappears to reduce the long-term benefits. There is a need for a better understanding ofways of reducing methanogenesis in a safe and consistent manner. This is the subject ofthe recently commissioned Defra Research Project AC0209.

• Research has been undertaken, principally in Australia, on the development of anti-methanogenic vaccines to reduce CH4 emissions. Further research is needed toestablish long-term efficacy.

• Crop breeding: Recent research at IGER suggests that an increase in water-solublecarbohydrate in perennial ryegrass leads to a reduction in CH4 production (Lovett et al.,2006). A successful programme of genetic improvement of forage grasses and legumeshas led to the development of high-sugar grasses, and the potential for these to reduceCH4 output will be explored in Defra project AC0209.

• Recent research suggests that the microbial ecosystem in the rumen may be reflected inthe fatty acid profile of milk fat. Additional studies are needed to elucidate and verify therelationship between specific milk fatty acids and CH4 production, if proven valid, thiswould provide a useful and non-invasive tool to study changes in CH4 losses.

• Better definition of nutritional requirements is needed, to take account of new genetics,production systems, interactions between feeds etc.

• There is a need for a better understanding of the factors affecting the bioavailability of Cuand Zn in feed materials, together with developments of rapid and cost effective methodsof analysis. This would allow rations to be formulated where supply more closelymatches requirements, thereby reducing the need for large safety margins that havetraditionally been used in diet formulation.

• There is also a need to review and measure the extent and impact of heavy metals,pharmaceutical drugs and chemicals excreted on soil, water, air and biodiversity.

• A review is needed of the future supply of feeds to industry, changes due to new crops,pressure from demands for biofuel production, world trade and climate change.

• Ideas from New Zealand of feeding excess salt to cows to reduce urine hotspots and thedevelopment of a nitrification inhibitor bolus need to be reviewed to assess theirapplication in the UK. .

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• An educational programme is required to persuade dairy farmers and their advisors thatreducing P levels in diets to 0.45% will not have long-term adverse effects on dairy cowfertility.

• Research is needed to understand the effects of different dietary constituents on the ratioof soluble and insoluble P in manure.

2.3.2 Slurry Systems

• Improved quality and amount of information on farm practices (i.e. farm activity data) isneeded, via further development of existing (e.g. Farm Practices Survey, British Surveyof Fertiliser Practice) and new survey approaches – to improve the accuracy andreliability of catchment models and national inventories of emissions and to better informpolicy decisions on environmental protection strategies.

• Further development of software programs capable of informing/assisting decisionsacross the spectrum of livestock production and manure management systems isneeded. These can provide information to encourage the uptake of better technology ormanagement practices that can reduce environmental emissions.

• Options for reduced cost slurry storage – a soil stabilisation technique, involving lining ofsoil pits with a cement-based compound appears to offer a reduced cost slurry storageoption (capable of meeting EA requirements for very low permeability). There is anurgent requirement for investigation and, pending success of the technique,demonstration – as a result of the new minimum capacity (22-26 weeks storage for cattleand pig slurry) and <2 year period for compliance, from NVZ AP (Nitrate Vulnerable ZoneAction Programme) implementation.

• Review of livestock slurry for anaerobic digestion, within fully integrated farm systems,including a wide-ranging and robust life-cycle analysis.

2.3.3 Soil Compaction and Erosion

• The geographical extent of soil compaction in grasslands is unknown. Remote sensingtechniques may be able to contribute.

• How does soil compaction relate to stocking densities in different regions?• What effect does soil compaction have on soil micro- and meso-fauna? • Defra project SP0413 is attempting to use fallout radionuclide (i.e. Cs-137)

measurements to provide national scale data on rates of soil loss from agricultural landin England and Wales. This will help to inform soil loss rates on different types ofagricultural land in England.

2.3.4 Veterinary Medicines in Soil

• Typical concentrations of veterinary medicines in soil following slurry spreading inEngland and Wales are not known. Research to date has been limited to laboratorystudies on establishing degradation rates in soil and eco-toxic threshold concentrations.

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3. Summary of Impacts - Beef Farming Systems

For further information, refer to Appendix 1.

Key issues identified:

• Improved handling and management of manures as for the dairy sector. • Efficient production (fertility etc) to reduce numbers of unproductive stock and minimise

losses. Improved breeding to select for disease resistance and longevity of sucklercows.

• Evaluation of alternative out-wintering options (e.g. wood chip or straw-bedded pads)which appear to offer potential to reduce environmental emissions as well as reducingfarm costs.

• Improved accuracy of rationing, to improve efficiency of nutrient use including traceelements.

• Development of integrated grazing systems to the benefit of biodiversity.

3.1 Public Goods Delivered

The beef industry provides:

• Rural employment, directly on farms, over all of UK including upland areas, whereemployment opportunities are lower.

• Rural /urban employment in abattoirs and meat processing plants, feed manufacturingfactories, hauliers and livestock markets.

• Support of dependent ecosystems - bacteria, fungi, insects, beetles, birds and mammals• Extensive cattle grazing is a vital tool in maintaining some important wildlife habitats.• Beef cattle are fundamental to maintaining the landscape in areas of Special Scientific

Interest, AONB, National Parks and also upland and hill areas in general. They alsofeature in lowland parkland and river meadows and undulating land unsuitable forcropping.

• Maintenance of cultural and local heritage with a wide range of traditional breeds. • Beef cattle can utilise unimproved pasture and at correct stocking rates increase the

biodiversity of the sward. Cattle are especially valuable for controlling tough and coarsevegetation, encouraging a more diverse sward, which encourages invertebrates andbirds, and in managing wet grassland, important for waders.

• If hay is used for feeding, hay meadows are only cut once per year, after bird chickshave hatched. This supports flowers, seeds, insects and bird ecosystems.

• Cattle reduce unwanted scrub and bracken by trampling in areas of unimproved grazingand moorland.

• The correct stocking rates of cattle on moorland areas promote heather growth andhence butterflies and other insects.

• At very low stocking rates cattle are beneficial when grazed in woodland as they create amore diverse woodland structure.

• Grassland systems and the manure produced by livestock sustain the soil organic matterand can potentially enhance the physical properties of soil, including fertility.

• Well managed recycling of slurry and FYM is found to be beneficial to earthworms, whichsupport a large ecosystem of birds.

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• Muck pats in fields provide food and shelter to a wide range of invertebrates and hencefood for birds and bats.

• Beef farms tend to incorporate hedges and dry stone walls as division of the fields.Hedges support a wide range of flora and fauna and their linear form provides wildlifecorridors.

• Beef cows and growing cattle make use of by-products from the food industry e.g.distillers products, brewers grains etc, and waste from biofuel production.. The nutritionalrequirements of beef cattle are lower than high producing dairy cows and so they canmake use of lower quality waste products.

3.2 Environmental Impacts of Beef Farming Systems

3.2.1 Potential Negative Impacts (Beef farming)

Soil(see appendix 1.1 for detail)

• Soil compaction and erosion, caused by grazing, and particularly outwintering, at highstocking rates, manure spreading and silage making. When soil is compacted aerationand filtration rates are reduced leading to water run off and erosion. Compaction is ofless concern than with dairy cattle, as cattle are not moved for daily milking.

• Supplementary feeding areas can cause problems of localised compaction and nutrientrunoff if close to water courses, particularly a problem for outwintered animals.

• Microbial and invertebrate activity and hence degradation of cow pats can be reduced bypresence of veterinary medicines e.g. avermectins.

• Low levels of zinc in slurry/FYM, as a result of feed supplementation and use inveterinary medicines and from foot bathing, where cumulative additions of zinc can leadto a suppression of rhizobial activity in the soil. Zn reduces the ability of rhizobia to fixatmospheric nitrogen for plants.

Water(see appendix 1.2 for detail)

• Risk of water pollution from nutrients and pathogens from excreta produced at grazingand also from slurry spreading. Slurry produced often has higher dry matter content thanthat of dairy cows, because of the absence of washdown water addition from yards anddairy.

• Water contamination risk with pharmaceutical drugs and chemicals.

Air (see appendix 1.3 for detail)

• Cattle (dairy and beef) production accounts for the largest emission of ammonia,representing 56% of total UK agricultural emissions. Although emissions from beef cattleare lower than for dairy cattle since 96% of beef finishers and 81% of suckler cows arekept on straw bedded systems as opposed to slurry systems for manure handling. 74%of dairy cows are kept on a slurry system (FPS 2007).

• Cattle on high forage diets produce large amounts of CH4. The beef sector accounts forapproximately 45% of agricultural CH4 emissions and represents the highest contributionto total methane of all the livestock sectors. (See Table 1.4).

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Biodiversity(see appendix 1.4)

• Where silage cuts are taken 2 or 3 times per year from one field, this does not allowseed production and can potentially damage habitats.

3.2.2 Mitigation of Negative Impacts (Beef farming)

A wide range of mitigation methods have been widely researched and put to the industry.However there is no simple means of assessing the extent to which beef farmers haveadopted these approaches and, hence, the size of the overall potential impact. The FarmPractices Survey provides some information.

Reducing soil compaction/erosion

• Minimise impact on soil by moving feeding and drinking points if possible and keepingthem well away from watercourses (Defra ES0203, Cuttle et al., 2007).

• Reduce field stocking rates when soils are wet, particularly in outwintered stock (DefraES0203 and CoGAP - Soil).

• Use of tracks to minimise compaction on walkways (Defra ES0121).

Reducing nutrient/chemical/pathogen loss to water

• Avoid spreading slurry and FYM at high risk times (i.e. when there is a high risk of run-off; when soils are wet or cracked; or late in the growing season) (CoGAP – Water).Restrict slurry applications to periods with favourable soil conditions and crop growthstages where nutrient recovery is most effective (CoGAP – Water; Chambers et al, 1999;Chambers et al, 2001).

• Avoid harvesting grass for hay or silage in wet conditions (CoGAPs) and put in placecontrolled traffic systems to minimise damage.

• Fencing off river banks to prevent cattle access can substantially reduce bank erosion(sediment), and riverine inputs of nitrate (urine, faeces) and pathogens. This is nowincluded within Environmental Stewardship options.

There are many more mitigation points which are the same as for dairy production. Pleaserefer to the mitigation section for dairy (appendix 2.2.2).

3.3 Gaps in Knowledge and Future Research Needs (Beef farming)

Please refer to gaps in knowledge and future research needs in the dairy section that givesdetails about nutrition and slurry systems (see appendix 2.3).

3.3.1 Biodiversity

• A review of methods/incentives to promote mixed farming in the lowlands, to helpenhance the benefits of beef and sheep production is needed. This should complementthe intensive dairy and arable systems.

• Further development of methods of restoration for overgrazed land, to restore thedepleted biodiversity of grassland habitats is needed.

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• There is a need to assess areas where there is undergrazing and review policies torestore sustainable stocking rates.

• There is a need to review the most suitable methods for peat restoration and the bestgrazing policies to maintain their ecosystems. Defra project SP0565 aims to address thisissue.

3.3.2 Environmental Emissions

• Woodchip pads provide an important alternative to conventional buildings and concreteyards for overwintering beef cattle at potentially reduced cost. Whilst research hasdemonstrated some production, health and welfare benefits to stock, information of thepotential reduced risks of environmental emissions (to air and water) are, as yet poorlyquantified and understood. These aspects are being addressed by a SLP LINK researchproject (LK0676), starting October, 2007.

• More recently, there has been very strong interest in the use of straw bedded corrals, forout-wintering cattle without the production of slurry. These are temporary enclosuresestablished on field sites without removal of soil, with the estimated cumulative depth ofFYM of 0.5 – 1.2m, cleared and spread following the removal of cattle. Whilst thisapproach appears to offer an alternative to the high costs of extending slurry storage,where this may now be required under the revised NVZ Action Programme proposals, anassessment of the potential environmental emissions (including possible benefits) isurgently required.

• As in dairy cattle, there is an urgent need for improved quality and amount of informationon farm practices (i.e. farm activity data); to improve the accuracy and reliability ofcatchment model estimates and national inventories of emissions and to better informpolicy decisions on environmental protection strategies.

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4. Summary of Impacts - Sheep Farming Systems

For further information, refer to Appendix 2.

Key issues identified

• Increased efficiency of production and reduced numbers of unproductive stock. Thiswould include enhanced genetic selection for efficiency.

• Improved ration formulation to ensure efficient capture of nutrients.• Development of integrated grazing systems that deliver positive benefits to the

environment.

4.1 Public Goods Delivered:

The sheep industry provides:

• Maintenance of the landscape.• Grazing management of sensitive habitats – hill and upland but also some lowland. • Rural employment (declining) but associated businesses, markets, abattoirs, feed

merchants, pharmaceutical companies etc depend on the sheep sector for some of their business.• Sheep pastures tend to have higher soil organic matter than tillage land.• Improved biodiversity under controlled grazing. Maintenance of some valuable short-

sward habitats supporting some rare species.• Maintenance of field boundaries – hedges and stone walls as stock-proof fencing

allowing wildlife corridors and supporting biodiversity.• Grazing to manage valuable archaeological sites. • Improved soil pH on improved land, reducing the mobilisation of aluminium through soil

acidification and Al enrichment of water sources. Aluminium is toxic to life. Where sheepare reared, rough grasslands are often improved by spreading lime. This increases thepH, reduces soil acidity and reduces Al concentrations in the water.

• Maintenance of cultural heritage with a wide range of sheep breeds and systems ofproduction e.g. North Ronaldsay, Cotswold, Greyface Dartmoor etc.

4.2 Environmental Impacts of Sheep Farming Systems

4.2.1 Potential Negative impacts

Soil(see appendix 2.1)

• Soil erosion – overgrazing, grazing root crops, around feeding areas. • Soil compaction can have a significant impact on flood risk at a local level. • Veterinary medicines – residues in faeces and impact on invertebrates and soil micro-

organisms and the associated ecosystems.

Water(see appendix 2.2)

• Nitrate losses per unit area are much lower than from dairy and beef systems, but theabsolute area stocked by sheep in England and Wales is larger.

• Limited impact of nitrogen fertiliser as much less applied than for cattle systems.

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• Direct contamination of natural watercourses with faeces and urine, occasional run offfrom hardstanding areas.

• Sheep dip – occasional pollution of watercourses – much reduced impact throughlegislation and enforcement and better advice to farmers (see appendix 2.4.6).

Air(see appendix 2.3)

• Ammonia emissions from grazing sheep are estimated to be around 5% of the total fromUK agriculture (similar to the 4% from grazing cattle).

• Sheep produce CH4 that represents about 20% of agricultural CH4 emissions (see Table1.4).

Biodiversity(see appendix 2.4)

• Overgrazing (in the past) and destruction of some sensitive habitats. As sheep numbershave fallen and agri-environment schemes have been adopted, this is a diminishingproblem and undergrazing is likely to have a greater impact on biodiversity in the future.If left ungrazed, grassland (moorland and hill) will develop into scrub with regeneration oftrees and reduction in species diversity.

4.2.2 Mitigation of Negative Impacts (Sheep farming)

• To reduce N and P leaching from sheep grazing avoid pasture improvement on uplandand peat sites (already adopted).

• Select more efficient sheep in terms of reduced emissions, disease resistance, efficiencyof nutrient use etc

• Sheep dipping is heavily regulated with certificates of competence and dip disposallicensing (Ground Water Authorisations and CoGAP - Water). There has been a greateffort to inform farmers of safe use and disposal of spent dip and pollution incidents fromsheep dip in 2006/7 have been very few (Merriman 2007 personal comm). An enzymethat deactivates Diazinon has just been launched on the market. The increased use ofinjectable products for control of sheep scab has accelerated the reduction in pollutionincidents.

• Veterinary medicine residues in faeces are likely to have been reduced significantly asfarmers become more aware of the safe use of veterinary medicines and they take onthe SCOPS principles of worm control (to worm only when necessary and to use aspecific drug not a blanket treatment) (Abbot et al 2004).

• Research at Pontbren in Wales has shown that planting tree shelter belts across a slopecan reduce the risk of lowland flooding (by providing a high water infiltration rate areanext to potentially compacted grazing areas and reducing volumes of storm event runoff)and also provide cover for sheep during inclement weather

4.3 Gaps in Knowledge and Areas for Future Research

• Better definition of nutritional requirements for protein and trace elements are needed.Current estimates of requirements for sheep in the UK are outdated, and do not takeaccount of new breeding/genetics or methods of production (Robinson, 2002).

• In sheep housed indoors and fed with different legumes (lucerne, sulla, red clover,chicory and lotus), CH4 losses were reduced by between 20 and 55% as compared to

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animals grazing ryegrass/white clover mixtures (Ramirez-Restropo & Barry, 2005). Thisneeds further investigation.

• Further research is underway at IGER focused on identifying the genetic variationunderlying ‘environmental sustainability’ traits which have the potential to decrease CH4(and nitrogen) emissions per animal and per unit output. These include development offorage varieties with elevated levels of condensed tannins. Condensed tannins help toincrease N utilisation. There is also evidence that they have anthelmintic properties.

• Further development of integrated grazing systems that will help to enhance biodiversity.

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5. Summary of Impacts - Pig Farming Systems

For further information, refer to Appendix 3.

Key issues identified

• Improved handling and management of slurry and manure. • Improved management of outdoor pigs to reduce impacts on soil erosion and

compaction. Assessment of wider environmental impact of outdoor pigs. • Improved efficiency of nutrient use of feedstuffs, e.g. phase feeding for nitrogen and

opportunities to reduce phosphorus use and improve efficiency of P utilisation viaincreased use of dietary phytase.

5.1 Public Goods Delivered

The pig industry provides:

• Rural and semi-rural employment on pig farms.• Rural/urban employment in abattoirs, meat processing plants, animal feed factories and

associated suppliers.• Pig production uses a large range of co- and by-products from food and allied industries

– helping to reduce food waste. • Recycling of manure and slurry can potentially increase soil organic matter levels, which

can in turn improve soil physical and chemical fertility and reduce the need for chemicalfertilisers for cropping.

• Extensive ‘free range’ pigs can keep down rough pasture and control unwanted plantssuch as bracken.

• Outdoor pig production also contributes significantly to soil nutrient reserves, which canreduce the need for fertiliser inputs for subsequent crops.

5.2 Environmental Impacts of Pig Farming Systems

5.2.1 Negative Impacts

Soil(see appendix 3.1)

• Soil compaction and erosion can be high in poorly managed outdoor systems orfollowing unusually high rainfall. Unless stocked at low levels or moved frequently, pigswill remove all vegetation and will create dust/water bath areas.

• The remaining sow population and grower pigs are housed and therefore any soilcompaction is associated with the actual spreading of slurry onto land.

• Low levels of zinc in slurry/FYM can contribute to potentially toxic levels followingcumulative build up in the soil which may have a negative impact on rhizobial activity inthe soil.

• Soil and water contamination risk with heavy metals and antimicrobial drugs from slurryspreading and outdoor pigs. Outdoor pigs potentially contribute more as they are in aconfined area.

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Water(see appendix 3.2)

• Research evidence has shown that nitrate leaching after pig slurry applications canrepresent 13% of the total N applied in pig slurry, compared to 15% of broiler litter butonly 1% of cattle FYM (with its lower available N content).

• Leaching beneath manure heaps can be a substantial pathway for pollution to waterbodies. There is a risk of pathogen transfer to water, as result of point source and diffusepollution associated with manure storage and land application operations.

Air(see appendix 3.3)

• Ammonia losses from pig housing (9% of total UK agricultural ammonia emissions)depend on how the manure is managed, ventilation and the amount of litter on the floor.Livestock type has a pronounced effect on N2O emissions, with pig manure emitting tentimes the loss from a deep pit laying hen house, and five times the amount from anequivalent amount of cattle manure.

• Mean ammonia emissions from buildings with housed pigs have been found to bearound 35% greater from straw-based compared to slurry-based (fully-slatted)management systems

• Dust from indoor systems is attributable to the handling of bedding, feeding (often on thefloor) and straw muck systems.

• Indoor pig units are associated with odour, at its greatest during mucking out. • There is a relatively low risk of pathogen spread by air – mainly associated with dust

particles and bioaerosols, including virus particles and bacterial pathogens. • Noise can be an issue for people living near to pig farms, however in one study it was

found that the causes of nuisance noise were attributable to vehicle movements ratherthan to animals.

• Decomposition of pig manure contributes about 2 % to agricultural CH4 emissions.

Biodiversity(see appendix 3.4)

• Very little is known about the effects of outdoor pigs on biodiversity. In the area whereoutdoor pigs are kept, all ground vegetation can be destroyed which will affectinvertebrate and bird populations.

• Ammonia emissions close to pig buildings can acidify the surrounding area and changethe habitat but the extent of this is not known (but could be predicted using atmosphericdispersion modelling and established emission factors).

5.2.2 Mitigation of Negative Impacts (Pig farming)

Outdoor systems:• Establish good vegetation cover before stocking and plant species that pigs do not like to

eat (this is now a cross compliance issue).• Use fields for 2 years maximum and have them as part of a cereal rotation (Cross-

compliance).• Use persistent grass types suited to the locality.

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• Adjust stocking rates or rotate pigs according to soil type and condition. Maintainstocking rates at <25 sows per hectare (Farm Animal Welfare Council recommendation).

• Avoid steep areas and areas near water courses (CoGAP – Water and CrossComplience).

• Consider nose ringing the sows to minimise rooting about and destroying the vegetation(Welfare issue).

• Consider positioning of wallows and huts and move regularly (Industry Guidance).

Indoor pigs:• Line all slurry stores to achieve compliance with IPPC legislation and plan adequate

capacity to reduce risk of overflows to water bodies (beyond IPCC legislation).• Cover slurry stores or promote store crusting (addition of chopped straw) to reduce

gaseous emissions (ammonia) and odour problems (Smith et al., 2007), and therebyincrease the potential utilisation of the available N by vegetation.

• Ammonia losses can be further reduced by using a partly-slatted rather than a fully-slatted system (as the non-slatted floor area covering 50-75% of the pen acts as aphysical barrier between the air below the slats and air circulating in the house). Thisevidence suggests that a Dutch-style partly-slatted system presents the best opportunityto reduce ammonia losses from pig buildings.

• To limit potential pollution from pig manures apply the same principles as for cattle: e.g.restrictions of timing and loading of applied manures and slurries with high available N toland (avoid applications in autumn/winter - NVZ Action Programme proposals August2007 extend this to cover all soils) (Defra ES0203; CoGAP – Water; and NVZ rules).

• Improved manure handling and incorporation soon after spreading (CoGAP – Air).Application techniques provide significant potential for reducing ammonia emissions, withbroadcast spreading associated with the largest ammonia loss. Although bandapplications provide significant scope for reducing emissions following slurry application,the potential for emission reduction from pig slurries using band application techniques inthe UK is less than for cattle slurry, due to the very dilute nature of a high proportion ofpig slurry, which is already associated with relatively low emissions (WA0715;Misselbrook et al, 2004).

• Whilst the dilution of pig slurry provides a benefit in terms of reduced ammoniaemissions following land spreading, the same high dilution imposes an increased cost onslurry storage, handling and spreading and associated increased risk of water pollution.Attempts should be made to reduce the addition of water from drinker and mainsleakages, wash water addition and yard run-off (CoGAP – Water; ES0203; WU0102;WU0101).

• More extensive use of synthetic amino acids to help reduce the N content of diets andreduce N excretion.

• Use dietary enzymes to improve overall digestibility of the diet. • Phytase enzymes are widely used in pig diets to maximise use of available P and reduce

P excretion (ES0203). • Select feeds of higher P bioavailability. (Plant breeders are working on this aspect).• Keep animals in groups matched to age and sex although this can create stress when

separating animals. Groups should be matched up post weaning and kept in thosegroups wherever possible from then on. Phase feed to improve the match of the diet tothe growth stage of the animal (ES0203).

• Reduce levels of mineral supplementation if possible and use feeds of higherbioavailability of copper and zinc, e.g. chelated metals.

• Research has found the use of shelter belts reduces the high concentrations of ammoniareaching downwind locations, and may be particularly suitable when such units are inclose proximity to ecologically sensitive areas or population centres (as this approach willminimise both the risk of acidification and odour). Ammonia emissions can typically be

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reduced by 13% from slurry stores and 3% from land-spread fields through the use ofshelter belts (WA0719).

5.3 Gaps in Knowledge and Future Research Needs (Pig farming)

• Increase in the number – and reduction in the cost - of synthetic amino acids as a resultof technological developments – including the development of genetically modifiedmicro-organisms. This is likely to be largely industry driven.

• Cost effective methods of estimating feed digestibility (particularly amino acids), and thesynergistic effects of different ingredients need to be investigated.

• A national survey of feeding practices (to scope for further reduction in N output andother nutrients) needs to be carried out.

• Many feed producers and livestock farmers are reluctant to reduce dietary Pconcentrations because of uncertainty over the available P concentration. Rapid andcost effective methods of estimating available P content of feeds would provide greaterconfidence to reduce safety margins.

• Little is known about the localised effects of outdoor pig herds, in terms of N and P, andimpacts on the environment. Work is needed in this area.

• Ongoing research is quantifying the use of shelter belts of woodland vegetation adjacentto outdoor pig units in promoting the local deposition of N compounds (ammonia etc) andthereby limiting odour issues and atmospheric transport over longer distances.

• The substantial dilution of pig slurry in the UK industry is not consistent with knowndrinking water requirements of pig production, current understanding on sensible wash-down water requirements and likely leakages from drinkers. This implies significantadded costs for pig producers for water charges and additional handling and storagecosts. This suggests the need for a systematic water audit on a range of pig producers,to establish the cause of the high dilution and identify ways of economising on water useand reducing associated risks of water pollution.

• As in cattle, there is an urgent need for improved quality and amount of information onfarm practices (i.e. farm activity data); to improve the accuracy and reliability ofcatchment model estimates and national inventories of emissions and to better informpolicy decisions on environmental protection strategies. The use of remote sensingsurvey techniques would be particularly useful to understand extent and distribution ofoutdoor production.

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6. Summary of Impacts - Poultry Farming Systems

For further information, refer to Appendix 4.

Key issues identified

• Improved handling of manures.• Improved efficiency of nutrient use. • Assessment of environmental impact of free range poultry• Improved abatement of dust.

6.1 Public Goods Delivered

• Free range - landscape, sheds and rangelands• Rural and semi-rural employment• Employment in feed industry, abattoirs, transport, processors etc.• Regular additions of large quantities of poultry litter to land can potentially increase soil

organic carbon levels and improve soil fertility.• 670,000 tonnes of poultry litter are incinerated in power stations. According to the British

Poultry Council around 75% of the chicken litter produced is now incinerated to generateelectricity (although our own experience suggests this latter estimate is too high).

• Possible positive impact on vegetation growth where suitable range is provided for freerange poultry, but this is likely to be a very small land area.

6.2 Environmental Impacts of Poultry Farming Systems

6.2.1 Potential Negative Impacts

Soil(see appendix 4.1)

• Soil compaction is mainly restricted to the spreading of poultry litter and manure and is ofrelatively low importance compared to effects from cattle

• At the field level, zinc inputs from layer manure are higher than those from any otherlivestock manure. While heavy metal inputs occur from broiler litter, they areconsiderably lower than those from pig and layer manure.

• Free-range layers can potentially remove vegetation and cause soil compaction anderosion in isolated areas. However, any damage to soil structure may be offset by thereduced amount of manure that has to be spread to land. Within the free-range sector,soil erosion may potentially occur across approximately 9,000 hectares but generally invery localised areas.

• The use of anticoccidials in poultry production may potentially have an impact on soilmicrobiology

Water(see appendix 4.2)

• Poultry litter has a significant available N content, and is therefore at relatively greaterrisk of nitrate leaching following application to land (compared to low available N contentmaterials such as cattle FYM).

• Leaching and runoff beneath manure heaps can be a substantial pathway for pollution towater bodies

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Air(see appendix 4.3)

• Ammonia losses from poultry housing depends on manure management, ventilation, andthe amount of litter on the floor. Odour nuisance and ammonia emissions can be anissue close to poultry sheds if the litter is damp and when poultry muck is spread to land.

• The National Atmospheric Emissions Inventory estimates that housed broilers produce30% of the total fine dust emissions in the UK but it is unlikely that emissions fromintensive broiler farms in the UK would result in an exceedance of the air qualityobjectives.

• There is a relatively low risk of pathogen spread by air – mainly associated with dustparticles and bioaerosols, including virus particles and bacterial pathogens.

Biodiversity(see appendix 4.4)

• Very little is known about the effects of free range poultry on biodiversity.• Ammonia loss (from poultry manure) and re-deposition can lead to the acidification and

nutrient enrichment of sensitive habitats (e.g. lowland heath), leading to losses inbiodiversity.

6.2.2. Mitigation of Negative Impacts (Poultry farming)

• To limit potential pollution from poultry manures apply the same principles as for cattleand pigs: e.g. restrictions of timing and loading of applied manures with high available Nto land (avoiding applications in autumn/winter - NVZ Action Programme proposalsAugust 2007 extend this to cover all soils) (Defra ES0203; CoGAP – Water; and NVZrules).

• To limit ammonia emissions keep litter dry and use wood-shavings as opposed to strawand nipple drinkers rather than bell drinkers (CoGAP – Air).

• In layer production, frequent removal of manure from house via scraper or belt systems,greatly reduces ammonia emissions and in-house ammonia concentrations, improvingenvironment for birds and workers (CoGAP – Air).

Similarly, in-house drying of manure using fans, possibly with polythene ducting,stabilises the uric acid content of layer manure and, hence, rate of breakdown andrelease of ammonia (CoGAP – Air). This provides the extra benefit of improving Nrecovery in crops following land application of manure and reducing ammonia emissionsfollowing land application (WA0638; Smith et al, 2001).

• More extensive use of synthetic amino acids to help reduce the N content of diets andreduce N excretion (Mateos et al 2005).

• Phytase enzymes are widely used in poultry diets to maximise use of available P andreduce P excretion (ES0203).

• An ongoing research project (AC0104) is looking at emissions and abatement of dustfrom poultry houses in order to make a full assessment of the human health implicationsof poultry dust. AC0104 will look at emerging abatement techniques to

6.3 Gaps in Knowledge and Future Research Needs (Poultry)

• Measurements of ammonia emissions associated with free-range production – untilrecently the emission factor (EF) for surface applied layer manure was adopted withinthe UK Ammonia Emissions Inventory (UKAEI), though this is thought likely to be an

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overestimate and was reduced in the latest inventory estimates, on the basis ofextrapolation from other data (Smith et al, 2001).

Increase in the number – and reduction in the cost - of synthetic amino acids as a resultof technological developments – including the development of genetically modifiedmicro-organisms.

Development of rapid, cost effective methods of estimating feed digestibility (particularlyamino acids), and the synergistic effects of different ingredients.

Undertake a national survey of feeding practices – so that scope for further reduction inN output (and other nutrients) may be ascertained.

• Little is known of the localised effects of free-range (FR) poultry in terms of N and P,ammonia emissions and impacts on biodiversity. FR poultry tend to stay in their shedsunless the range offered affords some shelter and ‘cover’. The rapid increase in FRunits encouraged by the impending ban on battery cages could impact on theenvironment in close proximity to the poultry sheds. There will be an increase in free-range only if producers with hens currently in conventional laying cages choose toreplace these with FR units and not enriched laying cages. (If they move to FR ratherthan enriched cages, the effect of this expansion will be more marked in some areasthan others as it is very difficult to get planning permission for new units in certain areas).These effects need to be quantified.

Many feed producers and livestock farmers are reluctant to reduce dietary Pconcentrations because of uncertainty over the available P concentration. Rapid andcost effective methods of estimating available P content of feeds would provide greaterconfidence to reduce safety margins.

Research needs common to Pigs and Poultry

Better definition of amino acid requirements is needed to improve ration formulation. • Development of crops with low phytate-P content would assist in reducing dietary P

concentrations, but the use of transgenic pigs and poultry capable of secreting phytaseenzymes is unlikely to be acceptable to consumers of pig and poultry meat and eggs, atleast in the short to medium term.

Research is ongoing by feed additive manufacturers to develop phytase additives withgreater efficacy under a wider range of conditions, for use in non-ruminant rations.

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7. Overall Gaps in Knowledge Common to all Livestock Sectors

• Rapid flow through drainage systems in cracking clay soils is difficult to control and canrepresent a major pathway for loss of N, P and other pollutants (e.g. sediment,pathogens) to water bodies. Tracer studies have shown that the majority of thissediment and nutrients are surface-derived. Further work to explore different mitigationoptions to attenuate the sediment and nutrient loss are needed to limit pollutant loss bythis pathway and hence maximise the retention of sediment and nutrients within thefarming system.

• Improved accuracy in rationing livestock (particularly ruminants) so that inputs can bemore carefully controlled and targeted and outputs minimised. This could generatesignificant benefits in the efficiency of utilisation of nutrients.

• Continued developments in animal genetics to improve efficiency in breeding and foodconversion.

• Continued efforts to develop integrated grazing systems to the benefit of biodiversity andanimal production.

In all livestock categories, there is an urgent need for improved quality and amount of

information on farm practices (i.e. farm activity data); to improve the accuracy andreliability of catchment model estimates and national inventories of emissions and tobetter inform policy decisions on environmental protection strategies. The use of remotesensing survey techniques would be useful to understand the increasing extent anddistribution of outdoor pigs and free-range poultry production for both layers and broilers.Similarly there is an urgent need for representative and accurate data on feedingpractices across all sectors; this information would provide a valuable contribution tocurrent EU and Defra initiatives to develop a methodology for estimating regional nutrientbalances (Defra Farming Statistics, York).

• Better definition of trace element requirements, to take account of new genetics,production systems, interactions between feeds etc., and a better understanding offactors affecting the bioavailability of Cu and Zn in feed materials.

• Research has shown that remote sensing (airborne, satellite) has the potential to beused to help identify locations (e.g. outdoor pig units) and ground conditions (e.g. baresoil in poached areas). Such applications are of relevance for catchmentcharacterisation of landscapes (e.g. for Water Framework Directive or Habitats Directivepurposes), for regulatory enforcement, and for advice/support purposes.

• Farmers lack guidance on how to optimise manure and slurry spreading given availableequipment (tanker capacity etc), field areas, staff time, slurry volumes, and compliancewith environmental regulations (NVZs, GAEC etc). Further work developing the ADASSPREADS software tool (the prototype developed under NT1421 has already been usedsuccessfully in a number of projects, including some work outside the UK) would enableadvisers to minimise costs by optimising the efficient application of manures and slurries(and thereby limit the risk of environmental pollution).

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8. Current Defra Funded Projects

The list below shows a range of Defra projects currently underway that will report in the nextfew years and should provide valuable information to underpin policy in the future.

Dairy and beef cattle

AC0209 - Ruminant nutrition regimes to reduce methane and nitrogen emission

AC0406 - The optimisation and impacts of expanding biogas production - £306,759 -2006-2010

LS3310 - Reducing the wastage in the dairy herd - £321,092 - 2003-2008

LS3639 - Use of the dairy cow metabolome in plasma and milk to improve health, fertility,and nutrient utilisation for milk production - £577,500 - 2002-2007

OF0372 - Nutrient efficiency, milk quality and pathogen control on low-input and organicdairy farms incorporating home-grown alternative forage crops. - £255,993 - 2006-2009

OF0382 - Minimising medicine use in organic dairy herds through animal health and welfareplanning - £49,276 - 2007-2010

LS3408 - A comparison of mainstream and at risk cattle breeds for the management of thehills and uplands - £275,929 - 2004-2009

LS3523 - Healthiness and quality of beef produced from traditional and modern breedsreared in species-rich, unimproved grasslands - £834,478 – 2004-2008

LK0676 – Improved design and management of woodchip pads for livestock overwintering -£610,900 – 2007 – 2010.

PigsLK0973 - Development and evaluation of low-phytate wheat germplasm to reduce diffusephosphate pollution from pig and poultry production units - £385,287 - 2006-2010

LS3657 - Increasing nitrogen retention in saleable meat to benefit the environment andimprove eating quality in pigs - £603,460 - 2004-2007

SheepLS3407 - Optimal grazing management systems for sheep and beef cattle in the hills anduplands - £1,452,307 - 2004-2009

LS3656 - Optimising nutrition to increase carbon and nitrogen capture in ruminant products -£953,922 - 2004-2009

VM02504 - Management of the Environmental Inputs and Risks of Cypermethrin-basedSheep Dips - £97,745 – 2007-2008

WQ0121 - Upland agriculture – balancing productivity, water and soil quality - £15,107 -2007-2008

WQ0124 - Land management options for improving water quality in the uplands - £13,382 -2007-2008

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PoultryAC0104 - Emissions and abatement of dust from poultry houses - Centre for Ecology andHydrology, ADAS UK Ltd., Royal Veterinary College, Health & Safety Laboratory: 2006-2009

Livestock ManureAC0406 -The optimisation and impacts of expanding biogas production - £306,759 -2006-2010

ES0116 Field work to validate the manure incorporation volatilization system (MAVIS) -£900,331 2002-2007

IF0114 - The development of a fertiliser recommendation system - £380,000 - 2006-2008

IF0133 - Data resources for the Fertiliser Information System - £45,277 - 2007

SP0530 - Organic Manure and Crop Organic Carbon Returns - Effects on Soil Quality (Soil-QC - £988,476 - 2004-2009

WQ0103 - The National Inventory and map of livestock manure loadings to agricultural land(Manures-GIS) - £200,088 - 2007-2008

WQ0118 - Understanding the behaviour of livestock manure multiple pollutants throughcontrasting cracking clay soils - £799,358 – 2007-2008

LK0988 – Improved assessment of nutrient content in farm manures and biosolids usingNear Infrared Reflectance Spectroscopy (NIRS) - £857,513 – 2007 – 2010.

AC0102 - Animal welfare and ammonia emissions. ADAS and IGER. The overall objective of the project is to produce an inventory of ammonia emissions for UKagriculture for each of the years 2005 and 2006, required as the major part of the total UKammonia emissions inventory for annual submission to the EC under the National EmissionsCeilings Directive. The project looks at the effects that welfare regulations may have onammonia emissions.

Soil ErosionPE0120 - Phosphorus mobilisation with sediment and colloids through drained andundrained grasslands - £801,919 - 2005-2008

SP0413 - Documenting soil erosion rates on agricultural land in England and Wales - Part 2- £414,227 - 2005-2008

Veterinary MedicinesCB02047 - Desk study to review environmental risks from marketing GM veterinary andhuman medicines - £54,962 – 2007

Integrated Farm Management

IFO124 Integrated Farm Management (IFM) -Development of an integrated managementframework and approaches for livestock farming systems. 2007-2010.

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The overall objective is to provide information on IFM that farmers can use to improve theircontribution to biodiversity and landscape management at the same time as maintaining, oreven improving, their economic sustainability

The project is being led by IGER with input form other staff at BBSRC on ruminants andforage production, with pig and poultry expertise provided by ADAS.

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Review of the Scientific Literature

APPENDIX 1

Environmental Impacts of Dairy and Beef Farming

1.1 Soil

Dairy and beef systems can potentially have negative impacts on soil compaction throughtrampling, manure spreading, maize production, and silage making. Much will depend onhow the production system is managed. Compaction can lead to reduced production (andreduced efficiency of use of other inputs), surface run-off and soil erosion. Soil microbialactivity and the degradation of cow pats can potentially be inhibited through the addition ofveterinary medicines, such as avermectins. Small additions of zinc in slurry and FYM mayalso have an impact on Rhizobia activity.

1.1.2 Soil Compaction and Erosion

Housing dairy cattle is commonplace, whereas in some beef systems, livestock are outdoorsfor much of the winter (Anon, 2002a). Hence, there is the potential for these animals tocause more compaction than dairy cattle, despite having lower stocking densities.

Within dairy and some beef systems, there can be heavy reliance on conserved maize andother forage. Growing maize can increase the risk of soil compaction and cause significanterosion in certain situations (Withers and Bailey, 2003). However, forage maize is apalatable, high-energy silage that can improve efficiency and reduce N output whencompared with a purely grass diet.

1.1.2.1 Grazing

All livestock can potentially cause significant soil compaction, especially when stocking ratesare high and soils are wet (Angell and Phillips, 2006). Compaction tends to increase withincreasing livestock density. However, soil conditions and soil type are also crucial indetermining the degree of compaction and sward degradation (Stewart and Pullin, 2006).The risks of compaction therefore increase at the beginning and towards the end of thegrazing season when soils tend to be wetter (Patto et al., 1978; Heathwaite et al., 1990) –see Figure A1.1.

Any trend towards increased stocking rates, but particularly extended grazing, can increasethe risk of soil compaction from dairy cattle. In an extended grazing system, using fieldsaround the farmstead for calving may potentially increase compaction risk.

Overgrazing and trampling by stock can decrease surface infiltration by up to 80%(Heathwaite, 1989; Mulholland and Fullen, 1991). Pietola et al. (2005) have also shown thatcattle trampling at a drinking site on loamy soil reduced infiltration rates by 80% comparedwith undisturbed pasture.

Soils can act as effective sinks or sources for methane. Soil compaction can reduce theability of soils to act as sinks for methane (Sitaula et al., 2000). In grassland systems, thecontribution of these effects is very small in comparison with the methane produced directlyor indirectly from grazing animals. For example, grassland swards might take up 1.5-2.8 gmethane carbon/ha/day whereas livestock emissions are more typically 17.9 and 74.5 gmethane carbon/ha/day from lambs and calves respectively (CC0206).

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Jorajuria et al. (1997) showed that soil compaction can reduce dry matter yields of annualrye grass and white clover by 18-74%. Soil compaction can restrict the access of roots toboth water and nutrients, but the majority of deeper soil compaction (15-60 cm depth) iscaused by machinery (Batey and McKenzie, 2006). Compaction by livestock tends to berestricted to the top 0-15 cm of soil. However, grazing combined with compaction at 10-30cm depth from tillage under ryegrass can potentially give rise to reductions in yield (Milneand Hayes 2004).

It is important to note that the effects of compaction may be transitory, especially in claysoils, where significant restructuring can take place through natural wetting and drying cycles(Soane et al., 1987).

Even so, any extension to grazing in October and November or March and April will increasethe risk of soil compaction. However, extended grazing will also reduce the volumes of FYMand slurry for spreading in late winter, particularly where NVZ closed periods apply.Therefore, for any given stocking rate, extended grazing will increase the risks from grazingin wet conditions, but will reduce the amount or extent of compaction from slurry and FYMspreading.

Within the dairy sector, spring calving and extended grazing systems may potentiallyproduce greater soil compaction through trampling due to the tendency to graze intoOctober, when compared with an autumn calving system. However, high food intake fromOctober onwards associated with autumn calving may result in greater slurry production.This greater slurry production when compared with the spring calving system could give riseto greater compaction if more slurry is spread on moist soils in the spring.

Figure A1.1. The Probability of Grassland Poaching in Relation to the Growing andGrazing Seasons, and Potential Transpiration (adapted from Patto et al., 1978)

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Taking both grazing and manure spreading into account, compaction risk increases withstocking rate and when grazing or spreading coincide with wet soil conditions.

In recent years, the overall number of dairy cows has decreased in England and Wales, dueto a number of factors including reform of the Common Agricultural Policy, lower returns,increased input costs, and bovine tuberculosis (particularly in the south west) (Defra, 2006a).Cow numbers have tended to decrease faster in the east than in the west, resulting in aconcentration in the south west and west of England. However, while there have been somelocal increases in cow numbers, due to restructuring in the industry, stocking densities donot appear to have increased at the Joint Character Area (JCA) level (Defra, 2006a). In2005, on average, holdings increasing their cow numbers also increased their grasslandarea.

1.1.2.2 Manure Spreading

In relation to compaction by machinery, Douglas et al. (1992) reported that using reduced-ground-pressure traffic systems (e.g. low ground pressure tyres and controlled trafficsystems that use exactly the same tramlines over and over again.) compared toconventional systems could increase herbage dry matter yield of perennial ryegrass (Lolium)by 15% in 66% of the harvests. This suggests that conventional machinery can not onlycause sufficient soil compaction to impact on yields, but can also impact on other soilfunctions such as water storage and nutrient supply.

1.1.2.3 Maize Production

Fodder maize can increase the potential for soil erosion as it requires considerable soilcultivation, leaves a fine seedbed, and provides little ground cover for much of the season(Anon, 2002a). Similarly, the late harvesting of maize can contribute to soil erosion bydisturbing the soil, and removing crop cover at the start of the wettest period of the year.When maize is introduced onto steep slopes and susceptible soils that have been down tograss for many years, it can result in a rapid increase in erosion and soil loss at the locallevel.

Late harvested maize is particularly susceptible to soil compaction and erosion (Withers andBailey, 2003). Choosing an early variety and avoiding susceptible soils and steeper slopesmay significantly reduce the risks of compaction and erosion (Defra, 2006b).

Cover crops can lessen erosion by reducing runoff. In one study (Anon, 2001a), white cloverreduced runoff from maize fields by over 80%, but maize yields were reduced by 40%.

Cultivating across slope can reduce run-off volumes by 50% when compared with cultivationup and down slope (Anon, 2001a).Defra project SP0404 looked at methods of reducing runoff and sediment generation undermaize. It was somewhat inconclusive but did indicate that tillage methods could be aseffective as vegetative methods based on cover crops (Anon, 2001a).

Recent studies suggest that the amount of maize grown in the dairy sector is likely toincrease as the industry intensifies further (Boatman et al. 2006; Defra, 2006a). In 2006,135,000 hectares of maize were grown across all sectors in the UK (Defra, 2006c). Thisrepresents a 14% increase since 2004, and a 370% increase since 1990.

Attempts have been made to determine whether maize is replacing grassland in the majorityof cases (Defra, 2006a). However, It is not possible to use June survey data to follow

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individual land parcels between years and we therefore do not know the previous use of landnow utilised for maize. IACS/SPS data may allow such an analysis of change in land use.

1.1.2.4 Silage Making

Silage making can also cause soil compaction that can in turn have an impact on various soilfunctions. For example, compaction may potentially shift the bacteria:fungi ratio towardsfungal dominance, affect nematode community structure, and shift mesofauna andearthworms down the profile (Creamer pers. comm). However, there is very little data on theeffects of soil compaction on grassland soil ecology.

The overall impact of silage making can be reduced by avoiding wet conditions, using lowground pressure tyres and controlled traffic systems (Douglas et al., 1992).

Short-term grass leys can give rise to compaction problems (Godwin, 2003), but this is notthe case in all catchments. Spring re-seeding of grassland can lead to cultivation in wetconditions and extensive structural damage, so autumn re-seeds would be a better optionwhere soil quality is a priority.

There is a general lack of information regarding the geographical spread and extent ofcompaction caused by machinery on grassland soils (Godwin, pers. comm.).

1.1.3 Organic Matter

Dairy farming generates manure and the vast majority of herds rely on grassland. On thewhole, soil organic matter (SOM) under pasture tends to be higher than under arable land(Anon, 2002b).

Although additions of cattle slurry and FYM may not increase soil organic carbonsignificantly in the short-term (Bhogal et al., 2006), long-term additions can give rise toincreases in SOM status and can potentially improve soil quality and fertility (Mattingley etal., 1975: Johnston et al., 1989; Persson & Kirchmann, 1994; Haynes & Naidy, 1998; VanMeirvenne et al., 1996).

Percentage soil carbon (%C) tends towards a certain equilibrium level, depending on theamount and regularity of fertiliser and manure additions (Johnston & Poulson, 2005). So,where manure is no longer applied to soils with a high organic matter content, these soils willtend to lose soil carbon until they approach a new %C equilibrium value (Mattingley et al.,1975). This new value varies according to soil texture, and the amount of fertiliser andmanure applied each year (Johnston & Poulson, 2005). The soil acts as an important globalsink for carbon, and therefore has an important role to play in limiting CO2 levels. Grasslandsystems tend to have higher organic matter and organic carbon levels than arable land.

1.1.4 Microbial Activity

1.1.4.1 Heavy Metals

Zinc concentrations in cattle compound feeds are somewhat greater than publishednutritional requirements. However, compound feeds often only form a small part of the totaldiet, whilst providing the only source of supplementary minerals and trace elements. As wasthe case with dairy cattle, zinc and copper loadings to agricultural soils are small whencompared with sewage sludge, layer manure or pig slurry (Nicholson et al., 2003).

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The essential heavy metals (Cu, Zn, Cr, Mn and Ni) are naturally present in dairy feedmaterials. In addition, Cu and Zn may also be added to diets in the form of mineralsupplements. However, heavy metal additions from dairy cattle to land are much less thanthose from intensive pigs or laying hens. Zinc and copper loadings from cattle slurry toagricultural soils are around 1.0 kg/ha/yr and 0.3 kg/ha/yr respectively. The same loadingsfrom pig slurry amount to 2.2 and 1.7 kg/ha/yr, and those from sewage sludge are 4.5 and3.2 kg/ha/yr (Nicholson, 2001; Nicholson et al., 2003).

The gradual accumulation of zinc can have an impact on soil rhizobia bacteria and theirability to fix atmospheric nitrogen in association with clover and pea/bean rhizobia (Davisand Carlton-Smith, 1984; Vigerust and Selmer-Olsen, 1986; Gibbs et al., 2006). Reducingsupplementation of livestock diets could reduce the accumulation of heavy metals inagricultural soils and help avoid potentially serious impacts on grass/clover systems. Zincand copper inputs could be reduced through:

• matching feed concentrations to livestock requirements.• reducing safety margins.• increasing bioavailability through chelation, though evidence for this is inconsistent.

Recently, the European Commission has reduced the maximum levels of Cu and Zn in dietsof cattle, sheep, pigs and poultry which will reduce the levels of Cu and Zn applied to land inlivestock manure.

1.1.4.2 Veterinary Medicines

Additions of slurry and manure tend to increase soil respiration rates (Bhogal et al., 2006)because of the addition of fresh carbon sources. However, there is some evidence tosuggest that some veterinary medicines could impact on soil microbial activity and the abilityof soil fauna to degrade manure additions.

Within the dairy system, avermectins, coccidiostats, antibiotics (to control mastitis),hypochlorite, iodine, glutaraldehyde, and foot bath chemicals (formalin, zinc sulphate, coppersulphate) can all drain to slurry stores and be spread to land.

Beef cattle receive various wormers (e.g. ivermectin, albendazole, oxfendazole, andfenbendazole), coccidiostats are used in calf rearing, and footbath formulations and pour-onpreparations (permetrin, deltamethrin, cypermethrin, alphacypermethrin) may have animpact at a localised level.

Wash-off from the coats/skin of cattle treated with pour-on formulations can occur where theanimals are exposed to rain shortly after dosing (Bloom and Matheson, 1993). As in otherlivestock systems, use of ivermectin and doramectin may impact on dung and soil insectpopulations. Doramectin can have a low inhibitory effect on soil organisms, but is unlikely todo so in the concentrations likely to be excreted by cattle or sheep (Taylor, 1999).

The degradation of cow pats, a key determinant of SOM, can be retarded by the presence ofivermectin (340 d cf 80 d for an untreated pat) (Floate, 1998). This is primarily due to thetoxicity of ivermectins to dung insect populations (McCracken, 1993).

Similarly, repeated doses of antibiotics could significantly reduce the number of bacteria,resulting in a shift in the fungal: bacteria ratio (Thiele-Bruhn and Beck, 2005) and/or increasethe occurrence of antibiotic-resistant bacteria. However, a comparison of organic andconventional pasture land (Anon, 2002b) indicates that, to date, the disruption of

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fungal:bacteria ratios is not upheld in the field. Also, further research is required to establishthe extent to which agricultural practices influence gene resistance (Schmitt, 2005).

It should also be stressed that one of the acknowledged and valuable functions of soil is as afilter and buffer for various potential pollutants from water and air systems (Burauel &BaFmann, 2005; Defra, 2004). We should therefore question whether localised andtemporary disruption to microbial activity should be accepted as part of this function.

1.1.5 Soil pH

The use of fertilisers and manure tends to increase soil acidity (Chambers & Garwood,1998), which in turn can increase the availability of aluminium and heavy metals in soil(Anon, 1993). However, it is important that grassland and tillage land within the dairy sectoris limed on a regular basis to maintain productivity. Soil pH within dairy systems tends to bemaintained towards pH 6.0 for grassland and pH 6.5 for tillage land.

1.2 Water

Dairy farming is typically on intensive lowland grassland farms, many on moderate andheavy textured soils in areas with relatively high rainfall. Significant areas which are drainedoften have bypass flow (i.e. rapid flow to depth which bypasses much of the soil matrix)enhancing the connectivity between field and receptor (river) and the associated risk fornitrate leaching reaching water bodies. Suckler herds are kept on lowland, upland or hill.Beef finishing is typically on intensive lowland units.

In a survey of over 100 dairy farms, the average farm N surplus was 257 kg N/ha (NT1842),with typically less than 20% of the N entering the system being recovered in milk and animalproducts, the remainder is either retained in the soil or lost as environmental pollution to airor water.

Annual nitrate losses from grassland can be large (>50 kg N/ha) and are correlated with totalN inputs. Nitrate leaching tends to be less from cut compared to grazed swards due to themore localised grazing returns. Excreta deposited at grazing can have a major effect onleaching losses, as localised inputs (e.g. urine hotspots) can exceed 1000 kg/ha.Applications of slurries with high available N contents carry the greatest risk of nitrateleaching to water bodies compared to manures and FYM (NT0605, NT0601). High stockingdensities on a local field level can promote soil compaction, poaching and enhance runoffrisk to water bodies.

Poorly drained soils have an increased risk of surface runoff, which is exacerbated by slopeangle and high field-level stocking densities (overgrazing/poaching). The timing of fertiliserapplications is therefore critical (e.g. 10% of February urea applications were lost in runofffrom a research site in SW England).

For grass/clover swards (clover fixes 70-300 kg N/ha) the risk of nitrate leaching appearssimilar to “grass only” swards but net benefits are possible from the reduced agriculturalintensity.

Nitrate leaching increases following dry summers when reduced plant growth leads toreduced N uptake and greater unused reserves of mineral N in the soil at the start of winterdrainage (Rowden).

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Research comparing conventional management (RB209) against Best Management Practice(BMP) showed that reductions of up to 25% in fertiliser inputs could be achieved withoutcompromising grass yield (NT1829), with associated reductions in nitrate leaching risk.

Ploughing out grass in late summer and autumn results in very large nitrate leaching losses(e.g. up to 70 kg N/ha: NT1801) and should be avoided. Ploughing out in spring to establishnew leys substantially reduces leaching compared to autumn cultivation (although the risk ofnitrate loss is still enhanced in the first winter following establishment due to the new sward’slower dry matter production).

Applications of high available N manures and slurries in autumn and early winter to botharable (NT1402, NT1410, OC8906) and grass land (NT1404, NT1410, OC8906) result insubstantially higher nitrate leaching losses compared to later applications (e.g. January).Fiqure A1.2 shows the leaching risk from slurry and FYM spread at different times of theyear. Leaching losses from applications to grassland in September were lower than fromthose in October, due to the greater N uptake by the grass receiving the earlier application.Recent research has shown that nitrate leaching losses can also be substantial from heavytextured soils as well as freely draining ones, and that losses are much greater from highavailable N materials (e.g. dairy and pig slurries and poultry manure) compared to farmyardmanure (King et al 2005). This body of evidence supports the recent proposals to changeNVZ AP rules. Due to the lower N content and carbon-rich material, the risk of leaching fromfarmyard manures is substantially less than that from slurries.

Figure A1.2. Typical N Content in Cattle Slurry (left); and Potential Nitrate LeachingRisk From Dairy Slurry (middle) and Old Cattle Farmyard Manure (FYM) (right) Appliedto a Sandy Soil in Different Months Under Contrasting Annual Rainfall Conditions.Source: NVZ Action programme Evidence Papers

The NH4 content of solid manures typically represents <25% of the total N content whenfresh, and <10% after 3-6 months’ storage. As they contain relatively low concentrations ofNH4 compared to slurries, and have a high dry matter content (25-60%), solid manuresrepresent a low risk of loss to water bodies. The corollary to this is that the notably highermineral N content in beef and dairy slurries and their lower dry matter contents results intheir applications conveying a potentially much higher inherent risk of pollution to waterbodies through surface runoff or drainage.

Specifically, evidence has indicated that slurry application rates are the most important factorcontrolling N and P (and hence FIO) losses to water in situations where rainfall occursshortly after slurry applications (NT1405). Higher application rates promote soil capping,reduce infiltration rates, and increase surface runoff. N losses in runoff remain relatively lowwhere slurry application rates are limited to no more than 50 m3/ha.

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Analysis of dairy and pig slurries shows that mean mineral N content is an importantcomponent of the total N content (e.g. 29% in ES0121). Any loss of slurry from stores (e.g.leakage) can therefore represent a serious pollution pathway for N, P and FIO loss to waterbodies – with experimental data from more than 10m depth below three out of six unlinedslurry stores overlying sandstone and chalk aquifers revealing mineral N concentrations of83-622 mg/l (ES0121).

Extended season grazing can increase the risk of nitrate loss from cattle to water bodies,primarily via lateral flow or preferential movement to drains. Nitrate losses to water systemscan increase up to two-fold where field sites are drained, due to the improved connectivitybetween soil surface and receiving water body (NT1902).

Amongst the greatest losses of N, P and pathogens from grassland to water bodies occurswhen storm events follow shortly after manure applications or during/shortly after reseedingoperations (NT1005, NT1016, NT1032, PE0102). Losses of P to water bodies from landwhich has recently received manures tend to be dominated by the P in the applied manuresrather than indigenous soil P (NT1005, NT1011, NT1012, NT1028, NT1041, NT1043), andtend to be dominated by the dissolved phase. Such losses of P from surface appliedmanures and slurries can result in very high concentrations of molybdate-reactive P (i.e. thebiologically-available fraction) in surface runoff (up to 70 mg/l) and in tile drains (NT1011,NT1012, NT1028, NT1041), and consequently slurries with a high proportion (up to 60%) ofP in water-soluble forms are particularly at risk.

FIO studies revealed that on cattle farms where crypotsporidium was present, up to 95% ofcalves were affected, and that crypotsporidium oocysts have been lost to water systems byboth leaching and surface runoff following the surface application of cattle slurries (OC0912).Furthermore, drainage waters from fields grazed by cattle or where manures have beenapplied have been shown to contain E.coli concentrations in excess of EU limits for bathingwater quality (2000 cfu/100ml). The greatest risks to water quality from pathogens inlivestock excreta arises from direct manure spreading into watercourses; where surfacerunoff and/or drainflow occur from wet soils shortly following application; and runoff fromhardstanding areas and woodchip corrals (WA0804). Solutions to reduce the first two ofthese risks include the use of buffer strips around field margins where slurry is not applied;the improved calibration of slurry spreader machinery; and the application of slurry usinginjection, trailing hose or shoe equipment; coupled with the careful timing of spreadingoperations to minimise the risk of rainfall shortly after slurry applications. Collection andstorage of runoff from all hardstanding areas and woodchip corrals, and subsequent timelyapplication of this “dirty water” to land, will help reduce the last of the risks associated withpathogen loss to water identified above (WA0656).

Silage effluent from grass, maize and whole crop cereals is a powerful water pollutant which,if allowed to enter natural watercourses, can cause considerable damage to aquatic life.However it is considered to be point source pollution and so is associated with clearlydefined discharges, which will often be avoidable, with correct system design and goodmanagement practice.

1.2.1 Strategies to Reduce Water Pollution

• Restriction of timing and loading of applied manures and slurries with high available N toland (avoid applications in autumn/winter - NVZ Action Programme proposals August2007 extend this to cover all soils, not just freely draining soils; extended “closedperiods”).

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• Reduction in the N content of livestock excreta by modification of rations to more closelymeet the requirements of the animals. .

• There is evidence that cattle raised on organic farms produce manure with lower total Ncontents compared to conventional farms (5.2 and 6.3 kg/t respectively (Anon, 2006:OBS03 report)), and hence reduce issues associated with N loadings from manures andthe risk of pollution to water and air.

• Reducing local stocking rates (which will limit N and P inputs); reducing the length of thegrazing day and/or the grazing season; and adopting zero grazing are all key strategiesto mitigate the risk of water pollution arising from dairy and beef systems (NT2511).

• Incorporation of slurries with straw and bedding (FYM) in order to reduce leaching risk(by the inclusion of a carbonaceous substrate).

• Preventing direct access of livestock to water courses, periodic movement offeeding/water troughs to reduce poaching risk (linked to Environmental Stewardshipscheme), and collection of all runoff from hard standing areas, woodchip pads etc. willreduce the potential risk of pollution to water bodies. Woodchip pads in particular areperceived as low cost but have considerable space requirements and result inconcentrated leachate, so must be fully lined and drained.

• Do not apply slurry to steep slopes etc, or when the soil is wet or frozen (GAP).Incorporate applied manures and slurries into the soil as soon as possible, and do notleave them on the surface of compacted soils (NT1028).

• Transfers of N and P (and hence FIOs) following recent manure applications are a majorissue for wetter, grass-dominated areas such as Wales and SW England. Reducing thefrequency of reseeding operations, and careful timing of applications to avoid wet soils,and the incorporation of manures into the soil as soon as possible after application, willreduce the runoff risk and minimise ammonia losses.

• Establishment of ungrazed, unfertilised buffer strips at the edges of fields, and theconstruction of retention ponds/wetlands downstream of the agricultural area, are botheffective mitigation methods for reducing pollution from cattle systems reaching primaryriver systems.

• Fencing off river banks to prevent cattle access can substantially reduce bank erosion(sediment), and riverine inputs of nitrate (urine, faeces) and FIOs. This is now includedwithin Environmental Stewardship options.

• Correct setting of slurry spreader widths (NT1415, NT2002) and increased use ofmeasurements of available N in slurries (e.g. by sampling, or using Agros/Quantofixequipment) would improve the targeting of slurry N applications to land with the resultingbenefit of constraining the risk of pollution to both water and air. Limit slurry applicationsto reduce the risk of surface runoff (50m3/ha).

• Line all slurry stores to achieve compliance with IPPC legislation and reduce leakage towater bodies.

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• Better consideration for the P and N status of soils and the available N and P contents inmanures and slurries when determining application rates, timings and applicationmethods.

• Ploughing out grass in autumn releases up to 70 kg N/ha: reseeding should beundertaken early in spring so as to maximise the use of the N released by mineralisationand thereby reduce the potential for nitrate leaching.

• For fertilised grass systems, move from using urea to alternative fertiliser types (such asammonium nitrate), as this reduces the potential loss from ammonia volatilisation

1.3 Air

1.3.1 Methane

National CH4 emissions in 2000 were estimated at 2.377 million tonnes. Around 37% of UKCH4 emissions emanate from agriculture. Ruminant livestock make the largest contributionas CH4 is produced as a by-product of the microbial breakdown of carbohydrates in therumen. Decomposition of slurries and manures also generate CH4.

1.3.1.1 Factors Affecting Methane Production

• Level of feed intake: Increasing feed intake increases the rate at which feed passesthrough the rumen, leaving less time for microbial fermentation of the diet

• Carbohydrate level and type: In general, increasing the proportion of concentrate – andreducing the forage component – results in a reduction in CH4 excretion (as a proportionof total energy intake) although this has not always been observed. The form of thecarbohydrate can also influence CH4 production, mainly through effects on rumen pHand the microbial population.

• Addition of fats: Additions of oils and fats to ruminant diets have reduced CH4 production,but these effects have been attributed to a reduction in the amount of fermentablesubstrate rather than a direct effect on methanogenesis.

• Forage processing: Grinding and pelleting forage can markedly reduce CH4 production,but this is most likely the result of increased rate of passage through the rumen.

• Addition of ionophores: Addition of ionophores, particularly monensin, has been shownto reduce acetic:propionic acid ratio and production of CH4, although long-term studiessuggest that this effect may not be persistent. Although this feed additive is no longerpermitted.

1.3.1.2 Strategies for Reducing Methane Excretion

Mitigation strategies for reducing CH4 emissions include:

• Diet manipulation: Increasing the proportion of starch or sugar rich feed (e.g. cereals,molasses) and reducing the forage component is likely to be the most effective on-farmstrategy currently available for reducing CH4 production. However, this can haveconsequences on crop management, production costs and the quality of animal product

• Increasing efficiency: Increasing the efficiency of animal production will result inreductions in CH4 emission associated with maintenance requirements and non-productive stock. For example, Garnsworthy (2004) estimated that CH4 emissions by theUK dairy herd would be reduced by 10-11% if reproductive efficiency was restored to1995 levels, and that further improvements in fertility could reduce CH4 emissions by upto 24%.

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• There is also scope for reducing CH4 through animal breeding programmes by, forexample, breeding cows with greater longevity (thereby reducing replacement numbersas reported by Garnsworthy 2004) or cattle with improved feed conversion efficiency, i.e.less input for the same output.

• Anaerobic digestion of cattle manure enables the resulting CH4 to be collected and usedas fuel, which has the added benefit of reducing CO2 emissions by limiting the need forconventional energy systems derived from the burning of fossil fuels.

Despite the fact that methanogenesis represents an energy loss in ruminant livestockproduction, there appears to be little incentive at present for livestock producers to reduceCH4 production. Any changes in diet formulation are more likely to be as a result of changesin feed costs, availability or to manipulate product quality.

1.3.1.4 Areas for Further Development and Research

Feed additives: Ruminants are ideally suited to consume and digest forages, yet CH4production is greatest on high forage diets. Because of this, considerable research effort –in the UK and world-wide - is being devoted to identifying feed additives that act as CH4inhibitors for inclusion in high-forage diets. A number of supplements hold promise asstrategies to reduce CH4 excretion in ruminants; at present many of these compounds havedemonstrated effectiveness in vitro or in sheep, but have not been tested for their efficacy inlactating dairy cows, or the persistency of their effects. A Defra-funded research project atIGER (AC0209) has recently started to examine some of these with a view to developingthem for commercial use.

Recent research at IGER suggests that an increase in water-soluble carbohydrate inperennial ryegrass leads to a reduction in CH4 production (Lovett et al., 2006). A successfulprogramme of genetic improvement of forage grasses and legumes has led to thedevelopment of high-sugar grasses, and the potential for these to reduce CH4 output will beexplored in Defra project AC0209.

In sheep housed indoors and fed with different legumes (lucerne, sulla, red clover, chicoryand lotus), CH4 losses were reduced by between 20 and 55% as compared to animalsgrazing ryegrass/white clover mixtures (Ramirez-Restropo & Barry, 2005). Further researchis underway at IGER focused on identifying the genetic variation underlying ‘environmentalsustainability’ traits which have the potential to decrease CH4 (and nitrogen) emissions peranimal and per unit output. These include development of varieties with elevated levels ofcondensed tannins.

Research has been undertaken, principally in Australia, on the development of anti-methanogenic vaccines to reduce CH4 emissions. Although initial studies looked promising –and large numbers of cattle and sheep were vaccinated – further research is needed toestablish long-term efficacy.

Recent research (Vlaeminck et al., 2006) suggests that the microbial ecosystem in therumen may be reflected in the fatty acid profile of milk fat. This seems particularly true forodd- and branched-chain fatty acids (OBCFA), since these acids are synthesized by therumen bacteria and their excretion in milk reflects the microbes and microbial activity. TheOBCFA have been used to predict the duodenal flow of bacterial crude protein and therumen fermentation pattern. Although additional studies are needed to elucidate and verifythe relationship between milk OBCFA and CH4 production, if proven valid, this would providea useful and non-invasive tool to study changes in CH4 losses

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Around 10% of the CH4 loss from livestock is released from manures (Anon 2004), and CH4emissions decline to negligible levels by 10 days following application. Between 1.75 and 40kT per annum of CH4 is released from manure deposited during grazing by UK dairy cows,and this compares to 804 kT per annum from enteric fermentation (WA0604).

1.3.2 Ammonia and Nitrous Oxide

Cattle farming accounts for the largest emission of ammonia, representing 56% of totalagricultural emissions. Following excretion by grazing cattle, or the application of manuresto the soil surface, typically 10-60% of the readily available (i.e. ammonium) N is lost to theatmosphere by ammonia volatilisation. Gaseous losses are influenced by dry mattercontent, with around 65% of the ammonium-N in FYM typically lost as ammonia. The totalammoniacal nitrogen (TAN) content of fresh FYM is 25%, but only 10% after it has beenstored, and as a consequence, ammonia emissions are greater when fresh FYM is spreadon land.

Cattle account for just over 40% of the N2O emissions from agriculture with beef contributingsignificantly more (23%) than dairy cattle (17%). There are both direct and indirectemissions of N2O. Direct emissions are those emissions resulting from N inputs to soil (e.g.from faeces and urine at pasture, inorganic N fertilisers, manure applications to land),manure storage, crop residues and biological fixation by legumes. Indirect emissions arethose associated with NO3 leaching and N deposition from the atmosphere. The greatestproportion of N2O emissions comes from arable cropping (31%).

Denitrification losses are highly spatially and temporally variable, but reduced N fertiliserinputs through a tactical approach did not reduce annual denitrification losses. Losses fromgrazed swards tend to be slightly greater than cut swards due to the effect of slurry returnsto the grazed area (NT1801). Up to 60% of the denitrification losses occurred at 10-40 cmdepth in poorly drained soils, with the greatest losses following fertiliser events.

Due to the lower grazing intensities in organic farming systems compared to conventionalsystems, total N2O emissions from organic cattle have been found to be 57% lower thanthose from a comparable conventional farm (OBS3 report). Other researchers haveestimated this effect to be closer to a 20-25% reduction from organic systems.

Most nitrous oxide occurs as the manure and urine are deposited on the soil. However, aswith CH4, producing a given amount of product from a smaller number of high producinganimals reduces N2O emissions. Options for reducing the amount of nitrogen excreted peranimal include the replacement of nitrogen-rich forages with low protein forages such asmaize, and breeding grasses which have a better balance of energy and protein, e.g. thehigh sugar grasses bred at IGER Aberystwyth.

Analysis of aerosol dispersion of pathogens during slurry spreading indicates that somepathogens can be transported up to 1.5 km from the location of application (WA0804). Hightrajectory applications are to be prohibited (NVZ AP), but there remains the opportunity toreduce ammonia emissions and odour problems further through shallow injection or band-spreading using trailing hose and trailing shoe methods. Research has shown that bothtrailing hose (arable) and trailing shoe (grassland) methods can reduce ammonia (andassociated odour) emissions following slurry applications by 30-70% compared with surfacebroadcasting, and that cattle preferred grazing the bandspread/injected slurry areas(NT1401, NT2001). Ammonia losses can be reduced by incorporation of surface appliedmanures, or by shallow injection of slurries, although this does have a limited potential toincrease nitrate leaching losses (“pollution swapping”). The same research also revealed a

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notable additional positive associated with bandspreading - the perceived increase in totalspreading days (>140 days compared to <60 days for broadcast), following initial capitalinvestment in equipment.

Total ammonia emissions can be 26% higher from organic compared to conventionalsystems (OBS03 report) but this is difficult to explain in light of other work, although theseeffects are often localised. In loose-housed cattle systems, ammonia losses can be reducedby increased use of straw which absorbs the ammonia gas (i.e. mean emissions from slurry-based systems are 31% of the total ammoniacal N (TAN) excreted in the house compared to21% for straw-based systems. Comparing a straw-based system with one where anadditional 25% of straw has been used resulted in a reduction in ammonia losses by 35%(AM0103), although increased use of straw beyond that level did not result in any furtherdecreases in ammonia loss and introduced practical constraints.

Rapid incorporation of surface applied slurries and manures also substantially reducesammonia loss. Ploughing, disk harrowing, and straw incorporation of applied slurries havebeen found to reduce ammonia loss by 16%, 30% and 38% respectively, while incorporationof FYM by ploughing has been found to reduce ammonia emissions by around 90%.Incorporation of manures is an effective mitigation measure to reduce ammonia losses. Thisis especially the case for FYM as a greater proportion (around 80%) of the TAN is lost asammonia, as FYM is not washed into the soil as rapidly as slurry.

Ammonia emissions from manure stores are directly related to the storage surface arearather than the amount of manure stored. Emissions from slurry stores are stronglyinfluenced by whether it is covered, as well as wind speed, temperature, pH, and thefrequency of mixing. Covering tanks and slurry lagoons has been found to reduce ammoniaemissions by up to 80%, and by excluding rainwater from the store there is the added benefitof reducing the overall volume of material requiring storage and spreading.

Much of the ammonia loss during slurry spreading occurs during the first few hours, withemission rates decreasing rapidly thereafter. Mitigation options to reduce ammonia lossestherefore include rapid incorporation of applied manures and slurries.

Annual ammonia losses from hard standing areas are estimated at 18 kt NH3-N. In terms ofabatement measures on individual farms, pressure washing the hardstanding area reduces ammonia emissions by around 91%, although use of urease inhibitors has proved to haveinconsistent results (AM0111). However, although pressure washing is highly effective atreducing ammonia losses, it generates large additional volumes of dirty water (ca. 10-30litres/cow/day) which require storage and spreading to land.

The development of a natural crust on the surface of stored slurry reduces ammonia lossesby around 50% - but the development of such a crust will be hindered if stores are top-filled.

Most of the ammonia emissions from farmyard manure (FYM) heaps occurs within the first30 days of storage, and losses are increased if the heap is turned to encourage compostingor additional manure is added to the heap.

Losses of ammonia during and after grazing depend on the amount of fertiliser N applied topasture – high N applications increase herbage N contents, which increase the N content inthe excreta of grazing cattle (and hence the risk of N loss as ammonia to air, or as nitrate towater). Ammonia losses from grazing livestock are associated with the urine deposited onthe pasture. As urine usually infiltrates rapidly into the soil, ammonia losses are

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proportionately less from the urine from grazing animals compared to that from deposits toimpermeable floors in houses or onto hardstanding areas.

1.4 Biodiversity

In 2000 44% of all UK ammonia emissions came from cattle, including both dairy and beef(Defra 2000). The most widespread environmental problems arise when ammonia isdeposited from the atmosphere onto plants, soil and water. Most is deposited close to whereit is emitted, but some may be blown long distances before being deposited, often in rain.This is mainly over upland areas that receive high rainfall.

Ammonia, when deposited from the atmosphere onto land can enrich the nitrogen content ofhabitats. The semi-natural landscape tolerates only low levels of nutrients, and largeammonia deposits can disrupt the delicate balance of plant communities, favouring thegrowth of a few common, fast-growing species at the expense of a greater range of plants,often of conservation value. Nitrogen enrichment (also known as ‘terrestrial eutrophication’)threatens about a third of valuable ecosystems in the UK, including upland and lowlandheath, upland bog, semi-natural grassland and some woodlands.

When deposited in large quantities, ammonia can also cause some upland soil, streams andlakes to become acidic, affecting plants and aquatic biodiversity. Elevated pH and watertemperature and ammonia have been reported to be associated with frog embryo mortalityor malformations (Boyer and Grue, 1995; Ortiz-Santaliestra et al., 2006). The natterjack toad(Bufo calamita), which is intolerant of acidic waters, has been lost from several heathlandsites in the south-east of England (Beebee et al., 1990).

1.4.1 Impact of Dairy Systems

1.4.1.2 Intensively Managed Grassland

Modern dairy systems are largely dependent upon intensively managed grassland where thestructure and composition of the sward is very limited. The high nutrient status of the soil,maintained artificially by fertiliser use, encourages the rapid growth of agriculturallyproductive grasses, such as rye grass. This vigorous growth suppresses any smaller, slowergrowing species limiting the botanical diversity of the sward.

An exponential relationship has been identified between monetary returns and intensificationof farming methods over a wide range of grassland productivity’s and farm systems. Atintermediate to high levels of fertility, however, this exponential increase in financial benefitfrom intensification is associated with a decline in biodiversity and an acceleration of theecological processes driving species loss from grassland ecosystems. (Hodgson et al. 2005)

On livestock farms where nitrogen inputs were higher than 75 kg/ha, an average of threeforb species say what this is and what it indicates was found in grassland, whereas higherforb diversity was found only in grasslands receiving less than 15 kg/ha of nitrogen (Tallowin,unpublished, cited in McCracken & Tallowin 2004). A sward of limited plant diversityencourages an even pattern of grazing and so is also likely to have limited structuraldiversity. These two limitations will severely restrict the invertebrate population that caninhabit the sward. (Andrews and Rebane 1994, Thomas, 1984)

Many butterfly populations have suffered from loss of unimproved pasture (Rands andSotherton, 1986). Ploughing and reseeding old pastures with rye-grass Lolium swardseliminates all known larval food plants of British butterflies (Woiwod and Stewart, 1990).

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Sawfly numbers have suffered from a reduction in the number of longer-term grass leys(Barker et al., 1999) and insect diversity generally is lower in more intensively managedfields (di Giulio et al., 2001).

Intensification of lowland livestock farming over the past 50 years has reduced the suitabilityof grassland as a feeding and breeding habitat for birds. The most important direct effectshave been deterioration of the sward as nesting and wintering habitat, and loss of seedresources as food. Also, the abundance and diversity of invertebrates declines withreductions in sward diversity and structural complexity (Atkinson et al 2004).

Intensively managed grassland involves the use of nitrogen fertiliser to encourage optimumproduction. Amphibian insect prey and predators of amphibians such as fish can be verysensitive to nitrate levels in water. Several studies, for example, Oldham et al. (1997) andMarco et al. (1999) have shown that nitrates and nitrites adversely affect the growth andsurvival of amphibian larvae, causing reduced growth, increased incidence of deformities,paralysis and death. However, the application of manure or slurry to fields to improvepasture is beneficial to earthworm abundance (Wilson et al., 1999).

Dairy units normally use silage rather than hay for winter feeding. Grassland grown for silageusually consists of highly fertilised reseeded swards and two or three cuts may be taken inone summer. This allows little time for both grass and forb species to flower and set seed,and little opportunity for seed to enter the seed bank (McCracken & Tallowin 2004). Incontrast, hay is usually cut in mid- to late summer allowing many plants to have set seed.Also, seed will be released during handling and transportation and dung from stock fed haywill also contain large quantities of seed, which can be deposited back onto grassland with apossibility of germination. The environmental benefits of hay meadows are further describedin the sheep section below.

1.4.2 Impact of Beef Systems

1.4.2.1Unimproved Pasture

Beef cattle can utilise unimproved pasture, especially coarse vegetation or wet grassland,and are an important tool in maintaining and managing such areas. However, beefproduction may sometimes be an incentive to improve pasture and the environmentaldisadvantages of this are described in the dairy section above.

The biological features of grassland are profoundly influenced by, and in many casesfundamentally determined by, the grazing regime imposed upon it (Crofts and Jefferson1999). Work by Tallowin et al. (2005) and Buckingham & Peach (2005) provide an insightinto how modified grazing management can improve biodiversity and habitat quality forfarmland birds. Low input livestock systems are vital to maintain and restore the ecologicaldiversity of semi-natural lowland grasslands.

Old, unimproved grasslands, maintained by traditional management practices, includinglivestock grazing, are an important habitat. Grazing is essential to maintain the swardstructure characteristics required by waders and other ground nesting birds in wetgrasslands (Milsom et al 2001, Treweek et al. 1997).

Cattle use their tongues to pull tufts of vegetation into the mouth. This means that they donot graze vegetation too close to the ground and often leave tussocks of grass which areused by insects and small mammals. Because of their wide mouths cattle do not grazeselectively and as a result do not target flower heads and herbage which is important for

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botanically diverse habitats. Cattle are able to create their own access into rough areas andthe trampling of these areas can be an important way of controlling scrub (English Nature2005).

Habitat structure exerts a major influence on the distribution and abundance of arachnids(spiders, harvestmen, mites, ticks, scorpions and false-scorpions). Swards with variedstructure, including long stems and some bare patches can support most arachnids. Grazingherbivores affect the habitat structure and hence influence arachnid populations and theirabundance is directly related to grazing management. (Gibson et al., 1992, Rushton et al.,1989 and Dennis et al. 2001) Intensive grazing can lead to their virtual extinction (Thomasand Jepsen, 1997)

Species richness and abundance of butterflies are enhanced by low stocking rates, and thisis true for both butterfly species preferring short grasslands and those preferring tallgrasslands. (Wallis de Vries et al. 2005)

Two butterflies, the High Brown Fritillary Argynnis adippe and Pearl Bordered FritillaryBoloria euphrosyne are UK BAP priority species. Both are dependent upon a habitat bestmanaged by extensive cattle grazing. They require bracken interspersed with grassypatches and canopy gaps with abundant violets growing through the litter. The action ofcattle (or possibly ponies) is important to trample the bracken, breaking up the standingtrash, creating a network of paths and opening up the canopy to admit sunlight. Without suchmanagement of a site, bracken would quickly become too dense to support the violets andthe butterflies would disappear (English Nature, 2005)

The Limestone Country Project in the Yorkshire Dales was launched in 2002 as a responseto the poor condition of many important wildlife habitats. One of the key factors driving thequality of wildlife across the area was the gradual move away from cattle grazing on the highlimestone pastures to systems based almost entirely on sheep (Evans 2006).

The Moorland Project (ADAS – Defra Project BD1228) has shown the benefits of summergrazing with cattle for moorland regeneration by reducing competitive grasses.

Lyme's disease and louping ill are associated with tick infested upland pastures withbracken. Undergrazing, particularly with cattle, and inappropriate management is thought toassist in transmission of these two diseases (Silcock et al 2005).

The Brown Hare is recognised in the Biodiversity Action Plan, which calls for a doubling ofthis species' numbers by 2010 (UK BAP 1995). Hares are best sustained by mixed farmingsystems that provide them with a diversity of crops at different growth stages, so that shortgrass or crops are available all year round (Tapper and Barnes 1986).

Grazing is essential to maintain the sward structure characteristics required by waders andother ground nesting birds in wet grasslands (Milsom et al 2001). Coastal and floodplaingrazing marshes are particularly important for breeding and wintering waterfowl such assnipe, curlew and swans. These marshes also have ditches that are rich in aquatic plantsand invertebrates. Riverside flood meadows, subject to winter inundation, are also importantfor breeding and wintering waterfowl (English Nature 2005).

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1.4.2.2 Hay Meadows and Silage Fields

Today, silage is the most common method of conserving grass for cattle but some cattle arefed hay. See the section under sheep below.

1.4.2.3 Moorland and Heathland

Many moors and heaths are grazed by cattle and whilst heavy stocking rates, particularly inwet weather, can cause damage, cattle grazed at a low stocking rate and preferablyremoved in winter can be very beneficial. Dung left by grazing animals supports a richinvertebrate population, providing important feed for young birds and increasing theirchances of survival.

Cattle are generally unselective grazers and will eat coarse vegetation and dead plantmaterial. They avoid eating heather unless grasses and sedges are unavailable (Adamsonand Critchley 2007) Cattle are useful in reducing the amount of rank vegetation such astussocky Molinia on a site. However, they do not play a major role in scrub management andare not predominantly browsers, although they may break up scrub stands by trampling andpushing through them (Lake et al. 2001).

Cattle are less discriminate than sheep when grazing Calluna, and are more likely to causedamage through shoot death, uprooting and trampling. However, cattle grazing has lessimpact on regenerating heather than sheep, which tend to select the growing tips (vanWieren, 1989). Cattle grazing is not considered particularly suitable for Calluna dominatedstands in the uplands (Welch, 1984), but can be effective in reducing invasive grasses, suchas Nardus stricta, and encouraging Calluna regeneration (Lake et al. 2001).

Cattle selectively graze Molinia, enhancing opportunities for regeneration of dwarf shrubsand other species. Wet heath vegetation is unlikely to be restored by grazing with sheepalone. The mixed grazing regimes applied here were economically viable in the first year andhave potential for aiding restoration of wet heath vegetation. Long term effects will continueto be assessed (Critchley et al 2005).

The trampling effect of cattle can have a beneficial effect on the mat of dead vegetation thatforms under some types of grass. The hoof prints expose dormant seed and create a micro-climate that aids the establishment of a wide variety of plants. Trampling can break upstands of purple moor grass and can damage bracken, reducing its spread. However, cattleon wet heaths and blanket bogs can damage soils and vegetation in late autumn and winter(Scotland’s Moorland Forum 2003).

Supplementary feeding, especially involving the use of round feeders, can be damaging tothe immediate area. Loss of vegetation and poaching by heavy grazing may lead to erosion.Thus, the absence of vegetation and root systems to protect and stabilise the soil and thedisruption of the soil surface allow wind and water to wash soil away. This can lead to furthererosion as the less stable mineral soil layers are exposed. This is a consequence of over-grazing in British upland systems has been of serious concern (Bardgett et al., 1995;Thompson et al., 1995).

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1.4.2.4 Woodland and Trees

Grazing beef cattle in woodland or wood pasture is a common practice, especially to provideshelter to outwintered animals, and offers both benefits and disadvantages for theenvironment. At an extensive level, with low stocking rates it is generally beneficial tobiodiversity in that it prevents mass regeneration of trees and shrubs and reduces theexisting shrub layer, thereby reducing competition between trees for light, creating morevaried growth forms of trees and a greater variety of woodland structures, including openglades. This results in a greater diversity of habitats with increased light levels that arebeneficial to epiphytic lichens and invertebrates. Sunlit trunks are warmer, providing betterconditions for larval development and for wood-decaying fungi to fruit. Dominant groundflora species can be reduced (Read 2000, Armstrong et al. 2003). The Netted Carpet Moth Eustroma reticulatum is a UK BAP priority species dependent uponthe presence of grazing cattle in woodland over winter. This rare moth, mainly found in theLake District, is dependent upon its food plant, ‘touch-me-not balsam’, which grows in dampwoodland with dappled shade, high nitrogen and organic content soils and severe annualground disturbance (English Nature).

At higher stocking rates grazing can be detrimental to woodland and may result in acomplete lack of tree regeneration and poaching leading to infestations of pernicious weeds.Supplementary feed increases the nutrient levels of the soil via dung deposition and mayalso introduce new species and genetic variability via seeds. It can thus influence the plantcommunity. Animals also introduce chemicals into the woodland or wood pasture habitat, ofparticular concern in cattle treated with a long acting wormer bolus. Residues in faeces canpotentially affect invertebrates, especially those involved in the breakdown of dung, andinsectivorous species such as birds and bats that may suffer from a lack of prey (Read2000).

Trees can regenerate in the presence of cattle although the chances of achieving some treeregeneration (good or poor) decline as cattle grazing pressure increases. However, evenwhen cattle graze for 12 months of the year, there is still an approximately 30% chance ofachieving some tree regeneration. With no cattle grazing, there is only an approximately20% chance of achieving good tree regeneration and this declines as cattle grazing pressureincreases (Armstrong et al. 2003).

In wood, pasture or parkland situations individual trees may be used for shelter by cattle.Frequent trampling and poaching below the canopy can damage the roots and with a buildup of dung and urine the high nitrogen levels are detrimental to mycorrhizal fungi. (Read2000)

1.4.3 Veterinary Medicines

The avermectins, commonly used to treat parasites in cattle, are powerful insecticides.Exposure of dung living insects to avermectins can elicit a number of responses, includingadult and larval mortality, an effect on feeding, disruption of water balance, a reduction ingrowth rate, interference with moulting, inhibition of metamorphosis and/or pupation,prevention of adult emergence, disruption of mating and interference with egg productionand oviposition (Strong, 1993; Strong and Brown, 1987).

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As a consequence, dung from animals treated with avermectins may not support thedevelopment of either target or non-target insects. The possible indirect effects ofavermectin contaminated dung on vertebrate populations has also been highlighted (e.g.McCracken, 1993), their use may result in a depletion in the quantity and quality ofvertebrate food resources, which may be particularly critical during the breeding season orwhen young animals are foraging and fending for themselves.

The potential toxic effects of doramectin have been studied in species that typically breed orfeed on cattle dung. Researchers reported that mating and oviposition were unaffected bythe presence of doramectin at up to 250 µg kg-1 in dung, although larval development wasaffected at concentrations of between 64 and 250 µg kg-1 (Taylor, 1999).

Moxidectin is less toxic to dung-inhabiting insects than ivermectin, for example, it is 64 timesless toxic than ivermectin against Onthophagus gazella and Haemotobia irritans (Doherty etal., 1994; Strong and Wall, 1994).

The magnitude of this problem is not currently known and further work is needed to quantifythe impacts of faecal residues of anthelmintics on invertebrates and vertebrates.

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APPENDIX 2

2. Environmental Impacts of Sheep Farming

2.1 Soil

Where stocking densities do not cause compaction, and particularly where shepherding isused to move flocks between areas, sheep grazing can have a positive benefit as far as soilecology and wider biodiversity is concerned. Sheep production in the uplands canpotentially contribute towards sustaining soil erosion by water.

In the lowlands, stocking densities tend to be positively correlated with soil bulk density andnegatively correlated with infiltration rates. However, soil wetness can have an overridinginfluence on whether soil compaction and erosion occur. One potential “hot spot” is thegrazing of store lambs on stubble turnips, especially where this is carried out in wetconditions. However, on light textured soils near surface compaction can normally bealleviated using standard cultivation methods.

Sheep do not make a significant contribution to heavy metal loadings in agricultural soils.However, the drugs used for the control of internal and external parasites, either asinjections, dips (diazinon) or pour-ons can potentially impact on soil flora and fauna.

Soil organic matter (SOM) levels under grassland tend to be higher than under arable land.Another benefit of sheep production, particularly in the uplands is the improvement ofgrassland through liming. This raises soil pH and can potentially reduce the loss of solublealuminium in surface waters.

2.1.1 Soil Compaction and Erosion

A standing sheep can exert around 80 kPa of pressure on the soil surface. This canincrease to 200 kPa when the sheep moves (Willatt & Pullar, 1983). By comparison, anunloaded tractor exerts between 60-80 kPa of pressure (Blunden et al. 1994). These effectsare generally limited to the surface 5 cm of the soil (Greenwood et al. 1997) and the amountof damage will vary with the soil water content.

Increases in sheep stocking rates have been associated with:

• lower hydraulic conductivities and infiltration rates (Willatt & Puller, 1983; Greenwood etal., 1997)

• higher bulk densities (Langlands & Bennett 1973; Carroll et al., 2004)

However, the relationship between stocking rate and bulk density does not seem to beconsistent across all soil types.

Carroll et al. (2004) reported reduced infiltration rates and a compaction problem acrossthree Welsh upland sites, but there was no simple link between infiltration rates or bulkdensity and stocking rate. At ADAS Pwllpeiran, soil bulk density actually decreased from lowto high stocking rates. This relationship may be particular to mineral soils with a peaty toplayer and there seems to be a lack of information about the impact of livestock densities onthese soil types (Carrol et al., 2004).

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Although many studies have looked at the impact of stocking rate on the soil, most havelooked at lowland systems. Under these conditions a combination of heavy machinery useand grazing pressure may contribute to soil structural damage. In the case of store lambfinishing on stubble turnips, this can give rise to significant compaction and erosion,especially when soils are wet (Angell and Phillips, 2006).

In the uplands, while water erosion may be responsible for the initiation of erosion, sheep(and humans) are largely responsible for its continuance (McHugh & Harrod, 1999; Anon,2002c). In 1999, some 25,000 ha, or 2.5 per cent of the uplands of England and Wales wereaffected by erosion. On 6,541 ha, the erosion was directly attributable to the effect of sheepgrazing, walking and vehicles. Further increases in erosion occurred between 1999 and2002, with sheep grazing as the main cause. Although peat soils were most sensitive towater erosion, grazing animals and walkers were the main causes of erosion on mineralsoils (< 40 cm of peat in the top 80cm of soil). There was some evidence of recovery and re-vegetation during the foot-and-mouth outbreak of 2001.

The positioning of feed racks or supplementary feed blocks may exacerbate erosion.Shepherding (moving sheep) can reduce the potential for soil erosion by preventing localisedhigh stocking densities, but is unfortunately no longer financially viable (Parry et al., 2006).

Although overgrazing can lead to increased soil erosion, it is important to note thatundergrazing can lead to a change of habitat and an associated loss of desirable species.Current economic pressures are leading to a reduction in sheep numbers across large areasof the English uplands (Parry et al., 2006).

2.1.2 Microbial Activity

2.1.2.1 Heavy Metals

The heavy metal loading from sheep excreta is not thought to be significant at a local ornational scale (Nicholson et al., 2003).

2.1.2.2 Veterinary Medicines

Within the sheep sector, ivermectins and wormers are used widely and may influence thedegradation of dung (Floate, 1998). Cypermethrin sheep dips have now been withdrawn,but synthetic pyrethroid pour-ons (deltamethrin, high cis-cypermethrin, alpha cypermethrin)are still used. These present a slight risk to water, but the risk to soil is negligible, as there isnormally no excess for disposal. Only drips from sheep in holding pens will have an effect onsoil.

Organophosphate (diazinon) is now the main chemical used for sheep dipping. Diazinon istoxic to honey bees, earthworms and some other soil fauna (Larkin & Tjeerdema, 2000).Dips may therefore have a limited impact on soil organisms where these are spread underlicence.

However, the persistence of diazinon in soil can vary quite widely (Atterby et al., 2002;Boxall et al., 2002). The half-life ranges from 2 to 112 days, according to soil moisture andsoil type. Bacterial enzymes can speed the breakdown of diazinon and have been used intreating emergency situations such as spills. Diazinon seldom migrates below the top 2.5 cmin soil, but in high risk situations (shallow, stony soils and permeable rock) it may reachgroundwater (Atterby et al., 2002).

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In addition, one company claims that research carried out at the Central ScienceLaboratories in York suggests that an enzyme, derived from natural soil bacteria, is capableof reducing diazinon in spent sheep dip to trace levels within a few hours(http://www.animax-vet.com/index.php?option=content&task=view&id=69&Itemid=).

2.1.3 Soil pH

Defra project SP0201 attempted to assess the contribution of upland agricultural land to theacidity and aluminium (Al) content of surface waters (Anon. 1993). Surface water sampleswere collected from limed and unlimed mini-catchments over the winter’s of 1989/90 to1991/92 at ADAS Pwllpeiran (west Wales) and ADAS Redesdale (Northumberland). Thedata showed that inorganic Al concentrations (the form most toxic to fish) were highest inacidic waters, with increasing levels related to low topsoil pH values and elevatedexchangeable Al concentrations. The study showed that agricultural land can contribute tosurface water Al levels, with the amounts lost dependant upon topsoil pH levels and thebalance of land uses (i.e. forestry, moorland and agriculture) within a catchment.

This would suggest that where soils are not limed in a more extensive sheep rearing system,or if areas of improved pasture are abandoned, natural increases in soil acidity could lead tohigher inorganic Al concentrations in surface waters.

2.2 Water

Sheep are typically kept in extensive upland and more intensive lowland grassland systems.N inputs are lower and mostly originate from feed, low fertiliser additions, atmospheric Ndeposition, and N fixation. Nitrate losses per unit area are consequently lower than fromdairy and some beef systems, but the absolute area in England and Wales is larger. Nitrateleaching is influenced by drainage status, sward age, and weather, as well as N input(NT0601, NT1902). Nitrate leaching losses from sheep grazing upland pastures has beenestimated at 13-24 kg N/ha (15% clover: NT0802), and 2-46 kg N/ha (NT1602) with similarlosses from sheep grazed grass/clover systems compared to grass only swards receivingsimilar fertiliser N inputs to that fixed by the clover. These relatively modest losses fromland grazed by sheep to water systems are supported by other research on reseeded uplandpasture and Molina-dominated unimproved pasture in mid-Wales (NT1902).

Increasing fertiliser N rates allow more stock per unit area and hence increase the proportionof pasture affected by localised urine hotspots and herbage N content (which will increaseurine N content) – both factors will increase nitrate leaching losses.

2.3 Air

Ammonia emissions from grazing sheep are estimated to be around 5% of the total from UKagriculture (similar to the 4% from grazing cattle).

Sheep produce methane mainly from the mouth, at a rate of between 2 and 10% of grossenergy intake. Methane production is higher on standard grass and clover sward systems.As sheep are predominantly outside most of the year and rely on grass, their methanecontribution is high.

Strategies to reduce pollution from sheep systems

A key strategy to reduce pollution from sheep systems is to avoid pasture improvement onupland and peat sites.

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2.4 Biodiversity

Sheep production is often, but not always, a relatively extensive system, especially in theuplands. Many upland pastures are only suited to sheep production and nothing else.

2.4.1 Unimproved Grassland

Sheep are vital for management of some important grasslands, in particular the short, closecropped swards where small species of flora can survive, which would be shaded and out-competed in taller vegetation. For example, low, rosette formed plants thrive only in suchswards. Many species of both flora and fauna are adapted to these habitats and suffered adramatic decline with the advent of myxomatosis when the rabbit population plummeted.Rabbits are still prone to population fluctuations and so sheep grazing, subject to morehuman control, plays a vital role in maintaining these habitats. Chalk and limestonegrasslands, priority UK BAP habitats, were created by and for sheep and their continuedpresence is vital for the maintenance of these valuable habitats. Farm specialisation towardsarable cropping has reduced the availability of livestock in many lowland areas. The result isthe increasing dominance of coarse grasses such as Brachypodium pinnatum and false oatgrass Arrhenatherum elatius and invasion by scrub and woodland, leading to losses ofcalcareous grassland flora and fauna (UK BAP).

Sheep have thin mobile lips and move slowly over the sward nibbling the grass. They cangraze very close to the ground that can result in tight ‘lawn-like’ vegetation. Sheep are veryselective grazers and will target flowering plants that can have a negative impact on speciesdiversity. Sheep can push their way through scrub and can browse saplings preventing newgrowth. However, they find it harder to graze longer vegetation that is often trampled instead(English Nature 2005).

Sheep can be selective feeders, avoiding tall plants and tussocky areas, choosing smallplants and often selecting flowers over grass stems. These preferences lead to the creationof a diverse sward structure. Wethers (castrated rams) are less selective grazers and havea lower mineral requirement than lambs or ewes, and so will often feed on coarser and lesspalatable vegetation (Shaw et al. 1996).

Lowland calcareous grassland has a very rich flora, including many nationally rare andscarce species. It supports many different invertebrates including scarce butterflies like theadonis blue, the silver-spotted skipper and the wartbiter cricket. It also provides a feedingand breeding area for a number of scarce or declining birds including stone-curlews. Well-managed calcareous grassland has an open, grazed sward. Livestock grazing is essentialto maintain a species-rich sward; left ungrazed it can become covered in rank grasses andscrub and require expensive clearance work (English Nature 2005).

Where grazing is abandoned and vegetation grows tall ant hills are shaded, the nests aretoo cool and the colonies die out. Ants are a vital link in the life cycle of some butterflies,such as the chalkhill blue, adonis blue and large blue. The adonis blue Polyommatusbellargus is a striking turquoise blue butterfly and a priority UK BAP species. It is found onlyon short grazed chalk downland of southern England. The largest colonies occur on theclose cropped turf maintained by continuous heavy grazing with sheep and rabbits. Thelarge blue Maculinea arion is the largest and rarest of our blue butterflies. Grazing isessential to produce a suitable habitat of short turf with an abundance of wild thyme. (NaturalEngland) Most extinctions of large blue colonies have been caused by undergrazing(Thomas 1986).

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2.4.2 Hay Meadows and Silage Fields

Once characteristic of lowland England, hay meadows, (a priority BAP habitat), are now veryrare; where they remain they support species such as greenwinged orchid, adder’s-tonguefern and pepper saxifrage (English Nature 2005). Hay is made to feed sheep and cattle (andhorses) in winter and at other times of grass shortage. The action and management of sheepgrazing on the aftermath has been shown to be an essential element in the maintenance ofhay meadows of high ecological value.(Jefferson 2005, Smith & Rushton 1994, Smith et al.1996).

Grazing hay meadows after they have been cut controls competitive coarse grasses and thetrampling that occurs creates gaps in the vegetation allowing seedlings to grow. Thisensures a variety of species continue to flourish (English Nature 2005). Hay meadows thatare grazed after cutting include a dramatically higher number of species than those that arenot (Lawes et al. 1882, Williams 1978). Preventing autumn and spring grazing of haymeadows can have a more deleterious effect on species diversity than applying moderaterates of fertilisers (Younger & Smith 1994, Kirkham et al. 1996). Meadows that are laid up for hay from early spring to mid summer are good for groundnesting birds such as redshank and snipe that require cover. Meadow nesting birds havesuffered with the change from hay to silage due to earlier cutting dates and faster machinery(Andrews & Rebane1994). Silage fields are poor nesting habitats due to their dense fastgrowth, and early and frequent cutting. Hay is usually cut later in the summer, allowing timefor chicks to be reared and to fly before the nests are destroyed.

Hay fields contain a variety of grasses and broad-leaved plants, many of which will have setseed before cutting, providing far more food for seed-eaters than silage fields managed asryegrass monocultures cut before seed is set. Less seed food is available through the wintertoo, when the resulting fodder is fed to livestock. The large quantities of seed in dung, fromstock fed on seed-rich herbage, are another important food source that is lost to birds(Atkinson et al. 2004). Hay may provide certain economic advantages to some beef andsheep farmers as in recent years the costs of making big bale silage in particular haveincreased. Hay does not pose any pollution risk (associated with silage effluent), does notcreate waste plastic (other than from baler twine) and tends to pose less animal health risksthan silage (listeriosis abortion can be an issue in sheep fed poor silage.)

Hay meadows are very vulnerable as they are often small, isolated and in areas where thereis a lack of demand for hay and grazing. Without livestock grazing, these habitats becomedominated by tall grasses which suppress smaller plants and reduce the botanical richnessof the sward (English Nature 2005).

2.4.3 Moorland and Heathland

Sheep are important tools in successful moorland management because they selectivelygraze grasses when they are succulent in summer, reducing the risk of grasses dominatingdwarf shrubs, including heather (Scotland’s Moorland Forum 2003).

On grass communities within heathlands sheep tend to produce a short sward due to theirability to crop closely. Their light weight makes them less likely to damage lichen-rich swardsthan cattle and ponies (Lake et al. 2001). On dry heath they can damage Calluna byselectively grazing growing tips in autumn, but are less likely to damage mature anddegenerate Calluna through trampling. The amount of Calluna eaten will vary according to

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alternative sources of forage available (Milne & Grant, 1987; Bartolome, 2000), but is likelyto increase in the winter (Bullock, 1985). When the grasses die back in the autumn theyprefer heather and will continue to eat it until spring grass returns (Adamson & Critchley,2007).

In winter, sheep can cause heavy losses of heather on the lower reaches of moorland,particularly around areas where feed blocks or hay are provided (Scotland’s MoorlandForum 2003). The provision of supplementary feed tends to concentrate flocks in smallareas, leading to a degradation of the upland heather vegetation (Hudson & Newborn 1995;Milsom et al. 2003). Hay is sometimes placed upon areas of old heather to prevent it fromblowing away, but this leads to a concentration of trampling and grazing on vegetation leastable to withstand it. Urea-based feed blocks can also stimulate the sheep to eat moreroughage, which is usually taken as heather (Hudson & Newborn 1995), which can alsocontribute to the decline of the vegetation. Ideally, supplementary feeding on heathermoorlands should be given on areas of coarse grass or dead bracken, away from heatherstands.

A 5 year Defra funded project (ADAS report on BD1228) has just been completed and haslooked at environmentally sustainable and economically viable grazing systems for therestoration and maintenance of heather moorland in England and Wales. It has concludedthat site-specific grazing regimes can meet specific objectives for biodiversity andeconomics, but that moorland grazing is likely to be uneconomic without support.

2.4.4 Trees and Woodland

Sheep grazed in woodland, wood pasture or parkland may chew the bark of trees, in severecases killing them through ring barking (Read 2000). In parkland, or areas of low numbersof trees they can successfully be protected from sheep damage by guards.

Mineral supplements can be used to replace nutrients and change the diets of sheep, thusreducing the incidence of bark stripping trees (Read 2000).

2.4.5 Archaeology

Most of our best archaeological sites lie under grassland or semi-natural vegetation becausethey have not been damaged by ploughing, excavation or growth of tree or scrub roots.Grazing by sheep is the preferred method of managing underground historic features. Largeranimals may cause poaching, leading to erosion of the site and potential damage tounderground features or artefacts, especially in wet weather. Lack of grazing will allowscrub to develop, when damage will be caused by underground root systems.

2.4.6 Veterinary Medicines and Sheep Dip Chemicals

Sheep ectoparasites such as scab, blowfly, ticks and lice are controlled by using chemicalinsecticides either by immersion (dipping), ‘pour ons’, showers and jetters or injectables.Following dipping (and showers and jetters), residues of the chemical remain in the sheep’sfleece and may be lost to the environment through drips, sheep walking throughwatercourses, loss of wool, product misuse, and in processing of fleeces. A further potentialsource arises from the disposal of used sheep dip.

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The two major chemicals authorised as sheep dip by the Veterinary Medicines Directorate(VMD) are the organophosphate (OP) diazinon and the synthetic pyrethroid (SP)cypermethrin (not presently in use). Both highly effective against target pest species, theyare also toxic to invertebrates and fish at very low concentrations. Cypermethrin is up to1000 times more toxic to aquatic life than diazinon but diazinon has been linked with illhealth in sheep farmers.

Sheep dipping is far less common now (estimated that only about 10% of farmers dip theirsheep) so the issue of sheep dip contamination of soils and water is no longer ascontentious.

Cypermethrin and diazinon can persist in the environment for a period of days or weeksbefore being broken down by a combination of biotic and abiotic processes. Diazinon isbroken down more rapidly at acidic and alkaline pH than at neutral pH whereas cypermethrinbreakdown is favoured only under alkaline conditions. For cypermethrin, sorption ontosediments and biota is a further major fate process.

Investigations in Wales have shown severe declines in invertebrate biology caused bycontamination by sheep dip chemicals. Substantial impacts on invertebrates are likely toaffect fish stocks due to loss of food sources. Trout fisheries may also suffer reduced fishingincome because of effects on fly life hatches.

Like other OP insecticides, diazinon acts by inhibiting the enzyme acetyl cholinesterasewhich is involved in the transfer of nerve impulses.

Cypermethrin acts by altering ion permeability of nerve membranes, causing trains of nerveimpulses that ultimately immobilise sensitive organisms. It has also been shown to inhibitATPase enzymes involved in movement of ions against a concentration gradient; this actionis critical to fish and aquatic insects because these processes are used to regulate oxygenexchange.

A research programme undertaken by CEFAS between 1990-2002 has highlighted sublethaleffects of sheep dip chemicals (cypermethrin and diazinon) on salmonids at concentrationsclose to the EQS concentrations.

Croxford (2005) reviewed the impact of sheep dip chemicals on aquatic life, including effectson the olfactory system, reproductive physiology and behaviour of the salmon.

In laboratory studies, sheep dip chemicals cypermethrin and diazinon are shown to stronglyaffect honey bees, sometimes fatally (Larkin & Tjeerdema, 2000).

The practice of applying spent sheep dip to land as a means of disposal may haveimplications with regards to toxicity to sensitive terrestrial ecosystems. Acute toxicity studieshave shown diazinon to be highly toxic to earthworms (Larkin & Tjeerdema, 2000).

The mixing of spent sheep dip with slurry is a common method of disposal. However, thishas the potential to increase the number of pathogens available to be transported to wateras the sheep dip may inhibit protozoan populations beneficial to the degradation ofpathogens (Boucard et al., 2004).

Doramectin, used in the UK to treat sheep scab by injection, is cited as having a lowinhibitory effect on soil organisms, and only in concentrations that exceed the levels that arelikely to be excreted by treated sheep (Taylor, 1999).

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APPENDIX 3

3. Environmental Impact of Pig Farming

3.1 Soil

Pig production can potentially impact on soils through compaction and erosion (mainlyoutdoor systems) and through the addition of heavy metals and antimicrobials in slurry(indoor pigs) or dung (outdoor pigs).

The indoor system may also contribute towards soil compaction through the spreading ofslurry and manure, particularly in wet conditions. Compaction can lead to reducedproduction and the reduced efficiency of use of other inputs.

Additions of manure and slurry can potentially also increase soil organic matter levels, whichcan in turn improve soil physical and chemical properties.

3.1.1 Soil Compaction and Erosion

Impacts are most severe from outdoor pig production and this type of production isincreasing while indoor production is declining. Outdoor pigs can remain in a single area forone or two years and even in situations where a grass cover is established, the ground covercan soon be damaged through trampling and rooting. However, the extent to which erosionoccurs will depend on site-specific factors such as soil type, soil wetness and slope (MAFF,1999). Outdoor paddocks are normally established on free-draining soils, which are knownto be vulnerable to run-off and erosion (Evans, 1990).

About 39% of the UK sow herd is kept outdoors. This amounts to about 149,000 sows(Penlington, 2007). If one assumes a typical stocking rate of 25 sows per hectare, the totalarea concerned amounts to around 6,000 hectares. There has been a steady increase inoutdoor herds in response to the low capital set up costs, herd health problems, morestringent IPPC rules and pressure from retailers for an outdoor reared product.

Danks and Worthington’s (1997) survey of outdoor pig production noted that one in threefields showed evidence of runoff. This compares with the estimated risk of runoff occurringfrom bare fallow land of about 1 field in 20, and from a high risk crop such as sugar beet of 1field in 7 (Evans & Jaggard, 2003). Outdoor pig keepers are required to have soilmanagement plans drawn up to mitigate effects of soil compaction e.g. alternative‘roadways’, field/paddock entrances and run off i.e. avoiding low points in field and growinggrass as buffer zones to mop up runoff

In warm weather, breeding pigs need either wallows or sun shades so they can keep cooland also protect their skin. Wallows result in soil compaction and if sited near water coursescan result in severe erosion and loss of sediment and nutrients to water.

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3.1.2 Mitigation

The following methods may be used to mitigate the degree of compaction and soil erosioncaused by outdoor pigs:

• Establish good vegetation cover before stocking (this is now a cross compliance issue)• Undersow the previous crop• Use persistent grass types suited to the locality• Adjust stocking rates or rotate pigs according to soil type and condition• Maintain stocking rates at <25 sows per hectare (MAFF, 1998)• Avoid steep areas• Consider nose ringing – welfare issue• Consider positioning of wallows• Move weaner pens down slope after each batch• Change fence line position according to soil condition

3.1.3 Manure and Slurry Spreading

Hamza and Anderson (2005) include manure spreading as one of the main causes of soilcompaction on agricultural land. Pig manure production in England and Wales is estimatedto be about 10 million tonnes per year, with 4.5 million tonnes produced as slurry and 5.5million tonnes produced as FYM (Smith et al., 2000). Assuming an N content of 4 kg/m3 forslurry and 7 kg/t for FYM, and assuming that a maximum of 250 kg N per hectare can beapplied as manure in any calendar year (Defra Water Code and proposed Nitrate VulnerableZone Action Programme Rules), the area required for pig manure spreading amounts toaround 225,000 hectares.

The effects of manure spreading can be reduced through avoiding wet conditions and theuse of trailing hoses, low ground pressure tyres and controlled traffic systems. However, thelatter should not be used as an excuse to spread manure in wet conditions.

3.1.4 Microbial Activity

3.1.4.1 Heavy metals

In England and Wales, heavy metal loadings from pig slurry at the field scale amount to 2.5kg ha-1 a-1 for zinc and 1.5 kg ha-1 a-1for copper. In a review of the need for metal inputs tolivestock diets (Defra SP0516), additions of zinc and copper to pig diets were shown to beappreciably above nutritional requirements because producers want to ensure zincsufficiency and routinely use copper as a growth promoter. Levels have reducedconsiderably as a result of legislation but metals are given on veterinary prescription or as aprophylactic (e.g. the use of zinc to prevent scour in weaner pigs). Zinc oxide is widely usedacross the industry and pressure is mounting to reduce levels still further and to findalternative therapies to treat scouring in piglets.

A simple balance method was used for estimating the heavy metal content of pig and poultrymanures from a knowledge of feed heavy metal concentrations (Anon, 2001b). It wasshown that substantial reductions in zinc and copper loadings to agricultural land could bemade by reducing supplementation of pig diets. For example, it was estimated that total zincinputs to agricultural soils in England and Wales could be reduced from about 5,000 t a-1 toabout 4,200 t a-1 and copper inputs from about 1,600 t a-1 to about 1,150 t a-1. Therefore,reducing dietary trace element supplementation (particularly for pigs and poultry) would bean effective strategy for protecting soils from long-term heavy metal accumulation. Recently

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introduced EU feeding stuff legislation requires lower levels of zinc and copperconcentrations in some pig and cattle diets.

3.1.4.2 Veterinary Medicines

Antibiotics are given to pigs only when needed and as prescribed by a veterinary surgeon Ina recent survey of commercial pig farms (Stevens et al., 2007), 60-75% of farms usedantimicrobials in weaner rations, while 20-62% of farms used them in grower rations. Someantimicrobials are poorly absorbed by the gut and the parent compound or metabolites canbe excreted (Beconi-Barker et al., 1996; Donoho, 1987) and either deposited directly bygrazing animals or spread in slurry or FYM.

Summary data is available on the toxicity of antibacterial agents to earthworms andmicrobes (Boxall et al., 2002). For antibacterial agents, microbes are the most sensitive testspecies with minimum inhibitory concentrations (MICs) ranging from 100 (apramycin – usedacross sectors, but not in laying hens or dairy cattle) to 500,000 µg kg-1 (tiamulin – used inpigs and poultry) (VICH, 2000). However, little work has been done on how these levelsrelate to typical soil concentrations in the field.

Kay et al. (2005) have looked at the movement of antibiotics to water, but little work hasbeen done on the concentration of veterinary drugs in soil in the UK. In northern Germany,soil samples were taken from twelve different fields, 4-5 months after slurry had beenapplied (Hamscher et al., 2000a). The antibiotics, tetracycline and chlortetracycline weredetected in the top 30cm of nearly all samples at concentrations of between 1 and 32 µg kg1.In a subsequent study, the average distribution of tetracycline in the top 30 cm was between20 and 40 and chlortetracycline was generally below 5 µg kg-1 (Hamscher et al., 2000b).These concentrations are well below the minimum inhibitory concentration (MIC) for soilmicrobes of 100µg kg-1 (VICH).

3.1.4.3 Organic matter

As with other manure, heavy and regular applications of pig slurry and FYM have beenshown to increase soil organic carbon and improve soil fertility in the medium to long term(Bhogal et al. 2006; Hountin et al., 1997).

3.2 Water

Pig slurry is characterised by a high available N content which results in applications of pigslurry being at significant risk of nitrate leaching to water courses (see Figure A3.1).

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Figure A3.1 Typical Content of Pig Slurry (left); The Relative Risk of Nitrate LeachingFrom Pig Slurry and Other Materials Applied to Two Clay Sites (Middle); and thePotential Nitrate Leaching Risk From Pig Slurry (Right) Applied to a Sandy Soil inDifferent Months Under Contrasting Annual Rainfall Conditions.Sources: Defra projects ES0106 and NT1406; NVZ Action Programme Evidence Basepapers

Research evidence has shown nitrate leaching from pig systems can represent 13% of thetotal N applied in pig slurry, compared to 15% of broiler litter but only 1% of cattle FYM (withits lower available N content). In a separate project, nitrate leaching losses were 7% of totalN applied where autumn pig slurry was applied to uncultivated stubble, but only 1% of thetotal N applied where the slurry had been ploughed down or disked into the soil (NT2004).

Leaching of total N beneath pig manure heaps over a six month period has been found tovary from 10-185 mg/l (WA0716), and hence effective lining or sealing of such stores isessential to limit the risk of pollution to water bodies (also see comments under dairy/beefsystems concerning leakage from slurry stores).

Phytase included in pig diets can also increase excretal P returns and therefore increase thepotential loss of P from the agricultural landscape to water.

Outdoor pig production now represents a significant proportion of the national population(about 39 % quoted earlier), and is the largest outdoor herd in Europe. Outdoor pigs areoften sited on more freely drained soils to minimise treading damage, soil compaction,reduced infiltration effects, and associated welfare concerns. These effects can increasesurface runoff and sediment loss, and result in increased risk of loss of associated pollutants(N, P, pathogens) to water bodies, although leaching losses are generally not likely to besignificant (ES0121). If there is a further move to outdoors pigs then production couldspread to more marginal land types (heavier land/ higher rainfall) with higher risk of soildamage. A Defra Project, (IS0215 - Integrated production systems for outdoor pig breeding herds) islooking to identify and develop practical approaches for the outdoor pig breeding sector toreduce inputs and diffuse pollution whilst maintaining biodiversity, product quality, highanimal health and welfare standards and the competitiveness of the pig breeding sector.

3.3 Air

It has been estimated that around 80% of ammonia emissions are agriculturally derived. Ofthe total ammonia emission from all sectors, around 44% originate from cattle, 14% frompoultry and 9% from pigs (Defra, 2000).

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Gaseous losses, such as ammonia, from agricultural land are largely derived from freshapplications of manures and fertilisers (and to a lesser extent from livestock buildings) (King,2005). Measures that result in manure being left exposed on the surface for longer will tendto increase ammonia losses, while measures that encourage rapid incorporation will reduceammonia losses. Ammonia emissions typically increase by around 5% for every 1% increase inslurry dry matter content, while the ploughing down of FYM can reduce ammonia emissions byaround 90% (King, 2005). For further details see, for example, the “evidence base” papersaccompanying Defra’s 2007 NVZ consultation exercise which are available from:http://www.defra.gov.uk/environment/water/quality/nitrate/pdf/consultation-supportdocs.

Livestock type has a pronounced effect on N2O emissions, with pig manure emitting tentimes the amount from a deep pit laying hen house, and five times the amount from anequivalent amount of cattle manure kept outside (Anon, 2000).

The review undertaken by King (2005) concluded that there is evidence that ammonia lossesfrom buildings housing pigs were around 35% greater from straw-based compared to slurry-based (fully slatted) systems. Results from Defra project WA0720 provide evidence thatammonia losses from pig systems can be further reduced by using a partly-slatted ratherthan a fully-slatted system (as the non-slatted floor area covering 50-75% of the pen acts asa physical barrier between the air below the slats and air circulating in the house).

Covering slurry stores reduces emissions and excludes rainfall, thereby reducing the volumeto be stored and spread (also relevant to the cattle sector) – however as most ammonia lossis during spreading and housing, there is only a limited benefit from this pollution mitigationmethod.

Application techniques are a major mechanism for reducing ammonia emissions (see FigureA3.2. below), with broadcast spreading of slurry losing most ammonia. In contrast, King(2005) reported that band applications using trailing hose or trailing shoe systems reduce thesurface area exposed to air and can thereby reduce ammonia losses by 30-40% or more.Direct injection of dilute slurry can also reduce ammonia losses by 30-40% (ca. 7 cm depth)and up to 90% (ca. 25-30 cm depth), but 40% of UK soils are too stony for direct injection tobe a practical pollution mitigation option.

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Figure A3.2.Top Row: Conventional Applications of Pig Slurry Using a Raingun (left),and Via Broadcasting (Middle), and Top dressing Using a Boom (right).

Bottom Row: Strategies to Reduce Ammonia Volatilisation From Slurry ApplicationsInclude Open Slot Shallow Injection (left), Trailing Shoes (Middle), and Trailing Hoses(Right).

Ongoing research is quantifying the use of shelter belts of woodland vegetation adjacent tooutdoor pig units in promoting the local deposition of N compounds (ammonia etc) andthereby limiting odour issues and atmospheric transport over longer distances (Tang et al.1995). Other research has found that the use of shelter belts reduces the highconcentrations of ammonia reaching downwind locations, and may be particularly suitablewhen such units are in close proximity to ecologically sensitive areas or population centres(as this approach will minimise both the risk of acidification and odour). Ammonia emissionscan typically be reduced by 13% from slurry stores and 3% from land-spread fields throughthe use of shelter belts (WA0719).

Methane emissions are relatively low from pig and poultry houses (except weaners on slats).

IPPC regulations demand that large pig (over 750 sows or 2000 finisher pigs of over 30kg)and poultry producers apply for permits from the EA. These regulations are contributing tothe increase in outdoor pig units as outdoor systems do not need to comply.

Farm manures and slurries are significant sources of offensive odours and are the subject ofmany complaints from the public.

Research has enabled a wide range of detection and investigative techniques andapproaches to be developed including gas chromatography-mass spectrometry (GC-MS),olfactrometry, large scale odour chambers to pilot plants for measurement effects, which hasallowed quantification of the extent of odours to be determined.

A review of the literature in WA0205 indicated that about 30 compounds appeared to have adominant effect in people’s perception of odour from livestock waste.

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Other work has found that the air in pig housing can contain over 100 odours. These occurat very low concentrations compared to ammonia, but are responsible for the characteristicsmell of a piggery. Some of these odourants can be absorbed on dust particles, so reducingthe dust burden will also help to reduce the malodours.

Several projects have looked at ways of reducing odour from livestock. These are not all pigspecific:

Options for reducing odour emissions at all stages of farm waste production have beenidentified, for example by reducing the protein content in the diet (WA0609). Project WA0208suggested that biofilters were the most promising and least expensive technology for treatingodiferous air.

WA0609 also demonstrated that the major components of livestock odour could be dividedinto – sulphides, phenols, indoles and volatile fatty acids. Emission rates were determinedfor pig, chicken and cow wastes with the intention of using the data to produce an odouremissions inventory.

WA0604 measured the influence of livestock waste application on gaseous emissions andidentified likely controls.

On-farm odour nuisance problems were identified in WA0635 in which 60 livestock farms (ofall types) were visited. Of these, 20 had a specific odour nuisance problem identified. Theproject also reviewed the application of aerobic treatment technology on UK farms.

Other studies (WA0201) have looked at the practical on-farm options for reducing odoursfrom farm wastes and WA0203 attempted to devise economically viable options for thetreatment and spreading of waste. Reed bed treatments for controlling odour were examinedin WA0202. Other studies (e.g. WA0204 to WA0208) have looked at on-farm mechanicaland other options for the treatment of slurry during storage.

3.3.1 Strategies to Reduce Pollution from Pig Systems

Incorporate pig slurry/manure into soils by ploughing down or disking to reduce ammonialoss and the risk of surface runoff and associated loss of N and P to water bodies.

Line all slurry stores to achieve compliance with IPPC legislation and reduce leakage towater bodies.

Cover slurry stores and incorporate slurries using bandspreading equipment to reducegaseous emissions (ammonia) and odour problems, and thereby increase the potentialutilisation of the available N by vegetation

3.4 Biodiversity

In 2000 9% of ammonia emissions came from pigs (Defra 2000). See impacts of ammoniadescribed in the dairy section (appendix 1.4 above).

High concentrations of ammonia in the air can damage plants such as lichen, moss andheather, important components of balanced habitats. Such high concentrations are notwidespread in the UK, and usually only occur near major ammonia sources, such as largepig and poultry units. This is a concern when the unit is near valuable habitats.

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Pigs are normally associated with intensive methods of production, where environmentalimpacts are generally negative. However, extensive systems where hardy, traditional breedsof pig are grazed on semi-natural vegetation at very low stocking rates can have benefits,but this is not suited to economic mainstream production.

Pannage is an ancient right of common still exercised in some areas such as the New Forestand the Forest of Dean. In these areas pigs are valued for the speed at which they clear upacorns because by doing so they reduce the likelihood of acorn poisoning in other livestocksuch as cattle and ponies.

Pigs have been used to manage bracken (Read, 1994; Kennedy, 1998) and proved effectivein reducing stand density if used in conjunction with cutting or spraying (Read & Williams,1997). However, at inappropriate stocking levels the pig foraging strategy of digging forrhizomes is likely to result in significant loss of all vegetation cover.

Defra Project ISO215 is looking at the environmental impact of outdoor pigs and will bereporting on alternative cropping strategies (undersown cereals, root crops) and persistenceof different types of vegetation.

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APPENDIX 4

4. Environmental impact of Poultry farming

4.1 Soil

The majority of egg layers (63% in the UK) are housed in cages. For these, soil compactionand erosion is limited to that potentially caused by the spreading of poultry manure. Withinthe free range sector (now with a range area of about 9000 hectares), soil erosion maypotentially occur over localised areas close to the hen house.

Layer manure makes a significant contribution to zinc loadings at the field scale. The use ofanticoccidials may also potentially have an impact on soil microbiology.

Frequent and large additions of poultry manure can give rise to increases in soil organiccarbon and associated increases in soil fertility, particularly on light textured soils.

For poultry meat production soil compaction is mainly restricted to the spreading of poultrylitter and manure.

While heavy metal inputs occur from broiler litter, they are considerably lower than thosefrom pig and layer manure.

As is the case for layers, the use of anticoccidials may potentially have an impact on soilmicrobiology.

4.1.1 Soil Compaction and Erosion

Free range layers can potentially remove vegetation and cause soil compaction and erosionin isolated areas. However, any damage to soil structure may be offset by the reducedamount of manure that has to be spread to land.

There are about 9 million free range hens in the UK at any one time. These birds must haveaccess to ranging areas “mostly covered with vegetation”, and under EU Egg MarketingRegulations, the outside stocking density must not exceed 2,500 birds per hectare.However, the majority of UK free range hens come within the scope of the RSPCA’s“Freedom Food Scheme”, which sets a maximum outside stocking rate of 1,000 birds perhectare. At this rate, the free range flock covers a total area of around 9,000 hectares withsmall areas close to the hen house often completely devoid of vegetation. These areas maycontribute to the many erosion hot spots (others include outdoor pigs, and maize, sugar beetor potatoes grown on high risk land) that are thought to be responsible for the majority oflowland erosion in England and Wales (Boardman and Evans 1994).

Defra project SP0413 may provide more information about the relative contribution ofdifferent areas to overall soil erosion rates. It aims to investigate the potential of using falloutradionuclide (i.e. Cs-137) measurements to provide national scale data on rates of soil lossfrom agricultural land in England and Wales.

4.1.1.1 Spreading of Layer Manure and Broiler Litter

The other source of compaction from egg production is the spreading of poultry manure andlitter. 63% of laying hens are kept in cages. The manure from roughly 19 million birds must

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be spread to land along with the litter produced from broilers, although 670,000 tonnes ofbroiler litter is now incinerated in power stations (Shepherd et al., 2006).

The UK poultry flock (including layers and broilers) produces around 4 million tonnes ofpoultry manure per year (Chambers & Smith, 1998). This contains around 49,000 tonnes ofnitrogen following ammonia losses (31,000 t of N) and losses to incineration (20,100 t of N).To comply with the Defra Water Code, poultry manure applications to agricultural landshould supply no more than 250 kg total N/ha per annum. Poultry manures are thereforespread across around 200,000 hectares of agricultural land. When this is spread in wet soilconditions it can potentially lead to soil compaction (Larsen et al., 1994).

4.1.2 Microbiology

4.1.2.1 Heavy Metals

At the field level, zinc inputs from layer manure are higher than those from any otherlivestock manure, including pigs (Nicholson et al., 2003). Zinc inputs from layer manure toagricultural land in England and Wales amount to 2.7 kg Zn ha-1 a-1, while copper inputsamount to 0.4 kg Cu ha-1 a-1.

In a recent study commissioned by Defra SP0129 (Anon, 2001b), zinc and copperconcentrations in poultry diets appeared to be in excess of the published nutritionalrequirements. The study indicated that there was scope for reducing zinc and copperconcentrations in some poultry diets.

Heavy metal inputs from broiler litter are lower than those from pig and layer manure(Nicholson et al., 2003). Zinc inputs from broiler litter to agricultural land in England andWales amount to 1.1 kg Zn ha-1 a-1, while copper inputs amount to 0.2 kg Cu ha-1 a-1.However, as mentioned above, Defra project SP0129 (Anon, 2001b) concluded thatreducing dietary trace element supplementation would be an effective strategy for protectingsoils from long-term heavy metal accumulation.

Strategies for reducing heavy metal excretion could include:

• Lowering levels of supplementation through reducing EC maximum levels of inclusionand safety margins

• Improving the information on poultry nutrition “requirements”• Using feeds with higher bioavailability of Cu and Zn • Using chelated metals – if they are shown to have consistently higher bioavailability

4.1.2.2 Veterinary Medicines

Within the egg laying sector, anticoccidials (or coccidiostats) in most birds and wormers infree range egg layers are the main veterinary medicines used. For anticoccidials theconcentrations above which microbial inhibition has been detected range from 100 µg kg-1

(narasin) to 200,000 µg kg-1 (halofuginone) (VICH, 2000).

The wormer flubanvet (5% Flubendazole) is used when worms become a problem onpastures. However, it is not considered to be a significant environmental issue, as it is notroutinely incorporated into feed.

The only veterinary medicines routinely used in broiler feed are coccidiostats (see section 5).

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4.1.2.3 Soil Organic Matter

Regular additions of organic matter in the form of farm manures can potentially improve soilquality and fertility (Bhogal et al., 2006; Haynes & Naidu, 1998; Hountin et al., 1997; Persson& Kirchmann, 1994; Van Meirvenne et al., 1996), as illustrated for broiler litter by mediumterm measurements at ADAS Gleadthorpe (Figure A4.1).

Figure A4.1. Effect of Broiler Litter Application Rate on Topsoil Available WaterCapacity (AWC) at Gleadthorpe (Spring 2001).

4.2 Water

Poultry litter has a significant available N content, and is therefore at greatest risk of nitrateleaching following application to land (compared to low available N content materials such ascattle FYM).

The same issues concerning application timing, grassland/arable contrasts, soil type effects,and weather (drainage) relevant to the risk of pollution to water from dairy and beef manuresand slurries also apply to poultry manures. Specifically, poultry manure has relatively highavailable N contents and so is readily leachable from both arable and grassland (see FigureA4.2).

Leaching beneath manure heaps can be a substantial pathway for pollution to water bodies,with ammonium-N concentrations measured over a six month period varying from 38-11800mg/l (WA0716). There is also evidence that concentrations in leachate beneath broilerchicken litter heaps tend to be greater than concentrations beneath layer chicken manureheaps (ammonium-N concentrations of >2000 mg/l compared to <2000 mg/l) (WA0712).

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Figure A4.2. Nitrogen Leaching –Comparison Between Poultry Manure and FYM byLand Type and Time of Application. Data Collected Over 10 Site Years. Source:Chambers et al. (2000)

4.3 Air

Ammonia losses from poultry housing depend on how the manure is managed, ventilation,and the amount of litter on the floor. Poultry manure contains uric acid, which is converted toammonium and released as ammonia gas. The loss of ammonia is therefore stronglyinfluenced by whether the poultry excreta remains dry or becomes wet.

Defra project WA0651 reported that ammonia losses from broilers housed on straw (2g NH3-N/hour/500kg live-weight) were significantly greater than for those housed on woodshavings(1g NH3-N/hour/500kg live-weight). The same project also found that ammonia losses frombroilers using traditional bell drinkers (3.3g NH3-N/hour/500kg live-weight) were greater thanthose using nipple drinkers (1.1g NH3-N/hour/500kg live-weight).

The application of poultry litter also results in ammonia losses, with around 63% of the TANlost by volatilisation following application to land (King, 2005). As is the case for beef anddairy systems, incorporation reduces ammonia losses, with the ploughing down of poultrymanure reducing ammonia losses by around 95% (King, 2005). Due to the more friablenature of poultry manure, incorporation by disking is a more effective method of reducingammonia emissions than is the case for FYM. For poultry manure, minimising the moisturecontent can significantly reduce the resulting ammonia emissions.

To date no definite conclusions can be drawn about the potential health hazards ofagricultural, especially poultry, dust to the rural population as very little information isavailable on the properties of poultry dust aerosols in general and bio-aerosols in particular,including the viability/infectivity of airborne micro-organisms.

A monitoring study undertaken by South Norfolk Council in the vicinity of a broiler unitconcluded that it was unlikely that air quality objectives for fine dust would be exceeded.Given that the unit studied was a very large facility and residential properties were very closeto the sheds, it was considered unlikely that emissions from intensive broiler farms in the UKwould result in an exceedance of the air quality objectives unless background concentrationswere very high or there were other significant sources of fine dust in the area.

In general, the lifetime of viable organisms from poultry under ambient conditions is thoughtto be low, but measurements are lacking to corroborate this view. The die-off rate of micro-

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organisms emitted from animal housing is thought to be high due to a multiplicity of factorssuch as low humidity, oxygen toxicity and UV radiation. The likely exposure level to poultryaerosols in the rural population is also largely unknown.

The relative risk of dust and airborne bacteria as potential contaminants according to flooring(straw versus fully slatted) and feeding and their interaction within a finishing system wereexamined in LS3601. Dust emissions were found to be in line with previous values. Animalactivity is the largest factor influencing dust emission, hence no significant effects werefound for feeding treatment. Higher dust emissions were expected from the straw-basedsystem but this was not evident in the study. This was probably due to a relatively smalldepth of straw used compared to commercial practice.

SLP LINK Project LK0612 looked at the possibility of reducing aerial pollutant emissionsfrom broiler houses by dietary control. Diets ranged in protein and energy content andhouses were monitored for aerial emissions of dust and odour (and ammonia). Relationshipswere found between diet and emissions of dust and odour - highest dust and odouremissions occurred with the most extreme diets (lowest protein and highest energy) as aconsequence of unusually unsettled bird behaviour.

4.4 Strategies to Reduce Pollution from Poultry Systems

Manure handling issues are the same as for cattle systems e.g. restrictions of timing andloading of applied manures and slurries with high available N to land (avoid applications inautumn/winter - NVZ Action Programme proposals August 2007 extend this to cover allsoils).

An ongoing research project (AC0104) is looking at emissions and abatement of dust frompoultry houses in order to make a full assessment of the human health implications of poultrydust. Samples will be taken from the three most prevalent poultry systems – broilers, layinghens in cages and laying hens in barn systems, at the point of emission, in both summer andwinter. The samples are to be analysed for particle mass, particle size distribution and fineparticle composition, chemical and microbiological composition. In addition, samples will betaken at a range of distances downwind from the source and analysed for microbiologicalcomposition to determine the potential health implications of poultry dust.Abatement techniques such as “electrostatic precipitators” and “wet scrubbers” wereconsidered to be too expensive for widespread adoption, but changes in animal feed fromdry to “wet” materials offered some promise. However, no sure-fire method of abatement foragriculture was identified in WA0802. However, automatic spraying of diluted vegetable oil(5-10% oil in water) twice a day for 15 seconds during feeding times has been shown toreduce total dust concentrations by 50% or more.

AC0104 will look at emerging abatement techniques to reduce dust levels inside poultryhouses. The emphasis of the assessment will not only be on the efficacy of the abatementtechnique, but also on costs and practicality.

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4.5 Biodiversity

Systems of Egg and Poultry Meat Production

In 2000 14% of ammonia emissions came from poultry, including both egg and meatproducing units (Defra 2000). See also section on ammonia under Dairy section, above.

Data available on endogenous oestrogens (Shore et al., 1988) demonstrate that thesecompounds can be transported from poultry farms, via agricultural run-off to rivers andstreams. Oestrogen (as an endocrine disruptor) can affect reproduction in fish species.Increased concentrations of oestrogen can give rise to male fish gaining femalecharacteristics, which could in turn impact on reproduction - this has been studied in Atlanticsalmon and other species.

There is a scarcity of research about the impacts of poultry production on biodiversity.

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NT0601:To develop strategies to reduce N loss from grassland (new codesNT1602/NT1902). Defra.

NT0605: To quantify nitrate leaching from swards continuously grazed by cattle. Defra.

NT0802: To develop a predictive capacity for N loss from grassland (New code NT1806).Defra.

NT1005: Phosphorus loss from grassland soils. Defra.

NT1011: P losses from organic manures. Defra.

NT1012: Phosphate loss from cracking clay soils. Defra.

NT1016: Phosphorus transfer from grassland soils (continuation of NT1005). Defra.

NT1028: Measurements of phosphorus loss from manures. Defra.

NT1032: Quantification of P transfers from soil following tillage and re-seed of grasslandswards. Defra.

NT1041: Phosphorus losses from a lowland dairy farm. Defra.

NT1043: Scaling up estimates of phosphorus transfer effects from grassland plot tocatchment scale. Defra.

NT1319: Losses of nitrogen as dissolved organic N. Defra.

NT1401: Open Competition: Use of injectors and low trajectory spreaders. Defra.

NT1402: To improve guidelines on waste management practices which will minimise therisk….(NT0301). Defra.

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NT1404: Grassland manuring. Nitrogen loss and efficiency from use of organic manures(previously NT0301). Defra.

NT1405: N loss from organic manures (previously NT0309). Defra.

NT1410: Nitrate leaching risk from livestock manures (Previously NT0310). Defra.

NT1415: Improved precision of manure and slurry application. Defra.

NT1421: Economic evaluation of improved manure application technique (for AU NT20).Defra.

NT1518: The distribution of soluble organic nitrogen in arable soils. Defra.

NT1602:Understanding the grassland nitrogen cycle in order to improve fertiliserrecommendations (previously NT 0601). Defra.

NT1801: Additional measurements (organic soluble N and denitrificaton) from integrated Ngrassland farmlets. Defra.

NT1829: Further N cycle studies on farmlets. Defra.

NT1842: Desk studies which use models to predict N losses from farming systems. Defra.

NT1902: Control over losses of nitrogen from grassland soils (Previously NT0601). Defra.

NT1916: Leaching of soluble organic N. Defra.

NT2001: Integration of animal manures in crop and livestock farming systems: nutrientdemonstration farms. Defra.

NT2002: Effect of manure spreading imprecision on crop yield. Defra.

NT2004: Minimising nitrogen losses in drainage water following slurry applications to drainedclay soils (add-on to NT1028). Defra.

NT2511: Cost curve of nitrate mitigation options. Defra.

NT2603 - The behaviour of some different fertiliser-N materials - Initial field experiments

NT2604 - Ammonia emissions from nitrogen fertilisers: windtunnel construction

NT2605 - The behaviour of some different fertiliser-N materials - Main experiments

OC8906: Nitrogen leaching risk from livestock manures. Defra.

OC9012: Protozoan, bacterial and viral pathogens, farm animal wastes, and water. Defra.

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PE0102: Rationalising risk and scaling-up of on-farm practices to classify rates ofphosphorus transfer to grassland catchments. Defra.

PE0111: Towards understanding factors controlling transfer of phosphorus within and fromagricultural fields. Defra.

PE0205: Strategic placement and design of buffering features for sediment and P in thelandscape.

PE0206: Mitigation Options for Phosphorus and Sediment (MOPS). Defra.

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SP0516: Heavy Metal Content of Animal Manures and Implications for Soil Fertility. Defra.

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WA0604: To measure the influence of livestock waste application on gaseous emissionsfrom land and to identify likely controls. Defra.

WA0651 Ammonia fluxes within broiler litter and layer manure management systems. Defra

WA0656: Implications of potential measures to control pathogens associated with livestockmanure management. Defra.

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WA0712: Management techniques to minimise ammonia emissions during storage and landspreading of poultry manures. Defra.

WA0716: Management techniques to minimise ammonia emissions from solid manures.Defra.

WA0719: Impact of vegetation and/or other on-farm features on net ammonia emissionsfrom livestock farms (AMBER). Defra.

WA0720 Demonstrating opportunities for reducing ammonia emissions from pig housing(CTE003). Defra.

WA0804: Routes by which pathogens associated with livestock slurries & manure may betransferred from farm to wider environment. Defra.

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WU0101: Opportunities for Reducing Water Use in Agriculture. Thompson, A. J., King, J. A.,Smith, K. A. & Tiffin, D. H., June 2007

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