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the nutrient cycle: closing the loop S3567 29/5/07 09:47 Page 2

the nutrient cycle: closing the loop Edited by Hannah Hislop

Green Alliance is an independent charity. For 28 years we have worked with businesses and other environmental charities to make environmental solutions a priority in British politics. We work with representatives of all three of the main political parties to encourage new ideas, facilitate dialogue and secure new commitments to action and progress on the environment.

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Our thanks go to the Association of Rivers Trusts, the Environment Agency, Natural England, Northumbrian Water, the Pennon Group,Thames Water and Water UK for their support of this project.Thanks also to Clive Bates, Bob Breach, Jim Densham, Jane James and Helen Wakeham for their advice.The recommendations presented in this report are put forward by Green Alliance and do not necessarily represent the position of all project partners. S3567 oe n eeecs_43 _39 _19 notes andreferences _35 _31 _02 Rob Lillywhite, WarwickWarwick HRI, University energy andcostimplicationsoftoday’s nutrientcycle MacDonald,JMDensham,RDavisandSArmstrong-Brown,MA RSPB _26 and otherbiodiversity too muchofagoodthing?theimpactsnutrients onbirds _04 theCompostingAssociation Dr JaneGilbert, _13 the role ofcompostingin closingthenutrientsloop Professor MarkKibblewhite,Cranfield University implications offarmmanagementonthenutrientscycle Dr Stephen RSmith,ImperialCollegeLondon recycling biosolidstoland Dr Stephen Bolt,ADAS the waterindustry’s role intoday’s nutrientcycle Jiggy Lloyd, Green Alliance Associate the nutrientcycle: closingtheloop Ian Christie,Green Alliance Associate foreword contents 29/5/07

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2 foreword Ian Christie, Green Alliance Associate

Many of the environmental problems now seen as into the environment has brought immense short- contributing to unsustainable human development term gains in prosperity and output. But the price have this in common: they involve a relatively rapid could be long-term degradation of essential natural and large disturbance to the huge geochemical life-support systems – adding to the greenhouse cycles that help regulate the biosphere. Human effect, damaging water quality, reducing soil quality, sources of carbon dioxide and other greenhouse and soaking up resources in end-of-pipe pollution gases may not seem significant in the context of the control and damage limitation. whole Earth system or of geological time; but they have been sending a large enough volume of The nitrogen and phosphorus cycles are immensely emissions in a relatively short period into the complex and ‘leaky’, as made clear in the essays that

the nutrient cycle: closing the loop the nutrient cycle: atmosphere such that the overall natural balance of follow.The policy challenges are also complex, the carbon cycle is being disrupted. involving many established commercial interests, dependence on manufactured fertilisers, and the “ the nutrient cycle demands The potential dangers from need for a radical shift in nutrient use so that we action on the least climate change as a result of ‘close the loop’ and recycle as many nutrients as this recent disruption of the possible. glamorous and electorally carbon cycle are now appealing aspects of dominating political debate. There is another important cycle to consider when environmental policy” There is a risk, given the we address these policy challenges.That is the complexity and scale of the political attention cycle.The fabled ‘top of the climate challenge, that another cycle of great political agenda’ is always a crowded place, and significance will be neglected.This is the nutrient environmental concerns cannot be guaranteed to cycle – made up of two great geochemical fluxes, remain there, with the exception (one hopes) of those of nitrogen and phosphorus.The essays in this climate action.The risk is that climate policy comes booklet explore the scale of the disruption that to dominate debate and action at the expense of human development has unwittingly brought to other, related challenges. Nutrients policy is these cycles. As with the carbon cycle, we have vulnerable.The nutrient cycle demands action on the overloaded natural systems in a short span of time as least glamorous and electorally appealing aspects of we have industrialised, and in particular as we have environmental policy – soil management, farming developed and applied synthetic fertilisers. Again, as systems, the treatment of sewage sludge and so on. with the carbon cycle, our injection of vast The nutrient cycle is not getting the attention it quantities of nitrogen and phosphorus compounds deserves. S3567 rmtdb W n iRgoa.Scn,there Second, promoted by WWF andBioRegional. conceptrecently interest inthe ‘One Planet Living’ drawing onthegrowing ‘One PlanetFarming’, agriculture sectortotake theconceptof seriously there ishiscallfor the First, David Miliband. bothinvolving theEnvironment Secretary,noting, this respect two developments in2007are worth In debates onlanduseandthefuture offarming. cycleisofferednutrients by emerging toraisetheprofileopportunity ofthe essays Anothersignificant below. many are discussedinthe ofwhich measures loop, toclosethenutrients strategies for climate actionand connectionsbetweennecessary tomakeSo itwillbeimportant the that we know we canmake. and achieving thegreat gainsinresource efficiency intobalance, emissionsback bringing and nutrients, water rooted inclosedloopmanagement ofenergy, problemthe nutrients callsfor acommonapproach Dealingwiththeclimate threat and climate change. problems that couldbeexacerbated severely by and life-support systems–andasaclusterof unwitting overloading offundamentalnatural cycles biggergeneralproblemsubset ofamuch –our We issueasa needtoseethenutrients and soils. threats that overload nutrient posesfor water quality flash floodinganderosion –willinteractwiththe droughts, –over-heating, from climate disruption For many andprojected problems ofthecurrent civilsocietyandbusiness worldwide. governments, that isnow commandingattention rightly from closely connectedtotheproblem ofthecarboncycle cyclesfor whatnitrogen they andphosphorus are: The answer may ofthe betoseethedisruption 29/5/07

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3 we needtoseethe “ problem” bigger general subset ofamuch nutrients issueasa we torestore try thebalancewe have lost. forand openuphugeopportunities innovation as andattitudes, technologies rethinking ofpolicies, cyclesshouldpromptthe great urgent geochemical realisation that we have managed oneof todisrupt the Aswiththecarboncycle, prominence itdeserves. togiveanother opportunity cyclethe thenutrient andproduction ofbio-fuels–provides and wildlife, management oflandscape between food production, demands onfarming –what thebalanceshouldbe theemerging debate about themixof Finally, –inthiscasethenext80years.term on asustainable visionfor landuseover thelong and David Milibandhascalledfor anational debate is awide-rangingDefrareview inhandonlanduse,

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4 The nutrient cycle: closing the loop Jiggy Lloyd, Green Alliance Associate

“We are fertilising the Earth on a global scale and in other household products. Nutrients still cycle a largely uncontrolled experiment”, Global through the economy but the amount in circulation Environment Outlook, UNEP, 1999 is greatly increased. In the case of nitrogen, it is estimated that human activity has doubled the Society owes a lot to the nutrient cycle. As students amount in circulation; in the case of phosphorus, we of biology and geography know, virtually every have tripled the amount available since the industrial aspect of the modern economy is dependent on the revolution. fact that nutrients such as nitrogen and phosphorus circulate in different forms through water, air and This might not of itself be a concern but it needs to the soil. be considered alongside the indications that

the nutrient cycle: closing the loop the nutrient cycle: nutrients are also, on some occasions, turning up in Depicted neatly in the typical school textbook the wrong place. diagram, the N-cycle and the P-cycle look almost too good to be true.They are ‘true’ – even if, as the A water industry spends significant amounts of expert contributions to this pamphlet remind us, money removing phosphates from wastewater.There they are more complex than the textbooks can does not appear to be a definitive figure but some convey.And they are certainly ‘good’, in the sense estimate it to be around £35 million a year. that life could not function without them and the Furthermore, between 2005 and 2010, English modern economy relies on them. But water companies will have to incur capital nutrients are also a source of pollution and expenditure of about £300 million and annual “ human activity the dangers of nutrient overload are operating costs of £6 million to reduce nitrate levels has doubled recognised. So the question has to be asked – for the public drinking water supply. Removing the the amount of is the operation of the nutrient cycle as good phosphates is an energy-intensive process and also nitrogen in as it could be? relies (in most cases) on chemical dosing with ferric circulation” salts.The disposal of the nitrate-rich residues of The nutrient cycles of the modern world are drinking water treatment is a challenge that the very different from those that existed before industry currently addresses by blending with low the joys of burning fossil fuels were discovered, nitrate sources or removal via ultra filtration. before (in 1912) Haber and Bosch found they could synthesise nitrogen fertiliser and before phosphate This indicates a problem with nutrients when water was found to be beneficial to crop growth and is being treated for human consumption and use. important in the manufacture of detergents and What about nutrients at other stages in the cycle? S3567 29/5/07 09:47 Page 5

The Environment Agency tells us that diffuse inputs of expending both money and energy on manufacturing 5 nutrients are a major reason why our rivers are at risk fertiliser, and then further money and energy because of not meeting the Good Ecological Status (GES) we have to deal with nutrients in the wrong place. required by the EU Water Framework Directive by 2015. Specifically, nitrogen is cited as the problem for It doesn’t sound logical does it? about 40 per cent of rivers and phosphorus for nearly half of them. But of course logic is not the only factor. Nature and history come into the story. Nutrient pollution damages the countryside by altering plant growth rates, changing plant Nature dictates that nutrients do not cycle in perfect, communities and disrupting the food chain for leak-proof pathways.The miracle of nitrogen, in wildlife. Nutrient inputs also trigger eutrophication of particular, is its ability to exist in a range of different shallow lakes; declines in fish diversity may be traced forms. It is society’s bad luck that the form in which it back to this. is most available to the plants, nitrate, is also the form in which it most prone to move to other media –

About 40 per cent of UK emissions of nitrous oxide such as water. Phosphates are slightly less fickle – they closing the loop the nutrient cycle: (a potent greenhouse gas) come from agriculture; have a happier tendency to remain bound to mineral emissions are closely related to the form and the soil surfaces and incorporated into the molecular manner in which nutrients are applied. structure of soil organic matter. But they move too – and end up in the wrong places as a result. From the Meanwhile, we continue to add to the amount of perspective of the farming industry, the losses of nutrients in circulation and this has its own nitrogen and phosphorus that do occur (measured in environmental implications. Fertiliser manufacture for energy or in money) do not look bad in comparison the UK is believed to generate about six million with the value of the end product; they can be tonnes of carbon dioxide per year; some estimates compared quite favourably with efficiency ratios in suggest it may be 20 million tonnes or more. World other industrial processes (which do not have the supplies of phosphate rock are finite and the transport added challenge of taking place outdoors, at the mercy of phosphate fertiliser takes place over long distances. of the weather!). And since the chief domestic use of phosphates is in detergents, one might be tempted to Something seems not quite right here. On the one say that inevitably, the phosphates will end up in hand, nutrients circulate through the economy and the water. Nevertheless, we can’t ignore the consequences. environment and the total amount in circulation is sufficient to meet our needs.The nutrient content of History has got us to where we are today. Our ability available organic materials such as biosolids, green to add to the pre-1912 stock of nitrogen in circulation waste, biodegradeable municipal wastes and farmyard has been the key factor underpinning the notable manures is sufficient to replace all use of successes of UK agriculture, and in feeding the world’s manufactured fertilisers. On the other, we are growing population. S3567 29/5/07 09:47 Page 6

6 So, few would dare argue that we reduce the amount is going to occur globally as food production and of nutrients in circulation to their pre-industrial industrialisation continue to increase? levels; to do so would require an accompanying proposition as to how world food production would So whether your perspective is domestic or global, be maintained. And it would take a real optimist to the conclusion looks the same: conceive of a situation in which no fluxes within and between media happened and supply always • We need to stop relying on policy measures exactly matched demand, year in year out, regardless which tackle nutrients as individual substances of the nuances of the weather, the soil and the conflicting with desired standards for soil, water market. Even the most ardent advocates of precision or air; agriculture don’t claim we can be this clever. • And we need to start using a policy framework But there are clearly significant benefits to be which aims, at its core, to cycle nutrients realised if we can reduce the economic and through our economy with fewer unwanted environmental costs associated with nutrients in the effects (‘leaks’) and an overall gain in resource

the nutrient cycle: closing the loop the nutrient cycle: wrong place and reduce the need to manufacture efficiency. and transport additional nutrients in favour of using more effectively those that are already in circulation. This would be the policy framework based on closing the nutrient loop. It would have the “ some argue The immediate benefits would be a reduction following principles: that the global in greenhouse gas emissions – both carbon and nitrous oxide, improved water quality 1. The use of nutrients already in the economy nitrogen cycle with benefits for biodiversity, and less would take priority over the manufacture and has the expenditure of farmers’ money (on import of additional nutrients. potential to fertilisers) and water customers’ money (on 2. Nutrients would be transferred between the become as drinking water treatment). players in the nutrient cycle – the producers and significant as users of nutrients – because of their value; But there is a longer-term objective here as regulations governing nutrient concentrations or the global well.The elephant in the room (or hiding prescribing nutrient management practices would carbon cycle” between the pages of this pamphlet) is the be secondary. concern about the global implications of 3. Soils (cultivated or otherwise) would be nutrients. Some argue that the global nitrogen cycle explicitly recognised as part of the national has the potential to become as significant as the nutrient resource bank. global carbon cycle. It is certainly justified to ask 4. Innovations which aided the recycling and re-use ourselves the following: if the developed world has of nutrients and/or the maintenance of the inflated the nutrient cycle this much so far, with nutrient resource bank would be encouraged and these sorts of side effects, how much more damage could be supported using measures which S3567 29/5/07 09:47 Page 7

discouraged further additions to the nutrient underpin the transactions involved. Similar measures 7 cycle in excess of demand. are needed to ensure that as we divert biodegradable 5. Information on nutrient stores and transfers municipal waste from landfills, we make it possible (involving air, soil or water) would be used to to use the nutrients that it contains. establish, at national level, the size of our nutrient surplus and the options for limiting its growth. Such measures might seem to run counter to the suggestion that available land might be insufficient This policy would be used to deliver the benefits to receive the nutrients that are potentially available. noted above and also to ensure the UK is well As the contributions to this pamphlet demonstrate, positioned in a global debate about nutrients - limitations do arise and they, coupled with the rate- which is well overdue. response of crops to nitrogen fertilisers, have led to the current situation. Enabling measures must tackle Policies for closing the nutrient loop these limitations. If this framework were in place, what would need to For instance, a limitation on further use of biosolids be done differently from, or additionally to, the

on land is the mismatch between their available closing the loop the nutrient cycle: plethora of nutrient-related measures already in nutrient content and crop demand. In part, this is place? due to the effect of wastewater treatment in over- concentrating the phosphate load in relation to First, there are some obvious enabling measures, as nitrates. A case might therefore be made for a levy identified by the expert pieces in this pamphlet and on phosphates derived from non-dietary (detergent by the project partners/steering group. and industrial) sources, or a ban on some products containing phosphates. Discouraging their entry into The work already done by the water and food wastewater and/or using levy proceeds to stimulate sectors to devise a safe and workable system for the the ‘mining’ of phosphorus from wastewater would use of biosolids on land (the Safe Sludge Matrix and be a real example of closing the loop. related schemes) needs statutory underpinning.This will ensure that necessary investments can be made In some locations, a limitation on more effective use and, as importantly, financial commitments to less- of animal wastes is the farm storage infrastructure sustainable options avoided. that enables the nitrates, as well as the organic nitrogen they contain, to be returned to the land at We need to recognise the nutrient value of food and appropriate rates and timings. In others, diffuse composting wastes and encourage the diversion of inputs of agriculturally-derived phosphate may be these wastes from landfill to beneficial use on land. causing a water quality problem and a levy on A certification-use scheme, akin to the Safe Sludge phosphate inputs to farming (operated at the Matrix, would enable the food industry and land regional or catchment-level) might be a means of managers to make the necessary commitments and stimulating investment in nutrient recovery from S3567 29/5/07 09:47 Page 8

8 farm waste. Nutrient storage and nutrient recovery Policies based on closing the loop should also could be the starting point for a west-to-east transfer underpin our use of land management as a means of of nutrients that would help close the loop within achieving water quality objectives. If our aim is to the UK farming sector. manage nutrients better for the long-term, then it may well be the case that spending water customers’ The framework of a closed nutrient loop should also money on land management or land use adaptation illuminate, from the perspective of a resource schemes that will encourage nutrient storage in the efficient economy, two key debates.The first is the soil is at least as attractive an option as yet more case for and against a levy on nitrogen inputs to the expenditure on the energy-intensive treatment of economy.The contributions seem to suggest that point sources. Such schemes also have the potential improved agricultural knowledge and practice, with to provide other valuable benefits, such as important strong cost-drivers in farming backed up by nitrate wildlife habitats.These arrangements must be regulations and codes of good practice, are moving transparent, however, and a careful distinction us in the direction we want to go; if there is a case maintained between the most sustainable solution to for using price to tip the balance further in favour of an established problem, and arrangements that

the nutrient cycle: closing the loop the nutrient cycle: organic sources of nitrogen, it may be argued that might imply a long-term acceptance of poor energy taxes affecting fertiliser manufacture are practice. already doing this. However, these lack the benefit of revenue-recycling which could be used to support But closing the nutrient loop is also about attitudes the other measures already noted. to nutrients and an appreciation of their place in a sustainable economy. The second debate, related to the first, is how society should optimise the distribution of costs and There has been a commendable move to more benefits. Given that a totally closed loop may not be precise use of nutrients in agriculture, especially in feasible without a significant agricultural yield the arable and horticultural sector.This has been reduction, some remaining costs will be internal to stimulated by the drive for efficiency and and paid for by, the production system; others will challenging markets under the new farm support remain to be borne by society. regime. But it is not yet a universal approach and is associated, in the main, with enterprises making Improvements to feeding regimes in the intensive substantial use of manufactured fertilisers. livestock sector and access to precision farming techniques in intensive arable must feature in the We need a more widespread and wholesale advocacy closing the loop framework. Both are central to the of the soil as a nutrient bank. Well-managed, with aim of reducing nutrient losses and improving inputs not exceeding those that allow the system to efficiency. function properly, it supports land-based ecosystem services including food production and nutrient S3567 29/5/07 09:47 Page 9

management. Abused or disregarded, it becomes part A framework based on closing the nutrient loop will 9 of the problem. Nutrient management needs to inevitably raise questions about risks. It is important feature more strongly in cross-compliance.There is a that, for instance, the recycling of nutrients in strong case for requiring nutrient management plans composting and municipal wastes is seen to be a (i.e. the practice of ‘closing the loop’ at farm level scientific approach, not a throwback to ‘primitive and if necessary planning for the management of the practices’. But the current tendency to be over- surplus) on livestock units as part of cross- cautious about high profile and emotive risks compliance.The enabling measures noted above are obscures the equally significant, if different, risks of urgently needed to counter the caution about use of not acting sustainably. Closing the nutrient loop organic wastes that has been found amongst farmers, should be presented with this in mind. buyers and consumers, but we also need stronger messages about the long-term merits of organic, What is closing the loop? locked-in storage of nutrients. Global warming has At its simplest level, the concept of closing the loop, stimulated an appreciation of the difference between as applied to waste and resources, expresses a desire carbon that is locked-up in soil, biomass and fossil to move away from a linear process of resource

fuels, and that which is causing the increased carbon closing the loop the nutrient cycle: extraction, manufacture, consumption and disposal, concentration in the atmosphere; it shouldn’t take a towards a cyclical system where resources remain in similar crisis in nutrients to extend this appreciation use almost indefinitely. In global terms, and to nitrogen and phosphorus. particularly in ‘developed’ countries, a relatively small proportion of resources are cycled, or go “ abused or Away from the land round in loops, and a large proportion are in management community, disregarded, productive use for a very short time. soil becomes there is also scope to make nutrients a core concept in part of the This is unsustainable because it means: depletion of sustainability, alongside non-renewable resources (minerals and metals); problem” water and energy. Can we degradation of habitats, landscapes and biodiversity; capture the current high dangerous over-use of what should be renewable rate of ‘willingness to recycle’ with convincing resources and over-use of the environmental ‘sinks’ messages about the importance of food and needed to absorb the pollution we generate as we municipal waste composting as a means of produce and consume. Circulating resources around conserving nutrients? Is this a means of countering the economy, rather than just passing them through recycling-fatigue (why do I bother? what is it for?) once, reduces the environmental impacts associated with strong messages that are not just about energy with extraction of resources and disposal of waste. but nutrients as well? S3567

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10 The nitrogen cycle anditshumaninfluences andeffects The natural nitrogen cycle N2O (nitrous oxide) &NOx Nitrifying bacteria Denitrifying bacteria or Nitrates fungi warming Global Nitrates Lightning Run-off, leaching, eutrophication Nitrogen NOx from burning fossil fuels animal waste Decay and Nitrites Plants Animals Nitrogen gas in animal waste Decay and Nitrites Plants air Animals gas in leguminous plants orsoil air in root nodules of Fixed by bacteria Ammonia Nitrifying bacteria Ammonia Acid rain ozone, smog ground and Aerosols, Aerosols, S3567

Organic phosphate in 29/5/07 The natural phosphorus cycle anditshumaninfluences(shaded) Decomposing microbes plant biomass plant

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11 Erosion Phosphate inwater andsediments Phosphate insoil husbandry Animal Sedimentation formation of posphate rock posphate Agriculture millions of years Biosolids Fertiliser Food Human wastes phosphate rock phosphate e.g. detergents P inchemicals wastewater Mining of communities Treated Human

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09:47 on timeandlocation. asawhole.Inpractice, thereUK are significant variations depending this pamphlet.All figures are broad estimatesandillustrative ofthe This diagram isprovided tosummariseandillustrate informationin Nitrogen andphosphorus through theenvironment intheUK Public water supply

Other diffuse sources also contribute about About about About Page and household human waste Households: Further N&P Further products removal

25% Pis from agriculture 70% Nis from agriculture 65%of Pentering water is from STW effluent, 30%of Nentering water is from STW effluent, 12 Water (surfaceandgroundwater) Other diffuse sources Other diffuse sources also contribute households, About households, About Sewage Treatment Works(STWs) 85% of Pentering STWs is from 90%of Nentering STWs is from nuty flet Otherdiffuse sources effluents Industry: Sewage effluent about about 15%Pis from industry 10%Nis from industry Biosolids from combustion of fossil fuels atmosphere is intheform of NOx About atmosphere is from agriculture About 75% of newNentering the 25% of newNentering the Land Air Combustion processes S3567

mrvn ero er oee,thisdoesn’t However, quite improving year onyear. Agency shows that the qualityofourwaters is dataAnnual from theEnvironment monitoring thelessneedfor expensive treatment. water, the cleanerthereceiving water treatment plants: water intotheir drinking companies alsotake ‘raw’ Waterfrom sewage treatment works (STWs). influenced by thequalityofpointsourcedischarges surface water qualityis Firstly, in two separate ways. Water company activity interactswithwater quality Threats towaterquality and thequantityofthisvaluable resource. canaffect boththequality which the water cycle, there ispotentialtoimpactonvirtually allaspectsof outtheseessentialduties, Incarrying population. into itinordertoprovide tothe anessentialservice but tap companies donotmanage thewater cycle, thewater However, wastewater andtradeeffluent. treating totheenvironment andreturning andrecovering, supplying water tocustomers, treating and abstracting, role intoday’s society: The water hasafundamentalandinvaluable industry more andmore pressure onourwater resources. places from ouraffluentandgrowing population, combinedwithincreasing demands increase which, as thefrequency ofweather extremes seemsto ischanging for grantedfor toolongintheUK.This The water cycleisperhaps something we have taken Dr StephenBolt the waterindustry’s role intoday’s nutrient cycle 29/5/07

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13 nitrogen (N) probably from diffuseactive at risk compoundsof has identified that or are 38percentofrivers at risk Environment in theUKandelsewhere.The Agency impact significantly ontheecologyofwater bodies Pollution by isknown nitrogen andphosphorus to have ontheirhands. achallenge theUKanditswater companies Inshort, nitrates. waterdecontaminate from drinking pesticidesand invest increasing amountsofourmoney to companiesare having to Furthermore, pollution. England and Wales ofcontamination are from at risk Environment that mostofthewaters in Agency, alsoby the square witharecent assessment, (P). beyond thequantityalready removed ispotentially The costofincreasing Nremoval from sewage works response ofanaquatic system. that theN:Pratio hasan impact onthebiological oversimplification andincreasingly itisrecognised thisisalmostcertainly an However, andthesea. inestuaries being themore important (andhencemost nutrient ‘active’) inlandwithN itisrecognised that Pisthelimiting general, concentrations greater than30mgperlitre N. greater than0.1mgperlitre Pand30percent lengthscontain concentrations60 percentofriver Itisestimated that approximately sources. nutrient from point orprobably at risk, areof rivers at risk, but identifythat 18percent and Pfor pointsources, 2 The risk maps donotdistinguishbetweenThe risk N 1 and 47percentfrom phosphorus 3 In

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14 high, particularly where low-energy percolating the raw water source. In addition there is potential filters are currently used and would have to be for disposal challenges with the resultant high N replaced with high-energy solutions. Similarly, P wastewater. reduction is commonly carried out by chemical dosing with ferric or aluminium salts which have The solution? An integrated approach traces of hazardous substances.The less well- Nutrient pollution and associated problems in developed use of biological P removal has surface and groundwater are not new, nor is this a operational difficulties, and like N removal also problem restricted to the UK. Most of Europe has increases energy consumption. similar challenges, and there are many EU Directives that seek to tackle aspects of the problem. For Removal of N and P from sewage works must instance, the Urban Waste Water Directive aims to therefore be carried out in conjunction with identify and protect sensitive waters suffering from effective diffuse pollution control.The worst-case eutrophication, triggering significant investment by scenario is that despite high dosing levels of iron the water industry in phosphorus removal at the and/or aluminium salts coupled with increasingly larger-scale sewage treatment works. Other

the nutrient cycle: closing the loop the nutrient cycle: energy hungry processes, levels of phosphorus may Directives, such as the Habitats Directive, seek to still not be low enough in the water to result in a limit nutrients reaching the environment. Indeed, by biological response. In other words, all the dis- 2010, over half the inland population of East Anglia benefits of an engineering solution (an area particularly prone to eutrophication) will be with none of the ecological benefits “ increasing control of served by sewage works with active P removal. achieved. Clearly this unsustainable point source N and P outcome must be resisted. inputs will achieve The most recent EU Directive impacting on water quality and water resources is the Water Framework Although not driven by little unless diffuse Directive (WFD), which seeks to achieve good environmental drivers, the Drinking pollution is ecological and chemical status for all water bodies Water Inspectorate (DWI) simultaneously by 2015. Clearly, key to this ambitious target will be requirement to achieve 50mg/l N the successful control of nutrients reaching water. addressed” for drinking water does have This will be achieved by setting Programmes of increasingly important financial Measures (PoMs): actions that will need to be implications for the water undertaken on a catchment scale to decrease companies.The least costly (both in terms of energy pollution. and cost to customer) method is to blend high nitrate water with a low nitrate source so that the However, in order to meet this ambitious target, it is resultant drinking water passes the standard. first important to understand sources of pollutants However, in some areas low nitrate water is and factors that affect their transport to water.The becoming increasingly scarce and will inevitably first thing is to ‘apportion’ pollutants to sources, i.e. increase the amount of expensive N removal from S3567 philosophy moves away from what we have doneto ofapproaches.This sources andusingavariety several tackling pollution approach toasolution, callsfor anintegrated which often complex, Itisclearthat thesituation is pollution sources. scientific hydrology understandingofcatchment and we therefore needagood our water resources, To decisionsthat aimtoprotect important support insummer.drought periods oftreatedhigh proportion sewage effluent during Many intheUKconsist ofa rivers are very different. flowsand winterwhenriver off andagricultural run there are significant differences between summer 21 percentfrom inorganic fertiliser. sewage works with59percentfrom and livestock only 18percentPisfrom the Norfolk broads, whereas inthe in Ant catchment from agriculture, cent ofPtothe Warwickshire with30percent Avon, sewage works are responsible for 62per example, For andat differentcatchments timesoftheyear. bothbetween clear that there are large variations, anditis apportion NandPinputs toacatchment, outinseekingto workMuch hasbeencarried to understandtheproblem. were asfailing oftencriticised size ofthedischarge, concentrations onasewage works dependingonthe imposingfixed Indeedprevious standards, targets. ofachievingmeasures its hasarealistic chance orbasinsothat anycatchment programme of to first know thesourcesofNandPintoa Itistherefore important simultaneously addressed. achieve littleunlessdiffusepollutionis will for examplefrom sewage treatment works, Increasing control ofpointsourceNandPinputs, be confident about from where they derive. 29/5/07

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15 4 In addition, our majorchallenge. diffusepollutionisnow tackling relatively quickly, approach hascertainly brought improvements Whereas this cleanuppointsourcesat allcosts. date: ult r eyepnie aderogation canbe quality are very expensive, means where that theoptions toimprove water which consideration of ‘disproportionate cost’, the excessive cost? Sensibly, WFD doesallow are thesestandardsachievable withoutincurring thenleadstoacontentiousissue- determined.This for must thenbe thecatchment ‘budget’ anutrient secondly, status and, must bedetermined in ordertoachieve goodecologicalandchemical aconcentration limitfor inwater anutrient Firstly, measures istobebasedon soundscience. ofsuccess andiftheprogramme of stand achance require answering pollutioncontrol ifnutrient isto questionsthat somecrucial therefore, There are, sources. seek toapportion therelative between contribution they didnot critically, however, from diffusesource, waters from pointsourceandthoseat at risk risk mapsthe distinguishedbetween WFD standards.The controlled waters orprobably at risk offailing at risk Environment maps soughttoidentify Agency risk biological response inthereceiving watercourse.The sources ishighly likely tofail toachieve any Settingstandardsfor individual level. catchment atmeasures the transport todealwithnutrient theprogramme of tostructure be necessary itwill If theUKistoachieve thegoalsof WFD, the catchmentscale - Actions ‘on theground’

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16 sought. Even more problematic is how excessive cost Where next? should be calculated - clearly it needs to include all From a water company perspective, it will be very the three pillars of sustainable development - important that the issue of nutrient control is indeed environmental, social and economic. If there are based on robust catchment based apportionment, areas where derogations would need to be sought since it may be attractive to the regulators to over from the European Union on grounds of excessive control point source N and P discharges to cost, then this will require robust evidence to compensate for lack of control of the diffuse inputs. support the case.This could be costly and time Over control of point sources should be avoided on consuming and serious consideration needs to be three grounds: economic (poor value for money), given now to how this could be achieved. social (water bills would need to increase with limited or no value to the customer), and The alternative to basing the programme of environmental (very stringent N and P limits would measures on sound science is to implement an be heavily energy dependent). iterative ‘best endeavours’ strategy.This approach seeks to implement measures “ SCaMP’s vision Given this risk, it is puzzling that

the nutrient cycle: closing the loop the nutrient cycle: that are achievable with limited Ofwat (now the Water Services resources. For instance, a catchment includes Regulation Authority, the water officer may seek to implement farm improvements in industry economic regulator) took management plans based only on what water quality as well the view that the water industry can be relatively easily and as a focus on bird should not contribute to WFD- inexpensively achieved and not on driven catchment management what is needed to achieve WFD populations and schemes in the 2004 periodic standards. An example of this would biodiversity” review since the water companies be to seek to implement a soil had invested so much in point management plan to reduce sediment source control.There is a strong argument that some loading and associated P loss to the local involvement, including financial, in widespread watercourse.This approach would probably result in catchment management to answer the questions a programme of measures with further reductions in above would be very much in water customers’ best P (and possibly) N standards on point sources, interest and in the medium to long term would coupled with farm nutrient management plans provide high value for money.Although Ofwat did seeking to reduce diffuse sources of nutrient.This not allow catchment management projects as part of integrated approach is probably the least cost option, the AMP4 programme (2005-2010), there is one but could well be interpreted as planning to fail and notable exception of United Utilities’ SCaMP could be subject to third party challenge and (Sustainable Catchment Management Programme). ultimately possible infraction proceedings by the EU. SCaMP’s vision includes improvements in water quality as well as a focus on bird populations and S3567 hshrs.Hwvr unless there were However, financial phosphorus). ammoniumand consisting ofmagnesium, substance (awhitecrystalline in theformofstruvite sewage works andhencehelpingto recycle usable P Pfrom there are known for technologies ‘mining’ Conversely,to sewage works by upto10percent. water maystandards indrinking increase Ploading solvency (leadsolubility)tomeettighterlead compounds toreduce plumbo- of phosphorus theincrease indosingrates However, sewage works. detergents cansignificantly reduce Pinputtoa for instancetheintroduction oflow P sewage works, There issomescopefor reducing inputsto nutrient review negotiations. discuss apossible unitedapproach totheperiodic approaches andare meetingto such exploring Several water companiesare interested in 2009. reviewapproach projects inthenextperiodic in Ofwat willtake amore favourable view ofcatchment Itishopedthat in Ofwat’s final determination. forward by otherwater companieswere notallowed similarapproaches put Unfortunately, groundwater. address specific nitrate andpesticideissuesin officerscatchment employed by thecompany seekto Wessex Water topostpone AMP4 investment while Ofwat alsorecognised theadvantages inallowing management.catchment with theRSPBtodevelop anintegrated approach to The programme isbeingdeveloped inconjunction lobbying between thedraftandfinal determination. Ofwat recognised thestrength oftheRSPB addition, andRightsof Countryside Way In Act (CROW). therefore have specific dutiesofcare underthe Utilities own some57,000hectares oflandand biodiversity.This was allowed partly sinceUnited 29/5/07

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17 prpit n utial anr there must bea appropriate and sustainable manner, order tocontrol bothdiffuseandpointsourcesinan Itisbecomingincreasingly clearthat in be sought. status are achievable orwhetherderogations needto whether thetargets ofgoodecologicalandchemical Only thencanwe make decisions asto needed. basedsolutions is andwholecatchment catchment quantitative understandingastosourceswithina A water suppliescannotbeover-emphasised. on ournatural aquatic ecosystemsanddrinking cycleanditsimpact ofthenutrient The importance abstraction licences). consents(andindirectlydischarge through possible from thewater through andotherindustry control ofpointsourceswhere fullcostrecovery is thisincreases pressure on addressed effectively, owns andultimately pays for diffuse pollutionisnot Ifthematter ofwho simple linkcanbeeffective. itisunlikely that thisvery competes at agloballevel, sinceproduce procurement However, be necessary. infarming practicethat mayorder tofundchanges would oftheproduce in seektoincrease theprice principle thenthe ‘polluter pays’ be underestimated), must not andaerial transport input (althoughurban, Iftheissueisagricultural be effectively regulated. difficulty ofwhopays for thecontrol andhow itcan there istheadditional pollution control isrequired, diffuse asseemslikely, If, appropriate manner. measures needstotarget inan sourcesofnutrient thentheprogramme of calculated andtargets set, budgetOnce anutrient is for at risk acatchment attractions. althoughithasclearenvironmentaltechnology would befor thewater toinvest industry inthis incentives itisdifficult toseewhat there driver

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18 fundamental increase in both the scale and pace of progress towards these goals. With the programme of measures only three years away, there is a very real risk that a lack of overarching regulatory ownership of catchment control will lead to the failure to implement the WFD in an appropriate manner. More work is needed to look at ways to incentivise reductions in nutrient input to sewage works and the potential for nutrient recovery before discharging to controlled waters.The continued control of point source nutrient inputs needs to be considered alongside diffuse pollution and a catchment approach to better controlling the nutrient cycle adopted.

the nutrient cycle: closing the loop the nutrient cycle: Dr Stephen Bolt is head of integrated water and environmental management, ADAS S3567 and a residue, primary sludge.The nextstage sludge.The primary and aresidue, settledsewage, This process produces an effluent, are removed sedimentation process. by aprimary first involves separating thesolidsthatsludge.The stages totheproduction that ofsewage contribute Wastewater treatment typically hasthree principal Wastewater treatment –thebasics by industry. usedinthehomeor assurfactants, such chemicals, but alsoincludealarge rangeoforganic processes, sourcesandindustrial from dietary primarily constituents originate asammonia.These such inorganic moleculesnaturally present inwastewater biodegradable organic matter andreduced of forms treatment constituentsrequiring areimportant most tothewaterdischarged environment.The sothat thetreated effluentcanbesafely surfaces, andcollectedasdrainageindustry from paved from discharged homesand from urbanwastewater, produced asaconsequenceoftheremoval ofsolids Itis by-product ofurbanwastewater treatment. residual andinevitable, Sewage sludgeisan essential, ofsustainability. andacornerstone principle effectively equivalent ofthisbasic themodern cyclebynutrient usingsewage sludgeonfarmland is Closingthe ofsustainableprinciples development. advanced humansocietiesasoneofthekey for crop production was recognised by theearliest Recycling organic residuals onlandtoimprove soil Dr StephenRSmith recycling biosolidstoland 29/5/07

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19 xml,aarbcdgsino te rcse,to anaerobic digestionorotherprocesses, example, for by, combined togetherfor subsequenttreatment, andare then solidscontent, increase thedry sludges are usually prethickened separately to andsecondary Primary concentration insludge. thussignificantly raisingits to thesewage sludge, removed wastewater during treatment istransferred Phosphorus chloride. ferric for example, with, recovered dosingtechniques by usingchemical but ismore widelycan alsoberemoved biologically, Phosphorus gas that isreleased totheatmosphere. reduces nitrates tonitrogen which denitrification, known as Nitrogen removal isabiologicalprocess, respectively). 15 percent, 25and 60, sources isequivalent toapproximately: detergent andindustrial from dietary, contribution from detergent residues (therelative phosphorus andinthecaseofphosphorus, sources, from dietary predominantly elementsoriginate These nutrient nitrate withtracesofammonia)andphosphorus. ismainly nitrogen intheform of (which nutrients, consentstosurfacedischarge waters for the being increasingly introduced tomeetthetightening Athirdstage oftreatment is ammonia tonitrate. biodegradable inorganic constituentsandnitrify community ofmicroorganisms that oxidise This steprelies ontheactivitiesofacomplex ofaerobicmost commonform biologicaltreatment. sludgeprocess –the settled sewage by the ‘activated’ removes soluble from the andcolloidalmaterial

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20 generate a product that is suitable for recycling as a incinerators operating in the UK, but it is amongst fertiliser and soil conditioner on farmland. the most expensive of the treatment options available for sludge with high capital and operating costs. The management options Incineration is a treatment process that maximises dry solids destruction, however, a significant amount Approximately 1.4 million tonnes dry solids of of residual non-combustible ash material, typically sewage sludge are produced annually in the UK.The equivalent to 35-40 per cent of the initial sludge dry main outlets for managing the residual sludge from solids, remains requiring final disposal, usually by wastewater treatment are shown in Figure 1. landfilling. In some cases the ash may be classified as hazardous waste potentially increasing disposal The practice of dispersal at sea was ended by the EU problems and costs. Urban Wastewater Treatment Directive in 1998. Landfilling has never been regarded as a long-term Obtaining sufficient solids content is critical for sustainable option for sludge disposal by the UK autothermic combustion of the sludge to take place, water industry, although it provides a short-term or otherwise additional fuel is necessary to support emergency disposal route if necessary.The Landfill

the nutrient cycle: closing the loop the nutrient cycle: combustion.This is particularly challenging for Directive also places restrictions on the disposal of sludge due to its high initial moisture content biodegradable waste to landfill. (sludge initially contains 95–97 per cent water).

60, 4.4% With the most advanced technology available, the energy balance of an efficiently run incinerator plant 150, 11.0% Farmland may be self-sustaining without the need for an Landfill external fuel source, but there is little capacity to Incineration generate additional power from the process.The 265, 19.4% Land restoration recovery of surplus energy could improve in future Other with the development of more energy efficient processes and effective sludge dewatering 15, 1.1% 878, 64.2% technology. For the time being, and until suitable uses for the residual ash are found, incineration should be considered as a disposal method, with Figure 1:The main outlets for sewage sludge management in the little opportunity for value recovery. Incineration is UK for 2004 (values denote t x 1000 and per cent total justified, and is currently the only viable option production of dry solids) available, when the concentrations of contaminants in the sludge prohibit its use in agriculture or when Incineration the sewage treatment works is located within a large Incineration has played a sizable role in sludge conurbation and agricultural land is inaccessible. management in the past and is likely to do so in future.There are currently nine sewage sludge S3567

nln:inits19th on land: manuretypes oflivestock ororganic residual spread totheenvironmentgreater risk thanmany other Land application ofsludgedoesnotrepresent any mesophilic anaerobic digestion. cent ofsludgeproduced intheUKistreated by more than50per Currently, to thenational grid. powerof theelectrical issupplied generated which there may ofapproximately beasurplus 20percent plant operation canusually bemetandtypically powerelectrical demandfor wastewater treatment the Heat isusedfor digesterheating; generation. used for combinedheat andpower (CHP) renewable energy ofmethanegasthat intheform is alsohastheadvantagewhich ofproducing type ofconventional sludgetreatment process, Mesophilic anaerobic digestionisthemostcommon sludge istreated before itcanbeusedonland. All in theUKisrecycled tofarmland (Figure 1). about 64percentoftheannual sludgeproduction Currently, and organic matter containedinsludge. significant benefit from recycling ofthenutrients the only management optionthat provides well-established practiceintheUKandrepresents Applying sewage sludgetofarmland isalongand Recycling biosolidstofarmland UK law by theSludge(UseIn Agriculture) was transposedinto which Directive 86/278/EEC, recycling isregulatedAgricultural by European environment and humanhealthare minimised. controlstatutory toensure any tothe potentialrisks practicereceives the humanpopulation.The controlled useofsludgeon farmland todiseasein noted that there was noevidence linkingthe the Royal CommissiononEnvironmental Pollution 29/5/07

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21 , neisos production anduseofdangerous on emissions, restrictions years withimproved practices, industrial have declinedmarkedly insludgeover thepast30 andofpersistentorganic pollutants zinc andcopper, as such Concentrations ofpotentially toxic elements, sludge are theotherpotentialconcern. Contaminantsin research. further sothisisanarea requiring however, from sludgeare poorly understood, responsible for producing malodour mechanisms recycling operations.The tosuccessful odour are critical and effective measures tocontrol perceptions about recycling sludge, influencing negative public Odour isprobably factor thesinglemostimportant aswell asthepathogen content. disease vectors, Sludge treatment isdesignedtoreduce odourand circumstances. Option (BPEO)for sludgemanagement undermost in agriculture astheBestPracticable Environmental UK government considersrecycling sewage sludge the Asaresult, prevention ofdiseasetransmission. providing aneffective approach tothe multi-barrier the numbers ofpathogens that may bepresent, treatment processes designedtosignificantly reduce The Codealsoincludesalistofeffective sludge natural attenuation ofpathogenic microorganisms. land afterapplication asaprecaution toenable the ontheuseof sludge amendedsoilandrestrictions values for potentially toxic elementsinsewage Two features important ofthecontrols includelimit regulation.statutory Agricultural UseofSewage Sludge Regulations 1989(asamended). also supports the also supports A CodeofPractice for applyingsewage “ in theUK” established practice is alongandwell- sludge tofarmland

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22 substances within European Union, as well as The Safe Sludge Matrix was adopted by the UK water effective trade effluent control measures taken by the industry voluntarily in 1999 and Defra agreed to water industry. incorporate these measures in an amendment of the current Statutory Instrument and Code of Practice. The most recent important development influencing So far this undertaking has not been fulfilled: the land spreading of sludge is the voluntary agreement first consultation on the proposals to amend the between the water utilities and food retail sector, statutory controls for the agricultural use of sludge known as the Safe Sludge Matrix, which defined closed in January 2003.The apparent lack of more specifically the acceptable uses of sludge on progress on this important issue has been a serious different categories of crops.The constraint to the agricultural Matrix introduced a two-tier system recycling of biosolids in some for use on cropped land, according “ the apparent lack of areas, and has the potential to to the degree of treatment of the progress on this severely undermine confidence in sludge. It ended the practice of important issue has the practice within some sectors of applying untreated sludge on land been a serious the food industry that control the the nutrient cycle: closing the loop the nutrient cycle: used for food production in constraint to the availability of the land bank for December 1999, and use for non- applying sludge. Concerns have also food, industrial crops in December agricultural recycling been expressed by a number of 2005.The categories of sludge that of biosolids” important sectors within the food are acceptable for land spreading are industry that international markets defined as conventionally or and brands could be damaged by enhanced treated and specific microbiological the use of sludge in the crop production cycle. Given standards apply to each category. Furthermore, that recycling on farmland is recognised as the BPEO sludge treatment processes are managed following by government, a positive and proactive stance by the Hazard Assessment Critical Control Point system, Defra, the Scottish Executive, the Food Standards introduced by the food industry, to ensure that the Agency, the Environment Agency, and Scottish microbiological quality standards are met. Sludge Environmental Protection Agency is essential to may be applied to farmland as a liquid product, underpin confidence in agricultural recycling within typically with a dry solids content of 2-5 per cent, the food and agricultural industries as a whole.This but increasingly it is dewatered mechanically to could include supporting the Sustainable Organic reduce transportation costs.The dewatering process, Resources Partnership (SORP), a stakeholder by centrifuge or belt press, produces a stackable cake partnership that aims to provide a national forum for containing approximately 25 per cent dry solids. sharing and disseminating information on all Treated sludge that is suitable for beneficial use on organic materials applied to land to encourage the land is increasingly referred to as ‘biosolids’ to use of organic residuals on land as a long-term distinguish this as a product from untreated sludge. sustainable activity and resource. S3567

approximately 3percentofthetotalNapplied toall nitrogen toagricultural systems isequivalent to ofbiosolids contribution insludge.The this nutrient treatment canmore thandouble theconcentration of removal phosphorus wastewater during However, for nitrogen and2-3percentfor phosphorus. biosolids are typically intherangeof4-5percent The totalconcentrations in dewatered of nutrients The role ofbiosolidsinclosing theloop organic residuals. an integrated land-basedapproach for recycling indeveloping willbecritical which (ALOWANCE), Organic Waste – A National Capacity Estimator Landand Agricultural accept organic residuals: quantify thenational capacity ofagricultural land to currently fundingthedevelopment ofatoolto Defrais organic answer generated.To material this, available toreceive thevolume of there issufficient land the WFD, constraints that may berequired by andotherfuture (NVZs), rates inNitrate Vulnerable Zones onapplicationand therestrictions amounts ofwastes goingtoland given theincreased whether, questionarises in future.The available landbank for spreading allorganic materials there willbegreater competitionfor the landfill), duetotheirdiversion from biowastes, industrial and increases (includingcompostedmaterials volume oforganic resources recycled toland Asthetotal for example. manures, of livestock isacomparativelywhich smallinputrelative tothat 1 percentoftheagricultural landinbiosolids, are nutrients tolessthan returned At anational level, 29/5/07

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23 “ thenotionalfertiliser region of£20million” in biosolidsisthe the nutrientssupplied replacement value of availability product (nitrogen availability in thiscase sludge toprevent spreading ofthishighnitrogen ontiming applicationsrestrictions ofliquiddigested 250kg Nperhectare in any and 12monthperiod isalsoamaximum field-based limitof hectare.There For grassland theUKlimitis250kgper Directive. incompliancewiththeEUNitrates per hectare, manures (includingsludge)toarable landis170kg amount ofnitrogen that canbeapplied inallorganic average maximum farm-based limitonthetotal an Within NVZs, the nitrogen contentofthe sludge. Spreading rates by usedintheUKare determined may have anitrogen availability ofupto25percent. which for example, with solidfarmyard manure, compares wellcontent ofartificial fertiliser.This approximately 35-40percentofthetotalnitrogen replacement value ofbiosolidsisequivalent to biosolids showed that thenitrogen fertiliser beneficial elementssuppliedinsludge nutrient Other biosolids isintheregion of£20million. replacement value suppliedin ofthenutrients thenotionalfertiliser artificial fertiliser.Together, mineral fertilisers -asignificant quantityrelative to approximately in 15percentofthetotalphosphorus equivalent to largersupplies amuch contribution, ontheotherhand, suppliedinsludge, Phosphorus crops inmineralfertilisers. inGreat Britain London onarangeofdewatered investigations College by Imperial Recentfield response value. nitrogen replacement andyield farmers for acceptingsludgeisthe A majoreconomicincentive to and magnesium. include usefulquantitiesofsulphur

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24 is approximately 60 per cent, due to the large health. Recycling phosphorus in biosolids is content of mineral nitrogen, and is similar to therefore a key prerogative for long-term livestock slurry) in the autumn period, when there sustainability. Phosphorus recovery during is greatest risk of nitrate leaching.The Code of Good wastewater treatment is highly efficient and the Agricultural Practice for the Protection of Water (The sludge is an effective phosphorus fertiliser source Water Code) recommends a limit of 500kg N per that closes the nutrient loop through the food chain, hectare in alternate years for dewatered sludge types provided it is carefully managed. Under these outside the NVZs in England and Wales, and 250kg circumstances, it may not be necessary to control N per hectare is allowed per year for liquid forms. inputs of phosphorus to the wastewater collection The rates of sludge application are adjusted in system. In any case, the largest input of phosphorus accordance with these limits on maximum nitrogen originates from dietary sources, which emphasises additions. Consequently, the water industry adheres the important link apparent between recycling in to strict controls on the amounts of nitrogen that sludge and the food chain. can be applied in sludge, and the timing and frequency of sludge applications within, as well as Much research has been completed to determine the

the nutrient cycle: closing the loop the nutrient cycle: outside, NVZs, to reduce potential impacts on water fertiliser replacement value of nitrogen, and to a resources of nitrate leaching from agricultural lesser extent phosphorus, in sludge: the phosphorus utilisation. availability in sludge is typically given as 50 per cent relative to mineral fertiliser.This information is In terms of the sustainability of the practice, readily available to operators and farmers in the form recycling phosphorus in the food chain is arguably of advisory fertiliser recommendations, for example more important than for nitrogen. Sludge provides a the Fertiliser Recommendations for Agricultural and long-term maintenance dressing for this nutrient Horticultural Crops (RB 209). Phosphorus inputs in and can replace phosphorus inputs from inorganic sludge exceed the demand of the first receiving fertilisers in a crop rotation. Recycling phosphorus crop, however, recommendations are given on the to soil in biosolids has a much wider global benefit basis that a single dressing of dewatered biosolids than simply reducing farmers’ costs, however, by will supply adequate phosphate for most three to contributing to the conservation of geological four year crop rotations.This is justified on the basis mineral phosphorus reserves and reducing external that phosphorus is retained in sludge-amended soil; inputs of geogenic cadmium into the food chain. recent research shows that phosphorus applied in World reserves of currently exploitable phosphate this form is bioavailable to crops, yet it is less rock are estimated to be 40 billion tonnes and, at the susceptible to leaching and run-off compared to present rate of consumption (150 million tonnes per applications in livestock manures. However, year), this will be exhausted within 250 years. improved understanding of the release of residual Cadmium inputs to soil from rock phosphate phosphorus applied to soil in biosolids in the fertiliser production has also been a concern with growing seasons after application is an area long-term implications for soil fertility and human requiring further attention to more precisely define S3567

savings infertiliser costs. reduced pollutionaswell asproviding economic direct ofimproved benefits interms useand nutrient progress couldbemadeinthisarea andwould have Further totheenvironment. and lossesofnutrients impactsoncrop quality toreduce wastage, critical mineral fertiliser applications toamendedsoilis by adjustingsupplementary organic manures, aswell asinother value provided by biosolids, that fullaccountistakenEnsuring ofthenutrient water environment. soil inbiosolidsandavoid unacceptable lossestothe pragmatic approach tomanaging inputsto nutrient to receivingnutrients waters may provide a ofcontributing ofitspotentialrisk interms varies Recognisingthat land recycling biosolidswould be. likely totake andwhat theirpotentialimpacton unclear at thisstage what thesemeasures form are Itis particularly onnitrogen andphosphorus. focussing pollution from agricultural sources, action islikely to be taken toreduce diffuse implementing theEU Water Framework Directive, AstheUKmoves towards amended soil. balanceinsludge- phosphorus the long-term 29/5/07 department ofcivilandenvironmental engineering, department

Dr StephenR.Smithisdirector ofthecentre for environmental control andwastemanagement, 09:47

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25 Imperial CollegeLondon

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26 implications of farm management on the nutrient cycle Professor Mark Kibblewhite

Farm businesses produce food to make profits. sometimes causing damage via nutrient enrichment Nutrients are valuable resources that should be to sensitive ecosystems, such as heath land, or managed effectively to support profitable contributing to acid rain.The amount of nitrogen production; they are imported onto farms in animal deposited to soil surfaces in England and Wales has feed, organic manures, composts and waste materials not reduced materially over the past two decades. spread to land, as well as in chemical fertilisers. Large reduction in non-agricultural industrial Unfortunately, agricultural systems use nutrients emissions have lowered long-range nitrogen exports inefficiently, particularly nitrogen and phosphorus, to Scandinavia but agriculture and other sources

the nutrient cycle: closing the loop the nutrient cycle: and ‘leakage’ to the wider environment is such as transport, have ensured that local deposition widespread, substantial and, at some level, inevitable. has persisted.The quantities being deposited vary geographically but often exceed 20kg per hectare About half the nitrogen added to soil as fertiliser for per year, which is biologically significant.The arable crops and grass is either emitted to the majority of nitrate in UK surface waters is from atmosphere as ammonia, nitrous oxide or other agriculture. Excess nitrate entering ground and gaseous forms, or finds its way into surface and surface waters compromises natural ecosystems and ground waters as nitrate.The conversion efficiency degrades water supplies. Nitrate nitrogen persists in of nitrogen in feedstuffs to animal protein is less many aquifers for decades so their pollution is than 10 per cent, and a significant proportion of the irreversible in the medium-term.The environmental nitrogen in manures and slurries is emitted to the damage from agriculture to the wider UK economy environment, rather than being incorporated into arising from these different nitrogen emissions to air the soil, taken up by plants and so either and water – nutrient removal by the water industry, incorporated into food products or recycled in the greenhouse gas emissions, and remediation of agricultural system. Agriculture accounts for about damaged aquatic and terrestrial habitats – is 60 per cent of UK emissions of nitrous oxide, a gas considerable. which is 296 times more potent as a greenhouse gas than carbon dioxide. Some 90 per cent of UK About a quarter of the phosphate in UK surface ammonia emissions to air are from agriculture. waters is thought to be from agricultural sources, Nitrogen emitted to the atmosphere as ammonia (although this can vary widely from less than 10 per returns to land as wet and dry deposition, cent in the Thames to over 60 per cent in western S3567 oe pollutingthan awell managed intensive one. more, oreven poorly managed extensive systemcanbeas, a influenced by theeffectiveness ofmanagement; In allcasestheimpactoffarming systemsisstrongly phosphate-containing sediments intosurface waters. animal wastes andwhere soilerosion releases particularly becauseofnitrogen emissionsfrom farming remains significant inextensive systems, Nonethelesstheenvironmental impactof reduced. totheenvironmentthe risk from leakage nutrient is inputsare lower and Inextensive systems, uplands. Examples are sheepandbeef cattle production inthe levels andrelying more onnatural cycles. nutrient production by controlling inputsat maintenance optimise profits where landisnotsuitedtointensive Extensive systems to water andairare likely. are usedtomaximiseyieldsandsogreater emissions inputs highnutrient Inthesesystems, production. densitiesandlarge-scale pigandpoultry stocking withhigher andcattle enterprises dairy production, oilseedandpotato Examplesare cereal, feed. includingfertiliser andanimal via larger inputs, systems maximiseproduction andprofits perhectare Intensive is between intensive andextensive systems. Ausefuldistinction scales ofagricultural production. There isgreat andvariability variety inthetypesand availabilitynutrient causesexcessive algalgrowth. leads toeutrophication -aconditionwhere high damages theseecosystemsandinmore severe cases aswell asothersources, pollution from agriculture, phosphate biodiversities reflect thisconstraint; aquatic ecosystemsandtheircharacteristic availability ofphosphate limitstheproductivity of natural manures andslurries.The fertilisers, by crops andgrassofthephosphate present in Wales). 29/5/07 5 This isaconsequenceofinefficient uptake

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27 only at nutrients return levels canbesafely which but tobesustainable itmust also food production, assoilandwater aprofitable tosupport such level of requires Agriculture natural resources environment. release energy from andintothe andmaterials systemsare openones-theyAgricultural absorb and environment ifprotective measures are insufficient. may which present tothe agreater risk conditions, maximise profits market underunsupported be managed inlarger andmore intensive unitsto used for commodityproduction canbeexpectedto Butconversely landthat continues tobe agriculture. reduce theenvironmental burden from ofnutrients trends willtendto Such extensive approaches. withdrawing from production oradoptingmore appear tobe marginal enterprises livestock intheUK, decision-making differently. Atpresent, influencinglandmanagers’ as well asdown, cangoup themarket prices However, market prices. not sufficient tofully recover production costsat where cereal andothercommoditycrop yieldsare it makes sensetoputarable landdown tograss, payments,the decouplingofproduction andsupport with For example, to extensive landmanagement. Policy (CAP)islikely toencourage shift apermanent reform oftheCommon The mid-term Agricultural nutrients. can sustainfood production whilereleasing fewer agricultural systemsandmanagement practicesthat for societyistoencourage theadoptionof paying challenge for theenvironmental damage.The is which andwidersociety, profitable farming, inputsisapre-conditionuse ofhighernutrient for whoperceive that continued agricultural businesses, atensionexistsbetween Not surprisingly,

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28 absorbed by these same natural resources. Overall, poultry units controlled under the Pollution current emissions of nutrients exceed the capacity of Prevention and Control (PPC) regulations. the wider environment to absorb them. Better information is needed on “ in the absence of The introduction of Single Farm the natural capacity of local regulatory Payments, accompanied by cross environments to assimilate nutrients compliance measures, is a highly and on the emissions from different controls, it pays to important step towards encouraging agricultural systems. And where apply a little more better land and soil management, and capacity is exceeded, agriculture has fertiliser than is this should reduce nutrient emissions to to change, either by reducing strictly necessary” the environment. For example, the emissions through improved requirement for implementation of a efficiency, reducing production, or soil management plan to reduce erosion shifting to a different type of production.This risk will lower the risk of transfer to surface waters change is unlikely to happen if left to market forces of phosphate bound to soil particles. Looking ahead, because many environmental damage costs are not further CAP reform may offer opportunities to

the nutrient cycle: closing the loop the nutrient cycle: included in on-farm costs.The benefits of nutrient introduce cross-compliance conditions or agri- additions accrue to the farmer while many damage environment measures that require specific actions costs present beyond the farm gate and are met to reduce nitrogen and other nutrient emissions, in elsewhere, either directly as remediation costs or return for continued support payments. A good start through loss of resource quality.And it is irrational has been made with agri-environment schemes, for a farmer seeking to maximise individual farm which include measures such as buffer zones to profit to forego profit for the benefit of the wider limit phosphate pollution of surface waters. community. Nutrients such as nitrogen are relatively cheap and are a highly cost-effective means to Better management of nutrients within intensive improve yields of arable crops and grass. In the systems is both needed and possible. Greater policy absence of regulatory controls, it pays to apply a emphasis is needed on supporting the development little more fertiliser than is strictly necessary, as an of improved technology and encouraging its insurance against reduced yields, even if this causes widespread adoption.The role of the agricultural environmental damage. A legal framework that engineer is critical.There is existing commercial addresses this market failure is essential, which may technology which can reduce nutrient inputs while include a mix of environmental regulations, sustaining or even slightly increasing yields, based incentives and voluntary measures.The current legal on precision nutrient application rates derived from framework is incomplete. For example, Nitrate analysis of information about soil conditions, Vulnerable Zones (NVZs) may protect the water previous cropping and weather patterns.These environment, but at present there are no controls on precision agriculture techniques have the potential to nitrogen emissions from agriculture to the materially reduce polluting emissions to air and atmosphere, except from those larger pig and water but have not been targeted by UK policy, S3567 oe agrdiyuis o xml:tominimise For example: cover larger units. dairy including by anextensionofthePPCregulations to argues for which theircloserregulation; and air, foropportunities emissionstoboth water nutrient present many asmany such units, dairy ones, combine someintensive practiceswith extensive farms that management infrastructure.Those andextensive systemswithlittlewaste containment, havewhich facilities for constructed waste with bothintensive animalproduction systems, there are different but associated significant risks neither bepredictable Intruth, oravoided entirely. surface wet waters andthismay during periods spread from winterhousingmay bewashed into directly grazingor animal wastes arising during For example, losses tothewiderenvironment. offugitive increases therisk which easily controlled, they are alsoless fixation nitrogen, ofatmospheric cyclingandonnaturalnutrient inputsandbiological andrely lessnutrients systems import more on Whilethese efficient intheiruseofnutrients. agricultural systemsandalsoorganic onesmore istomake extensive challenge A particular emissions. toreducing greenhouse contribution gas important managementnutrient aswell asmakingan offers bettercontrols which on application toland, via anaerobic digestioninplaceofdirect slurry are shiftingtoenergyindustry recovery from slurries Andtheleadersinpig waste nitrogen emissions. reducing increase protein conversion efficiency, which introducing altered regimes, nutritional theanimalsectoris More positively, technology. incentives toadopt(precision agriculture) this UKfarmers need adopted elsewhere intheworld. although they are mature andhave beenwidely 29/5/07

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29 topee o hs abetterunderstandingis For this, atmosphere. istolowerpriority nitrogen emissionstothe but theimmediate high precision techniques, asby introducing such improved management, isscopefor nitrogen andphosphate fertilisers.There processes that release towater nutrients from There isarelatively goodunderstandingofthe agricultural system. totherequirementsmatched ofthe additionsarenutrient notestimated and maymaterials theenvironment harm if Nonethelesslandspreading such sludge. infoodnutrients wastes andsewage meansofrecycling is animportant service recovered intoproduction.This theysome ofthenutrients containare or beincinerated canandare spread onlandwhere Organic that would materials otherwisegotolandfill includingwaste management. fibre production, otherthanfood deliversAgriculture and services stores andadditionalwinter-housing.slurry as such managementbetter nutrient infrastructure, combination ofregulation andcapital for support viaa clear scopetoimprove performance, is sominimisingemissions.There production cycle, maximise recovery intothe back ofnutrients tolandatreturned rates andwithtimingsthat treated and stored, animal wastes are collected, goodpracticerequires Current that management. inadequate investment inhousingandwaste of thelandinwintermonthswhere there is densitiesmay capacitystocking exceedthecarrying andlocal often beconstrainedby grazingschedules, but can applications grassiscritical, topermanent thetimingoffertiliser losses totheenvironment, “ UK farmersneed UK “ technology” agriculture adopt precision incentives to

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30 required of the processes and “ continued CAP patterns of nitrogen releases to reform should the atmosphere, especially from grazed land, as a basis for encourage a shift effective controls and innovative to more extensive technology. systems, especially on Continued CAP reform should poorer land, as the encourage a shift to more extensive systems, especially on link between poorer land, as the link between subsidy and yields subsidy and yields is broken.This is broken” should lower overall agricultural emissions of nutrients to the environment. But CAP reform

the nutrient cycle: closing the loop the nutrient cycle: will also drive the emergence of larger intensive and mixed intensive-extensive operations that may present higher environmental risks.There is an urgent need to ensure that more intensive agricultural systems are not sited where there is inadequate environmental capacity to absorb their emissions. Alongside this there is a requirement for a combination of public investment in research and incentives and advisory services that are targeted at improving the efficiency of nutrient use, via new and better adoption of existing technology and higher standards of management.

Mark Kibblewhite is head of the natural resources department and Professor of applied soil sciences at the National Soil Resources Institute, Cranfield University S3567 this historical knowledgethis historical was discardedandithas towards Intherush industrialisation, diminished. organic matter tosoilshasbecomeseverely link between food production surplus andreturning Revolution since theIndustrial thiscrucial However, tothesoil. nutrients ofreturning importance farmers recognised throughout the history studies, Even withoutthebenefit ofscientific 4,000 years. overmaintaining soilfertility andstructure some highpopulation densitiesand supporting Ithasbeenconsidered thekey to centuries. animal manure waste hasbeenpractisedinChinafor togetherwithothervegetable and nightsoil, matter, compostingofhumanfaecaland notechnology.The composting tookplacewithlittleinputfrom people For ofthat thevast time, majority the dawn oftime. hastaken placesince biodegradable organic matter, compost through aerobic decompositionof theprocess ofproducing that istosay, composting, mightstillbeyoung,While theindustry and nitrogen tothesoil. landfill significant andreturning amountsofcarbon reducing toincreasing recycling, contribution ismakingapositive which pound industry gardencompostheapsfrom toamultimillion back Inlittlemore thantenyears ithasgrown in theUK. isarelativelyThe compostingindustry new arrival Dr JaneGilbert the nutrientsloop the role ofcompostinginclosing 29/5/07

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31 is thesubstratum ofallthat isliving.” andyet thisfertility could accumulate, oflife onlyfertility centuries which a generation hasswept intotheseasoil intheuncontrolled handsof destruction andhisbesomof himself notexcepted; fallen uponevery livingthingwithinhisreach, blight has Hiswithering the world hasever endured. “Man isthemostextravagant accelerator ofwaste published nearly ago: a century evenKing ring today truer thanwhenthey were first we are only now words rectifying.The ofDrF.H. a lossofvaluable andorganic nutrients matter which inadvertently resulted in in ourgrowing urbanareas, inordertosafeguard public health or incineration, aslandfill such disposalmethods, sanitary requiring and as Classifyingthesematerials ‘wastes’ soil. ofrecycling organicimportance tothe waste back scientists andfarmers have onceagain recognised the only beeninrelatively recent years that mainstream potent greenhouse gasmethaneintotheatmosphere. aimstoreduce emissions ofthe which (EC/31/99), this development hasbeentheEULandfill Directive behind driver principal begun toactuponthem.The questioned andthat European governments have hasbeen impact ofthesewaste disposal techniques It isonly inrecent years that theenvironmental 6 “ compostinghas the dawnoftime” taken placesince

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32 The Directive sets binding targets for member states increase yields over three to five years of repeated to divert biodegradable municipal waste from application. Furthermore, compost also has a landfill; the knock-on effect of this is that local potentially large market in restoring and ‘repairing’ authorities in the UK are now collecting garden and soil on brownfield sites such as former factories and food wastes separately for biological treatment, industrial areas, as it can be an ideal component in either through composting or anaerobic digestion. topsoil manufacture where existing soil is scarce or The UK’s composting industry currently processes in of poor quality. excess of three million tonnes of waste a year, producing more than a million tonnes of compost. Most notably though, composts have a direct impact Impressive though this may sound, especially when on the soil’s physical structure, helping to increase compared to the few thousand tonnes composted in organic matter content, improve structure and the early nineties, this increased need for recycling workability, reducing erosion and compaction as means that the composting industry is set well as acting as a sponge to help hold- to witness somewhere between a three and “ compost can in moisture.This water-retention five-fold increase in production within the play a pivotal capacity has direct agronomic benefits the nutrient cycle: closing the loop the nutrient cycle: next 10-15 years. role in the especially as parts of the UK are now starting to experience greater periods of The benefits of compost use are wide and adoption of low rainfall followed by intense varied.The ‘black gold’ loved by gardeners sustainable precipitation. An added benefit is that is now the subject of serious scientific practises” the organic matter acts as a buffer, study by academics across the world, who helping to mop up and retain inorganic have begun to translate qualitative effects into fertilisers that would otherwise run-off and pollute quantitative benefits.The complexity of soils and the water courses. flora and fauna they support suggest that benefits are diverse, with synergistic effects observed in long- Compost, being a living substrate, introduces term trials. beneficial microorganisms into the soil, and helps provide food for indigenous soil fauna.The A range of research projects and trials have been development of ever more sophisticated molecular carried out in the last five years to prove the benefit biology techniques has moved the understanding of of compost use in a range of applications.The the microbiology of composting to new horizons. evidence from these trials has shown that compost Scientists are now able to track the growth and can play a pivotal role in the adoption of sustainable succession of microbial communities during practises in certain markets. Compost’s moisture composting and assess how these interact with soil retention capabilities and its slow release nutrients microbes. One area that is receiving considerable have made it an attractive option to landscapers and interest is the ability of composts to suppress plant horticulturists. Recent trials in agriculture have pathogens. Research into the disease suppressive shown that the application of compost to soil can effects of compost began in the United States over S3567 from England and Wales show that percentage of Figures thisbenefit cannotbeoverstated. century, significant organic thelast matter lossduring situ microbes tohelpgenerate more organic matter isretaineda proportion inthesoilandusedby soil Rather, the nitrogen incompostis usedasafertiliser. inGermanyResearch hassuggestedthat notallof conventional fertiliser applications were observed. years yieldincreases of7percentcompared with studies intheUKhave suggestedthat afterthree Recent numerous globally. field-scale trials long-term application tocrops have beendemonstrated in benefits ofcompost subsequent years.The but alsoin yields notonly initsyear ofapplication, helpimprove soilfertility andcrop therefore, can, Compostuse are over observed ofyears. aperiod are released intothesoilover timesothat benefits that ofnutrients composts helpsbuild upa ‘bank’ meansthat applying year ofapplication.This is typically available for plantgrowth thefirst during 15 percentofthetotalnitrogen contentincompost Intemperate regions between 10- in different ways. PandKare available toplants The macronutrients N, compostscontainarangeofplantnutrients. Notably, environmental problems. over theyears beenlinked tonumerous have which farmer’s reliance onartificial pesticides, the application ofcompostcanhelpreduce a Where thesepathogens are ofagronomic concern, for diseasesuppression isgreen waste compost. that hasreal Onematerial potential plant diseases. made from wastes awiderangeoffeedstock on intotheeffectsamount ofresearch ofcomposts there hasbeenasignificant Sincethen, 30 years ago. 29/5/07 steU,i atclr hasexperienced inparticular, AstheUK, .

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33 in 7 1995. 1980- from 35percentto42intheperiod soils withlessthan3.6percentorganic matter rose Common Agricultural Policy Common Agricultural hasreplaced previousScheme theSinglePayment In theUK, health. environment tohuman or harm tothe used withoutrisk classified asfully recycled and sufficient toensure that therecovered product canbe isconsidered and compliancewiththesecriteria the production ofcompost from specific waste types, for The QualityProtocol for Compost setsoutcriteria professional inplacetomeetthis demand. industry compost totheirsoilandbecausethere isa and farmers whoknow thebenefits ofapplying developers horticulturists, demand from landscapers, becauseofthegrowing Itwas chosen protocol. recovered waste typetobesubjectaquality Compostisthefirsta waste inEnglandand Wales. Compost meansthat itneednolongerbeclassified as PAS 100standardandtheQualityProtocol for Compostproduced tomeettheBSI assured compost. The UKnow produces aready supply ofquality million carsayear. dioxide emissionsequivalent tothoseofover a biowaste couldhave thepotentialtooffsetcarbon composting anestimated 15milliontonnesof Association hasprovisionally calculated that Composting carbon dioxide emissions.The thusmitigating can helpcountersomeofthisloss, thecontrolled application ofcompost By inference, that lossofsoilcarbonislinked toclimate change. 8 Recent research publishedRecent research in composting15million “ Nature a millioncars ayear” emissions equivalent to to offsetcarbondioxide could have thepotential tonnes ofbiowaste suggests 9

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34 payment schemes. Organic matter decline in nutrients present in quality compost will provide a European soils is one the main emerging issues in EU source of food for microbes in the soil and help policy terms, because it is threatening the capacity of farmers to move as close as possible to closing the soils within EU Member States to remain fertile and organic loop. to keep performing their environmental functions. In order to receive their subsidy payment, farmers must With our rush towards the use of fertilisers the comply with Statutory Management Requirements organic loop has been broken; it’s time that we and Good Agricultural Environmental Condition reconnected that link between organic waste and the (GAEC) standards. Better productivity is linked with soils on which they arose in the first place. Farmers good soil management that prevents soil erosion throughout history have known that it was important from fields.The effective maintenance of soil organic to return waste to the soil, they might not have matter and good soil structure are central to meeting known why it was important or what they were the GAEC standards. In addition, agri-environment doing but they knew it was important and that it schemes within the UK provide additional funding to worked.The use of inorganic fertilisers may have had farmers and other land managers who deliver short-term benefits but it has had massive

the nutrient cycle: closing the loop the nutrient cycle: effective environmental management on their land. repercussions in the longer run.This will change. Although the schemes differ in some details, soil and Recycling and composting are high on the manure management planning is a common element government’s agenda, the Quality Protocol for to all. Compost has been published and there is a real desire amongst the public to recycle and take more care of “ it’s time that we The Composting Association believes that the environment. With potentially in excess of 7 reconnected the the relevance of certified quality assured million tonnes of compost produced every year, this link between composts should be made more apparent could represent just under a million tonnes of in government GAEC standards, agri- organic carbon and over 50,000 tonnes of nitrogen organic waste and environment scheme guidance and in any which would otherwise be lost. We now have the the soils on which associated guidance on the reformed knowledge and the opportunity to improve the they arose in the Common Agricultural Policy, and that quality of soil and to move in the right direction; our first place” government considers policy drivers that agri-environment schemes need to reflect this. would provide a clear link between biowaste and soil management practices. Applying compost to the soil will have major benefits to the environment. After all, there’s a reason why Soil comprises a delicate balance of minerals and farmers have been doing it for 40 centuries. living organisms but our recent emphasis on applying inorganic fertilisers has rapidly destroyed Dr Jane Gilbert is chief executive this ecosystem. Compost can play a vital role in of the Composting Association returning nutrients to the soil and thereby arrest the decline in the quality of soil in this country.The S3567

habitats. aquatic habitats anduplandmoorlowland heath It focusses onfarmland, ontheimpactsofnutrients andnitrogen onUKbirdpopulations.phosphorus indirect effects (includingfood-chain) of adetailedreviewsummarises oftheevidence for chapter detail at theeffects onhabitats.This species but theeffects canbeviewed by lookingin pressures tothedecline in individual contributing disentangle theeffects from ofnutrients theother Itisdifficult to consequences for wildlife. natural andsemi-natural habitats withknock-on directlyBoth thesenutrients affect plantgrowth in availablephosphorus revolution. sincetheindustrial theamountofbiologically availablealso tripled Humanshave thatforms canaffect theenvironment. fixation ofnitrogen gasfrom theatmosphere into humanactivityhasmore thandoubled the scale, Onaglobal specificially nitrogen andphosphorus. tothenatural - cyclingofplantnutrients changes intensification have been accompaniedby dramatic andagricultural Industrialisation countryside. thefertility ofthe Human activityisaltering M AMacDonald,JDensham,RDavisandSArmstrong-Brown and otherbiodiversity the impactofnutrientsonbirds too muchofagoodthing? 29/5/07

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35 10 plants andanimalsinfarmland. number ofconsequences for non-crop hasa also alterthesehabitats.This field margins intheapplication process Fertilisers applied onto grass swards. denser andmore crops uniform and growthearlier spring andleadtotaller, Fertilisers promote faster and indirect. ofwildlife impactsarethe majority but appliedof nutrients totheland, Some organisms are directly affected by thetoxicity Vegetation structure from theagricultural system. orwhenunused are nutrients dispersed on farmland; affect whennutrients non-crop plants consequences; intensification hasnegative environmental Problems when arise agriculture sincethe1950s. amassivehelped todrive intensification of Inorganic fertiliser usehasbeenonefactor that has are grown andmanaged. includinggrassland, crops, increasing yieldsandhave theway helpedto change growth acceleration are ofnutrients properties key to plant Farmland isadeliberately fertilised habitat.The Farmland humanactivityhas “ environment” affect the into formsthatcan the atmosphere nitrogen gasfrom the fixationof more thandoubled

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36 Species richness management. It has probably also had the greatest Increased fertiliser applications generally reduce the effect on farmland bird populations because in variety of plant species found in fields.The first to addition to reducing food resources, nest destruction disappear are the most sensitive plants which cannot during silage cutting has a major impact on ground 14 tolerate increased nutrient levels or compete with nesting birds such as whinchat and corncrake. nutrient hungry crops, for example, lambs succory Furthermore, intensive grazing on fertilised and annual knowle.This can have knock-on effects grassland can lead to increased nest trampling in 15 for invertebrate species such as butterflies and ground nesting species such as skylark and 16 carabid beetles11 which require these plants as hosts, lapwing. and has the potential to decrease invertebrate biodiversity on farmland. Farming systems At the landscape scale the use of inorganic fertilisers Whilst some plant eating invertebrates may benefit has led to changes in patterns of land-use by from the increased nutritive content of fertilised releasing farmers from the need to graze livestock crops and grass, some, such as grasshoppers and for manure production and/or to rotate leguminous

the nutrient cycle: closing the loop the nutrient cycle: crickets, are adapted to a specific sward structure crops in order to provide plant nutrients. As a result within fields. When fertilisers cause a change to the there has been a loss of mixed farming landscapes structure of plants these insects are affected12 but in and a polarisation of agriculture in the United addition, they are disturbed by intensive grazing and Kingdom towards arable farming in the south and cutting regimes because of their longer life cycles east, and pastoral farming in the north and west. and relatively low recolonisation ability.This means Birds such as starling and lapwing prefer the that they are more likely to disappear from juxtaposition of arable fields and pasture and are intensively managed farmland.The loss of these large likely to have been affected by the loss of mixed invertebrates may also be a major cause of impacts farming from the landscape.17 on birds, such as cirl bunting and red-backed shrike, and breeding waders in grassland.13 Dense grass and Aquatic habitats crops also dry the soil forcing earthworms deeper In some forms nitrogen and phosphorus can be into the ground making them unavailable to birds transported away from their intended targets, for such as snipe, starling and chough, that probe the example in silage fields, and can disrupt habitats soil for food. elsewhere. Nutrients also enter the aquatic environment as pollution from some sewage Land management treatment works.This pollution can cause aquatic Silage production, with its intensive use of fertilisers systems to become eutrophic with complex and for rapid grass growth and repeated cutting, highly localised effects on the food-chain.There are probably has the most radical effect on vegetation winners and losers when aquatic habitats become and the food-chain of wildlife, of any farmland eutrophic: increases in nutrient concentrations may S3567

ed sdb itrs known ashover. usedby bitterns, reed, floating of form caused thedeclineofaparticular Broads where increases innitrates inwater have hasbeen seenintheNorfolk change Anexampleofthis communities. and compositionofplant thestructure inchanging of nutrients also meanitisaffected by theaction adaptation tolife inreedbeds may andits major food itemsinBritain oneofits by thisreduction inthenumbers ofrudd, food supply. to feed onthemsuffer from theresultant reduced dive from which thesurface aspochard, such birds, Diving sensitive asmolluscs. groups ofspeciessuch leadingtoalossof at thebottomofwater bodies, conditions canradically affect theinvertebrates living for exampleeutrophic sensitive tonutrients, Invertebrate communities infreshwater are also andrudd. tench bream becomingdominantat theexpenseofperch, and withroach leads toareduction offish diversity, Eutrophication ofshallowrelatively lakes quickly. quality andimpactsonbiodiversity beingnoticable eutrophication withtheresultant shiftsinwater freshwater lakes are especially susceptible to Shallow minor increases loadings. innutrient andplantlifenutrients makingthemsensitive to Upland lakes intheUKare mostly naturally low in Upland freshwater lakes sites. habitats speciesrely onwhich for food andnesting but canradically toogreat impactthe achange be beneficial towildlife by increasing food supply 29/5/07

09:47 20 Phosphates are commonly transported 18

The rare bittern mayThe rare bittern beaffected Page

37 19 shallow freshwater “ eutrophication” susceptible to lakes are especially their replacement by algalmats andphytoplankton and asseagrass such andeelgrassbeds, communities, occurs ittypically leadstoadeclineinplant where eutrophication However, through withwater. because they are generally more flushed quickly coastal waters where theireffects are lesspersistent flowingNutrients downstream and esturaries reach Estuaries andcoastalwaters crayfish. freshwater pearlmussel andnative white-clawed andaffect andhatch, salmonid eggstosurvive cloggravel neededfor of submerged plants, prevent thegrowth themselves canalsocloudwater, phosphate levels inwater but thesediments ofpollutioncanincrease mechanism sediments.This to theaquatic environment by beingboundto ssedc,may not. as shelduck, such specific prey requirements orforaging habits, althoughbirdswith from sewage outflows, example, for from inputs, humaninfluencednutrient birdsgenerally benefit eutrophic tidalareas.These provide abundant food resources toshorebirds in relatively tolerantofeutrophic conditionsandcan like andpolychaetes the mud ragworm shrimp are as such Smallaquatic crustaceans ofwater. stretch blooms. invertebrates andfish inanaffected killing occur infreshwater too, phenomenoncan the foodchain.This flush offood for organisms higherup to thesurface providing ashort-term water ofoxygen andforce invertebrates 21 22 This growth the canstarve

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38 Upland moor and lowland heath deposition. A number of bird species have been Upland moor and lowland heath, dominated by identified as sensitive to heather loss, especially red heather, are naturally nutrient poor habitats that are grouse and stonechat. It is, therefore, possible that sensitive to increases in nutrient inputs. Fertilisers these birds are adversely affected by the impacts of are not generally applied to moorland or lowland atmospheric nutrient deposition. heathland as a land management tool. Instead, increases in nutrient loading are the result of Conclusions atmospheric nitrogen deposition.This source of Increased levels of nutrients are damaging habitats nitrogen has increased enormously over the past across the UK. Nutrient pollution force-feeds the century, despite some reductions over the past two countryside, altering plant growth rates, changing decades. plant communities and disrupting the food chain for wildlife. Red backed shrike is now extinct in the UK; Vegetation its decline was largely driven by management Heather cover in UK upland moorland and lowland change linked to fertiliser application to grassland. heath declined by 40 per cent between 1947 and This process also helped drive corncrake and cirl the nutrient cycle: closing the loop the nutrient cycle: 198023 due to overgrazing, afforestation, conversion bunting to the brink of extinction in the UK.These to farmland, invasion of grasses, and succession to two species are slowly recovering as a result of scrub. Nitrogen deposition in the form of nitrous intensive conservation effort.Tougher action must be oxides may have accelerated these processes, such as taken to ensure the efficient use and recycling of by increasing the nitrogen content of heather leaves, nitrogen and phosphorus, and limit losses to the affecting the plant’s structure leaving it sensitive to environment.The knowledge and technologies exist drying and attack by heather beetle,24 which feeds to achieve this, through capturing and re-using the exclusively on it. Exacerbated by grazing nutrients present in organic wastes. Now, policies are disturbance, dieback can occur which allows grasses required to put this knowledge into practice, to invade, themselves fertilised by the atmospheric through a mixture of better regulation, incentives nitrogen. Plant-eating invertebrates may be helped and education. by the enhanced nutritive value of heather or through a preference for grasses but ultimately This article is a summary of a recent evidence changes to the mosaic of grass and heather and review by RSPB. The full report is available at intensive grazing of moorland will remove foliage to http://www.rspb.org.uk/ourwork/policy/ the detriment of these invertebrate communities. water/issues/diffuse.asp

Birds In upland moorland, the shift from heather to grass moorland over a large scale is likely to be the most important indirect effect on birds of nitrogen S3567 breakdown ofplantandanimalremains inthesoil. growth that are normally provided from the nitrogen compoundsammoniumandnitrate for Plantsneedthe ‘reactive’ animals inthat form. andcannotbeusedbynitrogen isinert plantsand problem isthat atmospheric cent nitrogen.The there isnoshortage sinceouratmosphere is80per Globally, for plantgrowth. and plantsiscritical Itisa componentoftheDNA ofallanimals element. perhaps Nitrogen isanessentialelement, withsynthesisedfertilisers.nutrients farmers addtothenaturally available production, To ensure onagricultural aneconomicreturn adequate bigmarketable willform nutrients heads. maynutrients fail acurdwhereas toform thosewith crop at all–cauliflowers grown withlimited be thedifference between amarketable crop andno can additionalnutrients Invegetable crops, nutrients. receivedthat ofacrop which noadditional crop ofwell-fertilised winterwheat willbedouble yieldofa respond positively toaddednutrients.The All food crops withtheexceptionoflegumes inefficiencies. natural cyclesandare prone toleakages and However they are of nitrogen andphosphorus. cyclesintheUKare nutrient those most important thetwo allagricultural production, Underpinning Rob Lillywhite today’s nutrientcycle energy andcostimplicationsof 29/5/07

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39 the essential by over 90percent”. theglobal reactive N cycleisbeingperturbed cent, bycarbon cycleisbeingperturbed lessthan10per “Whiletheglobal Programme (GANE)suggests, The GlobalNitrogen Enrichment Thematic doubling ofthereactive nitrogen inthebiosphere. inorganic fertilisersindustrial have sinceresulted ina of years andthemanufacture but industrialisation of ornatural nitrogenbackground cyclefor hundreds beensupplementingthe ofcourse, Humans have, agriculture andfood production. linked tothisprocess that revolutionized modern increase inworld population since1910canbe thelarge Infact, supply. can supplementthis ‘natural’ from theatmosphere by theHaber-Bosch process manufactured usingnitrogen Synthesised fertilisers, agriculture andpower generation add two industries, Within theUK, cent ofthenitrogen suppliedtoit. production ofbeefusesonly 9per the systems are even more inefficient: Otheragricultural nitrogen inthesoil. only able totake up50percent ofthe are most efficient usersofnitrogen, the Cereal crops, nitrogen inefficient. the fact that food production is tothe increasedattributed demandfor food andto 25 The increase canbe whiletheglobal “ over 90per cent” by being perturbed reactive Ncycle is cent, theglobal less than10per by being perturbed carbon cycle is

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between them 2 million tonnes of new reactive 28 40 of 5.29 tonnes of CO2, which means that the 0.5 nitrogen to the environment every year: 1.1 million million tonnes of nitrogen lost as leachate every year tonnes of nitrogen fertiliser, 0.4 million tonnes of required 20 million GJ to manufacture and emitted agricultural nitrous oxides and ammonia and 0.5 the equivalent of 2.65 million tonnes CO2. In total, million tonnes of nitrogen oxides from the the 1.1 million tonnes of nitrogen fertiliser used in combustion of fossil fuels. Although only the the UK required 44 million GJ of energy to nitrogen fertiliser is deliberately applied to manufacture and emitted the equivalent of 5.8 agricultural soils, the other compounds are also million tonnes CO2. returned to the soils as wet and dry deposition.26 The cost of transporting and applying fertiliser The costs and implications of adding this much requires some assumptions but we estimate that nitrogen to the UK environment on an annual basis another 1.3 million GJ are required to transport and are significant, but defining and quantifying them is apply the unused nitrogen, equivalent to another not easy. Some are financial; some environmental - 0.01 million tonnes of CO2. and there is no easy way to make them comparable.

the nutrient cycle: closing the loop the nutrient cycle: Unused reactive nitrogen has been accumulating The nitrogen cycle, due to the mobility of nitrate, is within our environment for years.The task of inherently leaky and the subsequent environmental assessing and if necessary making safe or removing effects of excess nitrogen are well documented: that nitrogen is the responsibility of the acidified soils, loss of plant diversity and high nitrate Environment Agency and water companies. In levels and eutrophication in fresh and marine England approximately 29 per cent of all rivers are waters. Whilst most people would agree that classified as having nitrate concentrations greater “ agriculture these effects have a negative value it is far than 30 mg/l with some areas such as the midlands, and power more difficult to ascertain their cost. Let’s start Anglian and Thames recording concentrations of up generation with the basics. Every year half a million to 80 mg/l. Wales, Scotland and Northern Ireland add between tonnes of nitrogen is leached from agriculture have much lower levels due to less intensive them two soils. Although it’s only partially true, for the agriculture. In order to meet the EU drinking water purposes of this exercise we will assume that limit of 50 mg/l, water companies must either million tonnes this is all commercial ammonium nitrate blend high concentration water with lower of new fertiliser costing £160 per tonne (£464 per concentration water or must remove nitrate by ion reactive tonne of nitrogen). In financial terms, this exchange or reverse osmosis. Both of these processes nitrogen to the means that £232 million is wasted.27 are expensive to construct and operate: Ofwat has environment suggested that between 2005 and 2010, English Costs can also be measured in terms of the water companies will have to incur capital every year” energy used.To manufacture one tonne of expenditure of about £300m and annual operating nitrogen for ammonium-nitrate fertiliser takes costs of £6m to reduce nitrate levels for the public 40 gigajoules (GJ) and releases the equivalent drinking water supply. S3567 at ersnsol .5prcn.Inmany waste represents only 1.85percent. food is£16,000million sothe£296millionbillfor it significant? The farm gate value ofUKproduced Butis removing water itfrom issubstantial. drinking fertiliser and£55millionthat isspentannually in Economically the£241millioncostof unused food production. contrasted against thegains: must be bethey economicorphysical, environment, andtheirimpactonthe lossesofnutrients However, carbon dioxide. 3320 tonnesofoilequivalent and10,000tonnesof for 27,800tonnesis139,000GJor tonne which cyclewelost withinthenutrient willuse5GJper However ofassessing theenergy for thepurposes phosphate that canrelease 3.8GJpertonne. by super subsequentprocessing intotriple althoughthisenergy inputcouldbeoffset per tonne, phosphate withanaveragerock energy inputof5GJ Phosphate fertilisers are manufactured from mined phosphate) is£8.9millionpoundswasted. superphosphate (or£319pertonneof triple assuming anaverage costof£150pertonnefor lost from thesoilonanannual basiswhich estimate isthat 10percentofapplied phosphates are best current and therefore lesslikely toleach.The eutrophication althoughthey are lessmobileinsoil Phosphates like nitrates are implicated in theUKused278,000tonnesin2004. which of isphosphate, The fertiliser ofphosphorus form water companiesof£6millionperannum. direct costsare by thoseoperating costsborne the significant environmental cost-althoughtheonly that cost£232milliontomanufacture alsohasa unused agricultural nitrogen fertiliser In summary, 29/5/07

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41 reducing the impactofapplied nutrients. perhaps we needtoexplore different ways of but evila necessary of food part production then position andacceptthat leakages andtoppingupare Ifwe have that reached land outofagriculture. reduced food production andtakingvast swathes of reductions willonlyfurther comeat the expenseof andthat thepointofdiminishingreturns is nearing It ispossible that inagriculture theuseofnutrients output. without any reduction inoverall agricultural tonnes, from 2.1milliontonnesperannum to1.8million appliedamount ofnutrients intheUKhasdropped time plantphysiology hasn’t but thetotal changed Inthat reducing year onyear for thelasttenyears. losttotheenvironmentthese nutrients have been production systemsandtherefore theamountsof inagricultural useofnutrients production.The natural biologicalefficiency andoverall food not beconsidered inisolation but incontextof they should However, isolation appear substantial. the UK’s ifconsidered in cycleswhich nutrient So there are certainly costs involved inleakages from between inputandoutput. systems but thesefigures stillillustrate thelarge gap are otherenergy inputsintoagricultural production Ofcoursethere contained withinunused fertiliser. isover which tentimestheamount million GJ, feedstock’s production isestimated tobe548 contained withinUKproduced food andanimal embodiedenergy slightly more difficult.The Summing uptheleakage ofenergy interms is acceptable. that levelcommercial industries ofwaste would be

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42 If UK agriculture cannot do without added nutrients increased financial costs of implementing and using then perhaps we need to rethink the form that those new systems but far more importantly, the general nutrients take. What would happen if we didn’t use public would need to accept the concept of reusing synthesised fertiliser and grew all our food using biodegradable organic material as alternatives to some of the strategies lifted from organic farming? synthesised fertiliser and would have to accept that Synthesised ammonium nitrate, as remarked on the true cost of food is higher than it is now. earlier, is very energy expensive to produce. So However, in the long term, the benefits in terms of replacing it with low energy alternatives would improvements to the environment and energy saved reduce the energy bill and perhaps diffuse pollution could be substantial. as well. Alternatives do exist, for example, bulky ‘natural’ materials such as farm yard manures, In these days of increasing environmental awareness, slurries, composts, sewage sludges and digestates ecological footprints, climate change and air miles, contain plant nutrients and are readily available but the task of reconnecting the general public to food have been largely replaced in modern conventional and farming is already underway. Recycling and agriculture by more easily handled synthesised reusing materials is now part of our everyday lives so

the nutrient cycle: closing the loop the nutrient cycle: granular fertilisers. Although concerns regarding extending that concept to the reuse of manures and hazards to both health and the environment have sewage sludges would seem logical. In the last few been expressed for some of these materials, these are years, public opinion has shifted to a point where the overcome by adhering to existing strict Codes of green agenda is no longer a minority position, so Practice such as the Safe Sludge Matrix and the selling the new fertiliser has already begun although “ the general new Quality Protocol for Compost. it would take determined government action and the public would support of the green and environmental groups to have to If the concerns of the Environment Agency, the make the change possible. However, if we are reduce accept that major retailers and their customers can be or replace synthesised fertilisers, reduce our energy the true cost overcome there is no shortage of these natural demand and close the loop we need to start by materials since meeting the demands of the overcoming our own prejudices. of food is Landfill Directive will ensure that biodegradable higher than organic material which in the past would have Whether food is produced domestically or imported, it is now” been land filled is now available for spreading to ‘leakages’ and ‘topping up’ are unavoidable land. In terms of overall nutrient supply, a components of agricultural systems. Different combination of source segregated biodegradable management strategies in agriculture and UK and municipal waste, green waste, sewage sludge and European legislation have reduced the impacts and farmyard manures could replace all use of costs over the years, however there is still room for manufactured fertilisers. However, a note of caution improvement. here.To implement such a complete sea change in agricultural practice would involve not only engaging Rob Lillywhite is a researcher at Warwick HRI, University UK farmers but also government and the general of Warwick. He co-authoured the Biffaward public. Farmers would initially have to bear the mass balance study, Nitrogen UK S3567

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09:47 7Wlo,AM,ikr,JA n rwe ..2001, S.J. andBrowne, J.A. A.M.,Vickery, Wilson, 17 1990, M., 16 Shrubb, 8Lah .. ono,MG,Klo ... atan . uan .adEt,B 1977, B. andEntz, W. Numann, J., Hartmann, J.R.M., Kelso, M.G., Johnson, J.M., Leach, 18 0Aln . eln . nadr .and I. Enlander, C., Mellon, D., 20 Allen, 2004, G., Watson, and R.R. Boar, C.F., 19 Crook, 1983, B., Moss, 1Hret ..1999, R.A. 21 Herbert, 2Bro,NHK,JnsTE,Asi,GE,Wt,GA,Rhic,MM and M.M. Rehfisch, G.A., Watt, G.E., Austin, Jones,T.E., N.H.K., 22 Burton, 2004, C.J., Hutchins, 3Topo,DBA,Mcoad .. ase,JH and J.H. Marsden, A.J., MacDonald, D.B.A., 23 Thompson, 1995, C.A., Galbraith, 4Busig ...and A.M.H. 24 Brunsting, 1985, G.W., Heil, 5Llyht,R and R. 25 Lillywhite, 2005, C., Rahn, 8JnsnTK n oghu,G,2003, G., andKongshaug, Jenssen,T.K. 28 Commercialammoniumnitrate covert fertiliser contains34.5percent nitrogen.To weight of 27 depositionoccurs whenanitrogen compoundisremoved Dry from theatmosphere by contactwith 26

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44 7 pp115-127. 37, vanellus consequences andsolutions 1971. percid fishesandtheirhabitat toeutrophication reductions inorganic andnutrientloadingonbirdpopulations inestuariesandcoastalwaters ofEngland Wales populations 590. Peterborough. EnglishNature, 586, No. Report EnglishNature Research byReport theBTO for EnglishNature, some competingplantspeciesinheathlands pp163-178. Conservation 71, vegetation change andsomeobjectives for nature conservation importance, areview ofinternational Great Britain: irgn divideby 2.9. nitrogen, nitrogen toweight offertiliser multiply by 2.9ortoconvert weight of fertiliser toweight of occurs whenanitrogen compoundisdissolved intowater vapour tolandasrain. andreturned Wet that subsequently particle deposition the surface falls ofthelandoranaerial-borne toland. h nentoa etlsrScey rceig o 0,1-28. 509, Proceedings No. FertiliserThe International Society, breeding inEnglandand Wales in1998 rs id ,pp327-336. Birds7, Irish , Effects ofagricultural change onnestinglapwings Vanellus vanellus inEnglandand Wales Nitrogen cyclingincoastalmarineecosystems Nitrogen eott h rasAtoiy owc,UK. Norwich, totheBroads Report Authority, , io 4 pp23-26. Oikos 44, , Nitrogen UK Nitrogen ora fteFseisRsac or fCnd 4 1964- BoardofCanada34, Research Journal oftheFisheries , Energy consumption andgreenhousegas emissionsinfertiliser production idSuy4,pp2-17. BirdStudy 48, , The roleofnutrientsintheinteractions between aherbivorous beetleand h eln fteresapi h ofl raln:causes, The declineofthereedswamp intheNorfolk Broadland: 6 Warwick HRI p6, , Numbers and distribution of northern lapwings Numbers anddistribution ofnorthern og eg iigdcs recent changes inwintering Lough Neagh divingducks: ESMcoilg eiw 3 pp563- FEMSMicrobiology Reviews 23, , Upland heather moorland in . Vanellus Phase 2report Responses of . Bird Study Bird . Biological , Effects of , , S3567 29/5/07 09:47 Page 45 S3567 29/5/07 09:47 Page 46