schulte et al lough - teagasc

Tearmann: Irish journal of agri-environmental research, 7, 211-228, 2009

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Lough Melvin: Developing cost-effective measuresto prevent phosphorus enrichment of a unique

aquatic habitat

R.P.O. Schulte1*, D.G. Doody2, P. Byrne1, C. Cockerill3,

O.T. Carton1

1Teagasc, Johnstown Castle Environment Research Centre, Wexford, Ireland2Agri-Food and Biosciences Institute, Newforge Lane, Belfast, BT9 5PX, Northern Ireland

3Gibson Institute for Land, Food and Environment, School of Biological Sciences,Queen’s University Belfast, Belfast, BT9 7BL, Northern Ireland

*Corresponding author: [email protected]

AbstractLough Melvin, located on the border of Leitrim (Republic of Ireland) and Fermanagh (Northern Ireland),is unique among Irish lakes, supporting a fish community typical of a natural post-glacial salmonid lake,and has been designated as a Special Area of Conservation (SAC). The biodiversity of the lake is vulnera-ble to changes in water quality resulting from eutrophication, and over the last 15 years, phosphorus (P)concentrations have increased to the upper range of mesotrophic classification. Agriculture has beenreported as one of the main contributors of P loadings to the lake, which poses an apparent paradox inlight of the low-intensity nature of farming practices in the catchment. The objectives of the project report-ed on here were to identify the dominant P pressure and pathway risks governing P loss in the catchment,and to evaluate and select potential mitigation measures, based on an assessment of cost-effectiveness andfarmer preference. Throughout this project, we employed an explicitly participatory approach, with farmerstakeholders inputting directly into the identification and evaluation of mitigation measures. We identi-fied risks on 50 survey farms by using the modified P Ranking Scheme. A suite of 25 potential mitigationstrategies was identified from the literature and on-farm interviews. For each measure, we derived the orderof magnitude of potential costs, impact, and cost-effectiveness, and measures were preferentially ranked by25 participating farmers. The resulting ranking of measures showed that support for nutrient managementplanning and soil analysis was the most cost-effective and popular measure aimed at reducing P pressuresin the long term, while installation of sediment traps in drainage ditches was the most cost-effective andpopular measure aimed at reducing P transport vectors in the short term. We demonstrate that throughthis careful evaluation and selection of mitigation measures, over 50% of potential total reduction in P losscan be achieved at c. 5% of potential total cost. In addition, we show that measures commonly proposedto mitigate against “high-visibility risks” are not necessarily cost-effective or acceptable to farmer stake-holders. The results of this study are specific to the biophysical environment and farming context of theLough Melvin catchment, however, we suggest that the approach taken in our project may be used as atemplate for the formulation of regional catchment management plans, such as the draft river basin dis-trict management plans required under the Water Framework Directive.

Key Index Words: Eutrophication, Nutrient Management Plan, Phosphorus Ranking Scheme, WaterFramework Directive.

IInnttrroodduuccttiioonnContextLough Melvin is a cross-border lake, locatedon the border of Leitrim (Republic of Ireland,RoI) and Fermanagh (Northern Ireland, NI).It is unique among Irish lakes, supporting afish community typical of a natural post-glacial salmonid lake, with three distinct andunique strains of Brown trout, Atlantic salmonand one of only two populations of Arctic charwithin NI. Lough Melvin is a mesotrophiclake, which has been designated as a SpecialArea of Conservation (SAC) under the EUHabitats Directive (Doody et al., 2007). Thebiodiversity of the lake is recognised as beingvulnerable to changes in water quality result-ing from eutrophication.

Campbell and Foy (2008) reported thattotal P levels in Lough Melvin increased by50% between 1995/1996 and 2001/2002,and have remained above 25µg l-1 since, i.e.within the upper range of mesotrophic classi-fication. Due to the peat staining in the lakethis increase in P has to date not been accom-panied by an increase in mean chlorophyll aconcentrations in the lake (Girvan and Foy,2006). Previous studies (Girvan and Foy,2003) established that P concentrations inLough Melvin had increased as a result of mul-tiple landuse pressures. The three primary lan-duses in the catchment are agriculture, forestry

and housing, with agriculture and forestryaccounting for approximately 13,576 ha and5,657 ha, respectively. Forestry within thecatchment is predominantly comprised ofconiferous plantations. Housing in the catch-ment consists of one-off houses dispersedthroughout the catchment and three villages –Kinlough, Kiltyclogher and Garrison. Girvanand Foy (2003) identified agriculture as thelargest single contributor to the P loadings,accounting for more than half of the totalannual P loading into the lake.

Agriculture in the Lough Melvin catchmentLocal agricultural activity is largely restrictedto extensive grazing with sheep and cattle, as aresult of the major soil groups within thecatchment, i.e. peats (40%) and gleys (47%),which are typically poorly draining and have alow production potential. Cattle are housedfor long periods (up to 6 months) over thewinter months due to soil drainage conditions,susceptibility to poaching, and poor grass per-formance. Winter forage is primarily silage,but hay is also used. Winter forage is supple-mented with concentrate feed rations.Suckler/beef farm enterprises typically involvespring calving followed by summer grazingand overwintering, with calves sold on the fol-lowing spring.

The findings of Girvan and Foy (2003)

Tearmann, the Irish journal of agri-environmental research, VOL 7, 2009

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Table 1: Soil test ranges and interpretation of the Soil P Index (Coulter and Lalor, 2008) 667

Soil P Index Morgan’s Soil P range

(mg l-1

)

Interpretation

1 0.0 – 3.0 Soil is P deficient; build-up of soil P required. Insignificant risk of

P loss.

2 3.1 – 5.0 Low soil P status: build-up of soil P is required for productive

agriculture. Very low risk of P loss.

3 5.1 – 8.0 Target soil P status: only maintenance rates of P required. Low

risk of P loss.

4 > 8.0 Excess soil P status: no agronomic response to P applications.

Risk of P loss increases within this Index.

Table 1: Soil test ranges and interpretation of the Soil P Index (Coulter and Lalor, 2008)

present an apparent paradox, given the lowintensity of farm practices in the LoughMelvin catchment. Agricultural census datafrom the Central Statistics Office (CSO) inthe RoI and from the Department ofAgriculture and Rural Development (DARD)in NI (Table 2) show that the average stockingdensity in the catchment is low, at 0.5 live-stock units (LSU) per hectare. While this live-stock density represents a significant increasesince the previous census in 1991 (Crowley,2003), it is still well within the grazing capac-ity of the soils within the catchment, whichLee and Walsh (1973) estimated to range from0.5 to 2.6 LSU ha-1. Surprisingly, less than37% of farmers within the RoI part of theLough Melvin catchment are participating inthe Rural Environment Protection Scheme(REPS) as compared to 60% participation inthe rest of Co. Leitrim.

Agri-environmental legislationAgriculture in the RoI and NI is subject tocurrent and proposed new legislation aimed atlimiting nutrient losses from agriculture towater, i.e. the EU Nitrates Directive(91/676/EEC) and the EU Water FrameworkDirective (2000/60/EC). The WaterFramework Directive requires the formulationof management plans for individual RiverBasin Districts (RBD) that address threats towater quality from all sectors of society, with aview to achieving “good quality status” for allwaterbodies by 2015. Within the current draftRBD Management Plans, the Nitrates ActionProgramme has been proposed as the basicmeasure for agriculture. Measures to control P

loss, particularly those of diffuse origin, arecentral to the Nitrates Directive, and manda-tory measures to reduce nutrient losses towater have been implemented through theEuropean Communities Good AgriculturalPractice for Protection of Waters Regulations(S.I. 378-2006 and S.I. 101-2009) in the RoI,and through The Nitrates Action ProgrammeRegulations 2006 and the Phosphorus Use inAgriculture Regulations 2006 in NI. Theseregulations include limitations to stockingrates, closed periods for land-application oforganic manures and chemical fertiliser, live-stock manure storage requirements, farmyardmanagement, and limitations to nitrogen andphosphorus application rates.

Within the context of the WaterFramework Directive supplementary measuresmay be considered, should future trends inwater quality not respond favourably to thebasic measures. Most of the draft RBD man-agement plans contain supplementary mea-sures for “protected areas” within the RBD,i.e. areas with sensitive ecosystems, most ofwhich have been designated as candidateSACs under the Habitat Directive. The notionof potential supplementary measures isextremely unpopular amongst the farmingcommunity, in light of the perception that thecurrent Nitrates Action Programme is alreadyplacing multiple stringent legislative con-straints on farming practices. However, it islikely that stricter water quality standards willbe imposed on sensitive aquatic and riparianecosystems, over and above the water qualitystandards targeted in the Nitrates and WaterFramework Directives (Anonymous, 2008;

SCHULTE, DOODY, BYRNE, COCKERILL, CARTON: Lough Melvin: Developing cost-effective measures

to prevent phosphorus enrichment of a unique aquatic habitat

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Table 2: Livestock census data of the Lough Melvin catchment. Source: Central Statistics Office 668

(RoI) and Department of Agriculture and Rural Development (NI). 669

Livestock category

Total RoI Total NI Catchment total

Total LU equivalents

Cattle 3,891 3,635 7,526 5,074

Sheep 12,199 1,342 13,541 1,896

Catchment average stocking rate (LU ha-1

) 0.5

670

Table 2: Livestock census data of the Lough Melvin catchment. Source: Central Statistics Office(RoI) and Department of Agriculture and Rural Development (NI).

McGarrigle, 2008)In the event that the introduction of sup-

plementary measures is inevitable and necessi-tated by legislation, it is imperative that suchmeasures fulfil the following criteria:1. Measures should be spatially targeted and

scientifically proven to address key-risks ofnutrient loss to water;

2. Measures should be assessed for cost-effec-tiveness (Finnegan, 2009), and represent alow ratio between total cost and totalreduction in nutrient loss;

3. The cost of measures should not be bornedisproportionately by individual sectors ofsociety (Finnegan, 2009);

4. Measures should be developed in closeconsultation with stakeholders, with aview to ensuring that the measures arepractical, implementable and adoptedwith a high participation rate (Doody etal., 2009).

Research objectivesIn this context, we set out to explore the para-dox of how low-intensity agriculture in theLough Melvin catchment may contribute toeutrophication of the lake and identify catch-ment specific practices to which current legis-lation may not be relevant. This study waspart of a larger project, the Lough MelvinNutrient Reduction Programme, which wasset up to draft a catchment management pro-gramme spanning all economic sectors withinthe catchment, The study presented in thispaper had two specific objectives:1. To identify the key-risks associated with P

loss from agriculture to water, in the con-text of the biophysical environment andspecific farm practices of the LoughMelvin catchment;

2. To evaluate and select agri-environmentalmeasures that address these key-risks basedon cost-effectiveness and farmer prefer-ence.

MMaatteerriiaallss aanndd MMeetthhooddssThroughout this study, we adopted an explic-itly participatory approach, with a view tocombining the objectivity of scientificresearch with the innate knowledge and valuesof stakeholders so as to develop a suite of agri-environmental measures that are scientificallyrobust while incorporating human and socialfactors. The merits of this participatoryapproach to the outcomes of this study arefurther explored in Doody et al. (2009).

Risk identificationThis aspect of the methodology comprisedfour components: 1) farm selection; 2) farmsystems survey; 3) farmyard survey; 4) field-by-field survey.

For the selection of the 50 survey farms,the criteria employed included the following:• Representative number of farms from NI

and the RoI;• Inclusion of a range of contrasting farm

enterprises found within the catchment;• Inclusion of both participants and non-

participants in voluntary agri-environmen-tal schemes;

• Wide spatial distribution within the catch-ment. Farmers fitting these criteria were contact-

ed either directly or through intermediariesand the project was outlined to them.Participation in the study was on a voluntarybasis and so ultimately it was the willingnessof farmers to participate that determinedwhich farmers participated. Multiple visits tothe participating farm were required to com-plete the survey, depending on farm size orlimitations such as the timing of recent slurryor fertiliser applications. The farm systemssurvey was developed and carried out to col-lect sufficient information from the farmer toascertain general information on the farm andfarming practices, including: farm area, land-use within that area, livestock numbers, hous-ing facilities or out-wintering details and dura-tion, fodder production, import of feed andfertiliser use.

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Subsequently a field-by-field and farmyardrisk assessment, utilising the modified PRanking Scheme (mPRS) developed byMagette et al. (2007), was carried out (Table3). This comprised an assessment of the sourceand transport factors pertinent to P loss. Therisk of P loss due to applications of P is theproduct of the usage and timing factor (S1).The risk of P loss due to soil P concentrationsis the product of soil P and desorption risk(S2). The sum of these (S1 + S2 + S3) gives thesource sub-score (where S3 is the risk associat-ed with the farmyard). The transport sub-score is the product of the distance factor (T1)and the connectivity factor (T2). The productof the source sub-score and transport sub-score gives the overall risk score for the field.The justifications for use of these factors arefully described in Magette et al. (2007): somefactors have a greater impact (“weight”) on Ploss than others and depending on the magni-tude of each factor, a numerical risk level or“score” is assigned. In order to determine therisk for P loss from each site, the products offactor weightings and scores are summed.

All the data collected during the field-by-field risk assessments was imported intoArcGIS 9.0©. Map layers were created foreach mPRS factor listed in Table 3. GIS layers

representing each mPRS factor were geo-processed in ArcGIS 9.0© to form a singlelayer representing all the factors and providinga risk score for each of the fields surveyed.Each field was classified as low risk (score <10.8), medium (10.8 < score < 21.6) or highrisk (score > 21.6) for P loss, in line with thethreshold values for each of these risk cate-gories, established by Magette et al. (2007).ArcGIS 9.0© was also used to identify areaswithin the Lough Melvin catchment that werewithin 200 m of a watercourse. This was doneusing the ‘buffer’ function in ArcGIS 9.0©

Fields were sampled individually butwhere appropriate, some parts of the farmswere block-sampled where soil type, cropping,and treatment of lands were similar during theprevious 5 years or more; this included blocksof up to 10 ha in upland areas with naturalvegetation typical of upland peat soils. Soilsampling followed the standard Teagasc proce-dure with a composite sample of 20 corestaken in each field to a depth of 10 cm in a“W” pattern across the field. Unusual spotslike feeding areas, gateways, and dung patcheswere avoided. The samples were analysed forpH, Morgan’s P, potassium, magnesium andlime requirement using standard procedures atthe Teagasc Soil Laboratory in Johnstown



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Table 3: Risk Factor Categories, specified in the mPRS. For full details and specifications of 671

classifications, see Magette et al. (2007). 672

Factor Description Weight Low Risk Medium Risk High Risk

P Usage Rate 1 0-5 kg P ha-1

5-10 kg P ha-1

>10 kg P ha-1

S1

P Application Timing 0.9 Low risk Medium risk High risk

Soil P 0.8 0 – 5 mg P l-1

5.1-8 mg P l-1

>8 mg P l-1

S2

Desorption Risk 1 Low Moderate High

S3 Farmyard Risk 0.8 Good Moderate Poor

T1 Transport Distance 0.75 >500 m 200 – 500 m 0 – 200 m

T2 Connectivity 0.75 Low risk Moderate risk High risk

673

Table 3: Risk Factor Categories, specified in the mPRS. For full details and specifications of classifications, see Magette et al. (2007).

Castle, Wexford (Coulter and Lalor, 2008).The Morgan P test was used throughout thecatchment as this is the soil P test that wasused to calibrate the mPRS (Magette et al.,2007). In the RoI, a P index system is com-monly used to interpret Morgan’s P results foragronomic and environmental purposes. Forgrassland, Coulter and Lalor (2009) define 4bands within this Index, which are sum-marised in Table 1.

Identification of potential measuresSubsequent to the risk assessment, measureswere identified to address the key-risks, usingthe scientific literature and consultation withresearchers and farmers. The participation offarmers was considered central to the success-ful identification of measures that farmerswould be willing to implement. As part of thisconsultation process questionnaires weredeveloped to obtain direct input from 25 ofthe 50 participating farmers within the catch-ment with a view to using the results from thequestionnaire and the discussions with farm-ers in the development of a preliminary list ofpotential measures. The 25 farmers wereselected based on farm type, farm size, farmerage, farmer gender, and location (i.e. NI andRoI) to ensure that the participants represent-ed a range of perspectives from within thefarming community in the catchment.

Evaluation of potential measuresThe technical robustness and ease of imple-mentation of the potential measures wereassessed during two stakeholder workshops,attended by personnel from the Departmentof Agriculture and Food (RoI), DARD (NI),Environmental Protection Agency (RoI),Agri-Food and BioSciences Institute (NI),Northern Regional Fisheries Board (RoI), andTeagasc. The stakeholders assessed the mea-sures from the perspective of their potentialuptake by farmers, ease of administration, sci-entific soundness, environmental effective-ness, side-effects on productivity, side-effectson the environment, and practical limitations,

so as to identify a short-list of measures forfurther evaluation.

The cost-effectiveness of measures wasassessed as the ratio between the cost of imple-mentation of each measure (in € per ha), andthe total potential reduction in P loss fromagriculture to water associated with each mea-sure (in kg P per ha). The cost of each measurewas calculated as the sum of material costs,labour costs, and opportunity costs, depreciat-ed over the life-span of each measure. Theimpact of most measures was quantified byapplying reduction effectiveness coefficients,as reported in the scientific literature, to thespecific biophysical environment and farmpractices in the Lough Melvin catchment. Fullcomputational details are documented in thetechnical report (Byrne et al., 2008); here, weprovide one example for the assessment of costand impact of one potential measure, i.e. thefencing off of all water courses and substitut-ing livestock access to streams and the lakewith animal operated drinking troughs.

The costs associated with this measureincluded fencing costs, the cost of animal-operated drinkers and the loss of revenue fromland taken out of production. These costswere in the region of €0.90 per m of fence and€350 per ha taken out of production perannum. Using GIS it was estimated that thereis 386 km of watercourses in the catchment,therefore potentially 772,000 m of fencingwould be required at a total cost of €694,800.Assuming a 10-year depreciation period forfencing, these costs equate to €69,480 perannum. An animal-operated water drinkercosts €500 to install. Using GIS, we estab-lished that the average field size is c. 1 ha. Onedrinker would be required for each fieldaffected. Using GIS, it is estimated that thereare 8,000 fields within 200 m of a water-course. Assuming all these require a drinker,the total cost of these would be €4,000,000.Spread over ten years, this would amount to€400,000 per annum. For a 1.5 m margin,116 ha are taken out of production equatingto an opportunity cost of €40,600. Therefore


216



217

the total annual cost of this measure for thecatchment would be in the order of €510,080.

Using CORINE land-cover maps of theLough Melvin Catchment, and export coeffi-cients reported by Smith et al. (2005), Byrneet al. (2008) estimated that the total P-loadingfrom agriculture amounted to 8,018 kg perannum. With a total agricultural area of13,576 ha, this amounts to an average P lossof 0.59 kg P ha-1 yr-1. Fogg et al. (2005)reported an 8% P removal efficiency for a 1.5m grass buffer, which in the L. Melvin catch-ment context equates to a P removal of 0.047kg P ha-1 yr-1. This measure is likely to be onlyeffective for fields within 200 m of the water-course, i.e. fields with a high risk classificationfor T1 transport distance factor of the mPRS.Using GIS it was estimated that approximate-ly 8,000 ha are within 200 m of a watercourse.Thus, if 0.047 kg of P was retained over eachof these 8,000 ha, the total P reduction wouldequate to 376 kg P yr-1. Therefore the costeffectiveness of the measure was quantified as€510,080 / 376 kg P = €1,357 kg-1 P.

Farmer preference for the short-listed mea-sures was assessed by face-to-face interviewswith 25 of the 50 participating farmers basedon structured questionnaires. The group of 25farmers asked to evaluate the measures wasmutually exclusive with the group of 25 farm-ers that had been asked to assist in identifyingpotential measures (see above). A list of miti-gation measures, grouped by risk category, waspresented to these farmers and they were askedto rank, in order of preference, the mitigationoptions according to their practicality andlikelihood for uptake.

RReessuullttssRisk identificationResults from the mPRS showed that most ofthe surveyed area was classified as either “highrisk” (31%) or “medium risk” (30%). Analysisof the results showed that “high risk” areaswere those where transport vectors (pathwayfactors) coincided with pressure factors.The main pathway factors included:

• Poor soil drainage: For 47% of the catch-ment area, the soils had been classified asgleys (Lee and Walsh, 1973). These soils arecharacterised by impeded drainage capaci-ty, resulting in mainly surface drainage ofexcess rainfall. Schulte et al. (2006) found ahigh frequency of overland flow events onpoorly-drained soils in the North-West ofIreland, based on modelling of soil mois-ture dynamics as a function of soil drainageand spatio-temporal rainfall patterns. As aresult, only 19% of fields assessed in themPRS were allocated a low risk classifica-tion for connectivity (T2), with 70% and11% classified as medium and high risk,respectively.

• Small distance from fields to water courses:Figure 1 demonstrates that over 60% offields in the catchment area are locatedwithin 200 m of the nearest watercourse,corresponding to a high risk classificationin the transport distance factor (T1) of themPRS. Approximately 30% of fields sur-veyed were located more than 500 m fromthe nearest watercourse, corresponding to alow risk classification for the T1 factor ofthe mPRS.

The main pressure factors included:• A high desorption risk: The County

Leitrim Resource Survey (Lee and Walsh,1973) found that peat soils account for40% of the catchment. Daly et al. (2001)found that soils with an organic mattercontent >20% (peat soils, peaty gleys, peatypodzols) have reduced P-sorption capacity,due to their low iron and aluminium con-tents, as well as the competitive effect oforganic matter substances such as organicacids for sorption sites. As a result, 98% offields assessed in the mPRS were allocated ahigh risk classification for P desorption(S2).

• Elevated STP levels: Figure 2 shows that on22% of the fields surveyed within thecatchments, STP exceeded 8 mg l-1, equat-ing to Index 4 in the RoI (Coulter and

Lalor, 2008), and to a high risk classifica-tion in the Soil P factor (S2) of the mPRS.Soils in Index 4 have soil P reserves inexcess of agronomic requirements and areassociated with increased risk of P loss towater if pressures coincide with transportfactors (Schulte and Lalor, 2008).

• P-inputs: 42% of fields surveyed received Pinputs in excess of 10 kg ha-1, including37% of fields in Index 4, which require noP inputs for agronomic purposes (Table 1).In light of the small number of fields wherehigh P-inputs would be required for build-up of STP (Figure 2), the prevalence ofhigh P-input rates suggests significantscope for improved nutrient management.

Furthermore, the interactions between pres-sure and pathway factors gave rise to signifi-cant challenges for sustainable slurry spread-ing: due to geo-physical constraints, only halfof fields in the catchment are accessible tomachinery for land application of slurry. Thisconstraint has led to historically repeatedapplications in many of these fields, which has

resulted in locally elevated STP levels (P Index4).

Evaluation of measuresThe potential agri-environmental measures formitigating P loss to water, as identified in ourreview of the international literature andfarmer questionnaires, were grouped andrationalised into the 25 discrete measures, list-ed in Table 5.

At the stakeholder workshops, there wasno consensus on the effectiveness and prefer-ence of measures, apart from the provision ofnutrient management support for a two-yearperiod. Therefore, all 25 measures identifiedwere short-listed and evaluated for cost,impact, cost-effectiveness and farmer’s prefer-ence.

Taking into consideration the complex,heterogeneous and variable nature of P exportfrom agricultural land, the cost-effectivenessfigures were based on the best informationavailable at present. While our estimates of thecost and impact of each measure were tenta-

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Figure 1: Distance from watercourses. Source: Campbell and Foy (2008).

tive, they provided exploratory indications ofthe relative cost-effectiveness of the variousmeasures, as these differed by orders of magni-tude. Therefore we categorised the cost effec-tiveness (€ per kg P) of each potential mea-sure, as well as its total impact (potentialreduction in P loss), its total cost of imple-mentation across the catchment (€) and its rel-ative popularity ranking into four categoriesthat represented four orders of magnitude(Table 4). Our results are summarised in Table5, hierarchically ranked by cost-effectiveness,total costs, and farmer’s preference, respective-ly.

Potential measures bearing the lowest totalcost (cost category A) were:• Feeding low-P concentrates: High-P con-

centrates may be substituted by low-P con-centrates on a cost-neutral basis. This mea-sure involves replacing dairy nuts with beefnuts, which have a similar cost but containa lower P-concentration (c. 0.1 percentageunits). This measure is not expected to haveany negative effects on livestock perfor-mance due to the low P-requirements ofdrystock, which accounts for most of live-stock within the catchment. However, thetotal impact of this measure was not con-



219

Figure 2: Frequency distribution of Soil Test P levels (Morgan’s extract, mg l-1) in surveyedfields. The line indicates the lower boundary of P Index 4.

Table 4: Categorisation of cost effectiveness, total impact, total costs and popularity of the P loss 674

mitigation measures 675

Cost effectiveness

(€ kg–1

P)

Total costs

(€)

Total impact

(kg P)

Relative popularity

(farmers’ preference)

A < 10 < 10,000 > 1,000 Popular

B 10 – 100 10,000 – 100,000 100 – 1,000 Acceptable

C 100 – 1,000 100,000 – 1,000,000 10 – 100 Unacceptable

D > 1,000 > 1,000,000 < 10 N/A

676

Table 4: Categorisation of cost effectiveness, total impact, total costs and popularity of the Ploss mitigation measures


220

Table 5: Cost-effectiveness, total impact, total costs and popularity of the P loss mitigation 677

measures. See Table 4 for the description of A, B, C, D categories. 678

Measure Cost effectiveness

Total cost Total impact

Preference

Feed low P concentrates A A B A

Not replacing P on Index 4 silage area A A C B

Free advisory service and NMP A B A A

Reduce overall stocking rate (sheep) B B A B

Sedimentation barriers in drainage ditches B C A A

Reduce overall stocking rate (suckler cows) B C A B

Move troughs regularly B N/A N/A C

Run-off / run-on interception ditches C B C B

Grass buffer strip (2.5 m) B/C C A B

Reduce stock by selling calves in autumn C C A B

Willow/alder buffer strip (5.0 m) C C B B

Grass buffer strip (1.5 m) C C B B

Plough and reseed Index 4 soils C C B C

Re-route runoff from roads to sediment traps C C B N/A

Wetlands at base of slopes C D A C

Hedgerows across slopes D B C A

Gravel hardcore around troughs D B D A

Move troughs away from high risk areas D B D B

Gravel hardcore around gateways near streams

D C B A

Move gateways from high risk areas D C B C

Fence off water courses D C B N/A

Fence off water courses with 1.5 m buffer strip D D B N/A

Reduce Target Index to Index 2 D N/A N/A C

Linear wetlands within drainage ditches D N/A N/A C

Only buy fodder produced within the catchment

D N/A N/A C

679

Table 5: Cost-effectiveness, total impact, total costs and popularity of the P loss mitigation measures. See Table 4 for the description of A, B, C, D categories.



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sidered large, due to the small quantities ofhigh-P concentrates used within the catch-ment (<25% of farmers surveyed).

• Not replacing P on Index 4 silage areas:Soils with STP Index 4 have soil P reservesin excess of agronomic requirements; there-fore withholding fertiliser P on these soilscould be achieved on a cost-neutral or cost-saving basis. However, withholding slurryapplications from Index 4 soils is depen-dent on the availability of fields with lowerSTP levels in which slurry application isnot geo-physically constrained.

Potential measures bearing the highest totalcosts (cost category D) included:• Installation of wetlands at the base of

slopes: This measure would be very expen-sive due to the high installation costs andopportunity costs associated with takingland out of agricultural production.

• Fencing off watercourses, leaving a grassbuffer of 1.5 m: This potential measure wasvery expensive due to the large quantity offencing and animal-operated drinkers thatwould be required as a function of thedense natural surface drainage networkwithin the catchment. The cost of this mea-sure could potentially be reduced by shar-ing one drinker between two fields, wher-ever this is physically possible. In theunlikely event that a drinker could beshared between two fields in all cases, thecost of this measure would be in cost cate-gory C.

The three potential measures that would deliv-er the highest total impact (impact category A)were:• Support in Nutrient Management

Planning (NMP) and Soil Analysis: Thismeasure involves soil sampling, whichwould lead to the identification of Index 4soils and soils with an OM content inexcess of 20% (“peaty soils”). Subsequentsupport in Nutrient Management Planningwould negate further P surplus applica-tions, and in the long term reduce STP onIndex 4 soils.

• A voluntary reduction in stocking numbersby 15% would directly reduce the quantityof P in slurry and risk of P loss. Farmersexpressed a willingness to reduce stockingrate at compensation rates of €300 persuckler cow or €30 per ewe.

• Installation of sediment traps in drainageditches: sediment traps in drainage ditcheshave been reported to reduce P-concentra-tions directly by 35% (Maguire et al.,2008).

Measures that would deliver the lowest totalimpact (impact category D) were the measuresaimed at mitigating P loss from soil surround-ing in-field water troughs, i.e. putting hard-core gravel around troughs or moving troughsaway from water courses. Although it has beenwell-established that soils around troughs maybe prone to P loss due to local poaching anddeposition of excreta (e.g. Singh et al., 2008),our GIS modeling studies suggested that thetotal area affected and the total potential Plosses were insignificant at catchment scale,amounting to less than 10 kg per year for theentire catchment.

The three most cost-effective measures(cost-effectiveness category A) were: feeding oflow-P concentrates, not replacing P on Index4 silage grounds, and support in NMP andsoil analysis. Of these measures, only the sup-port in NMP and soil analysis would both becost-effective and have a large total impact onP loss from agriculture.

The three measures that were least cost-effective (cost-effectiveness category D) werefencing of watercourses with included bufferstrip (1.5 m), and putting hardcore gravelaround troughs or moving troughs away fromwater courses.

Measures that were allocated a high rela-tive preference rating by farmers (preferencecategory A) included feeding low-P concen-trates, support in NMP and soil analysis,installing sediment traps in drainage ditches,installing hedgerows across slopes and puttinghardcore gravel around troughs.

Measures that were allocated a low relative

preference rating by farmers (preference cate-gory C) included ploughing and reseeding ofIndex 4 soils, installing wetlands at the base ofslopes or in drainage ditches, moving gatewaysfrom high risk areas, moving troughs regular-ly, reducing the target STP index from Index3 to Index 2, and only buying fodder pro-duced within the catchment.

In Figure 3, we have ranked and illustrat-ed the cost-effectiveness of each potentialmeasure by plotting the cumulative relativeimpact of all potential measures against theircumulative relative costs. This figure demon-strates that over 36% of the total potentialreduction in P loss could be achieved at lessthan 1% of total potential costs; over 50% of

the total potential reduction in P loss could beachieved at just over 5% of total potentialcosts.

DDiissccuussssiioonnRisk identificationThe pressure-pathway concept (Haygarth etal., 2005), as quantified in the mPRS(Magette et al., 2007) successfully identifiedthe main risks of P loss from agriculture towater, and helped explain the apparent para-dox of how low-intensity agriculture may con-tribute to P-enrichment of Lough Melvin.Despite some limitations in accounting forsite specific condition such as slope or over-grazing, the mPRS allowed us to identify the


222Figure 3: Relationship between cumulative relative impact and cumulative relative costs of 685

potential measures when ranked hierarchically by cost-effectiveness, total costs and farmer 686

preference. Relative impact was expressed as reduction in P loss (kg) proportional to total 687

potential maximum reduction in P loss (kg); relative costs were expressed as cost (€) proportional 688

to total potential maximum costs. 689

costs and impact of measures

Feed low P concentratesNot replacing P on Index 4 silage area

Free advisory service and NM P

Reduce overall stocking rate (sheep)

Sedimentation barriers in drainage ditches

Reduce overall stocking rate (suckler cows)

Run-o ff / run-on interception ditchesGrass buffer strip (2.5m)

Reduce stock by selling calves in autumn

Willow/alder buffer strip (5.0m)Grass buffer strip (1.5m)

Plough index 4 so ilsSediment traps fo r road run-off

Wetlands

HedgerowsM ove troughs, move gateways, gravel

Fence off water courses + 1.5m buffer strip

cu

mu

lati

ve

re

lati

ve

im

pa

ct

cumulative relative costs

Figure 3: Relationship between cumulative relative impact and cumulative relative costs ofpotential measures when ranked hierarchically by cost-effectiveness, total costs and farmer pref-erence. Relative impact was expressed as reduction in P loss (kg) proportional to total potentialmaximum reduction in P loss (kg); relative costs were expressed as cost (€) proportional to totalpotential maximum costs.

factors contributing to either high source ortransport risks and made it possible to identi-fy suitable mitigation measures which willeither reduce the source of P or interrupt thetransport pathway. Sharpley et al. (2003) con-cluded that the flexibility and robustness ofthe P risk indexing approach has been demon-strated by its widespread adoption throughoutthe United States and that risks of P loss couldbe decreased if relevant mitigation measureswere implemented at high risk areas identifiedusing the P index approach. Strauss et al.(2007) demonstrated that when BestManagement Practices (BMP) to control sedi-ment loss were targeted at Critical Source Area(CSA) comprising just 6% of the catchmentarea, this resulted in a decrease of 31-61% insediment export when compared to conven-tional management practices.

Our risk identification assessment showedthat due to the very high connectivity andomnipresent surface drainage, localised pres-sures, arising from the historic concentrationof P onto the proportion of the catchmentthat consists of improved grassland, pose animmediate risk factor. In many cases, this localconcentration of P is the result of historicallyrepetitive applications of slurry to specificfields; in many cases STP levels in these fieldsnow exceed 8 mg l-1, placing them in STPIndex 4. Slurry management in the catchmentis challenging due to the physical constraintsof the land, i.e. the small number of fields thatare accessible with slurry spreading machinery.

In many cases, local P-pressures are com-pounded by the absence of soil P tests andassociated nutrient management plans. In theRoI, S.I. 101-2009 states that in the absenceof a soil test, STP Index 3 may be assumed. Inthe Lough Melvin catchment, this means thatorganic and fertiliser P may be applied tounidentified STP Index 4 soils. While thispractice is compliant with S.I. 101-2009, itrepresents an unnecessary direct fertiliser costto farmers and it adds to local concentrationof soil P above agronomically optimum levels.Contrastingly, in the NI part of the catch-

ment, chemical P fertilisers may only beapplied if soil analysis shows that there is arequirement for P applications after takinginto account the availability of P from appliedmanures; this is potentially an approach thatwould have merits across the entire catch-ment. In the RoI part of the catchment, NMPand soil analysis could be facilitated by incen-tivising participation in the REPS scheme,which already includes these as mandatorymeasures.

An interesting outcome from this study isthat the dominant risk factors identified didnot necessarily equate with the traditionallyperceived risks associated with less intensivefarming, such as access of livestock to waterand localised poaching of soils around watertroughs. While such risk factors are highly vis-ible and represent a direct connectivitybetween nutrients and receiving waterbodies,their impact was insignificant when consid-ered at catchment scale. Conversely, the unex-pected prevalence of STP Index 4 soils is notvisible or identifiable without active soil test-ing, yet was identified as the dominant pres-sure risk factor.

Evaluation of measuresIn light of the above, support in NMP and soiltesting was identified as the most cost-effectiveand preferential mitigation measure in theLough Melvin catchment, accounting for35% of total potential reductions in P loss atminimum costs. This measure was preferen-tially selected by farmers, as it was not consid-ered to be a measure “over and above” S.I.101-2009, and therefore it was not consideredto add further environmental restrictions tofarm practices. Instead, it was viewed as a mea-sure that would facilitate economic optimisa-tion within the constraint of current legisla-tion, with potential environmental benefits asa side-effect. However, it should be noted thatin the Lough Melvin catchment, full slurrymanagement planning in compliance with S.I.101-2009 may be constrained by the limitedavailability of slurry spreadlands: In some



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cases, the withholding of slurry from Index 4soils and the rerouting of slurry to STP Index1, 2, and 3 soils may be severely restricted bythe lack of machinery access to such lowerindex soils.

Our finding that NMP constitutes themost cost-effective approach to reducing risksof nutrient loss to water is in line with manystudies reported in the literature. For example,Cherry et al. (2008) advocated the use ofnutrient budgeting to improve nutrient man-agement and identify farms where the poten-tial for nutrient surpluses and losses are high.Oenema and Roest (1998) hypothesised thatimplementation of the MINAS nutrient bud-geting system in the Netherlands would resultin an 82% decrease in farm P surplusesbetween 1985 and 2008. Although theseauthors concluded that an improvement inwater quality due to the decrease in nutrientsurpluses could not be expected in the short-term, a detailed survey by Goodlass et al.(2003) on budgeting systems, such as nutrientmanagement plans, found that 65% of‘expert’ respondents indicated that the bud-geting systems have positive environmentalimpacts by reducing surpluses and improvingwaste disposal. In their review of 50 farm bud-geting systems in Europe, Goodlass et al.(2003) suggested that the most successfulbudgeting systems were those that involvedregular technical input from farm advisors.

However, it is well established that thereduction of P pressures from soil is a veryslow process. For example, a large-scale studyon P-dynamics of Irish soils (Herlihy et al.,2004) investigated the time required for STPIndex 4 soils to return to their agro-environ-mental optimum (STP Index 3). Under the“best-case scenario”, i.e. continuous removalof nutrients through silage cutting, and inabsence of any nutrient applications, thisstudy concluded that at least four years wererequired for soils to return to STP Index 3. Inthe Lough Melvin catchment, longer timeperiods may be required, as nutrient removalrates in the catchment are expected to be

lower, and consistent withholding of organic Pfrom STP Index 4 soil may not be possible inall cases.

Considering this time-lag, we expect that,while support in NMP may significantlyreduce P-pressures and potential P losses towater in the long term, the effectiveness of thismeasure may not become apparent in theshort-term (Oenema and Roest, 1998). Inorder to reduce P losses in the short-term, mit-igation measures would be required thataddress P-pathways by remediation of trans-port vectors. In this study, sediment traps indrainage ditches were identified as a potentialpathway mitigation measure that is both cost-effective and preferentially selected by farmers.Controlled drainage in ditches has beendemonstrated as an effective measure fordecreasing P export from agricultural soil(Wesstrom and Messing, 2006; Maguire et al.,2008; Kroger et al., 2008). For instance,Kroger et al. (2008) demonstrated that con-trolled drainage ditches resulted in a 44%decrease in inorganic P in drainage waterbefore it entered a watercourse. However, itwas also highlighted that the ditch couldpotentially become a source of P and sorequired careful management (Kroger et al.,2008).

A surprising outcome of the farm surveyswas the relative high preferential ranking ofmeasures aimed at reducing stocking rates,either by reducing suckler cow or ewe num-bers, or by selling young stock in autumnbefore the housing period. From the farmerinterviews it transpired that this measure waspreferentially selected by farmers who wereconsidering reducing stock numbers evenwithout compensation, based on economicconsiderations and labour requirements. Apotential measure to provide compensationfor such reductions in stocking rates proved tobe popular among these stakeholders.However, it is worth considering that such ameasure would be less effective if localisedreductions in stock numbers would be accom-panied by proportional increases in stock


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numbers elsewhere within the catchment, orwould be followed by future increases as aresult of rental agreements or land ownershipchanges; therefore this measure would requirecareful consideration and management.

Furthermore, the international literaturesuggests that this relationship between stock-ing rate and water quality may be site-specificas the evidence on the nature of this relation-ship is inconclusive (Schepers and Francis,1982; Capece et al., 2007). Schepers andFrancis (1982) demonstrated that an increasein stocking density results in a decrease inwater quality, while Capece et al. (2007)found no effect on water quality over a rangeof stocking rates. Where farmers adhere toBMPs for grazing, the impact of the decreasein stocking rate may be limited (Tunney et al.,2007). However, the corresponding decreasein slurry production may reduce risks of inci-dental losses of P and the build-up of P in thesoil due to repeated application to selectedfields.

Evaluation of participatory approachThe combined assessment of cost-effectivenessand farmer preference in this project yieldednew and interesting insights into factors thatdetermine the effectiveness, uptake and imple-mentation of mitigation measures, which arefurther explored in Doody et al. (2009).Examination of the results presented in Figure4 shows that farmer preference for individualmeasures was strongly concurrent with thecosts of these measures, even though these

costs primarily refer to societal costs ratherthan direct farm costs. Figure 4 shows thatthere was no relationship between farmer pref-erence and impact of individual measures. Ingeneral, farmers expressed preference for mea-sures that would be relatively easy to imple-ment and that would not require significantchanges to daily farm practices or ongoinglabour inputs. A low preference was allocatedspecifically to measures that were consideredto reverse the historic process of land improve-ment, such as the installation of wetlands,ploughing of STP Index 4 soils, or reducingthe target STP Index to Index 2.

It should be borne in mind that the cost-effective and preferred measures, identified inthe current study, are specific to the biophysi-cal conditions in the Lough Melvin catch-ment, as well as its context of specific agricul-tural practices. While the findings of our studymay, with caution, be extrapolated to catch-ments with characteristics similar to theLough Melvin catchment, they should not beextrapolated to catchments with contrastinggeological, pedological or agro-meteorologicalconditions, nor indeed to catchments withcontrasting farming systems or farm practices.For example, the low cost-effectiveness of thefencing off of water courses arose specificallyfrom the concurrence of low stocking ratesand a very dense natural surface drainage net-work, resulting in a very high ratio of fencingdistance per livestock unit; this ratio may besignificantly different in other biophysicalenvironments, which would impact on the

Figure 4: Concurrence of farmer preference categories with a) cost-effectiveness categories; b) cost categories; c) impact categories.

cost-effectiveness of this measure. The effec-tiveness of fencing may also be significantlydifferent if measures are required to mitigatewater quality parameters other than P, e.g.mitigation of sediment loss. Similarly, mea-sures aimed at providing compensation forvoluntary reductions in stock numbers mayreceive different preference rankings in catch-ments with economically contrasting farm sys-tems.

This contextual specificity of the effective-ness and preference ranking of potential mea-sures supports the concept of a regionalisedapproach to the protection of water quality. Inprinciple, such an approach is facilitatedunder the Water Framework Directive, whichis based on the formulation of ManagementPlans for individual River Basin Districts(www.wfdireland.ie). Although the results ofour Lough Melvin project are specific to itsbiophysical environment and agricultural con-text, the approach and methodology used heremay and possibly should be used as a templatein other sensitive catchments. For example,some of the current draft River Basin DistrictManagement Plans propose additional mea-sures to mitigate P loss from agriculture, with-out cost-effectiveness assessments or extensivefarmer consultation, which raises concerns notonly for farmers, but also from an economiceffectiveness point of view; as an alternative, aparticipatory and cross-disciplinary approachsimilar to the one in the current study wouldnot only potentially improve value-for-money,but would also be more likely to result inimproved uptake, participation, and ultimate-ly effectiveness (see Doody et al., 2009).

CCoonncclluussiioonnssThis study successfully identified the key-riskfactors governing P loss from low-intensityfarming to the mesotrophic Lough Melvin,and selected appropriate mitigation measuresbased on cost-effectiveness and farmer prefer-ence. The key findings of our study are:1. The apparent paradox of low-intensity

farming contributing to P-enrichment can

be explained by the omnipresence of trans-port vectors and localised accumulation ofP in soils, as a result of historically repeti-tive slurry applications and low participa-tion rates in soil P testing. The practice ofrepetitive slurry applications on a limitednumber of fields is driven by the geo-phys-ically poor accessibility for slurry spread-ing equipment in large parts of the catch-ment.

2. Support for nutrient management plan-ning and soil P testing was the most cost-effective and preferentially selected mea-sure aimed at reducing P pressures.However, the associated reduction in pres-sure will only become apparent over atime-span of multiple years. Installation ofsediment traps was identified as the mostcost-effective and preferentially selectedmeasure to reduce pathway vectors. Thismeasure is expected to reduce risk of P lossto water immediately following installa-tion.

3. By evaluating the cost-effectiveness andfarmer preference of potential measures,we were able to identify a suite of mitiga-tion measures with the potential toaccount for more than 50% of the totalpotential reduction in P loss, for c. 5% ofthe potential total cost. Some of the mea-sures aimed at mitigating “high-visibilityrisks”, such as fencing off of water courses,were not selected because of their low cost-effectiveness.

4. The high cost-effectiveness and farmerpreference of the selected measures are spe-cific to catchments with biophysical envi-ronments and farming systems similar tothose in the Lough Melvin catchment, andcannot be applied to contrasting environ-ments or farming systems without con-text-specific reassessment. However, theparticipatory and cross-disciplinaryapproach taken in this project may be usedas a template to formulate regionalisedcatchment management plans.


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AAcckknnoowwlleeddggeemmeennttssThis project was part of the Lough MelvinNutrient Reduction Programme, administeredby the Northern Regional Fisheries Board(Republic of Ireland) and funded by INTER-REG IIIa, administered by the Environmentand Heritage Service (Northern Ireland).

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