DEPARTMENT for ENVIRONMENT, FOOD and RURAL AFFAIRS
Research and Development
CSG 15
Final Project Report
(Not to be used for LINK projects)
Two hard copies of this form should be returned to:
Research Policy and International Division, Final Reports Unit
DEFRA, Area 301
Cromwell House, Dean Stanley Street, London, SW1P 3JH.
An electronic version should be e-mailed to [email protected]
Project title
Cost Curve Assessment of Phosphorus Mitigation Options Relevant to UK
Agriculture
DEFRA project code
PEO203
Contractor organisation
and location
Soil Science and Environmental Quality Team
Institute of Grassland and Environmental Research
North Wyke Research Station
Okehampton
Devon, EX20 2SB, UK
Total DEFRA project costs
Project start date
£ 126,108
01/09/01
Project end date
30/09/03
Executive summary (maximum 2 sides A4)
Defra has a policy responsibility to assess the contribution of agriculture to phosphorus (P) loss and devise management practices
which minimise this loss. This project involved a review and an examination of the potentially most useful options in terms of their costeffectiveness, acceptability to the industry, practicality and time-scale of effectiveness and ultimately resulted in a simple cost-curve
assessment of P mitigation strategies. In an additional piece of work that was commissioned during summer 2003, we explored land
uses for achieving ‘good ecological status’ of waterbodies in England and Wales for N and P. Previous funded research has examined
P mitigation strategies and categorised the options (e.g. NT1018) into aspects of soil fertility management, soil conservation,
land/livestock management and water quality management. Measures need to be examined to help to develop a basis for policy
changes for P mitigation. This project focussed on (1) localised farm scale measures (main project) and (2) broad scale land use
scenarios (additional contract). The main project was conducted by IGER, ADAS and Imperial College and had four main objectives:
1. Collate results from previous research on the P mitigation options relevant to losses from agricultural systems both in England and
Wales and relevant overseas countries.
2. Examine these options in terms of their cost-effectiveness, acceptability to the industry, practicality and time-scale of effectiveness.
3. Produce a simple cost-curve assessment of P mitigation strategies.
4. Suggest future areas of research where gaps in knowledge have been identified.
An additional contract was commissioned in the final year that involved IGER, ADAS, Reading and DARDNI that requested that we
addressed an additional objective:
5. To produce a report on Land use for achieving ‘good ecological status’ of waterbodies in England and Wales.
This objective has already been reported to Defra (Appendix 1) and is not reported directly in this CSG15.
In the main project, agricultural practice data were integrated with costs and applicability to produce a matrix of mitigation measures.
This was derived from expert knowledge, reviews of the literature (Haygarth et al., 2002; Sims and Sharpley, 2004) and some overseas
visits and exchanges. In January 2003, we held a Workshop with Defra and research colleagues to discuss the mitigation matrix. In
order to compare P transfers and explore the effects of different mitigation options, it was necessary to construct a simple means of
systematically comparing different model farming options using a P expert system, created within an Excel spreadsheet. The
‘Phosphorus loss estimation for agricultural systems with mitigation measures’ (PLEASE) expert system was designed especially to
help compare potential P losses under different model farm scenarios and used input data for each farm model system scenario. The
PLEASE approach was used to estimate risk of (1) solubilisation (that may lead to leaching) (2) physical detachment of particles (that
CSG 15 (Rev. 6/02)
1
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
may lead to erosion) and (3) incidental losses. For each measure we estimated (1) initial P loss; (2) reduction in P loss due to measure
and; (3) cost of the measure, that could subsequently be costed in £ per kg P reduced. In the separate exercise (additional contract)
we used export coefficient modelling to explore likely changes in land use over England and Wales that may be required to bring about
a necessary estimated reduction in P and N in water.
Mitigation measures were divided according to the schematic breakdown adopted in the co-ordination (PEO101), indicators (PEO112)
and PSYCHIC (PEO202) projects; namely inputs, mobilisation and transport. For input control we identified 15 measures that aim to
reduce P surpluses and therefore are primarily targeted at reducing build-up of P in the soil and the potential for P loss in the longer
term. For example, if we were to stop putting P fertiliser on arable land of > P index 4 and at the same time to halve the amount of P
fertiliser on land of > index 3, there is potential to reduce the P inputs by 90,000 tonnes and total losses by 320 tonnes. All of this could
be achieved at zero cost. Mobilisation control is divided into those measures that inhibit solubilisation and detachment. There are 19
mobilisation control measures and one example is minimum tillage that might be applied to ‘combinable’ crops and could reduce P loss
by nearly 2000 tonnes (or about ~1 kg per hectare). To achieve this, we estimate it could cost £45,000 per tonne, requiring a high farm
capital investment. Transport control includes those measures (6 of them identified) that aim to reduce either the channelisation of
run-off, or entrap the particulate and soluble P load before it enters the watercourse. One example is grass buffers that could be
potentially applied to arable and grassland areas. Here, we estimated that there is potential to reduce P loss by 1100 tonnes at a cost
of £3790 per tonne. These options therefore largely control rather than prevent P loss. In the additional contract, considering land use
options at the broad scale, we showed that it might be possible to reduce nutrient export with gross changes in agricultural land use.
However, in order to achieve ‘good ecological status’ these would have to be large and there are many uncertainties.
This project has helped (1) illustrate areas where we lack knowledge and highlight priority areas for future research on P mitigation and
(2) provide a preliminary identification of the key P mitigation measures. Input and mobilisation options are designed to control P loss
at the point of origin that is more in keeping with the underlying principle behind the Water Framework Directive. As such, they can be
more widely adopted and with a greater degree of success than transport options, whose effectiveness is severely limited by local site
conditions. Clearly transport options are most dependent on the hydrological linkages between the field and the watercourse, which are
unpredictable and vary considerably both spatially and temporally. Transport options therefore require careful targeting to be effective,
are more sensitive to local site conditions and might frequently fail during extreme events. One can therefore consider that the degree
of uncertainty over effectiveness, and hence inapplicability for national adoption, increases along the source-mobilisation-transport
continuum. Related projects on nitrate (NT2511) and other diffuse pollutants (ESO121) are now underway. In respect of the land use
scenarios that were explored as part of the additional contract, we favour the need for smaller scale, more targeted catchment or
system specific measures that address fundamental changes in the way we use and manage the landscape in context with farm
systems.
This desk exercise has helped to highlight a number of key areas where we need more information on mitigation. These are expanded
under 1-6 below:
1. Established field evidence for P mitigation is sparse, especially for UK. Although we have made use of international information
with colleagues around the world, further investigations are necessary for UK conditions. Thus, in most cases, we have had to
make informed ‘best judgements’ on what is ‘perceived’ for the UK rather than what is ‘known’.
2. Cost and effectiveness may vary considerably with location so we need more case study examples to demonstrate individual
options success or combined options collectively.
3. The PLEASE system and its associated coefficients were derived from expert judgement by team discussion and consensus,
derived from the literature reviewing exercise. The system was not calibrated or validated and uncertainties, which will be high,
are not quantified. Considerable caution must therefore be attached to interpretation of the information, and especially when using
it to provide a basis for longer-term predictions of changes in the P cycles.
4. Further work is required to assess the relative importance of the different processes of loss (and hence potential effectiveness of
options) on the overall P loss from a farming/landscape type. This is clearly dependent on the geographical location, climate,
landscape (geology and slope) and farming system. For example, incidental P loss is probably far more significant in grassland
farming systems in south-west England than in arable farms in East Anglia.
5. In respect of the land use scenarios modelling, we should now explore a range of scenarios for each region based not only on
estimates of the greatest sources of nutrient flux in each region, but also on expert judgement on possible future scenarios for
sustainable production in rural environments.
6. Finally, new farm and catchment system level mitigation work is much needed.
CSG 15 (Rev. 6/02)
2
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Scientific report (maximum 20 sides A4)
INTRODUCTION
Defra has a policy responsibility to assess the contribution of agriculture to phosphorus (P) loss and devise management
practices which minimise this loss. This project involved a review and an examination of the potentially most useful
options in terms of their cost-effectiveness, acceptability to the industry, practicality and time-scale of effectiveness and
ultimately resulted in a simple cost-curve assessment of P mitigation strategies. In an additional piece of work that was
commissioned during summer 2003, we explored land uses for achieving ‘good ecological status’ of waterbodies in
England and Wales for N and P. Previous funded research has examined P mitigation strategies and categorised the
options (e.g. NT1018) into aspects of soil fertility management, soil conservation, land/livestock management and water
quality management. Measures need to be examined to help to develop a basis for policy changes for P mitigation. This
project focussed on (1) localised farm scale measures (main project) and (2) broad scale land use scenarios (additional
contract).
The main project was conducted by IGER, ADAS and Imperial College and had four main objectives:
1. Collate results from previous research on the P mitigation options relevant to losses from agricultural systems both in
England and Wales and relevant overseas countries.
2. Examine these options in terms of their cost-effectiveness, acceptability to the industry, practicality and time-scale of
effectiveness.
3. Produce a simple cost-curve assessment of P mitigation strategies.
4. Suggest future areas of research where gaps in knowledge have been identified.
An additional contract was commissioned in the final year that involved IGER, ADAS, Reading and DARDNI that
requested that we addressed an additional objective:
To produce a report on Land use for achieving ‘good ecological status’ of waterbodies in England and Wales.
This objective has already been reported to Defra (Appendix 1) and is not reported directly in this CSG15.
RESULTS FROM PREVIOUS RESEARCH ON PHOSPHORUS MITIGATION OPTIONS
(OBJECTIVE 1)
Information on mitigation measures is collated in Appendix 2, which shows a matrix of options that can be used in terms
of their applicability, cost and potential effectiveness to the industry. This was derived from expert knowledge, reviews of
the literature, and some overseas visits (Switzerland, Appendix 3, Norway, Appendix 4). On 14th January 2003, we held
a Workshop with Defra and research colleagues to discuss the draft matrix. The key finding is that knowledge on the
effectiveness of mitigation measures is sparce, especially in terms of proven mitigation measures for UK systems. In
many cases, the effects of individual measures are variable depending on the particular site conditions, and often
combinations of measures have been tested without an understanding the relative contribution of each measure. General
broad statements have therefore been employed and most often linked to more tangible indicators of change. For
example, Sharpley and Rekolainen (1997) concluded that ‘nutrient management is the most effective Best Management
Practice (BMP)’. Strauss et al. (2003) reviewed 123 published papers on the effect of minimum tillage and mulching on P
loss and used probability theory to predict that these measures would reduce run-off by 20% and P loss by 60-70%
compared to conventional ploughing. The review highlighted the variation in treatment effects due to site specificity and
concluded that more individual site data would not greatly alter this overall conclusion. Therefore we have had to make
generic inferences about what might be applicable to England and Wales, rather than what was proven, or demonstrated.
It is very important that the users of this report are fully aware of these limitations. This was used to draft a mitigation
matrix and this formed the basis of how we proceeded with modelling and cost calculations outlined below.
EXAMINATION OF OPTIONS (OBJECTIVE 2)
Overview
In this section we needed to convert the qualitative matrix of options (Appendix 2) into a structured and quantifiable
framework that allowed us to compare our options in terms of effectiveness and cost. This required a strong definition of
key model farm scenarios, so that the effectiveness and economic cost calculations both had well-defined model space in
which to operate. Effectiveness was derived from the ‘Phosphorus loss estimation for agricultural systems with mitigation
measures’ (PLEASE) expert system. Economic cost was calculated based on defined and transparent assumptions. All
of these are given below.
CSG 15 (Rev. 6/02)
3
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Model farm scenarios
A number of farming systems were created that represented key typologies for England and Wales. These are presented
in Table 1. Various data sources were used to create these scenarios. The sources are acknowledged in the column
called notes and/or in the notes below the table.
Effectiveness: Phosphorus loss estimation for agricultural systems with mitigation measures: how the PLEASE
Expert System works
In order to systematically compare P transfers and explore the effects of different mitigation options, it was necessary to
construct a simple means of analysing different options using a P expert system, created within an excel spreadsheet and
based on simple and transparent assumptions. The median P content of soil was taken from the representative soil
sampling (RSSS) National Soil Inventory database held by the National Soil Resources Institute, using resampled
arable/ley grassland (804 samples) site in 1994/95 and permanent (managed) grassland (780 samples) sites in 1995/96
(0-15 cm)(Owens and Deeks, 2003). This information was used to estimate the starting P index and total P for each
scenario. Total P for all scenarios was 670 mg kg-1. PLEASE used a constant soil bulk density of 1.33 g cm -3 and all
inventories and estimates are based on the 0-10 cm soil depth.
The approach adopted in PLEASE was to estimate risk of (i) solubilisation (that may lead to leaching) (ii) physical
detachment of particles (that may lead to erosion) and (iii) incidental losses. Incidental P losses were estimated as a
proportion of total P inputs (from farm scenarios in Table 1). Detachment was estimated as a proportion of total soil P.
Olsen P was derived from the soil P index provided from the RSSS database and, in order to achieve mass balance, was
normalised and expressed as a proportion of total soil P. Solubilised P was thus estimated as a proportion of the
normalised Olsen P. It was necessary to operate two types of system. System 1 represented a ‘solubilisation dominated’
system, similar to that observed for grassland systems (Haygarth et al., 1998) and starting losses were of the order 1-2 kg
ha-1 year-1. System 2 represented a ‘detachment dominated’ system, where detachment and incidental losses were
enhanced due to bare soil and readiness for rapid overland transport (Harrod and Theurer, 2002; Haygarth and Jarvis,
2002) and starting losses were of the order >3.5 kg ha-1 year-1.
The system was operated within an excel spreadsheet and was run on annual time steps and was able to account for and
reiterate changes in accumulated soil Olsen P through the time series. It thus had the potential to examine, within a
simple mass-balance framework, potential long-term consequences of changes in input/output and due to mitigation
measures.
The PLEASE system and its associated coefficients were derived from expert judgement by team discussion and
consensus. The system was not calibrated or validated and uncertainties, which will be high, are not quantified.
Considerable caution must therefore be attached to interpretation of the information, and especially when using it as base
for longer-term predictions of changes in the P cycles.
In Table 3 we show the outputs from the PLEASE expert system as applied to the model scenarios, without mitigation
measures applied. Total estimated P losses range from 1.6 kg P ha year -1 (for all grassland) to losses of 4.1 kg P ha
year-1 (for potatoes). These values are realistic and fall within ranges of measured published values (Haygarth and
Jarvis, 1999, 2002). The relative proportions of solubilisation / incidental / detachment vary between scenarios. We also
present predictions from PLEASE for loss rates in 2010 and 2015. These estimates show a considerable increase in the
estimated P loss if current practices continue unabated. However, we need to use caution in interpreting these long-term
predictions, as the PLEASE expert system assumes that the rate of increase is linear and related to input, which is not
tested and may be incorrect and / or too simplistic. In the long term, the predictions from the system may therefore
represent an over estimation and in any interpretations we need to be aware that the approach does not take into account
long term changes in soil P cycling that may occur.
Using outputs from PLEASE
Following from the qualitative matrix (Appendix 2), we revised the structure following discussions with Defra and other
experts and stakeholders and created a ‘working’ matrix, shown in Tables 4-6 respectively. The working matrix defined
exactly the chosen measures and scenarios to which they where applicable and these measures are labelled 1-40. In
Table 4, input reduction measures are presented down the columns and this includes measures 1-15. In broad terms, the
potential to reduce inputs to England and Wales agriculture is high. In Table 5, potential scenarios to reduce mobilisation
of P are illustrated, which includes measures 16-34 (19 options). For each measure, we have quantitatively assessed the
potential to affect P loss via detachment, solubilisation or incidental loss. This is based on expert judgement by team
discussion and consensus derived from the literature. This information has been used to manipulate PLEASE and modify
CSG 15 (1/00)
4
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
the coefficient of export (originally shown in Table 2) by the amount shown in the right hand column of Table 5. In Table 6
(measures 35-40, 6 options) we show potential to mitigate transport of mobilised P. Again, for each measure, we have
quantitatively assessed the potential to affect P loss via detachment, solubilisation or incidental. This is again based on
expert judgement by team discussion and consensus derived from the literature. This information has been used to
manipulate PLEASE and modify the coefficient of export (originally shown in Table 2) by the amount shown in the right
hand column of Table 6.
In Tables 7 and 8, we present the mitigation effectiveness for all of the 40 measures described in Tables 4-6. In the right
hand side of the table the potential tonnage mitigated for each measure scaled (using livestock numbers or areas of land
use) to England and Wales is presented. For measures 1-15 that are concerned with input modification only, we present
both the potential to affect changes in total P inputs to farm systems (Table 7) and the subsequent losses that arise from
this change in input estimated from the PLEASE expert system (Table 8). For the remaining measures 16-40, all the
outputs are generated from the PLEASE expert system (Table 8).
Considerable caution is required in combining measures using information supplied in Table 7, and this should only be
achieved through expert knowledge. For example, it would be incorrect to assume that by combining a number of
detachment-mitigating measures (e.g. measures 28 - minimum tillage - and 29 - contour cultivation) that the effects are
additive; we neither have evidence for this nor was the PLEASE expert system designed with this in mind. Second,
although obvious to many, the farm model scenarios are not mutually exclusive and are often composites of greater
systems. For example, spring planted roots and vegetables and cereals are both part composites of all arable. Despite
these difficulties, we have however shown in Table 9 the combined effects of the measures (1-40) applied to each
scenario farm system and that can form the basis for example cost curves in Figures 1-5.
Economic costs, assumptions and calculations
There is a large range of savings in terms of avoiding P loss to the environment, but whether these are economically
attractive depends on the costs of changing agricultural practice. Economic costs have been calculated on an enterprise
basis, both for clarity and to avoid the complications associated with the many different farming systems and situations
found around the country. ‘Standard’ data have been taken where possible, but for many of the on-farm operations,
personal communications with experienced ADAS consultants and a range of contractors have been used. Since the
calculations have been carried out on an enterprise basis, any affects on the labour or machinery requirements of a farm,
or the effect on the ancillary industries, or the rural community, has not been considered.
Measures for reducing phosphorus inputs (also cross refer to Table 4) (measures 1-15)
Avoiding or reducing phosphorus fertiliser applications (measures 1-6)
With regard to measures 1 to 6, farmers and growers generally perceive that applying P fertilisers is a good investment.
They have the perception that this is not vulnerable to leaching and thus high P input levels provided a form of security,
encouraging root growth in wheat crops, for example. The reduction in avoiding or reducing P fertilisers can be carried at
no extra cost and indeed will bring savings in terms of money not spent on unnecessary fertiliser and the time saved in
spreading it. These are clearly very attractive measures, but there may be consequences for rural infrastructure as
supply companies lose business.
Precision farming can be carried out on a number of levels, from soil and yield mapping and applying appropriate
fertilisers to more sophisticated techniques involving real time weed monitoring and patch spraying. With regard to
fertiliser application, it may mean no phosphate fertiliser or increased phosphate fertiliser depending on the values in any
given spot of the field. It has been assessed at zero cost because most farmers will make savings on inputs overall.
Avoiding or reducing phosphorus use by livestock management (measures 7-13)
Reducing feed phosphate input to dairy cows (measure 7): relatively high P levels have been seen as attractive to avoid
problems of cow health and there would be no cost to reducing addition. In the case of non-ruminants, phytase addition
to rations for non-ruminants has been an increasingly used option in recent years. This enzyme is able to unlock
phosphate in foods, which is unavailable to pigs and poultry. Phytase is manufactured by a number of companies. The
rate of inclusion of various phytase products varies depending on the manufacturer of the phytase and feed and the
ingredients used. A common product is Natuphos, produced by BASF. The inclusion rate of Natuphos by BOCM Paul’s
is 100 g per tonne of feed for pig rations and broilers (table fowls) and 80g per tonne for layers at a cost of £1 to £0.80p
per tonne. Lowering the dichlorophosphate use offsets this cost by 1.15kg tonne of feed produced. This small cost is
insignificant compared with the variation in the bulk ingredients in the ration and most products are re-formulated
approximately monthly as market conditions change. Therefore, a zero cost has been applied to the use of phytase
(Lawlor and Lynch, 2000; Owers and Wilson, 2003).
CSG 15 (1/00)
5
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Reducing stocking density of dairy cows will make a substantial difference to the P input but also the economic output of
the enterprise. Most agricultural enterprises are carried out on an intensive basis to maximise the income per hectare.
This measure was aimed at 5% of dairy herds that are intensive units in vulnerable areas. The calculation is based on a
25% reduction in head for 5% of intensive dairy. The difference between current and reduced performance will be in
going from a gross margin of £2000 per forage hectare @ 2.25 cows per forage hectares to £1600 per forage hectare @
1.75 cows per forage hectares, that is a total cost of £400 per ha (Nix, 2003). For this sector of the industry, this would
mean a cost approaching £17.25 million. Any costs in terms of losing justification for employing labour have not been
included (Nix, 2003).
Reducing stocking density in lowland sheep takes a similar approach for the lowland sheep enterprise, but relevant to a
greater proportion than in dairy, hence a cost of approximately £72.65 million (Nix, 2003). Specifically, the calculation is
based on a 25% reduction per head for 20% of sheep. The output per ewe @ 1.45 lambs per ewe = £51.4/ewe and the
output per ewe @ 1.6 lambs per ewe = £57.9/ewe, the average is £54.65. Reducing stocking levels from 12 ewes per
hectare to 9 ewes per hectare = 3 x £54.65 = £163.95, say £164/ha (Nix, 2003).
Changing inputs of phosphorus by changes in land use
Changing from arable to beef and sheep considers moving from arable to beef and sheep in 5% of the arable area. This
might cover some of the marginal land, which has been brought into arable production over the last 25 years or so. In
principle, there are problems with the viability of this in terms of the demand for beef and sheep meat and how this
additional production could disrupt the home and the export markets. There is also the problem that many farmers would
wish to avoid the 7 days a week commitment to livestock. However, as an economic exercise and assuming rents at
current levels, there would be a major cost in terms of lost output of beef and sheep compared with arable, adding up to a
total of just under £75.8 million (Defra, 2001; Nix, 2003). Specifically, the changes are based on wheat. For harvest
2002, wheat yielding 6.2t/ha @£55/t produces a gross margin of £307 including IACS, but for harvest 2003, @ £75/t, the
gross margin is £431 (ADAS). Gross margins for break crops will be in a similar range. Lowland grazing rental averages
£111/ha (Defra, 2001). Assuming £70/tonne is a longer-term average price for wheat, the arable gross margin would be
£400/ha and the difference between this and renting for beef and sheep would be £290/ha.
The change from arable to willow coppice has been seen as a zero cost option. By taking into account the area aid
payments and the planting grants and assuming continuity of demand for the cuttings, there would be no effective
difference, certainly in the first five years of production. This is because, over a six year period, the gross margin for
Short Rotation Coppice would be similar to wheat, depending on yields, that is approximately £430/ha (Nix, 2003),
therefore zero cost. Arguments could be made in terms of the changes in machinery complements, the reduction in
terms of labour and the common use of sewage sludge at establishment and harvest, causing high short term levels of
phosphate availability. This could be the subject of a separate project, but there could be changes to the rural community
as well as environmental changes.
Measures associated with reducing mobilisation by solubilisation (also cross refer to Table 5) (measures 16-25)
Changes in the management of phosphorus fertiliser
At present, many arable farmers apply phosphate fertiliser when it suits them to do so, which in many cases is at times
other than drilling. This allows them to drill crops with no time delay due to fertiliser spreading, which can be carried out,
for example in the spring after nitrogen application, using the same logic as in current phosphate use (see measures 1 to
5). The use of slowly available P fertilisers could be conducted at zero cost, because there is no difference in cost of
fertiliser or application.
The cost of this incorporation has assumed that farmers might be able to apply phosphate fertilisers to half the land where
it is needed, but contractors would be needed to do the other half in order to avoid loss of timeliness of crop
establishment. The net cost per hectare treated by a contractor would be some £4/ha, thus the average per hectare
would be £2/ha, but total almost £10.5 million for all arable land (Basford, 2003).
Placement means combine drilling, that is using a seed hopper and a fertiliser hopper on the seed drill and applying the
fertiliser in the channels with the seed. This takes time to carry out in terms of taking the fertiliser to the field, filling the
drill and whilst the drill is carrying fertiliser, it can carry less seed, slowing down the process further. Very few farmers still
use combine drills except small farms, which happen to own one and still use it because they are not constrained by
such tight control on a small area. There are major technical problems with any intention to move to combine drilling.
Most arable farmers would need to employ a contractor, who would need to buy a combine drill to provide the service and
air assisted drills in use in recent years. However, it has been assumed that a contract charge £6/ha above the cost of
CSG 15 (1/00)
6
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
the farmer drilling the crop would be appropriate (Dewes and Basford, 2003; Nix, 2003). This results in a huge cost of
almost £31.4 million for all arable land.
Improved fertiliser application timing to reduce incidental losses could be improved for say half of all arable and
grassland, but contractors would be needed to carry out the rest at a net cost of £4/ha more than the farmer’s (Dewes and
Basford, 2003; Nix, 2003). The total cost would be £2/ha over all the land, giving a total of almost £19.9 million on all
arable and grassland.
Changes associated with manure management
Incorporation of manure could be applied to a range of fodder crops and could reduce incidental losses because the
manure is incorporated rather than left vulnerable to incidental losses on the soil surface. There is a steady increase in
the number of farms growing forage maize from the south up to the midlands. There is a technology transfer issue for this
method, but as more is grown, more land becomes available to dispose of slurry at appropriate rates by incorporation. In
grass silage, which is usually taken in the second year of temporary grass, dressings of slurry would be lower and less
frequent than for forage maize. Further north and in the uplands, stubble turnips are an option. The farmer would benefit
from additional quality feed in both cases. In arable crops, some slurry could be applied at the appropriate time,
depending on soil mineral nitrogen, but too much will promote lodging. Therefore, incorporation can be carried out on a
range of crops and would not incur any additional costs.
Slurry injection is a contract operation, often carried out by trailing a pipe supplying the injection machine on the tractor
with liquid slurry. This should reduce incidental losses because the P source was injected into the soil rather than left
vulnerable on the soil surface. Application costs are around £60 per hour (Agro Business Consultants, 2001; Basford,
2003) and it is possible to cover 2ha per hour, making the average cost £30/ha. If measure could be applied to all dairy
farms, the total cost would be £26.58 million.
Reduction in incidental losses could also be brought about by improved use of timing windows of slurry additions on dairy
farms. Intensive dairy farms generally aim for a slurry storage period of 180 days to take them through the winter. Slurry
storage capacity is based on average rates of slurry production and rainfall, which in wet years can make a significant
difference to the volume of slurry to be spread. In most years, farmers might expect to spread a proportion of their slurry
early in the New Year ‘on the frost’ or in late March/early April when slurry stores are becoming filled to capacity.
This cost assessment has assumed additional 30 days slurry storage for a herd of 200 cows. In this time, each cow
would produce 1.2m 3 slurry (Nix, 2003) or 240m3 for 200 cows. Slurry storage varies between lagoons and above ground
stores with an average cost of £25m3. For a 200 cow herd, the cost would be £25 x 1.2 x 200 = £6,000, say £6,800
including an allowance for rainwater. On 100ha, this would cost £68/ha. Total cost of additional storage at £68/ha would
be £60.26 million for the whole of dairying.
Reducing the rate of manure application to grassland would replace low rate irrigation with loading and spreading
because the slurry would be applied to a wider area. This cost has assumed that the rate of slurry per unit area
application would be halved. This would mean moving from a low rate irrigation system to a contract application system
for half of the slurry over a 180 day winter storage period. In a 200 cow herd, the slurry from 100 cows would be 40 l per
day per cow (Nix, 2003) for 180 days, 7200 l, plus an allowance for dirty water, a total of say 8000l/cow or 8 m 3 or 800 m3
for 100 cows. Assuming 3 trips per hour @ 4m3, 12m3 per hour spreading by contractor @ £40/hr (Nix, 2003; Turner,
2003), 800 m3 would require 67 hours at a total of £2,666, say £2,700 to load and spread, compared with low rate
irrigation at very low cost. A 200 cow herd would require ca 100 ha (2 cows per forage hectare) and the cost per hectare
would be £27/ha, a total of almost £24 million.
Restrict of livestock access in marginal places/times
This could be applied to both the diary and the outdoor pig industry. For dairying, it has been assumed that this would
occur in the autumn and spring. Autumn grass would be lost because it would not be reached before winter. Spring
growth would be part of the grazing rotation. During housing, cows consume approximately 1.5 bales of silage a week
depending on quality. Assuming 4 weeks exclusion @ 1.5 bales of silage per week per cow @ £4/bale, the cows will
consume six bales at a cost of £24/cow, which equates to £48 @ 2 cows per ha. An addition would be required for some
electric fencing, perhaps 200m for the occasional wet place at a cost of £5/m, that is £1000, or £218 pa over five years.
Erection and removal costs would be £50 (Brade, 2003; Nix, 2003). Taking a 200 cow herd on a total of 100 ha, this
would be £2.68/ha. The total cost of bulk feed and fencing would be £48 plus £2.68 per hectare, approximately £51/ha, a
total cost of almost £2.26 million.
For outdoor pigs, there would be a need to use an electric fence in vulnerable parts of field. Outdoor pigs are reared on
generally free draining land and an allowance has been made for 100 m of electric fence (£5 per m) for small areas of the
CSG 15 (1/00)
7
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
field. Spreading the cost over five years, £500 over five years is equivalent to £109 per annum. There would be erection
and removal twice a year at £100, giving a total annual cost of say £200 or £25/ha for 8ha field, a total cost of £34,435.
Measures associated with reducing mobilisation by detachment (also cross refer to Table 5) (measures 26-34)
Changes in cropping
Cover cropping is a ‘hit and miss affair’ and attempts to drill cover crops can often be unsuccessful. It has been assumed
that a cover crop would be sown in the autumn for a spring root crop to protect the soil over the winter. Cultivation costs
would be applicable after the main cultivation for the field. These would be some £17.50/ha plus £50/ha average cost for
the seed, a total of £67.50/ha (Basford, 2003; Nix, 2003). Total cost for root crops would be £3.3 million.
For avoidance of late sowing in high risk areas, it has been assumed that earlier drilling would be used to enable
completion of the drilling campaign by the end of September and 10% of the arable area would be cultivated and drilled
by a contractor at £65/ha (Dewes and Basford, 2003). Total cost would be £34 million.
Cultivation management
Minimum tillage is increasing on arable farms, less so on smaller units because of the capital cost of the equipment and it
is not made for small-scale operation. Minimum tillage therefore saves in cost per ha, but can be costly in terms of
investment, with up to £150,000 for a 1,000 acre unit. Smaller farms will keep conventional systems until the equipment
is worn out and then they will need to go to a contractor or acquire the equipment through a syndicate, for example.
Assuming the work is carried out by a contractor, the cost would be £50/ha (Dewes and Basford, 2003) for the heavy
work and the farmer could then carry out the drilling himself. Total cost of £87.7 million for ‘combinable crops’.
For the contour cultivation measure, a nominal 10% additional time has been used to cultivate the land at, say £10/ha
(Dewes and Basford, 2003). This would cover normal operations, but if more sophisticated techniques, such as a hillside
combine, were to be used, the cost would be higher. The total cost would be £13 million for all arable crops.
Soil stabilisers are rarely used in the UK because of their cost. They are applicable to very light soils subject to blowing in
strong winds. These are found in eastern counties in Norfolk in the Fens in Cambridgeshire and Lincolnshire and north
Lincolnshire principally. One example, Vinamul supplied in 200l barrels @ £1.46/l and is applied at 165l/ha, giving a total
cost of £240/ha for the chemical plus spraying £7/ha, that is £247/ha (Hutchinson, 2003). The total cost for such soils
would be £6.45 million.
For mulching, many combinable crops are harvested using a combine harvester with a mounted straw chopper. This
creates mulch of the chaff and stems of the old crop at no cost. However, where the farmer might expect to sell the straw
for livestock bedding or to a power station, there would be a loss of income of some £20/ha (Dewes and Basford, 2003), a
total of almost £6 million for 10% of all cereals.
Tramlines are established in combinable crops at drilling. In autumn crops, this can result in gullies forming over the
winter where rainwater runs down carrying suspended and dissolved solids. An alternative is for the farmer to create
tramlines in spring by spraying out. Spraying at £7/ha (Dewes and Basford, 2003) for standard spraying at perhaps a
slower speed plus the cost of Paraquat a total of £9/ha, a total of just over £7 million for 15% of all arable crops.
Increasing surface roughness will create problems on a range of soils. For example, on heavier soils, problems will arise
from clods breaking down later in the season as a result of weathering due to wetting and drying and frost. This will
release late germinating weed seeds, which will be difficult to control, but black-grass is the only serious worry in terms of
crop competition. However, this will be expensive to control by spraying at £30/ha for Lexus/Stomp or Atlantis. There
would also be a consequential crop loss of perhaps half a tonne per hectare @ £70/t = £35/ha at medium term prices
(£84/t in September 2003). A third problem could be slugs, which would cost £6/ha for metaldehyde or £11/ha for the
more effective methiocarb plus £7/ha for quad bike application (Dewes and Basford, 2003). Total of £30 plus £35 plus
£11 plus £7 = £83/ha. In spring cereals, there would be problems of poor germination, additional sprays and attack by
rooks, for example. In sugar beet, there would be similar problems to winter crops. Potatoes are a more difficult crop,
because normal cultivation creates a fine textured ridge, but if the soil were left in a coarser condition, similar problems to
winter cereals would occur in terms of late emerging weeds. The total cost could be £108 million for all arable crops.
Additional subsoiling is a contract operation and will cost £45/ha or £23.5 million for all arable cropland. It will have some
effect on reducing detachment.
CSG 15 (1/00)
8
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Measures associated with reducing transport of phosphorus (also cross refer to Table 6) (measures 35-40)
For constructing wetlands/sedimentation ponds, it has been assumed that 0.25% of the arable and grassland to which it
applies would be needed as sedimentation ponds, i.e. 0.5 ha per 200ha or 5,000 m 2. This would apply to 10% of arable
and grassland. Excavation costs for this size project would be £2.30 m 3, or £11,500 plus fencing cost assuming a 10m x
500m excavation. For arable, this would cost £3,216, a total of £14,716 per 200 ha or £73.58/ha. For dairy, the fencing
costs would be a little higher at £3,800, a total of £15,300 per 200 ha or £76.5/ha. Excavation cost £2.30 m 2 quoted by
three civil engineering contractors in Cambridgeshire, who are involved in reservoir construction. The cost of £2.30 m 2
may be avoided on a sand site where the sand could be sold. The total cost would be £73.58/ha or £38.46 million for the
relevant arable land and £76.5/ha or £36.04 million for the relevant area of grassland, giving an overall total of £74.5
million.
To move gateways away from points of drainage i.e. from down to up slope would incur an average cost £200 in an 8 ha
field or £25/ha (Brade, 2003; Nix, 2003). For 25% of all arable and grassland, the total cost would be almost £24.85
million.
To install hedges and make fields smaller, assuming an average field size of 8 ha of dimensions 250 m x 320 m and
hedging with backfencing, the cost of 250m of hedge is £2,250, £280/ha (Nix, 2003). The total cost would be just over
£139 million.
To install farm track sediment traps, this measure assumes that on farm tracks, there will be sediment traps needed at a
rate of one for 50ha. Each trap would be approximately 4 m 3 and cost £350 to install (Brade, 2003; Nix, 2003). The cost
per ha would therefore be £7/ha. The total cost for all arable and grassland would be almost £7 million.
For riparian zones, the simplest option is to go for a 6m wide grass strip, sown with, for example, a Countryside
Stewardship Scheme mix. Assuming the field will be cultivated as normal, which would include headlands, the additional
costs would for drilling the margin and the grass mixture. Drilling at £20/ha (Nix, 2003) and seed at £2/kg sown at
17kg/ha is £34/ha (Simpson, 2003). This produces a figure of £54 per ha drilled. Assuming an 8ha field, the boundary
may be 250 x 320m. The riverside boundary may be 320m at 6m width, 1920m 2, or approximately 0.2ha at a cost of
£10.80 in an 8ha field or £1.35/ha arable or grass. Crop loss needs to be taken into account. For arable, 0.2 ha wheat at
7t/ha is 1.4t at a price of £70/t (see Measure 33). This totals £98 in an 8ha field or £12.25/ha of field. For grass, it has
been assumed that it would be grazed, but not fertilised. There would be a loss of 0.2ha at 5t/ha i.e. 1t of silage dry
matter (half the commercial crop) at £10/t (hay at £40/t and 80% DM, silage at 20% DM (Nix, 2003)), that is £10 in an 8ha
field or £1.25/ha of field. Total cost for arable would be £1.35/ha of field for drilling the grass buffer plus £12.25 for the
loss of crop, a total of £13.60/ha and for grassland £1.35 for drilling the grass buffer plus £1.25 for the loss of crop, a total
of £2.60/ha. The total cost for 5% of all arable and grassland would be just over £4.16 million.
Grass buffers are calculated the same as for riparian zones, that is assuming only one side of a field was a grass buffer.
COST-CURVE ASSESSMENT OF P MITIGATION STRATEGIES (OBJECTIVE 3): A GENERAL DISCUSSION OF
MITIGATION POTENTIAL FOR ENGLAND AND WALES
Cost-effectiveness of measures
Input measures
Input measures (Numbers 1-15 in Table 8) include those designed to reduce annual P inputs to the land surface, thereby
minimising surplus P and preventing unnecessary increases in soil P concentrations. These measures are feasible
because of the bank of residual P that has accumulated in a large proportion of soils in England and Wales, and the high
level of ‘insurance’ P application in fertilizers and feeds which has historically been adopted on farms to maximise
productivity. Precision farming is a potential mechanism by which more accurate targeting of P inputs can be
implemented through the use of specialised soil sampling strategies, and application technologies, that can apply
differential amounts of fertilizer to different areas of the field according to soil nutrient status and yield potential. Changes
in stocking density and reversion of P-rich arable fields to extensive use are more strategic options that have a much
greater social and economic impact on the farming system.
There is good evidence to indicate that high P soils (Index 3+) can be allowed to rundown, and that ‘insurance’ levels of
feed P inputs can be reduced without significantly affecting crop or animal performance (Johnston et al., 2001; Sims and
Sharpley, 2004). The level of fertilizer P reduction or omission, and the level of feed P input reductions adopted in this
CSG 15 (1/00)
9
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
projects’ scenarios are conservative and can be adopted with real savings in costs (Table 7). The largest potential saving
in fertilizer bills is on arable land because it has a higher proportion of P-rich soils than on grassland. The reductions in P
losses in the short term are relatively small (<0.2 kg P/ha), because P losses from land are dominated by residual soil P
levels (Withers and Lord, 2002), and are limited to reductions in incidental P losses. However, these options become
more significant in the longer term as soil P levels decline. The largest reductions in P loss due to lowering of fertilizer
inputs were to grassland and horticulture, reflecting the preferential accumulation of P at the surface in grassland soils
and the use of short season succession cropping in horticultural systems. The costs of reducing P inputs has been
assessed as zero for calculation of cost-effectiveness. In contrast, the cost-effectiveness of changing livestock density,
and to a lesser extent land use, was very high (up to £13,000/kg P saved) relative to any other measure (Table 8).
The forecast savings in fertilizer costs are overestimated because of the large reduction in P fertilizer inputs which has
already been evident in recent years. In Great Britain, fertilizer P has dropped by ca. 45,000 tonnes P over the last 5
years simply due to the current unprofitability of agriculture. There is also still debate over the extent to which reductions
in ‘insurance’ P feeding of dairy cattle might influence herd fertility in the longer term, even though there is good data to
show no reductions in milk output in short-term experiments (e.g. Wu and Satter, 2000). In contrast, phytase substitution
has been widely practised for some time in other EU countries with no ill effects (see Appendix 3), although P loss
reductions in the short-term are again small. It is still unclear whether precision farming is economically justified, or
confounded by the heterogeneity of field soils, errors introduced during routine sampling and analysis and the seasonality
of yield response (Edwards et al., 1997; Sylvester-Bradley et al., 1999).
Mobilization measures
Mobilization measures are those required to prevent the enrichment of storm runoff with soluble P from applications of
fertilizers and manures, and the enrichment of runoff with soil particles detached by erosion processes. There is a large
amount of evidence to indicate that substantial incidental losses of P occur in fields where fertilizers and manures are left
on the soil surface without incorporation, applied to wet soils or at very high rates (Haygarth and Jarvis, 1999; Withers et
al., 2003a). Liquid manures are particularly susceptible to P loss on sloping and underdrained fields due to the high
proportion of the slurry P in dissolved form. Similarly, high rates of particle mobilization are associated with fields that
have a high proportion of exposed soil over winter, are over-cultivated, compacted or cultivated up and down steep slopes
(Withers and Jarvis, 1998).
Reductions in P loss associated with mobilization measures (No’s 16-34) ranged up to 1.2 kg P/ha (Table 8). The largest
reductions were achieved by reducing the risk of particle dispersion by providing crop cover (measures 26, 27), reducing
runoff risk and the susceptibility of the soil to raindrop impact, or to the incidence of slaking and capping (measures 28,
29, 30, 31, 32, 33). Reducing incidental P losses by incorporation into the soil, or through better management of fresh
applications (e.g. timing), did not have a large influence on P loss relative to reducing soil vulnerability to erosion. This is
because high P loss rates are generally dominated by particulate P. In grassland systems, where P loss rates are lower,
the reductions in incidental P loss (e.g. in the range up to 0.2 kg P/ha) would become more significant (Table 8).
Differences in cost-effectiveness ranged from zero up to £415/kg P saved, but with a large number of the measures being
relatively cost-effective i.e. <£60 /kg P saved. Those measures which were less cost-effective were those that involved
the use of specialised machinery, increased dependence on other agrochemicals to control weeds and pests, or where
extra manure storage was required to give greater flexibility in timing of fertilizer and manure spreading.
Transport measures
Transport measures include those designed to prevent the delivery of mobilised P from the field to the watercourse. They
include end-of–pipe solutions such the strategic placement of riparian buffer strips (measure 39) and constructed
wetlands (measure 35), and reducing runoff velocity by diverting runoff (measure 36, 38), or creating more storage zones
within the landscape (measure 37). A number of recent reviews have concluded that these measures are variably
effective, may have limited lifespans and should not be relied upon to control P loss in isolation (Withers and Jarvis, 1998;
Uusi-Kamppa et al., 2000). However they also have a number of added benefits in terms of providing valuable wildlife
habitats, protection of stream banks and farmer interest.
Reductions in P loss associated with transport measures are larger than those associated with input and mobilisation
measures and ranged up to 2.2 kg P/ha (Table 8). The largest reductions were achieved by installing buffer zones and
constructed wetlands, the former also being very cost effective (£3-5/kg P saved). The cost-effectiveness of making fields
smaller by planting hedges was very low (£405/kg P saved), whilst the costs of constructed wetlands were surprisingly
CSG 15 (1/00)
10
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
modest in relation to the saving in P gained. Diverting track runoff to remove sediment was very cost-effective, but moving
gateways was not.
Farm System Scenarios
The cumulative impact on P loss of the individual measures selectively adopted on each scenario farming system is
shown in Figs 1 - 4. These are only examples of combinations of measures that might be adopted on farms and are not
exhaustive. The P losses estimated by the PLEASE Expert System indicate that the cumulative P loss attainable by the
measures selected was ca. 0.2 kg/ha for the upland system, 0.6 kg/ha for pigs, 0.9 kg/ha for the dairy system and 2.2
kg/ha for the arable system. These differences reflect not only differences in the relative effectiveness of the measures
but also the number selected. For example, only 3 measures were selected for the upland farming system, whilst 8, 9 and
13 measures were selected for the pigs, dairy and arable systems, respectively. There is clearly a link between the
number of measures adopted and the cumulative P loss achieved across the different systems suggesting that the scope
of P loss reduction is set by the interaction between the farming system and the landscape. For example, the few
measures selected for the upland system might indicate that P losses are probably influenced more by the landscape
than by agricultural management. The number of measures that need to be adopted on the farm will depend on the
amount of P reduction required (Figs. 1-4).
Within each farming system, the cost-effectiveness of each of the selected measures can be seen to vary quite
substantially with some measures reducing P loss substantially for very little cost, whilst other measures incur significant
benefits only at a relatively high cost. In the graphs the measures are ranked according to least cost, and not according to
cost-effectiveness to give a better idea what is achievable in practice for the cost-conscious farmer. The costeffectiveness (cost/kg P saved) of the individual measures is given in Table 8. For the upland system, installing a riparian
zone and installing sediment traps on farm tracks were similarly cost effective but moving gateways cost 12 times more
for the same amount of P saving (Fig. 1, Table 8). However, the overall cost for achieving the relatively small P loss
reduction achieved on the upland system was only £3.5/ha.
For outdoor pigs, a similar P loss reduction of ca. 0.25 kg P/ha was achieved by the same measures (No’s 36, 38, 39) for
a broadly similar cost (£3-4/ha) as in the uplands. The addition of phytase in the diet to lower excreted P did not cost
anything but did not greatly reduce P loss either so the impacts of measures 8 and 9 were very low, at least in the short
term (Fig. 2). In the longer term, this is an effective measure in reducing surplus P inputs – see Appendix 3. The next
measure was to restrict livestock access (No. 25). This measure was more cost effective than the previous measure (No.
36) because it achieved a greater P loss reduction but would cost the farmer more to implement. Making fields smaller by
installing hedges was very costly and did not appear to gain much P saving, whilst constructing a sedimentation pond was
more reasonably cost-effective at £93/kg P saved (Table 8). Restricting livestock access and construction of
sedimentation ponds gave the biggest reduction in P loss.
On the dairy system, a larger P loss reduction of ca. 0.5 kg/ha was achievable at relatively low cost (< £5/ha) due to
added benefit on P loss reduction of lowering fertilizer and feed P inputs (Fig. 3). Restricting livestock access had a much
lower impact on P loss in the dairy system than its adoption in the outdoor pig system and cost much more (Table 8). The
least cost-effective options in the dairy system were adjusting rates and timings of application (measures 22 and 23),
even though they achieved the most reductions in P loss (Fig. 3). This reflects the need to store slurry for longer periods
to allow the flexibility in spreading to avoid wet weather conditions and to more evenly distribute P around the farm.
Manipulation of slurry timing and construction of sedimentation ponds gave the biggest reduction in P loss. However, it is
interesting that it was more much cost-effective to construct a sedimentation pond than to alter slurry application timings
for similar reductions in P loss.
On the arable farm, the measures which gave the largest reduction in P loss were the adoption of minimum tillage,
leaving seedbeds rough, across slope cultivation and construction of sedimentation ponds (Fig. 4). Of these options, the
cross-slope cultivation was the most cost-effective (Table 8). As with the dairy farm, significant P loss reductions of the
order of 0.5 kg/ha or more could be achieved at relatively low cost (<£5/ha). Installing hedges to make fields smaller and
moving gateways was very cost-ineffective.
When comparing the farming system scenarios together, it is clear that P loss reductions above 0.5 kg P/ha in the dairy
farming sector are not only more difficult to achieve but also, and more importantly, will be very expensive (Fig. 5). This
suggests that alternative, or more innovative solutions are required. On arable farms, the scope to reduce losses is much
larger with a number of low-cost options available for adoption, as also found by Withers et al., 2003b. Certainly, P loss
reductions of 1 kg P/ha appear readily achievable at relatively low cost. For outdoor pigs more expensive options appear
necessary to achieve a worthwhile reduction in P loss.
CSG 15 (1/00)
11
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
The impact of all the combined input, mobilization and transport measures that might be adopted on the upland, outdoor
pigs, dairy and arable farming systems was modelled to assess the potential P loss reduction achievable, the costs and
overall cost-effectiveness if (Table 9). The largest reductions in P loss (up to 4 kg P/ha) were achieved on the arable and
outdoor pig farms, where P loss rates are greatly influenced by particulate P transport in runoff. On the dairy and upland
systems, maximum P loss reductions were ca. 2 and 1 kg P/ha, respectively. The costs of achieving those reductions
ranged from £254 –616/ha on the intensive lowland farms but only £35/ha for the upland farm. This reflects the number of
measures applicable to these farming systems. Lower costs were modelled for the subsequent years reflecting some
initial investment. The overall cost-effectiveness of adopting all possible measures was quite similar for the intensive
farms, ranging from £110/ha to £162/ha, again lowering substantially in subsequent years (Table 9).
Overall, the COSTCURVE analysis has shown that there are a number of measures which can be adopted to costeffectively control the mobilization and transport of P in dissolved and particulate form. The ranking of the measures in
terms of the least cost to the farm provides a useful way of deciding on which measures might be economically
acceptable and the likely impacts on P loss under the particular landscape conditions and farming system. There is
clearly a need to define what level of P loss is acceptable in order to define how far along the COSTCURVE line it is
necessary to go.
SUGGESTED FUTURE AREAS OF RESEARCH WHERE GAPS IN KNOWLEDGE HAVE BEEN IDENTIFIED
(OBJECTIVE 4).
Overview of future areas
This desk exercise has helped to highlight a number of key areas where we need more information on mitigation. These
are expanded under 1-6 below:
1. Established field evidence for P mitigation is sparse, especially for UK. Although we have made use of international
information with colleagues around the world, further investigations are necessary for UK conditions. Thus, in most
cases, we have had to make informed ‘best judgements’ on what is ‘perceived’ for the UK rather than what is ‘known’.
2. Cost and effectiveness may vary considerably with location so we need more case study examples to demonstrate
individual options success or combined options collectively, and any limitations identified.
3. The PLEASE system and its associated coefficients were derived from expert judgement by team discussion and
consensus, derived from the literature reviewing exercise. The system was not calibrated or validated and
uncertainties, which will be high, are not quantified. Considerable caution must therefore be attached to interpretation
of the information, and especially when using it to provide a basis for longer-term predictions of changes in the P
cycles.
4. Further work is required to assess the relative importance of the different processes of loss (and hence potential
effectiveness of options) on the overall P loss from a farming/landscape type. This is clearly dependent on the
geographical location, climate, landscape (geology and slope) and farming system. For example, incidental P loss is
probably far more significant in grassland farming systems in south-west England than in arable farms in East Anglia.
5. In respect of the land use scenarios modelling, we should now explore a range of scenarios for each region based not
only on estimates of the greatest sources of nutrient flux in each region, but also on expert judgement on possible
future scenarios for sustainable production in rural environments.
7. New farm and catchment system level mitigation work is much needed.
Specific suggestions for field testing of mitigation options
What is required now is to build on the previously funded work by evaluating the effectiveness of a range of options
targeted within key plots, farms and catchments. Future work will need to cater for the need to provide evidence that
particular options will work effectively at the specific location (e.g. field, track or building) they are targeted at, and that the
combined effect of a number of individual measures will be effective at the catchment scale. There will be a need to link
to (a) key demonstration events to aid facilitation, acceptance and identify barriers to uptake, (b) some appraisal of the
economics and practicalities that might influence their effectiveness at other locations, and (c) calibration and validation of
catchment-based decision support systems (e.g. PSYCHIC) that can model the individual and collective impact of the
options tested.
Key farms, plots and catchments will need to be selected to test the effect of integrated and targeted programme of
mitigation options appropriate to the landscape characteristics, farming systems and land management practices
influencing P concentrations and loads. Catchments ought to provide a contrast in landscape features/farming practices,
and should be selected on the basis of previous monitoring programmes, and information on land use, which can provide
a suitable baseline on which to evaluate the likely field and catchment response. Farms and catchments need to be
CSG 15 (1/00)
12
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
located within headwaters to minimise any impact from point sources and where the influence of mitigation options will be
most apparent.
Monitoring of effectiveness will need to be assessed (a) at the field scale through controlled runoff (plot) experiments,
similar to those which were successfully adopted within the Avon catchment, (b) at the farm scale through record keeping
of nutrient inputs and outputs, and soil P levels, and (c) at the catchment scale through intensive monitoring of storm
response at selected stream locations. Within catchments, mitigation options will need to be integrated to cover priority
measures. Measures will need to be considered according to the following categories:
1. Adoption of farm nutrient reduction measures by planning - to reduce surplus P, minimise soil P build-up in the longer
term and incidental loss in the short-term. This will include demonstration of balanced fertilizer usage, effective
substitution of manures for P fertilizers, timing and method of P inputs to avoid incidental losses on high-risk fields
and the practicalities of setting up manure trading credits.
2. Adoption of soil management measures identified by planning - to reduce the percentage of bare ground over winter,
ensure cultivations are timely, adopting appropriate cultivation techniques suited to the particular site and soil
conditions and strategic adoption of alternative land uses on high-risk sites, including reductions in stocking rates to
avoid poaching damage/sediment loss and proposed cross compliance options under CAP reform.
3. Adoption of specific solutions to key problem sites in catchments, for example, diverting farm track runoff, farm
building effluent, moving livestock feeders or gateways, fencing off river banks, restricting livestock access etc.
Overall conclusions
This project has helped (1) illustrate areas where we lack knowledge and highlight priority areas for future research on P
mitigation and (2) provide a preliminary identification of the key P mitigation measures. Source and mobilisation options
are designed to control P loss at the point of origin that is more in keeping with the underlying principle behind the Water
Framework Directive. As such, they can be more widely adopted and with a greater degree of success than transport
options, whose effectiveness is severely limited by local site conditions. Clearly transport options are most dependent on
the hydrological linkages between the field and the watercourse, which are unpredictable and vary considerably both
spatially and temporally. Transport options therefore require careful targeting to be effective, are more sensitive to local
site conditions and might frequently fail during extreme events. One can therefore consider that the degree of uncertainty
over effectiveness, and hence inapplicability for national adoption, increases along the source-mobilisation-transport
continuum. Related projects on nitrate (NT2511) and other diffuse pollutants (ESO121) are now underway. In respect of
the land use scenarios that were explored as part of the additional contract, we favour the need for smaller scale, more
targeted catchment or system specific measures that address fundamental changes in the way we use and manage the
landscape in context with farm systems.
REFERENCES CITED IN THIS REPORT
Agro Business Consultants (2001). "Farm Machinery Costs," 8/Ed. Agro Business Consultants, Melton Mowbray.
Basford, W. D. (2003). On the cost of cultivation and contractors for incorporation and slurry injection. (Personal
communication to D Harris, ed.). ADAS, Gleadthorpe Grange, Meden Vale, Mansfield, Notts., NG20 9PD.
Brade, M. (2003). On the erection and removal of electric fencing and hedging. (Personal communication to D Harris,
ed.). ADAS, Woodthorne, Wergs Road, Wolverhampton, WV6 8TQ.
Defra (2001). "Annual Survey of Tenanted Land - England 2001." Defra, London.
Dewes, M., and Basford, W. D. (2003). On the cost of fertilizer and spray applications. (Personal communication to D
Harris, ed.). ADAS Arable Limited, Goodbody's Business Centre, Albert Road, Retford, Notts. DN22 JD & ADAS
Gleadthorpe Grange, Meden Vale, Mansfield, Notts., NG20 9PD.
Edwards, A.C., Withers P.J.A. and Sims, T.J. 1997. Are current fertilizer recommendation systems for phosphorus
adequate? Proceedings of the Fertilizer Society. No. 404. Greenhill House, Thorpe Wood, Peterborough, UK.
Harrod, T. R., and Theurer, F. D. (2002). Sediment. In "Agriculture, Hydrology and Water Quality" (P. M. Haygarth and S.
C. Jarvis, eds.). CAB International, Wallingford.
Haygarth, P. M., Hepworth, L., and Jarvis, S. C. (1998). Forms of phosphorus transfer in hydrological pathways from soil
under grazed grassland. European Journal of Soil Science 49, 65-72.
Haygarth, P. M., and Jarvis, S. C. (1999). Transfer of phosphorus from agricultural soils. Advances in Agronomy 66, 195249.
Haygarth, P. M., and Jarvis, S. C., eds. (2002). "Agriculture, Hydrology and Water Quality," pp. 1-502. CABI Publishing,
Oxford, New York.
Hutchinson, H. L. (2003). On the supply of Vinamul. (Personal communication to D Harris, ed.). H. L. Hutchinsons Ltd,
Weasenham Lane, Wisbech, Cambs., PE13 2RN.
Johnston, A.E., Goulding, K.W.T., Poulton, P.R. and Chalmers A.G. (2001). Reducing fertiliser inputs: endangering arable
soil fertility? Proceedings of the Fertiliser Society No. 487, York, UK.
CSG 15 (1/00)
13
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Lawlor, P., and Lynch, B. (2000). "Formulating Feeds for Environmental Protection," The Society of Food Technologists,
Ireland.
Nix, J. (2003). "Farm Management Pocketbook," 33/Ed. Imperial College, Wye, Ashford, UK.
Owens, P. N., and Deeks, L. (2003). Revised phosphorus content of topsoils in the Herefordshire Wye and Hampshire
Avon catchments. National Soil Resources Institute Report, Cranfield University, UK.
Owers, M., and Wilson, S. (2003). On the use of phytase. (Personal communication to D Harris, ed.). BOCM Paul's P.O.
Box 39, 47, Key Street, Ipswich, IP4 1BX.
Sharpley, A.N., and Rekolainen, S. (1997). Phosphorus in agriculture and its environmental implications. p. 1-54. In
‘Phosphorus Loss from Soil to Water’ (H. Tunney, O.T. Carton, P.C. Brookes and A.E. Johnston, eds.). CAB
International Press, Cambridge, England.
Simpson, N. (2003). On the costs of drilling and seeding. (Personal communication to D Harris, ed.). ADAS Consulting
Limited, Boxworth, Cambridge, CB3 8NN.
Sims, J.T. and Sharpley, A.N. (2004). Phosphorus: Agriculture and the Environment, American Society of Agronomy,
Madison, WI. (in press).
Strauss P., Swoboda, D. and Blum W.E.H. (2003). How effective is mulching and minimum tillage to control runoff and
soil loss. Proceedings of „25 Years of Assessment of Erosion, Ghent, 22-26 September 2003, 545-550.
Turner, A. W. B. (2003). On contractor spreading of manure. (Personal communication to D Harris, ed.). ADAS,
Woodthorne, Wergs Road, Wolverhampton, WV6 8TQ.
Uusi-Kamppa, J., Braskerud, B., Jansson, J., Syverson, N. and Uusitalo, R. (2000). Buffer zones and constructed
wetlands as filters of agricultural phosphorus. Journal of Environmental Quality 29, 28-36.
Withers, P.J.A., and Jarvis S.C. (1998). Mitigation options for diffuse phosphorus loss to water. Soil Use and
Management 14, 186-192.
Withers, P.J.A. and Lord, E.I. (2002). Agricultural nutrient inputs to rivers and groundwaters in the UK: policy,
environmental management and research needs. Science of the Total Environment 282-283, 9-24.
Withers, P.J.A., Ulen, B., Stamm, C. and Bechmann, M. (2003a). Incidental phosphorus losses – are they significant and
can they be predicted? Jpournal of Soil Science and Plant Nutrition 166, 459-468.
Withers, P.J.A., Royle, S., Tucker, M., Watson, R., Scott, T., Silcock, P. and Dwyer. J. (2003b). Field Development of
Grant Aid Proposals for the Control of Diffuse Agricultural Pollution. R&D Technical Report P2-261/09/TR.
Environment Agency, Bristol. 97 pp.
Wu, Z. and Satter, L.D. (2000). Milk production and reproductive performance of dairy cows fed two concentrations of
phosphorus for two years. Journal of Dairy Science 83, 1052-1063.
OUTPUTS FROM THE TEAM
a) Events
Soils and the Environment, September 9 & 10, 2002, Seale-Hayne Faculty, University of Plymouth and North Wyke
Research Station. British Society of Soil Science Annual Meeting.
Estimated abatement of phosphorus and sediment from agriculture (also with PE0101). For Defra’s Diffuse Water
Pollution from Agriculture (DWPA) group and Invited Researchers. Elliot Room (conference centre) Rothamsted
Research, Harpenden. Organiser and Chair of Workshop, 14th January 2003.
Farming and Wildlife Advisory Group, 150 delegates to North Wyke on Sep 3 2003.
b) Reports and Publications
Haygarth, P. M., Turner, B. L., Fraser, A. I., Jarvis, S. C., Harrod, T. R., Nash, D. M. and Halliwell, D. J., 2000. Prioritising
mitigation of soil P transfer in relation to water flows, Grassland Farming, Balancing Environmental and Economic
Demands (Edited by K. Soegard, C. Ohlsson, J. Sehested. N. J. Hutchings, T. Kristensen) (Volume 5 of Grassland
Science in Europe), European Grassland Federation, Denmark.
Haygarth, P. M., Johnes, P., Butterfield, D., Foy, B. and Withers P. 2004. Land use for achieving ‘good ecological status’
of waterbodies in England and Wales: a theoretical exploration for nitrogen and phosphorus. Report to Defra DWPA
Group (Appendix 1).
Haygarth, P. M., Hutchins, M., and Withers, P.J. A. 2002. Theoretical and Practical Effectiveness of Phosphorus and
Associated Nutrient/Sediment Mitigation Measures in England and Wales. Review for DEFRA: Milestone 1a of Project
PE0203, 18th March 2002 (Appendix 3).
Editorial books and proceedings (generic)
Haygarth, P. M. and Jarvis, S. C. (2002). Agriculture, Hydrology and Water Quality, CAB International, Oxford and New
York, 502 pp.
CSG 15 (1/00)
14
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
Haygarth, P. M., Condron, L. M., Butler, P. J., and Chisholm, J. S., 2001. Connecting Phosphorus Transfer from
Agriculture to Impacts in Surface Waters, Proceedings of the International Phosphorus Transfer Workshop, 28th August to
1st September 2001, Plymouth, Devon, England, published by the Institute of Grassland and Environmental Research.
Popular
‘A Mission on Quality’ The Standard, page 7, Wednesday January 30 th 2002, Warrnambool, Victoria, Australia (Article by
Matt Neal).
ABC Western Victoria Radio Breakfast Show Live Interview, Wednesday January 30 th 2002 8.35 am. Soils and Water
Quality.
Haygarth, P. M., Scholefield, D. S. and Jarvis, S. C. 2003. Nutrients in Rivers. IGER Innovations 7, 58-63.
Haygarth, P. M. 2004. Practical agricultural benefits from phosphorus and nitrate programmes, Agriculture and the
Environment R&D Newsletter, Department for Environment, Food and Rural Affairs, 12, March 2004, p8.
CSG 15 (1/00)
15
Project
title
Cost Curve Assessment of Phosphorus Mitigation Options
Relevant to UK Agriculture
DEFRA
project code
PEO203
List of Tables Appended
Table 1. Farm model scenarios representative for England and Wales, based on data collated 1995-1999
Table 2. Coefficients of export used in the two types of ‘system’ that were used within PLEASE
Table 3. 'Starting' phosphorus losses estimated from PLEASE espert system for model systems (from Table 1) scenarios
using coeffiecients of export (from Table 2)
Table 4. Summary matrix of measures for reducing phosphorus inputs: All these measures will have a secondary effect
on mobilisation and transport that is not documented in this table.
Table 5. Summary matrix of phosphorus mitigation measures for mobilisation, with the estimated effects of the measure
on P loss
Table 6. Summary matrix of measures for reducing phosphorus transport
Table 7. Potential to mitigate phosphorus inputs to agriculture in England and Wales: Potential reductions and cost
benefits
Table 8. Estimated effect of mitigation measures on phosphorus losses using the PLEASE expert system: Potential
reductions and cost benefits
Table 9. Combined measures for selected 'best' options - combining input with mobilisation and transport
List of Figures Appended
Figure 1. Example cost curve of mitigation measures that can be combined in upland systems
Figure 2. Example cost curve of mitigation measures that can be combined in outdoor pig systems
Figure 3. Example cost curve of mitigation measures that can be combined in dairy systems
Figure 4. Example cost curve of mitigation measures that can be combined in arable systems
Figure 5. Example cost curves of mitigation measures comparing all systems
List of Documents Appended
Appendix 1. Land use for achieving ‘good ecological status’ of waterbodies in England and Wales: a theoretical
exploration for nitrogen and phosphorus – final report on objective 6
Appendix 2. Collation of mitigation options in terms of cost, effectiveness and acceptability, as discussed with Defra and
Stakeholders on 14th January 2003.
Appendix 3. Theoretical and Practical Effectiveness of Phosphorus and Associated Nutrient/Sediment Mitigation
Measures in England and Wales – review report originally submitted March 2002
Appendix 4. Report from Norway visit
Appendix 5. Report from Switzerland visit
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