Prevention of environmental pollution from agricultural activity: guidance

Code of good practice, giving practical advice to farmers and others on minimising pollution.


Section 6: nitrogen and phosphorus

Introduction

6.1 This section of the Code covers the steps which can be taken to reduce the risk of nitrate leaching, and is recommended to be followed by all farmers. The steps described in paragraphs 6A.1 to 6A.26 are mandatory for farmers in Nitrate Vulnerable Zones ("NVZs"). The rest of this section relates to all farmers.

6.2 Agricultural advisers are particularly requested to familiarise themselves with the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2003 ("the NVZ Action Programme Regulations") Farmers in NVZs must read, and use, the Scottish Executive's "Guidelines for farmers in nitrate vulnerable zones".

What is nitrate?

6.3 Nitrate occurs naturally in soil and is an essential plant nutrient. Sources of organic and inorganic nitrogen are used in agriculture to improve soil fertility and promote crop growth. Chemical fertilisers (containing nitrogen) usually contain nitrogen in the form of ammonium and nitrate. Nitrate is very soluble and is therefore at risk of being washed into watercourses and groundwater by leaching from the soil, especially in late autumn and early winter when soil may be bare or there is little crop uptake. Subsequent rainfall readily washes nitrate from the soil profile. The main sources and losses of nitrate to water are shown in the diagram:

6.4 See the appendix to this section for a detailed nitrogen cycle diagram which also includes nitrogen losses to air.

arrow chart

6.5 The terms used in this section for slurry, livestock manure, nitrogen fertiliser, chemical fertiliser, organic manures, crop requirement, autumn sown crop and fertiliser and manure plan are as defined in the NVZ Action Programme Regulations.

6.6 There is a high risk of water pollution from nitrate losses if livestock manures and slurries with a high proportion of their nitrogen content in soluble form (e.g. slurry and poultry manures) are applied when crop uptake is low or non-existent (i.e. in the autumn or winter period).

6.7 Typical leaching losses of available nitrogen from a slurry application are:

Time of application

Typical losses of available nitrogen (%)

Autumn

90%

Early Winter

60%

Late Winter

30%

Spring and Summer

0%

6.8 Nitrate leaching from application of farmyard manure is far lower, as most of its nitrogen is in organic rather than an immediately soluble form. This makes the timing of the spreading operation less critical.

What is phosphorus?

6.9 Phosphorus is an essential plant nutrient that occurs naturally in soils either as inorganic phosphate or as part of the organic matter. Phosphorus fertilisers, manures and slurries supply phosphate to improve soil fertility and to maintain plant growth. Once added to soils, phosphate is normally strongly bound to soil particles and has a very low solubility. Drainage water percolating through soils therefore normally contains very low concentrations of phosphate, except when soil phosphate levels are excessively high. Phosphate can also be lost from farmland if soil erosion occurs or due to surface run-off following the application of manures and slurries.

Why are nitrogen and phosphorus important?

6.10 Agricultural land is the main source of nitrate in many rivers and groundwaters. Nitrate concentration in rivers and groundwaters has been increasing in recent decades in many areas of Scotland. This is a cause for concern for two main reasons. Firstly, because of possible risks to human health posed by high levels of nitrate in drinking water. Secondly, elevated levels of nitrate and phosphorus are considered to be significant contributors to eutrophication. ("Eutrophication" is the enrichment of water by nitrogen compounds, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water.)

Nitrate Vulnerable Zones

6.11 You can check whether your farm is in an NVZ from the maps in the Scottish Executive's "Guidelines for farmers in NVZs", copies of which have been distributed. Alternatively, enquire at your local SEERAD office. If you do have land within an NVZ, you should follow the aforementioned "Guidelines".

Section 6A: Farmers in nitrate vulnerable zones ("NVZs")

Dos

**A1. Comply with the statutory requirements of the NVZ Action Programme Regulations if you are farming within an NVZ.

  • prepare and implement a fertiliser and manure plan

  • ensure that adequate records are kept for land within NVZs relating to livestock numbers, use of inorganic fertiliser and use of organic manures

**A2. Ensure that minimum storage requirements for livestock manure are provided for the purposes of the NVZ Action Programme Regulations, taking account of the need to comply with the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003.

  • locate any field midden at least 10m away from any clean surface water or field drain or watercourse and at least 50m from any spring, well or borehole

**A3. Take account of 'local environmental factors' before applying nitrogen fertilisers. These include:

  • soil conditions, type and slope

  • climatic conditions, rainfall and irrigation

  • land use and agricultural practice, including crop rotation systems

**A4. Apply nitrogen fertilisers in as accurate and uniform a manner as possible.

*A5. Any proposal to plough up pasture of high environmental or archaeological value, e.g. species-rich grassland, machair habitats, pastoral woodland and heather moorland, will require the consent of the relevant authority (e.g. SNH for land in SSSIs, SEERAD for land in an agri-environment agreement) or approval under the Environmental Impact Assessment (Uncultivated Land and Semi-Natural Areas) (Scotland) Regulations 2002 (SSI 2002/6). [GAEC measure 12]

A6. Produce and implement a farm nutrient plan.

A7. Sow winter cereals in time to establish a suitable crop cover in the autumn to winter period.

A8. Apply fertilisers only when soil conditions are suitable.

**A9. Spread organic manures at least 10m away from any clean surface water, field drain or watercourse, and at least 50m from springs, wells or boreholes that supply water for human consumption or use in dairies.

A10. Apply nitrogen fertilisers only when there is a specific crop requirement.

A11. Apply phosphorus fertiliser according to soil analysis and the needs of the crop. Always allow for the nutrients supplied by any organic manures.

A12. Analyse your soil for phosphorus to ensure that excess and unnecessary levels are not building up.

DON'Ts

**A1. Don't apply chemical fertiliser (containing nitrogen) within closed periods in the NVZ Action Programme Regulations unless there is a specific crop requirement (as referred to in the SE's "Guidelines for farmers in NVZs").

**A2. Don't apply chemical fertiliser (containing nitrogen) in a location or manner which makes it likely that the fertiliser will directly enter a watercourse.

**A3. Don't apply organic manure where the application would result in the total nitrogen (in kilograms) contained in organic manure applied per year to the land - including that deposited by animals - exceeding permitted rates in the NVZ Action Programme Regulations.

**A4. Don't apply slurry, poultry manures or liquid digested sewage sludge to sandy or shallow soils within closed periods in the NVZ Action Programme Regulations.

**A5. Don't apply nitrogen fertilisers in excess of crop requirements, or to any land if the soil is waterlogged.

**A6. Don't apply nitrogen fertilisers if the land is flooded, or if the soil has been frozen for 12 hours or longer in the preceding 24 hours.

**A7. Don't apply nitrogen fertilisers to any land covered with snow, or to steeply sloping fields.

A8. Don't allow livestock to foul watercourses by having uncontrolled access. Instead, provide water at drinking troughs, if at all possible.

A9. Don't plough up permanent pasture, if possible.

A10. Don't apply P and K chemical fertilisers (i.e. those which don't contain nitrogen) in a location or manner which makes it likely that the fertiliser will directly enter a watercourse.

A11. Don't over-compact soil.

What legislation must be complied with in NVZs?

6A.1 The Private Water Supplies (Scotland) Regulations 1992 are concerned with the quality of water supplied from private supplies in Scotland for drinking, washing or cooking or for food production purposes. These Regulations establish a maximum admissible nitrate concentration in water of 50 mg/l and are implemented by the local authorities.

6A.2 The Protection of Water Against Agricultural Nitrate Pollution (Scotland) Regulations 1996 transpose into Scots law the requirements of EC Nitrates Directive (91/676/EEC). These Regulations were amended by the Designation of Nitrate Vulnerable Zones (Scotland) Regulations 2002 and place a duty on the Scottish Ministers to identify and designate "NVZs" where surface freshwaters or groundwaters exceed, or could exceed, 50 mg/litre of nitrates and where waters are, or may become, eutrophic. The Scottish Ministers designate NVZs based on advice from SEPA, who monitor for nitrate in over 250 rivers and at 220 groundwater points across Scotland.

6A.3 The Scottish Ministers also have a duty to introduce mandatory action programme measures in NVZs with the aim of reducing water pollution from agricultural nitrates. These measures were introduced by the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2003.

6A.4 The Scottish Executive is the competent authority responsible for enforcing and checking farmer compliance with the Action Programme measures. SEERAD Agricultural Staff inspect the farms in question. Non-compliance with the measures can lead to statutory penalties.

6A.5 The action programme may be different for each NVZ or parts of NVZs and, as such, this section only gives a broad outline of requirements. Further details are available in the individual action programme for each NVZ. Check the SE's "Guidelines for farmers in NVZs"; if in doubt, your local SEERAD Area Office will be able to provide advice on measures which apply in your area.

6A.6 Farms at which slurry is produced are subject to the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003. Drainage from middens and high-level slatted buildings are included within the definition of slurry, whereas the solid manure itself is not. Such drainage is therefore covered by the Regulations and must be suitably collected and stored prior to land spreading. For new, substantially enlarged or substantially reconstructed slurry storage systems, the Regulations require the provision of adequate storage capacity (for the farm as a whole), taking account of the likely quantities of slurry and of the likely quantities of rainwater. SEPA may accept storage capacity of less than 6 months, but only where it can be demonstrated by a professionally prepared Farm Waste Management Plan that this will not cause harm to the environment or lead to a significant risk of pollution of controlled waters.

6A.7 It is an offence under environmental legislation to cause or knowingly permit any poisonous, noxious or polluting matter or any solid waste matter to enter any controlled waters. Farmers or their contractors may be liable to prosecution if livestock slurry or manure is allowed to enter a watercourse.

Mandatory measures in NVZs

Fertiliser and Manure Plan

6A.8 A Fertiliser and Manure Plan will help ensure that fertiliser use is cost effective and that nitrate leaching is low. Advice on how to prepare a Fertiliser and Manure Plan is given in the Scottish Executive NVZ Guidelines ( see Annex D). Nitrogen fertilisers should not be applied to land in excess of crop requirements, taking into account crop uptake and soil supply from soil organic matter, crop residues and organic manures. This rule requires that an assessment be made of the amount of nitrogen fertiliser required by each crop on each field each year. In doing so, full allowance should be made for the nitrogen available from soil organic matter, previous crop residues and from applications of organic manures. The land application of nitrogen fertilisers should take account of local environmental factors such as the influence of soil conditions, type and slope, climatic conditions, rainfall and irrigation and land use and agricultural practices, including crop rotation systems.

6A.9 Chemical fertilisers (containing nitrogen) must not be applied to land between:

  • 15 September and 15 or 20 February in the case of grassland

  • 1 September and 15 or 20 February in the case of other land unless there is a specific crop requirement during that time

[The "20 February" date applies to the Moray, Aberdeenshire and Banff and Buchan NVZs. For all other NVZs, the "15 February" date applies.]

6A.10 Nitrogen applied during this closed period is not generally required by crops and, if applied, is poorly utilised and at greater risk of leaching. Avoiding application of chemical fertiliser (containing nitrogen) during this period can therefore save costs.

6A.11 Nitrogen fertilisers should be applied to land in as accurate and uniform a manner as is practically possible, at the right rate, and without applying it to uncropped areas, hedges and ditches. This is consistent with good agricultural practice. All spreading equipment should therefore be tested regularly for accuracy of spreading and calibrated for the application rate required.

6A.12 Nitrogen fertilisers must not be applied to any land if:

  • the soil is waterlogged

  • the land is flooded

  • the soil has been frozen for 12 hours or longer in the preceding 24 hours

  • the land is covered with snow

6A.13 Application may be acceptable on days when early morning frost is predicted to thaw during the day, provided heavy rain is not forecast and other requirements of the NVZ Action Programme Regulations are met. Similar precautions should be taken with organic manures, especially slurries. It is important to ensure that the soil does not become compacted as a result of making such applications on frost.

6A.14 Nitrogen fertilisers should not be applied to steep slopes. The risk of run-off increases with slope. The legislation does not define a "steeply sloping field" in terms of the angle of slope, due to the complexity of landscape features and the fact that run-off is also influenced by other factors such as soil type and condition, ground cover and rainfall. In general, fields in the steeply sloping category are unlikely to be cultivated. Proximity to watercourses should also be taken into account due to the risk of causing water pollution by run-off from sloping land.

6A.15 Nitrogen fertilisers must be spread accurately on the cropped area without any direct contamination of any watercourse. Care must be taken to avoid direct contamination when spreading nitrogen fertiliser alongside streams, ditches, lochs with running or standing water. Direct application to temporarily dry ditches and blind ditches must also be prevented. Full width spreading machines should present few problems. Spinning disc and oscillating spout machines need careful operation. If appropriate, they should be fitted with headland deflector plates. 

Organic manures

6A.16 On sandy or shallow soils, slurry, poultry manures or liquid digested sewage sludge must not be applied within closed periods specified in the NVZ Action Programme Regulations. These periods are:

  • 1 October to 1 November, where the land is in grass or is to be sown with an autumn sown crop

  • 1 August to 1 November in any other case.

6A.17 The capacity of storage vessels for livestock manure must exceed the capacity required to store livestock manure produced throughout the longest period during which land application of livestock manure is prohibited by closed periods in the NVZ Action Programme Regulations.

6A.18 Organic manure must not be applied to land where the application would result in the total nitrogen (in kilograms) contained in organic manure exceeding:

  • 250 kg/ha of total nitrogen each year averaged over the area of grassland on the farm

  • 170 kg/ha of total nitrogen each year averaged over the area of the farm not in grass

6A.19 These limits apply to all organic manures, including that deposited by animals whilst grazing, and to all the agricultural land on the farm within the NVZ boundary. They include all other nitrogen-containing organic wastes such as sewage sludge but do not include chemical fertiliser.

6A.20 Where there is insufficient land on the farm to spread organic manures within the total nitrogen limits, either the number of livestock should be reduced or arrangements will need to be made to utilise any excess on other farmland in accordance with good agricultural practice.

6A.21 Applications of organic manure to individual fields must not exceed 250 kg/ha per year of total nitrogen, excluding any deposited by animals whilst occupying the field. This field limit applies in addition to, and in combination with, the overall farm limit. This approach allows some flexibility to adjust application rates according to crop nutrient requirements and field conditions. The area of the field used to calculate the 250 kg/ha limit should exclude any areas where manures should not be spread, such as the 10m exclusion zone from any watercourse. Remember that grazing deposition must be taken into account when calculating the farm-based limits for grassland and non-grassland areas.

6A.22 Organic manure must not be applied to any land less than 10m from a watercourse. This includes rivers and lochs and any temporarily dry ditches. To help protect the quality of groundwater, organic manures should not be applied within 50m of a spring, well or borehole that supplies water for human consumption, or which is to be used in farm dairies. This is a minimum distance and may need to be increased in the case of boreholes depending on local conditions.

Leafy vegetable residues

6A.23 Vegetable crop residues should be incorporated into the soil when an autumn sown crop is established. Alternatively, the residues should be incorporated into the soil with a binding material such as straw or appropriate paper mill sludge before 1 October or left untouched until 1 December at the earliest.

Records

6A.24 All farms must keep adequate records relating to:

  • livestock numbers

  • use of inorganic fertilisers

  • use of organic manures

6A.25 Records of the amount and date of applications of chemical fertilisers (containing nitrogen), livestock manures and slurries and other organic wastes will help with future calculations of nitrogen fertiliser requirements. The Scottish Executive "Guidelines for farmers in NVZs" gives details on how to keep such records so as to meet statutory requirements. The enforcing authority for the NVZ Action Programme Regulations in Scotland is the SEERAD Agricultural Staff.

6A.26 Soil sampling should be carried out at least once every four to five years to ensure that soil pH, phosphate and potash levels are at the optimum level. This will significantly improve the targeting and use of fertilisers whilst at the same time helping to minimise the losses of nitrogen and phosphorus to rivers, lochs and groundwater.

Section 6B - Measures relating to all farmers

Dos

**B1. Comply with the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003.

  • locate any field midden at least 10m away from any clean surface water or field drain or watercourse and at least 50m from any spring, well or borehole

*B2. Any proposal to plough up pasture of high environmental or archaeological value, e.g. species-rich grassland, machair habitats, pastoral woodland and heather moorland, will require the consent of the relevant authority (e.g. SNH for land in SSSIs, SEERAD for land in an agri-environment agreement) or approval under the Environmental Impact Assessment (Uncultivated Land and Semi-Natural Areas) (Scotland) Regulations 2002 (SSI 2002/6). [GAEC measure 12]

B3. Take account of 'local environmental factors' before applying nitrogen fertilisers. These include:

  • soil conditions, type and slope

  • climatic conditions, rainfall and irrigation

  • land use and agricultural practice, including crop rotation systems

B4. Apply nitrogen fertilisers in as accurate and uniform a manner as possible.

B5. Produce and implement a farm nutrient plan.

B6. Sow winter cereals in time to establish a suitable crop cover in the autumn to winter period.

B7. Apply fertilisers only when soil conditions are suitable.

B8. Spread organic manures at least 10m away from any clean surface water, field drain or watercourse, and at least 50m from springs, wells or boreholes that supply water for human consumption or use in dairies.

B9. Apply nitrogen fertilisers only when there is a specific crop requirement.

B10. Apply phosphorus fertiliser according to soil analysis and the needs of the crop. Always allow for the nutrients supplied by any organic manures.

B11. Analyse your soil for phosphorus to ensure that excess and unnecessary levels are not building up.

Don'ts

B1. Don't apply chemical fertiliser (containing nitrogen) in a location or manner which makes it likely that the fertiliser will directly enter a watercourse.

B2. Don't apply nitrogen fertilisers in excess of crop requirements, or to any land if the soil is waterlogged.

B3. Don't apply nitrogen fertilisers if the land is flooded, or if the soil has been frozen for 12 hours or longer in the preceding 24 hours.

B4. Don't apply nitrogen fertilisers to any land covered with snow, or to steeply sloping fields.

B5. Don't allow livestock to foul watercourses by having uncontrolled access. Instead, provide water at drinking troughs, wherever possible.

B6. Don't apply P and K chemical fertilisers (i.e. those which don't contain nitrogen) in a location or manner which makes it likely that the fertiliser will directly enter a watercourse.

B7. Don't over-compact soil.

What legislation must be complied with?

6B.1 The Private Water Supplies (Scotland) Regulations 1992 are concerned with the quality of water supplied from private supplies in Scotland for drinking, washing or cooking or for food production purposes. These Regulations establish a maximum admissible nitrate concentration in water of 50 mg/l and are implemented by the local authorities.

6B.2 Farms at which slurry is produced are subject to the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003. Drainage from middens and high-level slatted buildings are included within the definition of slurry, whereas the solid manure itself is not. Such drainage is therefore covered by the Regulations and must be suitably collected and stored prior to land spreading. For new, substantially enlarged or substantially reconstructed slurry storage systems, the Regulations require the provision of adequate storage capacity (for the farm as a whole), taking account of the likely quantities of slurry and of the likely quantities of rainwater. SEPA may accept storage capacity of less than six months, but only where it can be demonstrated by a professionally prepared Farm Waste Management Plan that this will not cause harm to the environment or lead to a significant risk of pollution of controlled waters.

6B.3 It is an offence under environmental legislation to cause or knowingly permit any poisonous, noxious or polluting matter or any solid waste matter to enter any controlled waters. Farmers or their contractors may be liable to prosecution if livestock slurry or manure is allowed to enter a watercourse.

Voluntary measures (all farmers)

Organic manures

6B.4 To help protect the quality of groundwater, organic manures should not be applied within 50 metres of a spring, well or borehole that supplies water for human consumption, or which is to be used in farm dairies. This is a minimum distance and may need to be increased in the case of boreholes depending on local conditions.

Permanent pasture

6B.5 Avoid ploughing up of permanent pastures, if possible, due to the flush of nitrate which can continue for several years after such action. If the permanent pasture is to be cropped or re-seeded, account should be taken of the nitrate release in calculating the fertiliser applications for the subsequent crop. If permanent pasture is to be re-seeded it is important to ensure that a full crop cover is established as quickly as possible, by early October at the latest.

Green cover

6B.6 Early sowing of winter cereals encourages more of the residual nitrate to be utilised by the newly established crops thereby reducing the potential for losses. Winter crops sown in late October/November will have little effect in reducing the amount of nitrate lost in the winter. A better strategy in arable areas, where growth of winter cereals is slow, is to grow spring cereals with the land remaining in stubble in winter as long as possible. This is particularly relevant to the Scottish climate and growing conditions.

6B.7 If possible, a cover or catch crop, such as Italian ryegrass, should be sown in fields that would otherwise be bare over the autumn and winter period.

6B.8 Leave cereal stubbles, straw and non-cereal and vegetable crop residues uncultivated over the winter to minimise nitrate leaching. Run-off from rutted or compacted ground can be a particular problem for some rotations, including potatoes and vegetables. The use of buffer strips can assist in reducing the impacts of soil erosion and nutrient losses.

Grazing

6B.9 Where intensive grazing is practised, up to 90% of the nitrogen is returned to the land as excreta and urine resulting in high soil concentrations of available N. The loss of nitrate from the grassland through leaching may therefore be high, if intensively grazed by cattle throughout the autumn.

6B.10 In order to prevent soil erosion and direct contamination of watercourses, livestock should, where possible, not have direct access to watercourses.

Chemical fertiliser (containing nitrogen)

6B.11 Chemical fertiliser (containing nitrogen) should not be applied to grassland until the spring, close to the time when the nitrogen is needed for grass growth, and only then if soil and weather conditions are suitable. Heavy rainfall immediately following application can result in most of the nitrogen fertiliser being lost through run-off. T-sums, which are usually made available in the farming press, provide a good guide to when nitrogen should be applied to grassland. The system is based on air temperature with the mean temperature from 1 January being added together (ignoring temperatures below 0°C). When the accumulated temperatures reach the sum of 200, this is considered to be the optimum time to apply nitrogen to maximise early grass yields. For arable crops, chemical fertiliser (containing nitrogen) should be applied at the start of periods of rapid crop growth and nitrogen uptake. Fertiliser applications should only be made when soil and weather conditions are suitable.

Soil conditions

6B.12 The risk of run-off and losses of nitrogen is increased in compacted soil. Physical damage to soils also reduces the rate of nitrogen uptake by the crop. This damage can to some extent be avoided by reducing the number of field operations particularly when the soil is vulnerable to damage (e.g. when wet, after frost, etc.). Low-pressure tyres can be a mixed blessing in that they limit compaction but may encourage field access in conditions which are really not suitable.

Fertiliser storage and handling

6B.13 Fertiliser stores should be sited well away from any clean surface water drain, watercourse, spring, well or borehole. Bylaws for the protection of public water supply sources may impose specific restrictions on using or storing fertilisers within a stated distance from the source. Storage containers for liquid fertilisers should be capable of being locked, suitably constructed for the intended purpose, watertight and treated with a protective coating resistant to corrosion from the contents. Although not a legal requirement, it is recommended that these tanks are bunded.

6B.14 Handling procedures for filling stores from road tankers and for transferring liquid fertilisers to the spreader should be such that the risks of accidental spillage are minimised. Tanks should not be overfilled and allowances should be made for expansion of the contents. Operators should be aware of these procedures, of the potential pollution problems arising from spillage, and of the emergency procedures to be followed.

6B.15 Store ammonium nitrate fertiliser securely, where there is no public access (and out of view from roads etc). Ideally, store this fertiliser in a locked building, and carry out regular stock checks. Under the Notification of Installations Handling Hazardous Substances Regulations, farmers should notify the Health and Safety Executive (HSE) if they are handling, or likely to handle or store, 150 tonnes or more of ammonium nitrate fertiliser. Further information about the safe handling and storage of fertiliser is given in HSE publications.

Buffer zones

6B.16 Leave, where possible, uncultivated strips of land adjoining watercourses and other sensitive habitats (e.g. wetlands, botanically rich pastures, etc.). This area can act as a buffer between the land under cultivation and the valuable habitat. Take into account natural heritage and conservation issues.

Phosphorus

6B.17 Phosphorus can contribute to eutrophication of freshwater habitats and is a particular threat to still or slow moving freshwaters. Although treatment works provide the major input in many catchments, agricultural land can also be a significant source of phosphorus input to watercourses.

6B.18 Phosphorus from agriculture can reach watercourses in various forms and by various routes. Their relative importance will depend on the particular catchment. The main losses are:

  • surface run-off, particularly of recently spread animal manures

  • erosion of soil particles

  • particulate and dissolved phosphorus in water flowing from land drains

6B.19 Phosphorus can also be leached to groundwater.

6B.20 You can help to minimise the risk of phosphorus from fertilisers and organic manures reaching a watercourse by following the good practice guidance for nitrate given in the preceding paragraphs of this section.

6B.21 The amount of phosphorus lost by erosion, leaching or drain flow will largely depend on the soil phosphorus level. The higher the soil phosphorus levels, the greater the potential loss. To minimise losses, you should not apply amounts of phosphorus fertiliser in excess of those recommended by an authoritative source. Regular soil sampling and analysis and nutrient budgeting is recommended.

Organic farming

6B.22 While organic farming does not use inorganic fertilisers, there are still risks of nitrate leaching due to organic manure use, grazing and ploughing-in of grass and crop residues. The mandatory measures contained in the NVZ Action Programmes given in paragraphs 6A.8 to 6A.26 must be complied with for organic farming. The further guidance to reduce nitrogen and phosphorus losses given in paragraphs 6B.4 to 6B.21 is also appropriate for organic farming.

General

6B.23 "The 4 Point Plan" provides an easy-to-follow guide to minimising pollution caused by farm run-off. It guides farmers through the steps required to draw up a risk assessment for manures and slurries, promotes dirty/clean water separation, provides advice on water margin management and identifies the nutrient value of slurry and manure (to promote their use as fertilisers). Copies are available from SEERAD Area Offices.

Appendix

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