What can I do in the short term?
Cultivate compacted tillage soils
WHY? Cultivation of soils that are compacted will help increase aeration of the soil and the amount of water that can infiltrate into the soil thereby reducing runoff.
HOW? Assess compaction levels on your farm by digging holes. Depending on the depth of compaction cultivate by ploughing, subsoiling or aerating. Carry out cultivation when the soil is dry to minimise further compaction and damage to the soil.
WHAT ARE THE EFFECTS? Alleviating compaction will reduce phosphate and sediment losses in the range of 10-50%. There may also be a small reduction in direct nitrous oxide emissions.
WHAT IS THE INDICATIVE COST? £25/ha based on cultivation cost. It is envisaged that it would be applied to 20% of tillage land area each year. (2011)
Cultivate and drill across the slope
WHY? On fields that are gently or moderately sloping, cultivating and drilling across the slope will reduce surface runoff and where it does occur, slow the movement of soil and sediment.
HOW? If you have gentle and moderate slopes consider cultivating across the slope. However for steeper fields this is not recommended as there is a risk of overturning tractors and may channel surface runoff which can cause erosion.
WHAT ARE THE EFFECTS? The ridges created across slopes provide a barrier to surface runoff. This will mean that phosphate and sediment losses will be reduced in the range of 40-80%.
WHAT IS THE INDICATIVE COST? £10 /ha based on additional time and planning for cultivations. (2011)
Maintain / improve field drainage systems
WHY? Functioning drainage systems allow water to move through the soil profile allowing the soil to be maintained in a well drained condition. This will extend the window of opportunity for machinery operations particularly in the autumn and spring. It will also minimise the risk of compaction and waterlogging and can reduce surface runoff. Poor drainage has a big impact on crop productivity and the management versatility of the land.
HOW? Actively maintain field drainage systems through jetting, reinstallation and moling drains.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be increased by 10-50% (compared with letting drains deteriorate) and as a result of these nitrate losses, ammonium and nitrite losses would also be increased. Direct nitrous oxide emissions would be decreased as the soil will be more aerobic. Phosphate and sediment losses would be increased by up to 10% as a result of greater losses through the drain.
WHAT IS THE INDICATIVE COST? £10/ha based on the need to mole drain 20% of the farm annually. (2011)
WHY? Maintaining field drainage systems and allowing them to function will reduce the risk of waterlogging, soil compaction, poaching and surface runoff.
HOW? Clean out ditches on a regular basis, this may include cutting vegetation in the bottom of the ditch to prevent flooding. It is good practice to also think about maintaining / improving field drainage systems (method above).
WHAT ARE THE EFFECTS? Nitrate leaching losses would be increased by up to 20% (this would also increase ammonium and nitrite losses as a result). Direct nitrous oxide emissions would be decreased as a result of more aerobic soil conditions. As a result of increased drainflow losses, phosphate and sediment losses would be increased by around 10%.
WHAT IS THE INDICATIVE COST? £18/ha based on contractor rates clearing 20% of ditches each year. (2011)
Fertiliser spreader calibration
WHY? Inaccurate fertiliser spreading can result in inconsistent application of fertiliser across the field. Over application can result in increased nitrate leaching losses as well as reduced crop yields through lodging. This is a low cost method that will improve crop growth and reduce diffuse pollution.
HOW? Tray tests are used to determine the co-efficient of variation (CV) and accuracy of fertiliser spreaders. A low CV (less than 10%) ensures fertiliser is spread evenly and all parts of the field receive the recommended rate. Fertiliser spreaders should be checked at least annually and ideally whenever the fertiliser type is changed.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by up to 5% along with associated nitrous oxide emissions.
WHAT IS THE INDICATIVE COST? £200/farm (typology used in the study) based on average contractor rates. (2011)
Use a fertiliser recommendation system
WHY? Use of a fertiliser recommendation system to plan fertiliser applications will reduce the risk of applying more nutrients than the crop needs and will minimise the risk of causing diffuse pollution and air pollution. Maintaining an appropriate balance between different nutrients (N, P and K) is also important to maximise the efficient uptake of all nutrients and reduce environmental losses.
HOW? Use a recommended system (e.g. RB209, PLANET, Tried and Tested) to plan artificial fertiliser applications to all crops, do not exceed recommended rates. Time fertiliser applications to minimise losses and take full account of nutrients in manures.
WHAT ARE THE EFFECTS? Nitrate leaching losses and phosphate losses would be reduced by up to 5%. Carbon dioxide emissions would be reduced by a small amount due to lower fertiliser use and production.
WHAT IS THE INDICATIVE COST? A saving of £10/ha on arable land based on a 5% reduction in fertiliser use. (2011)
Integrate fertiliser and manure nutrient supply
WHY? Studies suggest that farmers do not always make allowances for nutrients supplied in slurries and manures, when they are calculating fertiliser application rates. If allowances are made for these nutrients, in many cases this will result in a reduction in fertiliser inputs meaning reduced economic and environmental costs.
HOW? Use a fertiliser recommendation system (RB209, PLANET, MANNER) to make full allowances of nutrients supplied by organic manures. Use lab analysis to gain a better understanding of nutrient supplied by your home grown manures and slurries and deduct this from crop requirements when calculating artificial fertiliser rates.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by up to 10%, overall manure N use efficiency would be increased and artificial fertiliser N inputs reduced. Phosphate losses could be reduced by up to 10% (from applied fertiliser).
WHAT IS THE INDICATIVE COST? Savings of £30/ha on arable land based on greater allowances being made for manure nutrients and reduction in fertiliser inputs. (2011)
Do not apply manufactured fertiliser to high risk areas
WHY? By not applying fertiliser at any time to areas where it could easily be transferred to watercourses, the risk of nutrient pollution is reduced.
HOW? Don’t apply artificial fertiliser in areas of fields were there is direct access to a watercourse. These may include areas with a high number of open drains or next to ditches. In NVZs a no fertiliser spreading buffer zone of 2m from surface waters is compulsory.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by a small (2%) amount, soluble phosphate losses would be reduced by up to 10%.
WHAT IS THE INDICATIVE COST? £5/ha on arable land based on a small yield reduction as a result of delayed fertiliser applications. (2011)
Avoid spreading manufactured fertiliser to fields at high risk times
WHY? By avoiding fertiliser spreading at high risk times the available N and P for loss in surface runoff or drainflow is reduced. Surface runoff is most likely to occur where there is rainfall on sloping ground, or when soils are wet, frozen or snow covered.
HOW? Don’t spread N fertiliser between September and February when there is little or no crop uptake and there is a high risk of nitrate leaching loss. Closed spreading periods for manufactured fertiliser N already exist in NVZs unless a specific crop requirement can be justified. Make sure you adhere to closed periods if you are in an NVZ.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by up to 5% and phosphate losses would be reduced by up to 10%.
WHAT IS THE INDICATIVE COST? £5/ha on arable land based on a small yield reduction as a result of delayed fertiliser application. (2011)
Do not apply P fertiliser to high P index soils
WHY? Phosphate losses from soil by erosion increases rapidly when soil P Index reaches Index 4 or above.
HOW? Losses can be minimised by maintaining soil P levels at Index 2 or by allowing the P content of high index P soils to run down over time. Sample soils regularly to ascertain what your soil’s P index is. The run down of high soil P reserves is a gradual process; the full benefits will only be achieved in the longer term (more than 10 years).
WHAT ARE THE EFFECTS? Soluble phosphate losses would be reduced by up to 50%, and particulate phosphate losses by up to 30% over the long term.
WHAT IS THE INDICATIVE COST? Cost savings of £3-6/ha based on reductions in P fertiliser on high P index soils which are estimated to be on 10% of farm area. (2011)
Site solid manure field heaps away from watercourses / field drains
WHY? Keeping solid manure heaps away from watercourses and field drains reduces the risk of pollutant losses in surface runoff. This is a legal requirement in NVZ areas.
HOW? Don’t site field heaps within 10m of a watercourse or field drain. Benefits are likely to be greatest on medium / heavy soils where runoff risks are highest and field drains are likely to be present.
WHAT IS THE EFFECT? A small reduction in nitrate leaching losses and phosphate losses.
WHAT IS THE INDICATIVE COST? £1/ha based on additional time needed to plan the siting of manure heaps. (2011)
Manure spreader calibration
WHY? Even application of manures ensures that all parts of the field receive similar amounts of total and crop available nutrients. Over application of N can result in greater potential for leaching losses and higher soil N levels.
HOW? Determine actual rate and evenness of manure applied by the spreader and adjust it to achieve the desired rate.
WHAT IS THE EFFECT? Nitrate leaching losses would be reduced by a small amount. Overall manure N use efficiency would be increased and manufactured fertiliser N inputs reduced. Phosphate losses would be reduced by a small amount from slurry applications.
WHAT IS THE INDICATIVE COST? £350 per farm (type used in the study, 172ha) based on time to assess the evenness of manure spreading and field application rates. (2011)
Do not apply manure to high risk areas
WHY? High risk areas (e.g. next to a watercourse or borehole) are able to rapidly transport manure borne pollutants to watercourses.
HOW? Do not apply manure to field areas that are high risk e.g. directly adjacent to a watercourse, borehole, road culvert, shallow soils over fissured rock, or areas with a dense network or open drains or spring lines. These areas have a high degree of hydrological connectivity between the field and the watercourse. Do not spread slurry or solid manure within 10m of a watercourse or 50m of a spring, well or borehole. This is mandatory in NVZ areas.
WHAT IS THE EFFECT? Nitrate leaching losses would be reduced by a small amount (1%) and phosphate losses by around 2%.
WHAT IS THE INDICATIVE COST? £1/ha based on additional management time to plan manure spreading activities. (2011)
Do not spread slurry or poultry manure at high risk times
WHY? The high readily available N content in slurry and poultry manure means that if it is applied at times when surface runoff or flow into drains is likely, there will be a high pollution risk. Avoiding application in autumn and early winter will help reduce over winter Nitrate leaching losses.
HOW? Don’t apply slurry or poultry manure to fields where there is a high risk or surface runoff (when soils are wet / frozen or heavy rain is expected) or late in the growing season when there is no crop to utilise the added nitrogen. Applications later in winter and spring present less of a risk as there is less opportunity for nitrate leaching before crop growth commences.
WHAT IS THE EFFECT? Nitrate leaching losses would be reduced by up to 20% of total manure N applied and associated indirect nitrous oxide emissions. Ammonia emissions would be increased by a small amount as a result of more slurry being applied to grassland soils in summer. Overall manure N use efficiency would be increased and manufactured fertiliser N use reduced. Phosphate losses would be reduced by up to 50%.
WHAT IS THE INDICATIVE COST? £1/ha based on additional time to plan manure management activities. (2011)
Do not spread FYM to fields at high risk times
WHY? Risk of pollution is increased when solid manures are spread under conditions where heavy rain post application could transport nutrients and manure borne pollutants to surface water systems.
HOW? Avoid spreading straw based FYM to fields at times with a high risk of surface runoff. High risk times will be most frequent in winter where soils are wet, particularly in high rainfall areas.
WHAT IS THE EFFECT? Nitrate leaching losses will be reduced by a small amount (up to 5%) along with associated in direct nitrous oxide emissions. Overall crop N use efficiency would be increased (by a small amount) and manufactured fertiliser N use reduced. Phosphate losses in run off would be reduced by a small amount.
WHAT IS THE INDICATIVE COST? £1/ha based on additional management time to plan FYM spreading applications. (2011)
Incorporate manure into the soil
WHY? Rapid soil incorporation of manure can reduce pollutant losses in runoff and also reduce the exposed surface area of manure from which ammonia emissions can occur. Incorporation within 24hrs is mandatory in NVZ areas.
HOW? Incorporate rapidly using a plough, discs or tines, ideally within 6 hours of spreading for slurry, and 24hrs for solid manures. Ammonia emission reductions depend on the time period between manure application and soil incorporation, and on cultivation technique employed. For best results incorporate as soon as possible.
WHAT IS THE EFFECT? Ammonia emissions would be reduced by around 60% where soil incorporation by ploughing occurred 6 hours after slurry application, 40% with FYM and 70% with poultry manure which was incorporated by ploughing after 24hrs. Nitrate leaching losses and nitrous oxide emissions would be increased, however overall manure N use efficiency would be increased and fertiliser N additions would be reduced. Phosphate losses in surface runoff would be reduced.
WHAT IS THE INDICATIVE COST? £45/ha based on additional cultivation. (2011)
FARM INFRASTRUCTURE CHANGES
Resite gateways away from high risk areas
WHY? Many fields have gateways located at the bottom of the slope and near a watercourse. Gateways incur increased activity, and re-positioning gateways away from watercourses would decrease the potential for sediment and nutrient losses.
HOW? Move gates away from high risk surface runoff areas to lower risk areas on upper slopes.
WHAT IS THE EFFECT? Nitrate leaching losses would be reduced by a small amount (1%) and phosphate losses reduced by 10%.
WHAT IS THE INDICATIVE COST? £2-4/ha based on a removal of gateways and replacement with back fenced hedging on around 30% of fields. (2011)
What can I do in the medium term?
Cultivate land for crops in spring rather than autumn.
WHY? Autumn cultivation of land stimulates the mineralisation of N from organic matter at a time when there is little N uptake by the crop. By cultivating in spring the N will be available for uptake by the spring crops and there will be less risk of nutrient losses in surface runoff.
HOW? Cultivate arable land for spring crops in spring rather than the autumn and plough out grassland in spring. This method is mainly applicable to cultivation on light and medium soils prior to drilling spring crops or where there is a switch from winter to spring cereal cropping.
WHAT IS THE EFFECT? Nitrate leaching losses and phosphate losses would be reduced by 20-50%.
WHAT IS THE INDICATIVE COST? £100/ha based on a 25% reduction in spring combinable crop yields. (2011)
Leave autumn seedbeds rough
WHY? Leaving the autumn seedbed rough encourages surface water infiltration and reduces the risk of surface runoff.
HOW? Avoid creating a fine autumn seedbed that will slump. Reducing the number of cultivations, particularly from powered cultivation equipment will reduce the risk of surface runoff by preventing soil capping and enhancing infiltration rates. A rough seedbed also helps to break up any surface flow that is generated reducing the erosion risk.
WHAT ARE THE EFFECTS? There is limited field evidence that phosphate losses can be reduced by up to 20%. CO2 emissions would be reduced by a small amount from less cultivation.
WHAT IS THE INDICATIVE COST? £40/ha based on poorer crop establishment, and additional costs for pest and weed control. (2011)
Manage over winter tramlines
WHY? Tramlines can result in the channelling of surface water and the development of gullies on sloping erosion susceptible soils. Tramline management to improve water infiltration can help to reduce runoff and sediment loss.
HOW? Avoid the use of over winter tramlines where possible. If tramlines are present, then use tines to disrupt the tramlines to encourage infiltration of water into the soil. Use low ground pressure tyres on vehicles to help limit soil compaction.
WHAT ARE THE EFFECTS? There is limited field evidence that disrupting the tramlines can reduce phosphate losses by 30-50% on winter cereal land.
WHAT IS THE INDICATIVE COST? £10/ha based on a light cultivation to remove compaction and channelling created by tramlines. (2011)
Maintain and enhance soil organic matter levels
WHY? Low soil organic matter levels can give rise to soil structural problems and increase the risk of soil erosion. Maintaining and enhancing soil organic matter level helps to reduce the risks of surface runoff and erosion and improves the water holding capacity of the soil.
HOW? Regular additions of organic materials including livestock manures, biosolids, compost, digestate and ploughing in crop residues and stubbles will help boost organic matter levels in the soil. To minimise soil P accumulation and associated soluble P losses and mineral N levels in the soil, it is important to reduce fertiliser inputs to take account of the nutrients in organic matter.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be increased, especially when manures are applied in autumn (up to 20% of total N applied). Nitrous oxide and ammonia emissions would also be increased. Manufactured fertiliser N use would be reduced. Phosphate and sediment losses would be reduced long term but may be increased after applications of manures.
WHAT WILL IT COST? A saving of £170 per ha based on savings in fertiliser costs. This calculation involves impoting the organic matter and the receiving farm paying transport costs for a distance of 3km. If the manure has to be transported 10km the cost is £20 per ha. (2011)
Establish in-field grass buffer strips on tillage land
WHY? Buffer strips can reduce phosphate and sediment losses by slowing surface runoff and intercepting sediment.
HOW? Designate a strip ideally located along the land contour, on upper slopes or in valley bottoms to reduce and slow down surface runoff. They are particularly suitable for fields with long slopes where high volumes of surface runoff can be generated.
WHAT ARE THE EFFECTS? Reductions in nitrate leaching losses from the strip area would be similar to ungrazed grassland (about 90%). As artificial N is not applied to the buffer strips there would be a reduction in nitrous oxide emissions as well as ammonium and nitrate losses. Phosphate and sediment losses would be in the range 20-80%.
WHAT IS THE INDICATIVE COST? £800 per farm (based on farm typology used in study) calculated on crop yield losses and topping management with buffer strips occupying 1% of tillage land. (2011)
Establish riparian buffer strips
WHY? The buffer strip will act as a natural buffer feature to reduce the transfer of pollutants from agricultural land to water.
HOW? Establish vegetated and unfertilised grass / woodland buffer strips alongside watercourses. Ideally these strips will be free draining and have a good surface condition able to intercept surface runoff. These strips are particularly suitable for low lying and gently undulating landscapes where the topography does not concentrate the flow into channels.
WHAT ARE THE EFFECTS? Reductions in nitrate leaching losses from the strip area would be similar to ungrazed grassland (about 90%). As artificial N is not applied to the buffer strips there would be a reduction in nitrous oxide emissions, as well as ammonium and nitrite losses. Phosphate losses and sediment losses would be in the region 20-80%.
WHAT IS THE INDICATIVE COST? £2,400 per farm (based on farm typology used in the study) based on a loss of gross margin on 3% of the farmed area (172ha) plus establishment and topping and fencing costs in grassland fields. (2011)
Replace urea fertiliser with another nitrogen form
WHY? Urea and urea based fertilisers are associated with higher ammonia emissions than other forms of fertiliser N.
HOW? Replace urea or urea based fertiliser with another form possibly ammonium nitrate, ammonium phosphate or ammonium sulphate.
WHAT ARE THE EFFECTS? Nitrate leaching losses are likely to be increased by up to 5% and associated nitrous oxide emissions by around 20% as more mineral N is retained in the soil through reduced ammonia emissions to air. Ammonia and nitrite losses to water may be decreased by a small amount. Overall crop N use efficiency would be increased.
WHAT IS THE INDICATIVE COST? A cost saving of £5/ha as although urea is cheaper than ammonium nitrate per unit of N, higher ammonia losses from urea would result in a small yield penalty when compared with ammonium nitrate. (2011)
Incorporate a urease inhibitor with urea fertiliser
WHY? Urease inhibitors delay the conversion of urea to ammonium carbonate and this delay allows the urea fertiliser time to be washed into the soil, thus reducing the pH rise around the urea fertiliser. This means that ammonia emissions would be reduced.
HOW? Incorporate an inhibitor into solid urea or liquid urea / ammonium nitrate (UAN) solutions. This could be nBTPT which has been shown in trials to reduce ammonia emissions from solid urea by on average 70% and from liquid UAN by 40%.
WHAT ARE THE EFFECTS? Ammonia emissions would be reduced by around 70% from solid urea and 40% for UAN. As more mineral N is retained in the soil, nitrate leaching losses to water and nitrous oxide emissions to air would be increased by a small amount. Crop N use efficiency would also increase.
WHAT IS THE INDICATIVE COST? There is thought to be no net cost, as the costs were based on the inhibitor being added to the fertiliser at source and that the increased fertiliser costs were balanced by increased crop yields. (2011)
Use slurry band spreading application techniques
WHY? Ammonia volatilisation occurs from the surface of the slurry. Reducing the overall surface area of the slurry by applying the slurry in narrow bands will lead to a reduction in ammonia emissions. Applying slurry beneath the crop canopy avoids contamination of the crop with slurry and reduces odour. Using these techniques delivers a more uniform slurry application.
HOW? Instead of using a splash plate slurry tanker, consider the use of a trailing hose, trailing shoe, or a band spreader. Band spreading is generally a slower operation than splash plate tankers so labour requirements need to be considered.
WHAT ARE THE EFFECTS? Ammonia emissions efficiencies for slurry spreading are typically 30% for trailing hose and trailing shoe when the grass is short and 60% for trailing shoe when the grass is long (>10cm). Reducing ammonia emissions from applied slurry will increase nitrate leaching losses and nitrous oxide emissions. Overall crop N use efficiency would be increased and artificial N fertiliser use reduced. Odour will also be reduced from these methods of application.
WHAT IS THE INDICATIVE COST? £1/m3 of slurry based on contractor costs. (2011)
Use slurry injection application techniques
WHY? Ammonia volatilisation occurs from the surface of the slurry. By reducing the surface area through injecting the slurry, the emissions of ammonia will be greatly reduced.
HOW? Injection can be carried out through shallow injection which places the slurry in narrow surface slots or deep injection where the slurry is placed into the soil at a greater depth behind cultivation tines. Shallow injection is most suited to grassland, whereas deep injection is most suited to arable land prior to crop establishment.
WHAT ARE THE EFFECTS? Deep injection would achieve a 90% reduction and shallow injection a 70% reduction in ammonia emissions. Reducing these ammonia emissions will increase the potential for nitrate leaching losses and nitrous oxide emissions, however overall crop N use efficiency would be increased and the need for artificial fertiliser reduced.
WHAT IS THE INDICATIVE COST? £1.50 /m3 of slurry based on contractor costs. (2011)
FARM INFRASTRUCTURE CHANGES
Farm Track Management
WHY? Farm tracks can become conduits for nutrient and manure borne pollutants to be lost through surface runoff. On sloping land in wet conditions these tracks can become degraded quickly and form channels that will take large volumes of runoff.
HOW? Create well drained tracks with appropriate surfaces, avoiding routes with steep slopes, and avoiding directing runoff towards bare soil, roads or watercourses. Manage your tracks by improving track surfaces and repair damage promptly, and provide good drainage and divert runoff to adjacent grassed areas, soakaways or swales.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by a very small (1%) amount and phosphate and sediment losses by a small (2%) amount, manure borne pollutants would be reduced by a small amount.
WHAT IS THE INDICATIVE COST? £1-3/ha based on digging out a soakaway and installing drains across farm tracks, plus maintenance and clearing out every 4 years. (2011)
What can I do in the long term?
Adopt reduced cultivation systems
WHY? Reduced or no till cultivations rather than ploughing can retain the soil surface organic matter and preserve good soil structure with the resulting soil conditions improving water infiltration rates thereby reducing loss risks of phosphate and sediment.
HOW? Reduce cultivations using discs or tines to cultivate the soil surface as the primary cultivation in seedbed preparation (typically at 10-15cm cultivation depth) Consider direct drilling or broadcasting of seed. It is most common on medium and heavy soils and is less likely to be adopted in wetter parts of the country.
WHAT ARE THE EFFECTS? Nitrate leaching losses can be reduced by up to 20%, with indirect nitrous oxide emissions reduced as well. There is some evidence of increased direct nitrous oxide emissions. Phosphate and sediment loss reductions can be up to 60% on medium and heavy soils and up to 90% on light soils. C02 emissions would be reduced as a result of lower power requirements of reduced and no till management systems. Soil carbon storage would be increased by a small amount.
WHAT IS THE INDICATIVE COST? A saving of £40 per ha based on selling most cultivation equipment and using a contractor. (2011)
Use plants with improved nitrogen use efficiency
WHY? During the growing period the efficiency of fertiliser nitrogen uptake by the plant varies quite widely according to site conditions, soil N and plant physiology. If the plant can be made to be able to use more of the soil N, there would be expected reduced emissions of N to water and the air. Improving N use efficiency could potentially reduce fertiliser N additions.
HOW? Develop new plant varieties with improved genetic traits for the capture of soil N.
WHAT ARE THE EFFECTS? Nitrate leaching losses, ammonia emission and nitrous oxide emissions would be reduced by up to 10%. A small reduction in CO2 emissions would be experienced due to lower fertiliser N use.
WHAT IS THE INDICATIVE COST? A saving of £20/ha based on reduced fertiliser N inputs of 10% for the same amount of crop production. (2011)
Reduce manufactured fertiliser application rates
WHY? Limiting the amount of N fertiliser that is available to crops will reduce the quantity of nitrate left in the soil post harvest. Limiting phosphate fertiliser will, in the short term reduce the amount of soluble P lost, and in the long term will reduce the amount at risk of loss as particulate P.
HOW? Reduce the amount of manufactured N and P fertiliser applied to crops below the economic optimum rate. This would have a significant impact on crop yields (other than legumes).
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by up to 10% (from a 20% reduction in N fertiliser rates) as well as reductions in nitrous oxide and ammonia emissions. Phosphate loses would be reduced by up to 10%, plus longer term reduction through reduced soil P status.
WHAT IS THE INDICATIVE COST? A reduction in gross margin at a cost of £13,000 on the farm typology used in this study. (2011)
Use nitrification inhibitors
WHY? Nitrification inhibitors are chemicals that slow the rate of conversion of ammonium to nitrate, so that nitrate is formed at a rate that is in better synchrony with crop demand (i.e. slow release) and will thereby increase N use efficiency and reduce nitrous oxide emissions and nitrate leaching losses.
HOW? Add nitrification inhibitors to applied artificial fertilisers, organic manures and grazed pastures or to grazing stock.
WHAT ARE THE EFFECTS? Nitrate leaching losses of up to 35%, and direct nitrous oxide emissions of up to 70%. Ammonia emissions to water and air may be increased by a small amount. There is ongoing Defra research into the potential of nitrification inhibitors to reduce emissions.
WHAT IS THE INDICATIVE COST? £20/ha based on purchase costs. (2011)
FARM INFRASTRUCTURE CHANGES
Establish new hedges
WHY? Increasing the number of hedgerows can help to reduce sediment and associated nutrient losses by trapping and lowering surface runoff volumes. Hedges can also help to protect soils from wind erosion.
HOW? Plant new hedges along fence lines and use them to break up the hydrological connectivity of the landscape.
WHAT ARE THE EFFECTS? Nitrate leaching losses and nitrous oxide emissions would be reduced by a small (1%) amount, phosphate and sediment losses would be reduced by up to 20%.
WHAT IS THE INDICATIVE COST? £25-70/ha based on new hedge establishment, installing new gateways, and back fencing. (2011)
Establish and maintain artificial wetlands
WHY? Constructed wetlands can be used for the treatment of lightly contaminated runoff from farm hard standing areas and to intercept runoff water from a field or group of fields. They can trap sediment and reduce pollutant loads in water.
HOW? Construct or establish wetlands with fences and channels that will be sufficient to capture runoff and sediment from a field group or hard standing.
WHAT ARE THE EFFECTS? Nitrate losses could be reduced by 20%; however nitrous oxide emissions from the wetland may be increased. Phosphate losses would be reduced by up to 80% from arable fields. FIO losses would be reduced by up to 90%, methane and CO2 emissions are likely to increase.
WHAT IS THE INDICATIVE COST? £15/ha of arable land, based on a wetland system (covering 0.25% of arable area) and associated crop production losses. (2011)
LAND USE CHANGE
Convert arable land to unfertilised and ungrazed grass
WHY? There are only small losses of nitrates in drainage waters from grasslands when compared with arable land. The permanent vegetation cover minimises the erosion of soil particles and phosphates in surface runoff.
HOW? Change the land use from arable cropping to unfertilised grassland (without livestock) and associated manure inputs.
WHAT ARE THE EFFECTS? Conversion to ungrazed grasslands would reduce nitrate leaching losses by 90%. Nitrous oxide and ammonia emissions would be reduced by around 90%. Phosphate and sediment losses in runoff would be reduced by about 50%.
WHAT IS THE INDICATIVE COST? £100/ha based on a reduction in cropped area of 10% of arable land. (2011)
Arable reversion to low fertiliser input extensive grazing
WHY? N uptake by permanent grassland and immobilising N into accumulating soil organic matter provides a long term sink for N. There are only small losses of nitrate in drainage waters from arable reversion grasslands. The permanent vegetation cover minimised the erosion of soil particles and loss of associated P in runoff.
HOW? Change the land use from arable cropping to permanent grassland with a low stocking rate and low fertiliser inputs.
WHAT ARE THE EFFECTS? Conversion to extensive grazed grass would reduce nitrate leaching losses by around 80-90%. Ammonia and nitrite losses to water would also be reduced. Ammonia emissions from excreta in the field and handled manures would be increased. Phosphate losses would be reduced by around 50%. There would be a reduction in energy use and an increase in carbon storage in the grassland soils.
WHAT IS THE INDICATIVE COST? £100/ha based on the arable reversion to lowland grazing. (2011)
Convert arable / grassland to permanent woodlands
WHY? There are only small losses of nitrate in drainage waters from permanent woodlands and the permanent cover provided by leaf litter mulch and vegetation minimises the erosion of soil particles and loss of phosphate in surface runoff.
HOW? Change the land use from agricultural land to woodland. This method is more applicable to marginal arable land with a high erosion risk and / or close to surface waters. This is an extreme change in land use and is likely to be suitable for areas where converted land would have amenity and conservation value.
WHAT ARE THE EFFECTS? Conversion to woodland would reduce nitrate leaching losses by around 90%. Nitrous oxide and ammonia emissions would be reduced by around 90% as no fertiliser N would be applied. Phosphate losses would be expected to be reduced by around 50% provided best management practices were adopted. Converting to permanent woodland would increase soil carbon storage.
WHAT IS THE INDICATIVE COST? £150/ha based on a whole life cycle cost / income over 75 years. (2011)
Convert land to biomass cropping
WHY? Cultivation of arable land stimulates the mineralisation of organic matter, the release of soil N and carbon. Following establishment of perennial biomass crops, soils are not cultivated annually, reducing nitrate leaching losses. Lower levels of fertiliser N are used compared with arable crops, which reduces nitrate leaching losses.
HOW? Grow perennial biomass crops for example willow, poplar, and miscanthus to displace fossil fuel use, either through direct combustion or through bio fuel generation.
WHAT ARE THE EFFECTS? A reduction in nitrate leaching losses, ammonia emissions and nitrous oxide emissions of up to 50%. Phosphate losses in surface runoff can be reduced by up to 50% provided best soil management practices were adopted. Increased soil carbon storage would be in the range 1.9 to 7.0t CO2e/ha/yr.
WHAT IS THE INDICATIVE COST? A saving of £10/ha based on planting 25% of farmland area and no planting grants. (2011)
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