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Management of livestock manures to meet Nitrate Directive requirements - WT1006

Description
Implementation of the EC Nitrates Directive requires a 4-yearly review followed by implementation of an agreed Nitrates Action Programme (NAP). The next review is now due and will need evidence-based proposals for a revised NAP for discussion with industry stakeholders and the Commission, followed by implementation due in January 2013. During the last review, discussions with the industry and notably the Commission, highlighted specific topics where scientific evidence was weak. This caused some difficulties in reaching agreement between the Commission and Defra, which was only achieved by agreeing to a review of the scientific evidence on these topics, and new research undertaken where necessary to support any changes to the next NAP. The following studies are needed to provide a robust evidence base and recommendations to inform the review of the current NAP, to underpin proposals for discussion with stakeholders and the Commission, and to avoid the risk of infraction.

1. Pollution risk from storage of solid manures in temporary (up to 12 months) field heaps
Large quantities of solid manure (e.g. straw based FYM, poultry manure) are stored in field heaps in England and Wales, especially in arable crop rotations on heavy soils when autumn stubbles provide the only suitable land application window. The current NAP contains rules (Defra 2009a) that restrict the location of temporary field heaps. Existing UK information indicates that total N losses in leachate from solid manures are low. However, such losses have a high pollution potential in terms of biological oxygen demand (BOD), ammonium-N, etc. The temporary field storage of solid manures is an important farm practice which, if disallowed, would seriously impact farm practices and result in additional storage costs. Defra project WA0656 estimated that if all solid manures (around 30 mt/year) had to be stored on an impermeable base, this would cost £845 million in capital spend. The Commission would prefer all solid manure to be stored on an impermeable base and/or tougher restrictions to be placed on the siting of field heaps. They indicated that they would like to see further evidence to show the pollution risk associated with the practice, and have told DARD (Northern Ireland) that Britain will be carrying out further research.

2. Assessment of manure N availability coefficients
The current NAP requires farmers to allow for the crop available nitrogen content of organic manures, including the use of minimum manure N availability coefficients for livestock manures (Defra 2009b). Although the regulations have set these minima (which increase in January 2012), the Commission only agreed the British position on the condition that further research was undertaken to determine if higher coefficients might be included in a future NAP. The Commission wanted higher minima, similar to those established in some other Member States. The Commission see these figures as a means of driving improvements in farm practices that will lead to greater efficiency in on-farm nitrogen use.
Objective
The project work will be divided into the following Work Packages (WP).


1. To review existing scientific evidence and make recommendations for the development of proposals for the next Nitrates Action Programme (NAP)
• Pollutant losses from solid manures stored in temporary field heaps
• Minimum livestock manure N availability coefficients
2. To collate and provide scientific evidence and other knowledge to the Defra Nitrates team that will help to underpin the review of the current NAP and development of the next NAP.


WP1. Review and recommendations of pollutant losses from solid manures stored in temporary field heaps (Leader: John Williams)
Large quantities of solid manure (e.g. straw based FYM, poultry manure) are stored in field heaps in England and Wales. Common arable crop rotations of winter wheat followed by oilseed rape on the heavy soils that predominate in England and Wales, leave only a month or so for applying solid manures to stubbles in August/September. It is impractical to apply such manures to growing crops at other times of the year without causing smothering and/or creating soil compaction. Opportunities for more frequent applications occur with spring-sown crops and with grassland (including re-seeding), but having one general rule provides flexibility and avoids confusion. Twelve months temporary field storage of solid manure is allowed under the rules that implement the IPPC Directive for large pig and poultry farms. Existing UK information indicates that total N losses in leachate from solid manures are low. However, such losses have a high pollution potential in terms of biological oxygen demand (BOD), ammonium-N, etc. The temporary field storage of solid manures is an important farm practice which, if disallowed, would have very significant impact on farm practices and additional storage costs. Defra project WA0656 estimated that if all solid manures (around 30 mt/year) had to be stored on an impermeable base, this would cost £845 million in capital spend.

The Commission, however, would prefer all solid manure to be stored on an impermeable base or, as a minimum, for tougher restrictions to be placed on the siting of field heaps (in particular, for a shorter period than 12 months, and located more than 10m from surface water). They indicated that, as part of the discussions for the next NAP, they would like to see further evidence to show the pollution risk associated with the practice. Additionally, the Commission has told DARD (Northern Ireland) that Britain will be carrying out research to identify the pollution risk from storing poultry manure in temporary field heaps. The current NAP contains the following rules which restrict the location of field heaps to sites where the risk of pollutant losses to the environment are minimised.
• Field heaps must not be located:
o within 10m of a surface water or land drain;
o within 50m of a spring, well or borehole;
o on land likely to become waterlogged;
o on land likely to flood; or
o in any single position for more than 12 successive months.
• Poultry manure without bedding/litter which is stored in a field heap must be covered with an impermeable sheet (Chadwick, 2002, Sagoo, 2004).

The proposed work will:
• Review the current evidence base to establish concentrations of the main potential pollutants (nitrate, ammonium, phosphorus, organic matter/BOD and microbial pathogens) from solid manure stores and identify the factors that influence the nature and quantity of leachate produced. The study will review data from existing and previous Defra-funded projects (e.g. WA0716, WA0712, WQ0111, NIT18) and will assess the impact of factors including manure type, manure dry matter content, initial nutrient content, heap temperature, rainfall during storage, length of storage period etc. on the quality and quantity of leachate produced. Leachate loss patterns and how nutrient concentrations and volumes produced change with time will be reviewed, so that the potential risks of groundwater and surface water pollution from temporary field heaps can be assessed.
• Assess the losses of potential pollutants from field heaps located in accordance with (a) the current rules, and (b) more stringent rules (e.g. shorter storage periods, located further from watercourses).
• Review rules and advice in other MSs to minimise pollutant losses from temporary field heaps of solid manures.
• Identify gaps in knowledge gaps that require further investigation.
• The report will provide recommendations on whether to maintain or amend the current restrictions on the siting of field heaps, supported by robust evidence and clear arguments that can be presented to the Commission and stakeholders.
Defra projects:
WA0716 - Management techniques to minimise ammonia emissions from solid manures.
WA0712 - Management techniques to minimise ammonia emissions during storage and land spreading of poultry manures.
WQ0111 - Faecal indicator organism losses from farming systems.
NIT18 - Use of the NIT18 infrastructure for multi-pollutant monitoring.

WP2. Review and make recommendations for minimum livestock manure N efficiency coefficients (Leader: Fiona Nicholson)
A key element of the current NAP requires farmers to allow for the crop available nitrogen content of organic manures, including the use of minimum manure N availability coefficients for livestock manures. The following standard coefficients for crop available N (% of total N content) from livestock manure have been set. Farmers must use these percentages when calculating how much of the total nitrogen content from livestock manure applied to their land is available for crop uptake in the season following application (i.e. for the next crop grown).

Manure type Crop available N
(% of total N applied)
until 1st January 2012 Crop available N
(% of total N applied)
from 1st January 2012
Cattle slurry 20 35
Pig slurry 25 45
Poultry manure 20 30
Other livestock manures 10 10

Although the Nitrate Pollution Prevention Regulations 2008 has set these minimum manure N coefficients which will increase in January 2012 (Defra 2009b), the Commission only agreed the British position on the condition that further research was undertaken to determine if higher manure N coefficients might be included in future NAPs. During negotiations with the European Commission a particularly contentious issue was at what level the crop available N percentages should be established. The Commission wanted higher percentages similar to those established in some other Member States, and for a wider range of organic manures. The Commission see these figures as a means of driving improvements in farm practices that will lead to greater efficiency in on-farm nitrogen use.

The proposed work will:
• Review the existing evidence base and develop a robust methodology for identifying the manure N efficiency coefficients that are achievable for different types of livestock manure under different environmental conditions and manure management practices. ADAS holds a large database of manure N efficiency coefficients on arable and grassland crops exists from experiments undertaken during the last 20 years (over 200 site years). This database needs to be updated with data from recent projects (e.g. ES0115, ES0116, NT2006).
• Review the coefficients that have been established in other Member States, and how MSs have supported farmers to adjust their management practices to achieve these. Attendance by ADAS at the EC workshop on 19-20 November will provide an excellent opportunity to confirm existing and new information that is applicable in other MSs.
• Consider the environmental impacts of manure N coefficients for potential adoption in the next Nitrate Action Programme.
• Identify what manure management practices are necessary to achieve different manure N coefficients and what actions Government could take to support achievement of these.
• Identify gaps in information and the need for further field-based or other research.
• The report will make clear recommendations for minimum manure N efficiency coefficients of different livestock manures for potential adoption in the next NAP. The recommendations will be supported by robust evidence and clear arguments that can be presented to the Commission and stakeholders. Recommendations will be made for further R&D.
Defra projects:
ES0115 - Optimising slurry application timings to minimise nitrogen losses (OPTI-N).
ES0116 - Field work to validate the manure incorporation volatilization system (MAVIS).
NT2006 - Manure analysis database (MANDE).


Scientific and other technical knowledge from this project and other NVZ-related work will be provided to the Defra Nitrates team to meet agreed requirements associated with review of the NAP. The budget for this work is £20,000 which will be drawn down in agreement with the Defra Nitrates team and the grade/time used of ADAS consultants involved in the work.


Project Management
The project will be managed and co-ordinated by Peter Dampney, Principal Scientist, ADAS Boxworth who will be the main point of contact and interact with the Defra Nitrates team as appropriate.
Time-Scale and Cost
From: 2009

To: 2010

Cost: £87,560
Contractor / Funded Organisations
ADAS UK Ltd.
Keywords