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Air quality measurements on cracking clay soils (Linked to project WQ0118) - AC0111

The overall objective of this project is to improve our understanding on contrasting cracking clay soils of the interactions that occur between livestock manure multiple pollutant loss processes and pathways to the AIR (i.e ammonia and nitrous oxide) and water (i.e. nitrate-N, ammonium-N, phosphorus, sediment and microbial pathogens) environments.

In the region of 90 million tonnes of farm manures, supplying 450,000 tonnes of nitrogen (N) and 119,000 tonnes of phosphorus (P) are applied to agricultural land in the UK each year. These applications are a valuable source of plant available nutrients, however, they also pose a significant risk of diffuse air and water pollution. There is a recognised need to ensure that manure management strategies that aim to reduce one form of pollution (e.g. nitrate) do not exacerbate losses by another route (e.g. ammonia/nitrous oxide emissions to air, or ammonium-N/phosphorus/faecal indicator organisms - FIOs to water), so called ‘POLLUTION SWAPPING’.

To date, Defra’s work on ‘pollution swapping’ has largely been focused on free-draining soils, reflecting the importance of these soil types above ground water drinking supplies. However, the processes controlling gaseous N emissions to the atmosphere and nutrient /FIO losses to water on clay soils are known to be markedly different from structureless free-draining sandy soils. Moreover, the recent consultation on revisions to the Nitrate Vulnerable Zone-Action Programme (NVZ-AP) in England include a ‘closed-period’ for slurry application on all soil types in late autumn/winter. This will substantially increase the amount of slurry applied in the spring and summer months, which is likely to significantly influence both the amount and timing of nutrient losses to both air and water, and will have an estimated financial impact on the agricultural industry in excess of £500 MILLION.

Replicated field-scale farming system studies will be carried out utilising the Faringdon (Oxon.), ADAS Boxworth (Cambs.) and North Wyke Rowden (Devon) experimental platforms to quantify the impact of contrasting slurry management strategies on diffuse air and water pollution from cracking clay soils. Ammonia volatilisation losses and direct and indirect nitrous oxide emissions will be quantified from selected treatments in Defra Project WQ0118 'Understanding the behaviour of livestock manure multiple pollutants through contrasting cracking clay soils'. At North Wyke Rowden (harvest season 2009), the effects of contrasting cattle slurry application timings on drained and undrained grassland will be studied. At ADAS Boxworth (harvest season 2010), the effects of contrasting slurry types and slurry application timings to arable cropping systems will be studied. At Faringdon (harvest season 2011), the effects of contrasting cattle slurry application timings to winter wheat and grassland will be tested.

In total there will be 18 ammonia and 15 nitrous oxide measurement campaigns. Slurry applications will be made at a target rate of 50m3/ha and will comply with the revised NVZ Action Programme. At each site, the plots will be managed using commercial farm equipment and slurry applications will be made using bandspreaders to enable application to growing crops in spring/summer. Ammonia emissions will be measured for up to 7 days after application, using the micro-meterological mass balance technique with 'shuttle' passive diffusion samplers. Direct nitrous oxide emissions will be measured using the static chamber technique (5 chambers per plot) and measurements will continue for up to 12 months following slurry application, and will total up to 31 individual measurements following slurry application to meet scientific publication and IPCC reporting requirements. Indirect nitrous oxide emissions resulting from the subsequent deposition of emitted ammonia and leached nitrate will be based on the measured ammonia and nitrate leaching losses from the plots, using IPCC default values.

The ammonia volatilisation loss and direct and indirect nitrous oxide emission data collected in this study will be combined with measurements of nitrate, ammonium, phosphorus, FIO and sediment losses from Defra project WQ0118 to quantify the impacts on air and water quality of the contrasting slurry application timings on arable land and grassland. These data will be available to improve and refine field-scale ammonia and nitrous oxide export algorithms underpinning the MANNER-PSM, NARSES, UK_DNDC and N-GAUGE models. In addition, the direct and indirect nitrous oxide emission data will be used to underpin the development of country specific IPCC emission factors.

The results of this study will add value to the data collected in Defra Project WQ0118 and enable ‘win-win’ and ‘pollution swapping’ situations to be quantified for both air and water quality. These data are essential to enhance the scientific evidence base underpining the development of strategies to minimise diffuse pollution of the air and water environments. Such an integrated approach is the only way forward in tackling diffuse-pollution from livestock manures and farming systems to ensure that Defra meets it’s policy objectives of complying with existing and forthcoming Protocols and Directives (e.g. National Emission Ceilings Directive, Gothenburg Potocol, Kyoto Protocol, Nitrates Directive, Water Framework Directive, Bathing Waters and Shellfish Waters Directives, Freshwater Fish Directive etc.), and that the financial burdens placed on the agricultural industry to reduce diffuse pollution can be scientifically justified.
Time-Scale and Cost
From: 2008

To: 2014

Cost: £2,106,302
Contractor / Funded Organisations
Agriculture and Climate Change              
Air Quality              
Climate Change              
Renewable materials              
Sustainable Farming and Food Science