Managing Nitrogen and Phosphorus in Agriculture: A Catchment Evaluation of Mandatory Environmental Measures in Ireland.

In Ireland agriculture accounts for approximately 8% of GDP and is therefore an important national industry. The main agricultural enterprises are grassland based dairy and drystock, and tillage for cereals and potatoes. The impact of on farm activities on the environment, including water quality will have to be managed under the European Union Water Framework Directive and Nitrates Directives. Farmers are now bound by regulations (Statutory Instrument 101 of 2009) governing the application, storage and management of nitrogen (N) and phosphorus (P) on farms. These include:
·        An upper limit for livestock manure loading of 170 kg ha^-1 organic N each year
·        Over-winter manure storage requirements and periods during which application of manures and chemical fertilizers are prohibited.
·        Nutrients supply (quantity and timing) must match crop requirements.
·        Buffer zones are required between field margins and water courses when applying organic or chemical fertilizers.
·        Establishment and maintenance of green cover on arable farms during winter.

 Teagasc, the Irish Agriculture and Food Development Authority, is undertaking an Agricultural Catchments Programme to monitor the effectiveness of these measures with respect to water quality.
Seven headwater catchments ranging from 5-12 km² have been selected, representing the main Irish farming systems, ranges in agricultural intensities, soil types and vulnerabilities to N and P transfer to ground and surface waters. The research being conducted encompasses catchment scale audits on nutrient sources and mass flux delivery to streams, assessment of farm nutrient management practices over several years and demonstrative studies of the pathways of nutrient flows from source to catchment outlet. The Agricultural Catchments Programme aims to generate knowledge and evaluate solutions to protect water resources from N and P transfers while maintaining the productivity of Irish agricultural systems.