Agricultural practices and water quality on farms registered for derogation in 2012
Landbouwpraktijk en waterkwaliteit op landbouwbedrijven aangemeld voor derogatie in 2012
08 July 2014, PDF |
150 pages |
Hooijboer AEJ, de Koeijer TJ, van den Ham A, Boumans LJM, Prins H, Daatselaar CHG, Buis E
RIVM Report 680717038
The EU Nitrates Directive obligates member states to limit the use of livestock manure to a maximum of 170 kg of nitrogen per hectare per year. Dutch farms cultivating at least 70 percent of their total area as grassland were in 2012 allowed to deviate from this requirement under certain conditions, and apply up to 250 kg of nitrogen per hectare (this partial exemption is referred to as 'derogation'). The Netherlands is obligated to monitor agricultural practices and water quality at 300 farms to which derogation has been granted, and to submit an annual report on the results to the EU. This study examines farms that registered for derogation in 2012, and concludes that the average nitrate concentration in groundwater on these farms decreased between 2007 and 2013. This report was prepared by the National Institute for Public Health and the Environment (RIVM) in collaboration with LEI Wageningen UR (LEI). Agricultural practices The report also shows that, on average, derogation farms in 2012 used approx. 11 kg less nitrogen in livestock manure than the prescribed maximum of 250 kg of nitrogen per hectare. The quantity of nitrogen that can potentially leach into the groundwater in the form of nitrate is partly determined by the nitrogen soil surplus. This surplus is defined as the difference between nitrogen input (e.g. in the form of fertilisers) and nitrogen output (e.g. via milk). On average, the nitrogen soil surplus has not changed substantially between 2006 and 2012. Groundwater quality In 2012, the average groundwater nitrate concentration on derogation farms in the Sand Region amounted to 36 milligrammes per litre (mg/l) and was therefore below the nitrate standard of 50 mg/l. On average, farms in the Clay and Peat Regions had even lower nitrate concentrations (10 and 4 mg/l, respectively). With an average groundwater nitrate concentration of 55 mg/l, only derogation farms in the Loess Region exceed the standard. The difference between the regions is mainly caused by a higher percentage of soils prone to nitrogen leaching in the Sand and Loess Regions. Less denitrification occurs on these soils, and more nitrate can therefore leach into the groundwater.