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Agricultural practice and water quality at grassland farms registered for derogation in 2013 : Landbouwpraktijk en waterkwaliteit op landbouwbedrijven aangemeld voor derogatie in 2013

Synopsis

Pursuant to the EU Nitrates Directive, the member states are required to limit the use of livestock manure to a maximum of 170 kg of nitrogen per hectare per year. Dutch farms growing grass on at least 70 per cent of their total agricultural area were allowed to deviate from this requirement under certain conditions, and apply up to 250 kg of nitrogen per hectare in the form of livestock manure (this partial exemption is referred to as 'derogation'). The Netherlands are required to monitor agricultural practices and water quality at 300 farms which have been granted derogation, and to submit an annual report of the results to the EU. LEI Wageningen UR and RIVM will compile this annual report. This study examines farms that registered for derogation in 2013 and shows trends between 2006 and 2014. The report concludes that the average nitrate concentration in groundwater on these farms has stabilized or decreased in this period.

Agricultural practice
This report also shows that, in 2013, derogation farms used on average approximately 4 kg less nitrogen per hectare in the form of livestock manure than the permitted maximum of 250 kg nitrogen per hectare. The quantity of nitrogen that can potentially leach into groundwater as 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 fertilizers) and output (e.g. via milk). On average, the nitrogen soil surplus has not changed substantially during the period studied.

Groundwater quality
In 2013, the average nitrate concentration in groundwater on derogation farms in the Sand Region amounted to 37 milligrams per liter (mg/l) and was therefore below the standard of 50 mg/l. On average, farms in the Clay and Peat Regions had even lower nitrate concentrations (11 and 6 mg/l, respectively). Farms in the Loess Region, showing an average nitrate concentration in groundwater of 56 mg/l, however, exceeded the standard. The difference between the regions is mainly caused by a greater share 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.
 

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