Monitoring networks and modelling systems for assessing effectiveness of the EU Nitrates Directive Action Programmes: Approach by the Walloon Region (Belgium)

Wallonia (Southern Region of Belgium) has implemented the Nitrates Directive by designating four vulnerable zones (now 42% of the territory) and introducing a first Action programme at the start of November 2002 and a second one in 2007.
The Action programmes entail various means of reducing the risks of the pollution of water by nitrate: (a) struggle against nitrate losses in fields using a range of good agricultural practices, including certain restrictions on the use of fertilisers (quantities, spreading periods, soil conditions, etc.), (b) keeping a balance on each farm between the organic nitrogen produced and spreading capacities on agricultural land, (c) adapting storehouses for livestock effluent to a capacity of 6 months and (d) promoting transfers of livestock effluent between farms in excess balance and farms which still have a way of using it on their land.
The paper presents the principle of “soil nitrate residue” measurements (APL in French) that permits a yearly monitoring of the farming practices and constitutes a self-evaluation tool for the farmers.
The paper also introduces the reference model EPICgrid dedicated to nitrogen transfer modelling in the context of the Walloon region. Following the first comparison exercise, these tools are consistent and complementary approaches to help farmers and authorities in nitrogen management.
In the context of the Walloon region, dealing with deep groundwater bodies, fast indicators of potentially leachable nitrogen and nutrient fate modelling are the most practical way of assessing effectiveness of the EU nitrate directive action programmes.