Water Pollution Monitoring Of Nitrates Leaching From Agricultural Fields With Industrial Crop Harvesting Practices. The Belgian Case Of Onsite Lysimeters As A Monitoring Tool. Fonder Nathalie (1), Jean Marie Marcoen(2), Dimitri Xanthoulis (3) (1) Epuvaleau npo, Avenue de la Faculté d’Agronomie, 5030 Gembloux ; (2) GRENeRA, Geopedology Laboratory, Gembloux Agricultural University, Passage des déportés, 2, 5030 Gembloux ; (3) Gembloux Agricultural University, Department of Hydrology and Rural Hydraulics, Passage des déportés, 2, 5030 Gembloux ;

OUTLINES Climate : Cold Temperate, ocean influenced Latitude : 52°N Annual Temperature : 10°C Rainfall : mm/yr Rain Frequency : 200 days/yr

Belgium is a Kingdom with FEDERAL STATE GOV. 3 Communities, corresponding to population groups (language and culture) 3 Regions corresponding to economic autonomy desires (In charge of Agriculture and Water management, amongst other) Federal Government manage Army, Foreign Affairs, Public Health, Justice, Finance, Social Security, etc. 6 Mi Inh 1 Mi Inh 3,5 MI Inh Area = KM 2 Pop. 10,5 Mi Inh. Density 315 Inh/Km 2

Context 1991 : European Nitrate Directive (91/676/CEE) aims at moderating or preventing water pollution from nitrates released by agricultural practices 2000 : creation of NITRAWAL, npo as a consortium of 4 partners to provide support to farmers (1 from Water sector, 1 from agricultural sector, 2 scientific partners from Walloon universities – GRENeRA, ECOP) 2002 : Transposition into the Wallon law with the PGDA (Programme de Gestion Durable de l’Azote) / Sustainable Nitrogen Management Program - standards on mineral and organic fertilization rates - agricultural practices code 2005 : Condemnation by EU for non complete transcription - PGDA review process 2007 : New PGDA having impacts on the operation managements by farmers 2003 – now : scientific studies - test the relevance of the environmental indicator defined, - adequacy standards / water quality preservation, - advices on crop rotation and sequences

Material and method

Data collection

Crops rotation above lysimeters implementation

Results for Water Quantity Water Budget : Water collected = Infiltration water In Wallonia : Pluviometry = 100%, Infiltration = 6 to 28% In Lysimeters, Water collected = P + I – ETM (assumption to have a closed lysimeter) P= Pluviometry I = Irrigation ETM= ET * Kc (cultural coefficient) Results obtained over 5 drainage seasons = 12 to 14%

The Walloon Environmental indicator APL APL = Azote Potentiellement Lessivable / Potentially Leachable Nitrogen Issued from the “Survey Surface Agricole” (Agricultural Surface Survey) - 25 farms - total of 220 fields Annual sampling - first at spring, leading to fertilisation rate recommendations - secondly at autumn, to assess residue after harvest Annual APL (Environmental Indicator) is defined per crops and their related acceptable nitrogen residue in the soil after harvest. If above, - penalties for the farmers Lysimeter project : no plots received any negative assessment from the Environmental indicator Nevertheless, high to very high values of nitrate content are observed in lysimeters

Summary Table for Water Quality

Conclusion and recommendation - Lysimeters are reliable to collect representative seepage water amounts - Lysimeters confirm the reliability of APL Environmental Indicator - Unfortunately, respect of legislation ≠ water quality preservation - N management has to be defined over the whole crop rotation sequence and not per individual crops

Conclusion and recommendation -Cereals + inset crop / without OK / non OK - Sugar beet OK - Potato with no winter cover non OK - Any vegetable should have a winter cover crop - Spinach + beans (+ inset crop)non OK (OK) - Broad beans + Spinach or cabbage or wheat non OK Works in progress investigate : - specific crop sequences and rotations, - fertilisation recommendation rates for the different crops grown in the Belgian Walloon region

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