Predicting the ability of soils to accept the application of organic amendements in accordance with the metal soil policy threshold (Wallonia - Belgium)

Vandeuren, Aubry [UCL] Pereira, Benoît [UCL] Sonnet, Philippe [UCL] Bogaert, Patrick [UCL]

As in many parts of the world, land application of organic amendements such as sewage sludge known to contain trace metal elements motivated the walloon administration (Belgium) to establish a regulation to limit the spreading on soils with high contents of trace metal elements. This regulation requires to perform a soil analysis prior to application to check if the parcel meets the policy thresholds for trace metal elements. As most of the soil metal content analyses were below the policy thresholds, the walloon administration conducted a study leading to the establishment of a map recommending the necessity to impose a soil analysis before application. This paper presents an algorithm to determine for each agricultural parcel in Wallonia if it is able to receive spreading sludge according to soil metal content policy thresholds basing on the soil analyses performed in the frame of the implementation of the regulation. The principles of this algorithm combine both geostatistical methods, expert judgement and constraints imposed by the Administration. As a result more than 50% of agricultural parcels are located in zones where a soil analysis is not recommended, reducing thus costs for both the the administration and owners of agricultural parcels.