Evolution de la composition chimique des eaux de drainage dans un système d'épuration du lisier par le sol

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The current study reports on operational and performance aspects of a land treatment facility "Solepur", for managing surplus pig slurry (986 m³/ha/yr) over a 5-year period (1991-1995);followed by a monitoring phase on the status of the soil-water system over an additional 5-year period (1996-2000). When large applications of pig slurry are made to soil, intense microbial oxidation occurs which results in the breakdown of organic matter. Soil is able to retain most of the elements applied in slurry particularly in the 0-20 cm layer, 80% of the carbon, phosphorus, copper and zinc retained by the soil are located in this layer. Most of the immobilized nitrogen (70%) also accumulates in the topsoil. A number of elements including nitrate-nitrogen, potassium, calcium, chloride and sulphate were heavily leached at rates ranging from 400 to 600 kg ha^-1 yr^-1.