Validation of the model PLEASE at site scale

To test the suitability of the model PLEASE for prediction of P losses at site scale the model has been applied to a number of intensive and more extensive monitoring sites. The results of the model application to the individual sites showed that the model is able to show relative differences in leaching fluxes between sites i.e. to distinguish low leaching sites from sites with intermediate and high leaching fluxes. Poor results are obtained for peat soils and heavy clay soils due to the fact that processes like release of P from eutrophic peat layers and preferential flow through shrinkage cracks in clay soils are not accounted for in the model. In other soils major deviations between measured and simulated fluxes are often due to differences in measured and simulated concentration profiles