1. http://www.pearl.alterra.nl How are GeoPEARL assessments carried out? GeoPEARL is run for 250-6405 plots, depending on spatial detail wanted; The model is run for the area of potential usage only. This area is assumed equivalent to the area of the crop(s) for which a registration is requested; For each plot and crop-type, the model is run for 26, 46 or 66 years (FOCUS procedure); For each plot the median leaching concentration in time is extracted and put into a map.

2. http://www.pearl.alterra.nl To be specified by the user: Substance properties (start with standard dossier) Application schedule Number of plots (i.e. spatial detail wanted) One or more crops for which a registration is requested

3. http://www.pearl.alterra.nl Effect of area of use on pesticide authorisation (1) Maize is grown on slightly acidic sandy soils Potatoes are grown on light sandy clay soils and in ‘the Veenkolonien’

4. http://www.pearl.alterra.nl Effect of area of use on pesticide authorisation (2) Substance with pH-dependent sorption behaviour Light sandy clay soils and ‘the Veenkolonien’ Slightly acidic sandy soils

5. http://www.pearl.alterra.nl The target variable produced by the model: The 90 th percentile in space and the 50 th percentile in time of the leaching concentration at 1 m depth at the area of (potential) usage

6. http://www.pearl.alterra.nl Effect of area of usage on authorisation (cntd.) Unsafe in potatoes Safe in maize

7. http://www.pearl.alterra.nl Some conclusions from previous section: GeoPEARL explicitly considers the variation of the leaching process, so that it is now possible to evaluate the leaching for different crop types Consideration of the area of usage can have a strong effect on the authorisation decision