Lysimeter data in pesticide authorization

The assessment of the mobility of plant protection products in soil is a ve ry important part within the authorization procedure for pesticides in the Federal Republic of Germany. In recent years lysimeter studies have been proven to be the best methods t o assess the probability of pesticides entering into ground water. For subs tances with a DT50 value of more than 21 days and an adsorption constant Ko c of less than 500, computer-aided model calculations at realistic worst ca se conditions are first conducted. If a concentration of 0.1 mu g/l or more is calculated, lysimeter studies have to be carried out. An authorization of the plant protection product is only granted if the concentration of the active substance in the leachate is less than 0.1 mu g/l averaged over one year. The lysimeter concept was also adopted by the EU Directive 91/414/EE C where in special cases lysimeter or field studies for the assessment of t he mobility of active substances are required. In the last few years lysime ter studies were conducted for more than 40 active substances within the Ge rman authorization procedure.