To ensure that Denmark’s groundwater is not contaminated due to the agricultural use of approved pesticides, "The Danish Pesticide Leaching Assessment Programme” (PLAP) was initiated in 1998 by a parliamentary decision. 

PLAP is a monitoring programme that on the basis of measurements in test fields aims at providing an early warning of the risk of leaching of pesticides and/or degradation products for the following purposes: 

• To investigate whether application of approved pesticides according to regulations regarding maximum dosages under actual Danish field conditions can cause leaching into the groundwater of pesticides and/or their degradation products in concentrations above the EU limit of 0.1 ug/l. The individual substances are typically followed two years after application. An evaluation of the direct relation between the specific pesticide use on the test field and findings in the groundwater is obtained by the analysis of water samples from a depth of one meter (obtained via drains and suction cups) and from groundwater downstream as well as upstream of the trial field.
• To improve the scientific basis of the Danish authorities’ approval and regulatory procedures for pesticides based on the collected data on concentrations of pesticides and/or their metabolites in water collected from groundwater filters, drains and suction cups as well as information on crops, cultivation practices, climate, and soil water balance.

The PLAP monitoring system began in 1999 and has been operating without interruption ever since. In the beginning, PLAP comprised six test fields, but in 2003 this figure was reduced to five. With a field at Lund on the island of Zealand PLAP will with effect from July 1, 2017 again comprise six fields, as can be seen in the figure.

All information and publications related to the PLAP can be found on the PLAP website.