Today, PLAP includes six monitoring fields – two sandy fields and four clayey till fields – one of the sandy fields is currently on standby.
Besides the pesticide-related monitoring, which includes monitoring of the water balance and agricultural practices of the fields, the PLAP fields are applied for monitoring of other parameters, such as inorganic chemical parameters and bacteria.
Selection of fields
To apply the PLAP-monitoring data directly in the regulation of pesticides in Denmark, the fields have been selected to represent the Danish soil types and climatic conditions. Additionally, the clayey till fields have been selected because they have a tile drain system installed at the latest in 1940 to minimise any artificial transport pathways to the groundwater from the surface of the field.
The map shows the annual net precipitation across Denmark and the location of the six PLAP fields. The PLAP fields are located so they represent the span in net precipitation observed in Denmark: Jyndevad, Estrup, Silstrup and Tylstrup in Jylland and Faardrup and Lund on Sjælland.
Cultivation of the PLAP fields
The PLAP fields are cultivated in accordance with conventional agricultural practice as regards rotation of crops and soil preparation. Only approved pesticides for use in Denmark are applied and in maximum permitted doses.
The monitoring programme
Each PLAP field consists of a cultivated area surrounded by a grass buffer zone, where the installations for sampling and monitoring are established.
The installations include:
- Piezometers for measuring the groundwater table
- Suction cups for sampling soil water in 1 to 2 m depth
- Vertical screens in four depths wherefrom the groundwater is sampled either monthly or quarterly
- Horizontal screens in 2 and 3.5 m depths from where groundwater is sampled monthly at the clayey till fields
- Horizontal screens installed just beneath the groundwater table at the sandy fields (2.5 m at Jyndevad; 4.5 at Tylstrup
- A tile drain system underneath the cultivated area in 1.1–1.2 m depths (only at clayey till fields)
- Rain gauge
- TDR for measuring the water content of the soil down to 2 m depth
- Temperature sensors for measuring the soil temperature down to 2 m depth
- Sensors, transducers and V-notch for measuring drainage (only clayey fields).
- ISCO samplers for collecting the water flow proportional from the tile drain system