The EM38 sensor is an instrument which measures the apparent soil conductivity - i.e. how well the soil can conduct electricity. Under Danish conditions there has been found a good relation between apparent soil conductivity and soil clay content. Knowledge about the clay content is important when a) planning strategic soil sampling, b) evaluating soil sample data and c) calculating site specific application plans.
The EM38 method is well documented around the world by many research institutions.
EM38 mapping is done by pulling a sledge with the EM38 sensor after an ATV in parallel tracks across the field. By measuring the sensor position using a GPS, it is possible to obtain a large number of measurements and to produce a very detailed map of the apparent soil conductivity (clay content). This map is then used as an important basis for strategic soil sampling. EM38 surveys are only done once on a specific area as the values normally only change over large time spans.
EM38 soil surveying requires great care. Knowledge of soil properties and mode of operation of the EM38 sensor is essential for good results.