Dual EM surveys are undertaken by Precision Agronomics Australia to measure soil electrical conductivity allowing soil variability to be mapped. The EMprobe consists of horizontal and vertical electromagnetic fields that collect data simultaneously. The probe has a vertical measurement range of 1.5 metres and horizontal range of 0.5 metres, enabling a precise understanding of soil EM properties throughthesoilprofile.
Measurements are typically collected on 35m transects at around 20km/hr. In 100 hectares, approximately 10 – 12,000 electro magnetic and geo-referenced measurements are collected and recorded. An example of the raw collected data is shown on this image in Figure 1.
Once the measurements are taken the data is processed into an EM map from which can be used to start to determine and manage the relative variability of soils within a paddock or Farm.
The Soil Electromagnetic value relates to soil properties that are agronomically important, enabling a starting point for the management of soil variability.
With adequate soil testing, “ground truthing”, the EM map can be used as a proxy map of soil properties. Patterns of EM in field remain stable and only ever need to be collected once.