Dual EM surveys are taken by Precision Agronomics Australia to measure client’s soil electrical conductivity allowing soil variability to be mapped. The Dual EM Geonics machine measures vertical (to 1.5 metres) and horizontal (0.5 metres) electromagnetic currents simultaneously.
Measurements are collected on 35m transects at around 20km/hr. In 100 hectares, approx 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.
A good example of an EM map is in figure 2.
The Soil Electromagnetic value has no direct effect on crop growth, but relates to soil properties that are agronomically important, enabling us to begin to effectively manage this variability.
With adequate soil testing, “ground truthing”, the EM map can be used as a “surrogate” map of soil properties. Patterns of EM in field remain stable and only ever need to be collected once.