Application Guide
EM Conductivity Equipment for Agricultural Soil Mapping
Electromagnetic conductivity meters map soil variability across whole fields in a single pass, giving agronomists the zones they need for variable-rate seeding, fertilisation and irrigation.
Apparent electrical conductivity (ECa) of soil depends on clay content, moisture and salinity — exactly the properties that drive yield variation. A frequency-domain EM instrument towed on a sled behind an ATV records ECa continuously with GNSS positioning, without any ground contact.
Multi-coil instruments measure several depth ranges simultaneously, separating topsoil from subsoil variation, and many also record magnetic susceptibility.
Methods Compared
| Method | Detects | Typical Depth | Limitations |
|---|---|---|---|
| Single-depth EM conductivity (EM38-class) | Root-zone texture, salinity, moisture | ~0.75–1.5 m depending on orientation | One depth range per pass |
| Multi-coil EM (DUALEM, CMD) | Topsoil vs subsoil variation, layering | Several simultaneous depth ranges | More data to process; needs calibration lines |
| ERT (targeted) | Detailed soil profile, drainage, compaction | Several metres | Not practical for whole-field coverage |
Depths are typical field values — actual performance depends on ground conditions, target size and survey design.
From maps to management zones
ECa maps are calibrated against a small number of soil samples and combined with yield maps to define management zones. Because surveys are repeatable, they also track salinity and moisture changes over seasons.
Recommended Instruments
A selection from our catalog. We source many more models — tell us what you need.
Which Condition Tier?
Agricultural service providers often equip several survey rigs; Refurbished and Absolute Certified EM meters cut the cost per rig, while classic single-coil EM38 units are widely available as Refurbished or Surplus.
See the condition tier guide for what New, Refurbished, Absolute Certified and Surplus each include, or the industries overview for related sectors.
Frequently Asked Questions
What does EM38 measure?
The EM38 measures apparent electrical conductivity of the soil, which relates to clay content, moisture and salinity in the root zone.
Single-coil or multi-coil EM for agriculture?
Single-coil instruments are cheaper and simpler. Multi-coil instruments separate topsoil and subsoil variation in one pass, which is valuable for drainage, salinity and deeper texture changes.
Do I need ground contact for EM surveys?
No — EM conductivity meters are fully non-contact, which is why they can be towed at speed across fields.
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