Uses of EM Survey for Rapid Appraisal of Soil Issues
Robert Banks
Introduction
Uses
Cost of Technology
EM Survey as a Rapid Soil Evaluation Tool
Electromagnetic Induction (EM) Survey has become a common
means of assessing soils for salinity In the USA and Australia in
the past 20 years, however its uses are not simply limited to
salinity. Uses of EM include:
• Salinity
• Soil Depth mapping where depth is highly variable
• Soil moisture and Available Water Capacity (AWC) mapping if
serial EM is used
• Location of shallow groundwater sources
• Mapping of gross soil type through textural differences
• Mapping of gravel and sand lenses which may interfere with
construction of dams
• Acid Sulphate Soil mapping
EM31 mounted on a quad runner for rapid data collection
Use of EM31
• Penetration of up to 6 m possible in low conductivity terrain
• Same advantages as an EM38 for rapid data collection and
coverage
Both the EM38 and the EM31 data can be loaded into a standard
GIS or graphics package for data manipulation.
Limitations of Technology
All EM Surveys have limitations and the user must be aware that:
• EM surveys must be validated in the field and preferably a laboratory using the imagery to locate soil pits or cores
• Sometimes EM survey does not measure what you are looking for
• The data may reflect a soil or geology parameter which has a stronger signal than the target soil property (eg moisture instead of salinity)
• Very complex terrain and geology can make EM survey difficult to interpret.
EM38 (1.25 m slice) raw data
Use of EM38
• Penetration up to 2.75 m with depth slices available (0 – 25,
0 – 75, 0 ‐125 and 0 – 2.75 m) or agronomy zone of soils
• easily mounted on a 4 wheel motorcycle and cross linked
with GPS technology for rapid collection of data
• Allows coverage of 400 – 1, 000 Ha per day in relatively flat
land, with a data density of one point per 10 – 20 m.
TEMPLATE DESIGN © 2008
www.PosterPresentations.com
Prepared by Robert Banks, SoilFutures Consulting Pty Ltd 2014
Processed EM31 Image showing salt load of soils Processed and validated EM38 Image showing soil depth
The Think Soils Team has the experience to perform
EM Surveys for your purpose in your country or to set
up your team with EM technology and organise
training in use of the technology, and field validation
of EM data.
If your organisation wishes to purchase EM
technology, cost of operation is approximately USD
0.20 per Ha once the equipment is paid for.
Special Projects – International If you have a special project in mind, Think Soils can
organise its own contractors to perform EM surveys
in your country at a competitive consultancy rate.
Think Soils is a multi skilled team of bilingual Soil
Scientists with extensive experience in Asia, Europe
and Africa and can offer training in the use of the data
for your staff or students or see an EM project right
through for your purpose.
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