FAQ on EM and Gamma Radiometric Mapping

Question 1

Costs! How much does a soil survey cost?

Accepted Answer

VRT Solutions has worked hard to keep the costs of investing in this technology low on a per hectare basis. Generally, adoption of this technology can potentially pay back in savings and higher efficiency of inputs within one to two years, with everything after that becoming a reward for adoption. Interestingly, we have had clients in the past pay off their investment in a single application of VR lime! In other cases, there may be no reduction in the quantities required, however optimised distribution and better use of inputs is the target.

Question 2

What is an EM and Gamma Radiometric survey?

Accepted Answer

Dual EM surveys are undertaken by VRT Solutions to measure soil electrical conductivity allowing soil variability to be mapped. The EM probe 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 through the soil profile. The soil’s electromagnetic value relates to soil properties that are agronomically important, enabling a starting point for the management of soil variability.

Radiometric equipment is used to measure gamma ray emissions from the natural radioactive decay of elements within rocks and soil, in particular the emissions from isotopes of Potassium, Thorium and Uranium.

Radiometric measurements can be taken simultaneously with the Dual EM collection. The importance of having gamma data in tandem with EM data is sometimes crucial to accurately identification of soil type changes, particularly in areas where EM values are low.

For more information on using EM and Gamma together, see this research paper from the Grains Research & Development Corporation

Question 3

How often do I need to map my paddocks?

Accepted Answer

ONCE.

After the EM and gamma data has been collected, there will not be any major change in the readings in our lifetime. This is not the case if major soil renovation work is undertaken, but in most scenarios, this is unlikely.

Question 4

What does EM38 refer to?

Accepted Answer

An EM38 is a geophysical surveying instrument made by Geonics Limited in Canada. The EM38 is a popular instrument for EM soil mapping because it is lightweight and easy to use.

VRT Solutions has a range of electromagnetic induction (EMI) sensors to cater for each project requirements. VRT Solutions operates a DualEM 1s, DualEM 21s, and Geonics EM38 MKII. Generally the use of these instruments are referred to as EM surveys. Changes in EM readings across a typical paddock can be indicative of changes in salinity, clay percentage, and prescence of moisture and metal or several of these factors at once! In Western Australia, gamma radiometrics is a necessary sensor which provides a complimentary dataset which is collected simultaneously. We use both sensors together due to the high prevalence of low EM soils in WA.

In terms of standardising precision agriculture approach, EM38 surveys or DualEM surveys are becoming more commonplace as a starting point. An EM (Electromagnetic) and gamma radiometric soil survey offers a cost effective method to have a higher accuracy in variable rate (VR) applications. This in turn can lead to better cost recovery, and better crop performance.

Dual EM and Gamma Radiometric Experts

EM and gamma surveys help improve the efficacy of inputs. This can reduce costs and improve yields in suboptimal soils

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