EM38 & Gamma
EM38 is the most commonly used sensor in detecting changes in soil variability. EM38 technology relies on an electromagnetic pulse being sent from one end of the machine through the ground and feeding back into the other end of the machine. The resulting “pulse” is the apparent electrical conductivity (ECa).
The ECa can be influenced by several factors, some of these include the soil water content, soil salinity, and the relationship between clay content, clay type, depth to clay, or depth to rock.
An EM survey is site-specific and provides a snapshot of the apparent conductivity at that particular point in time. Targeted Ground truthing (often involving extensive soil sampling) is an essential step to understanding the nature of the soil variability the EM38 is detecting.
EM38 data is generally collected in conjunction with RTK elevation data providing information about the soil and elevation of the surveyed site. Understanding how the soil varies across a site allows for various changes in spatial management across the site. The technology is currently being utilised across industries including broad acre farming, horticulture and viticulture. It is also utilised by various research agencies to better understand variability across their sites.
Some of the uses in these industries include:
Variable-rate application (both water through automated irrigation, and nutrient application in both irrigated and broad acre systems),