As we're already into it this year, we thought it was time to give you a reminder about EM Surveying and how it all works. Today you'll get the first of a two part blog looking at the process, what you get from an EM Survey and what it can all be used for.
EM Survey – Part 1 - the process.
When we conduct an EM survey we are measuring the electrically
conductivity within the soil profile, the values have close links to the soil
texture properties, where clay gives a higher reading than silt that in turn
gives a higher reading than sand. So, by driving over a block of land you pick
up the differences in the soil texture at two different depths 0-50cm and 0-125cm.
Other factors have varying degrees of influence on the readings such as soil
bulk density and moisture within the profile at the time of the survey. High
salinity readings can have a huge influence on readings, but this is only in
specific areas of New Zealand. The EM data is logged using 2cm accurate RTK GPS,
so not only do we map the relative changes in soil texture, we are also
collecting valuable topography data at the same time.
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| Agri Optics' EM Survey setup with soil profile shown. The measurements penetrate 1.25m into the ground. |
We drive most commonly at 12m swaths across the area, but
closer resolution can be used for more intensive situations such as
viticulture. Once the survey has been conducted we write a report about the
findings from the two different EM layers, we then zone the EM data up into
different management areas and run topography generated maps. Once you have had
time to read through the report we arrange a meeting to then run through the
report with you in person if you so desire. We also supply the client with
software to view the data on their own computers and look at the different
layers plus make your own management zones if required. From this point we can
then focus on the areas of interest for your requirements.
The survey data has many uses, depending on the farming type
and location and includes but is not limited to the following; being the basis of variable rate irrigation
application maps, moisture probe placement, used in zonal soil sampling, in
dryland farming areas knowing where to put your effluent, to varying your
nitrogen use depending on the underling soil types and used for flood modelling.
It can also be used in conjunction with other layers of data such as yield
maps, biomass maps and as happens frequency used with the topography data. Over
the next few blogs I can drill into more detail on these different uses.
The EM season runs form the end of irrigation in the autumn
through to Spring, but from now onwards is the ideal timing. For more
information on EM surveying or to book one in for this season, please contact one of the Agri Optics team. Cheers, Chris.
