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Using Electromagnetic Soil Mapping in Precision Agriculture

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Video Transcript

EM mapping stands for electromagnetic mapping. Commonly in Australia we use EM38, which is a source of  technology. EM just sends signals into the soil. Depending on the soil type, that ranges from a metre down to a metre and a half. It’s measuring subsoil constraints basically. The big drivers are moisture, texture and salinity.

Secondary Drivers for EM Soil Mapping

Secondary drivers are sodicity and boron. EM originally was not made for doing surveys but through the combination of adding a GPS and a computer we can start collecting data and creating maps which are exactly like your yield maps off your header. So, adding a GPS to the header we’re taking the yield monitor and creating a map with it.

Same principle with the EM, you take a piece of information and spatially record it. EM38 correlates very well with yield, particularly in dry years and particularly in your mallee environments of a Dune Swale system. There’s a range of things farmers can do with EM38 depending on what the ground truthing returns to them.

Some of the easiest stuff is soil Amelioratoin. So an EM map picks up sodicity, and that farmer can respond straight away with a gypsum application and feel confident they’re putting the gypsum where it’s required.

Creating Long Term Soil Management Zones

More detailed stuff were finding is because EM correlates while soil profiles, particularly in the low rainfall environments, farmers are creating long term management zones that they use for fertilizing their crops. So they are aiming to fertilize where they’ve got potentially the most plant available water and are aiming to reduce fertilizer and seed.

Reducing puts overall where the EM is highest, where it’s most likely that in an average or below year, the yield is gonna drop away. EM38 has been identified to create these management zones where farmers can have these long term set zones and can fertilize accordingly. This not only reduces their risk, by taking the fertilizer off the heavy soils and putting it on the light soils, but it increases their returns. I mean other areas where you’ve got a good duplex soil, sand over clay, there’s been some really good work showing that EM can be used to map depth of clay.

And then this can be used with delving to always bring out consistent levels of clay or identify areas where the clay is too deep for delving. EM has been shown in certain situations to pick out differences between red and black soils in the high rainfall zones, and has been used for  and this leads to differences in PH. So, this has led to liming being more targeted and so farmers A: might be still putting on the same amount of lime but they are targeting to where it’s gonna get the best bang for their buck. Probably the best way to describe precision ag is a methodology.

It doesn’t, it’s not a way of actually solving all the world’s problems, but it’s a way of identifying them and going through the process where you try new things, trial, different treatments on different soil types and gradually build up your knowledge where you can start identifying zones where you will get a yield response to a particular practice.

The Nursery Approach – One or Two Paddocks

EM is just like all of the others PA technologies. It’s best off for farmers to start with a nursery approach, so do a small area, whether it’s one, two paddocks, to identify a new technology and how it applies to them. You generally don’t need too many skills to utilize the data like a lot of match farmers can identify what’s going on when they first see the map Follow up but once all the soil testing is combined all contractors should take soil test when they take a EM survey once that is combined with the farmers own historic knowledge and the agronomists knowledge that’s when the full package comes together and you generally start to kick the goals that you are looking for from variable rate.

Peter Treloar talks about electro-magnetic soil mapping in precision agriculture.

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