Could soil electrical conductivity maps give productivity a little jolt?

This easy-to-obtain data could be a way to use fertilizer and irrigation more effectively

Soil electrical conductivity data can reveal a lot about a field, says Lewis Baarda, seen here placing an instrument called an EM38 in a sled prior to field mapping.
Reading Time: 4 minutes

You might get a charge out of this — measuring the ability of soil to conduct electricity, turning that info into field maps of moisture, and then using that info to fertilize or irrigate more effectively.

Soil electrical conductivity is something that may already be measured on your farm.

“Often if farmers are getting their soil tested, they will get a measure of electrical conductivity as well,” said Lewis Baarda, manager of the field-tested program with Farming Smarter in Lethbridge.

His research team is measuring soil electrical conductivity with an instrument called an EM38, a sensor that is put in a plastic sled and pulled behind a quad. It takes readings “a couple of times a second” of electrical conductivity, with variations in the readings producing a snapshot of the field.

“These variations correspond quite closely to soil moisture and soil texture, and also salinity,” said Baarda.

“We don’t have to penetrate the soil at all, and we can quickly get a map of an entire quarter section of what the electrical conductivity is, rather than doing testing.”

Although soil textures of sand, silt and clay affect electrical conductivity, a reading can reveal a lot.

“Electrical conductivity varies strongly according to texture, but it does change according to how much moisture is there, which can relate to texture as well as ions in the soil,” he said. “That’s where salt comes in. Salt will really pop out on these electrical conductivity maps.”

“If you can gather soil moisture information a month after you seed, maybe that helps you zero in on more appropriate fertilizer levels.” – Lewis Baarda. photo: Supplied

Readings can then be used to characterize fields.

“Even though it can be tough to say what is making electrical conductivity readings what they are — without ground truthing — it’s quite effective for building zones in the field,” said Baarda. “If you get certain readings in this area, and certain readings in another area, there’s a very good chance that there’s something different about the soil properties between those areas that you might be able to manage with variable rate.”

Putting the data to use

Being able to map zones could provide a big advantage, he said.

“Often when farmers are looking at irrigating their fields and deciding how to irrigate, it is largely based on gathering information from one point of the field,” said Baarda. “So you may scout the field, you may do a hand check of the moisture level, or use a probe. You don’t get a sense for what is happening in that whole field.”

If the real-world experience lives up to the theory, the electrical conductivity zones could be translated into soil moisture zones and assist producers in making decisions on how much to irrigate or (if they have precision irrigation) how much to apply in different parts of a field.

But you don’t have to have irrigated land to benefit from the technology — it also has the potential for getting more bang from your fertilizer buck.

Taking readings is as simple as putting the EM38 in a sled and towing it behind a quad across a field. photo: Farming Smarter

Again, the theory is enticing: Moisture zone mapping could help producers with fertilizer management decisions.

No one knows how much rain will fall after seeding and so the dilemma when sowing fields is how much fertilizer to lay down.

“If you can gather soil moisture information a month after you seed, maybe that helps you zero in on more appropriate fertilizer levels,” said Baarda. “If you put down 60 to 80 per cent with seed, and then you have an opportunity to top up fertilizer in the places in the field where the electrical conductivity map forewarned high-yield projection, then you have an opportunity to use fertilizer and increase yields.

“So you’re sort of hedging your bets on the fertilizer piece.”

The study is trying to find evidence whether making that call based on soil conductivity works in real life. (For example, in one trial, the Farming Smarter research team placed 60 per cent of the recommended fertilizer rate and then topped up the remaining 40 per cent during the season.)

They haven’t crunched the numbers on their trials yet, but will be doing that this winter. But while there aren’t concrete results yet, Baarda is optimistic and said farmers could work with consultants to use electrical conductivity to make better decisions on their land.

A lot of equipment today now has soil electrical conductivity tech built in, he added.

“Because it is so cheap and reasonably easy to obtain, it could be a relatively easy dataset. I think it’s worth exploring what we can do with electrical conductivity,” he said.

About the author


Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."



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