Mid Canterbury’s rolling plains are what keep the region going - they grow our crops and raise our livestock.

But new mapping technology proves there’s nothing “plain” about our land.

Environmental consultancy Land and Water Science joined forces with Ellesmere Sustainable Agriculture (ESAi) for a field day all about dirt.

Consultancy director Clint Rissman, who’s present his life research groundwater and soil, showed farmers what happens beneath the soil that they turn each year, and how that affects a harvest.

“The Canterbury Plains is hugely complex,” Rissman said.

“A lot of farmers are making decision at paddock scale. They’re naturally attuned to the land, but our soil maps aren’t aligned with that knowledge.

“This mapping helps pick up the variability that most farmers are familiar with.”

The field day ran at David Birkett and Geoff Martin farm, out in Leeston, but brought farmers from across Mid Canterbury together to investigate a new type of soil mapping.

Right now, most farmers use the Landcare Research provided soil maps.

These tell you about what’s in the soil in any given area; how much clay, how stony it is, and even how much nitrate it could leach.

But the data those maps provide are not always accurate, or are averaged too broadly, ESAi’s project manager David Hewson said.

“A lot of that was collected 20 years ago, 40 years ago. It’s old.

“At the moment, as Clint’s explained, soil maps are at a 1 [metre] to 50,000 scale.

“This [new tech] enables us to get that number down to 1 to 10,000 or 20,000.”

The new tech in question is gamma ray spectroscopy, or radiometrics - “Sounds flash, but it's sort of like scanning the soil,” Rissman said.

Radiometrics provide a detailed breakdown of what’s in the soil, and are able to look deeper into the ground than the technology before it.

“We’ve just been looking at the top 600 millimetres and ignoring what goes on below,” Hewson said.

“I haven’t really understood what goes on underneath either.”

Once a paddock is mapped, a small patch gets excavated for some visual truthing.

The group visited a number of neighbouring paddocks and saw huge variations in the soil makeup, beyond the layer that was tilled each year.

One paddock was full of stones, but the next showed signs of internal rusting and stagnation, despite being a minute’s drive apart.

Rissman said radiometric mapping would often confirm suspicions a farmer already had about their land.

“I think a lot of farmers around here have a pretty good handle on the land.

“They probably know it in a bit more detail than scientists do, because they live and breathe it.”

Hewson hopes the field day will inspire farmers to investigate radiometric mapping fo rtheir own land.

“A thriving community is what they’re after.”

by Anisha Satya