Crop Advisor’s Casebook: Crop circles made by space invaders or salinity?

A Crop Advisor's Solution from the March 7, 2017 issue of Grainews

Canola plants were stunted or missing at the edges of and inside the small circles.
Josefine Bartlett photo: Supplied

Jim, a Fairview-area producer, dropped into our office for coffee one morning in early October last year. When he spotted me, he called me over, eager to show me some photos he had taken of one of his canola fields. Jim said he’d finished swathing the day before, and he found something unusual in this field.

“I’ve got crop circles in my last canola field. Maybe it’s aliens,” he joked. We examined the photos and had a good laugh, but he was curious about what was causing the circles and how to get rid of them.

The photos showed perfectly round crop circles scattered throughout that one field. Most were small (centimetres in diameter), however, a few were quite large (a metre or two in diameter).

“I came upon circle after circle, perfectly round, at least 50,” said Jim. Nevertheless, going by Jim’s photos, the affected area, overall, was minor.

I also noticed plants were stunted or missing at the edges of the circles. Inside the small circles, again, plants were stunted or missing altogether. Meanwhile, inside the few large crop circles, the plants appeared to be less affected, or had already recovered from whatever was stressing the crop.

Jim noticed the crop circles when he got into the field to swath. photo: Supplied

Jim wasn’t sure when the crop circles were formed because he only noticed them when he got into the field to swath.

However, Jim had some theories. One possibility, he thought, was the circles were caused by salt blocks previously placed in the field for cows, since the field had been pastureland. However, he reasoned out loud, that would be an absurd number of salt blocks, so, perhaps not.

Could those spots indicate where straw beds, or shelters, were made — from the pasture days, he asked. I thought this scenario was also unlikely, I told him, because of the round shape and varying sizes of the crop circles.

“You know, your mind really gets going when you sit in the swather for hours on end,” he said.

He also wondered if that field had a salinity issue influencing the availability of water and nutrients to the canola plants. Although soil salinity can affect plants in this way, I said, I was sure this was not the problem due to the unusual pattern throughout the field.

Jim had taken excellent photos of the crop circles, including close- ups. From these photos, I could tell what was causing the crop circles, and it had nothing to do with outer space, soil salinity or shelters.

Crop Advisor’s Solution: Nothing other worldly about these crop circles

While taking a break from swathing to stretch his legs, Jim had taken some excellent photos of the circles, including close-ups. In one, Jim had photographed whitish grey-coloured mushrooms growing around the crop circle’s edge — these were a dead giveaway. Fairy rings were the answer to Jim’s crop circle conundrum.

Fairy ring fungi grow in the soil absorbing nutrients. The fungi move outward as soil nutrients are depleted, creating circular shapes called fairy rings.

Unfortunately, there wasn’t much Jim could do about the fairy rings in his crop. These fungi are almost impossible to eliminate. His best option was to wait it out.

In other sectors, such as the turfgrass industry, it is thought the active ingredients in some fungicides act on these fungi, but there is no actual data to prove it works in cereal or canola crops. Furthermore, applying fungicide often doesn’t pencil out. Because fairy rings do not, generally, cause yield reductions, there is very little research conducted on this subject.

In the end, although highly entertaining, Jim’s crop circle damage looked worse than it was, as the effect on yield was negligible.

Josefine Bartlett works for Richardson Pioneer Ltd. in Fairview, Alta.

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