The effect of rising temperatures due to climate change on potato production.

As headlines during growing seasons repeatedly talk of record temperatures, potatoes are struggling to adapt. Climate change is pushing temperatures higher, which isn’t good news for spuds.

“Why is heat a problem? A lot of crops, if you’ve ever grown corn or any really warm season crop, the hotter it is, the faster they grow. Potatoes is not one of those,” Mike Thornton, a professor at the University of Idaho, said during a presentation at the Alberta Potato Conference and Tradeshow on Nov. 16, 2022.

Mike Thornton
Mike Thornton, a professor at the University of Idaho

Potatoes are native to the high altitudes of the Andes Mountains in South America where the 25 C days and 12 C nights are the perfect conditions for growing spuds. And while a little bit of heat doesn’t hurt potatoes, continuous heat does, Thornton said.

“Potato plants don’t like to be stressed by two different things at the same time. So, if you have nutrient stress and heat stress, you have pest problems and heat stress, water problems and heat stress, that makes it worse than just heat alone,” he added.

Thornton pointed to the Columbia Basin as an example. Temperatures there may soar above 37 C, so they have good soil for irrigating and managing moisture. This means that while the potatoes are under heat stress, they aren’t under moisture stress so they can still grow.

“Heat stress by itself is not a death sentence to potatoes. It’s how you deal with it that determines the outcome,” he added.

Heat stress on potatoes also depends on when the heat happens during the potato growth cycle. Thornton refers to the potato as a starch factory that takes sunlight, water and nutrients from the soil and carbon dioxide and oxygen from the air, turning it all into starch. Like every factory, the potato has building, maintenance, production, and packaging departments.

If you get heat early in the season, then the construction department will keep building while the production and packaging departments aren’t working causing lots of vines to grow but no tubers to form. If you have delayed tuber initiation, then you push back production in the factory leading to a later harvest and lower yields if frost comes before the tubers can catch up.

If the temperatures get too hot during photosynthesis, then the plant will stop operating as efficiently, Thornton said. Productivity of the plant starts to go down overall which means less starch is made and yields fall.

“The optimum temperature for growing vines is much higher than the optimum temperature for growing tubers,” Thornton said. “When you get hot conditions, you basically send a signal to this plant, keep growing leaves, keep that building department going, we can go forever… they worry less about what they put into the packaging department.”

The same signal that heat stress sends to a plant to keep building leaves is what you get from high nitrogen, he added. So, if you have a moderate upfront nitrogen program and you’re feeding the plants during the season, the plant deals with heat stress better.

Another way to fight back against heat stress is to have a moisture bank in your soil, Thornton recommended. Start with good early season moisture using irrigation so that when the plants need moisture during the heat later on you falling behind if your irrigation system can’t keep up.

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Ashley Robinson was raised on a mixed cattle and grain farm in southwestern Manitoba. She attended the University of Regina where she studied journalism. Following university, she has spent the better part of the past decade writing about agriculture in publications across Canada and internationally. Robinson’s agriculture writing has covered topics from rural issues to commodity markets. Since joining Seed World Group her work has focused on covering all aspects of the Canadian potato industry from planting to farm management, and agriculture in Alberta focusing on how the seed industry connects to farmer’s daily lives.