You can’t stop an extreme heat wave as it slams into your region, but you might be able to reduce the harm to your potato crop.

That’s the idea behind an Agriculture and Agri-Food Canada (AAFC) project to develop tools to help Alberta potato growers minimize heat stress impacts on tuber yields and quality.

Heat stress is a concern among global potato growers, and although it is not a constant source of pain for growers in Alberta, that doesn’t mean growers should not be aware of strategies, especially if warming trends persist.

Temperature has been cited by some as the single-most crucial uncontrollable factor when it comes to both the growth and yield of potatoes. Temperature plays a critical role in all stages of potato development, but the most critical stages for temperature have been identified as tuber initiation and bulking. The growth stage at which heat stress occurs can have implications not only on the potato’s overall development but also on the cultivar’s response to high temperatures.

For example, some research shows effects are more pronounced early stages of tuber formation (which can prompt drastic tuber yield reductions, according to 2013 research from Serock, Poland) than in later stages, which can lead to quality deterioration (as found in 2017 research from South Korea).

While developing heat-resistant varieties is also a major focus for researchers and breeders around the world, helping all potatoes stand up to the heat through management strategies is the key goal of this new AAFC project.

Jonathan Neilson, a research scientist with AAFC-Lethbridge, says although heat stress is not an annual issue for Alberta potato production, it is a recurring problem.

“Some years, we have really stressful heat conditions, and then other years we go into a cooler, wetter cycle. There have been a few heat dome events in recent years, with prolonged periods of around 35°C and sometimes even reaching 40°C,” says Nielson, who is leading the project.

So, while heat stress is not a constant source of problems on an annual basis, from a sustainability perspective, it’s something Alberta potato growers nevertheless must deal with.

Growers must learn to address the impacts on yields and quality – especially crucial if such head events become more frequent in the future, which many argue is a distinct possibility. The good news is, there appear to be strategies.

Heat stress basics
The impacts of heat events on potato crops depend on such factors as the potato variety, the crop growth stage when the event occurs, and the event’s duration and intensity.

Neilson notes that the optimal temperature for tuber production depends on a few factors like the potato variety, but it is usually somewhere in the range of 15 to 20°C.

Above 20°C, the tuber growth rate tends to decline. Once the temperature climbs even higher, results can be even more stark.

“Once the temperature gets over about 30°C, overall growth stops. And when temperatures oscillate between going over and then under that maximum temperature, you have photosynthesis and plant growth stopping and starting.”

How heat stress manifests in tubers
That stopping-and-starting can affect overall tuber yields – the tonnage, the average tuber size, and so on. It can also affect tuber quality, causing various types of deformities and other problems.

AAFC’s Jonathan Nielson is leading a project looking at practical strategies to reduce the impacts of heat stress.

“For example, you can get heat runners after a pause in tuber development. That’s where [instead of resuming an increase in tuber size when growth restarts], the tuber starts producing knobs because the eyes break dormancy and start growing out,” he says.

“Another possibility is secondary tuber sets. The plant sets the first set of tubers and then gets stressed out. But when growth restarts, instead of continuing to grow the first set, it will start producing a second set.

“As a result, you get tubers of different physiological age going into storage, so you get differences in the size profile.”

This means, for instance, you might get a mix of a lot of big tubers with a lot of small tubers.

“That is obviously not ideal because you want all your tubers to be within a certain size range that meets your contract.”
Another key impact of heat stress is the effect on fry colour. “If the tubers are immature or physiologically stressed, the sugar dynamics can change,” says Neilson.

That can result in a dark colour when the potatoes are fried, for a lower quality end-product – especially bad news for Alberta’s wildly successful processing sector.

“You can get overall dark French fries or dark chips. But you can also get different patterns; a more common one is sugar end, where the french fry is very dark at one end and light at the other.”

A suite of stress-related studies
Neilson’s heat stress project is one of a collection of weather-stress-related potato projects in his research program.

“Our goal is to develop the tools and methodologies to find stress-related problems, recommend a solution, and verify that the solution is actually working,” he continues. “Then once we’ve got all of those pieces in place, we want to give that to growers and have them use it,” he says.

So, one overall program objective is to develop methods to rapidly assess large amounts of field data to identify weather-stress problems in crops.

The idea is to be able to get the relevant stress information to growers in a timely enough manner so growers have an opportunity to deal with the stress problem in their fields before it becomes irreversible.

And the other key program objective is to work with methods shown to reduce stress impacts in a greenhouse, a laboratory, a different growing region or a different agricultural system, and adapt those methods for real-world potato production under Alberta conditions.

Neilson’s heat stress project is funded by the Potato Growers of Alberta (PGA).

He is also leading a nearly completed hail stress project, which received funding from Results Driven Agriculture Research and in-kind support from the PGA.

Additionally, Nielson has some AAFC-funded projects looking at how field operations can be managed to reduce general weather/climate stress in potatoes.

His program is designed to have these individual projects build on each other, with tools, methods, equipment and learnings from one project being applied to the other projects.

Addressing heat stress
The heat stress project’s first full field season was in 2024, and it will run for two more years. The field work is taking place at AAFC’s Vauxhall Research Farm.

The experimental setup includes methods to ensure high temperatures in the plots. For instance, Neilson and his research group are using greenhouse tunnels to simulate short-term heat stress.

The team is also planting drip lines along with the potatoes so they can circulate water that has been heated to different temperatures, in turn increasing the root zone temperature. After, the team is planning to use these lines to apply the products that they are testing to see if root zone placement boosts product effectiveness.

In the trials, they are measuring yields, temperatures and many other factors.

These data collection activities include flying drones over the plots weekly to take spectral measurements (measurements of different wavelengths of light to assess things like the crop and soil conditions), as well as taking spectral and physical measurements on the ground.

A drone image shows some of the heat-damaged plots.

The goal of the project is to evaluate some commercially available products that are shown to help with heat stress impacts in other parts of the world or other agricultural systems.

“We’re trying to work out the technicalities of making them work for Alberta growers, given the differences in our growing systems [from the rest of the world],” says Nielson.

By focusing on addressing some of the technical barriers for...

Potatoes in Canada

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