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Worried about pea disease? Try peaola

Intercropping peas and canola can minimize disease and lower production costs

With international pea processor Roquette opening a plant in Portage la Prairie, Man., in 2020, many growers will be thinking about taking advantage of the opportunity. Some, however, will be worried about one of the biggest challenges of growing peas: disease. There may be a solution, though. Researchers and experimental farmers are finding answers in intercropping. Scott Chalmers, diversification specialist with Manitoba Agriculture, explains.

The greatest risk of growing peas in Manitoba is disease, said Chalmers in a recent interview. The province’s richer, wetter soils are certainly a contributing factor. Intercropping, he said, can help growers manage disease.

“Most of the disease that Roquette would be concerned about, which is on the peas themselves, can be reduced by intercropping with canola,” he said.

In particular, intercropping can help mitigate issues from soil-borne diseases that spread during heavy rainfall. “If the plants are laying on the ground, it’s pretty much guaranteed that the plants are going to get bad disease,” he said. Intercropping with canola keeps the peas off the ground because the canola crop acts as scaffolding for the peas. The extra space beneath the canopy more easily dries out between rain incidents as well.

This farmer’s pea and lentil intercrop (peaola?) near Mariapolis, Man., in 2011 yielded 29 per cent more than the monocrops in his area.
photo: Courtesy of Scott Chalmers, Manitoba Agriculture

“Because the density of the canopy is so immense, the rain can’t splash the soil particles back up onto the plant, so it’s reducing the chance of disease,” said Chalmers.

Intercropping benefits

Manitoba Agriculture research shows that intercropping three crops — canola, peas and alfalfa — results in even lower incidents of disease.

Intercropping offers other benefits to pea growers that can lead to higher quality, including pest management. “The last two years we’ve had aphids on our peas,” said Chalmers. “And for whatever reason, when you intercrop with canola, the aphids don’t want to touch those peas.” Researchers suspect that bertha army worm and diamondback moths are not interested in intercropped peas either.

There are economic benefits as well. Chalmers has done some research looking at nutrient use in pea/canola (sometimes referred to as peaola), and has found that there’s no use adding nitrogen. “That’s because it gets tied up with the peas. The peas become lazy and they don’t want to fix nitrogen, and the canola gets outcompeted because the peas took up that nitrogen,” he said.

Demonstration plot near Hamiota, Man., of an intercrop of peas and canola (right) and straight canola (left). The canola is prone to shatter on the left, but not on the right where the peas have it tangled up. The peas in the intercrop had less disease in this intercrop than in a monocrop (not shown in the photo).
photo: Courtesy of Scott Chalmers, Manitoba Agriculture

Numbers show there’s a $10 to $15/acre savings to be found in intercropped peas and canola as compared to growing canola alone.

Production research

Researchers have also been looking at production methods. A 2014 report by Westman Agricultural Diversification Organization (WADO) concluded that mixed-row orientation (as opposed to alternating rows) produces greater total yields.

WADO also found that intercrops use more water in the soil and that is correlated to total yield, especially with canola, which Chalmers said is not surprising since canola is a deep-rooting crop. In high-rainfall years, yields were usually phenomenal, said Chalmers. But in drier years, like 2017 and 2018, yield benefits are small due to the lack of water.

In terms of economics, at the time of the research, peaola provided a greater net return than canola, but peas did not.

Harvesting two crops at once

Harvesting intercrops can be complicated, but it’s not impossible. When peas are harvested with canola, they’re usually straight cut with a regular combine header — a flex-header or rigid header — rather than swathed, explained Lana Shaw, manager of the South East Research Farm at Redvers, Sask.

“The tricky part is that sometimes the canola can take quite a while longer to mature than the peas,” she said. “Later-season peas are less risky, and there is a need for earlier Clearfield non-shatter canola varieties to meet the demand for an intercropping canola.”

This photo was taken at harvest time in 2017. Note how the peas are podding high and well off the ground.
photo: Courtesy of Scott Chalmers, Manitoba Agriculture

The combine threshing operation is relatively easy, she added, the main difference being that the fan speeds are turned down enough to ensure that the canola is not blown out the back of the combine.

The mixed grain ends up in the combine hopper and is separated later. Safe storage parameters of mixed grain have not been studied yet, so farmers are either separating shortly after harvest or carefully monitoring moisture and temperature until they can separate the crops later in the fall.

Ask a farmer

Brooks and Jen White have been experimenting with intercropping on their 6,800-farm in Pierson, Man., for about seven years now. Brooks says he seeds peas in a number of combinations, including with canola, oats, barley and multi-species mixes for grazing.

Peas and canola in the back of Brett McCrae’s grain truck, on his farm south of Brandon, Man.
photo: Courtesy of Scott Chalmers, Manitoba Agriculture

Intercropping has resulted in soil health improvements, said White, who now relies on fewer inputs as a result. He has also seen greater resilience to adverse weather, like hail, and less pressure from insect pests, including aphids and diamondback moths.

White straight cuts his peaola crops, using Diquat as a harvest aid. Peas and oats are swathed. “We have eliminated the need to roll our land for stones, as the intercrops help to grow the peas upright and hold them off the ground, allowing us to cut higher and leave more standing stubble,” he added.

He admits intercropping can be challenging at first, especially when it comes to logistics. “For some crops, another tank may be required in the drill, and another truck to handle it,” he said, adding that he premixes seed to eliminate that issue.

Seeding depth of the different crops can also be an issue, especially when soil conditions aren’t ideal. In good soil conditions, peas and canola can potentially work at the same depth, he said.

Augers set up to separate crops post-harvest on Brett McCrae’s farm, south of Brandon, Man.
photo: Courtesy of Scott Chalmers, Manitoba Agriculture

“Separation of the intercrops adds another operation, but we look at this as a way to add value and create employment,” White added.

Finally, he suggests finding a mentor. “I find people very willing to share ideas and experiences,” he said. “Have a goal in mind of what you are trying to accomplish with intercropping. For us it is part of a larger vision for our business plan that we have developed.”

About the author

Columnist

Melanie Epp is a freelance farm writer.

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