More diverse crop rotations are better, agronomically speaking, but economically speaking, the story is not always so clear. Cash flow in the immediate term sometimes takes centre stage when growing a high-profit crop such as canola.

But what if growing a more diverse rotation was just as profitable as growing canola in a one-in-two, or one-in-three year rotation? Furthermore, what if we could better quantify the other types of risk costs in terms of weed pressure, insects, or disease?

In this episode of the Canola School, Breanne Tidemann, research scientist at Agriculture and Agri-Food Canada at Lacombe, Alta., explains a research project that examines these two questions.

The project was passed down to Tidemann from her predecessor, Neil Harker, and includes sites at Lacombe and Lethbridge in Alberta, and at Melfort, Scott, and Swift Current, in Saskatchewan, covering a wide scope of climatic conditions and soil zones.

“By the time the project finished, which was last field season, we had had 12 years of continuous canola, and that was in comparison to a one-year out of canola, and two year out-of-canola rotations,” says Tidemann.

Watch the full video to hear more about how the research was set up and what was measured. Story continues below:

The first six years of research has been published, and the main take-away was that yield increased by five bu/ac when canola was included every second year, as compared to continuously. Yield increased again by another 5 bu/ac when moving canola to every three years.

For every year out of canola, there was a decrease in damage from root maggots and the frequency and severity of blackleg.

As for the economic side of the equation, “When we look at our net returns, what we’re seeing averaged across all sites and all years, there was really no significant difference between treatments, which is actually a good thing,” says Tidemann. “What we’re told is ‘I can make more money growing short rotation canola’ and what this is showing us is, in the long-term at least, that’s not necessarily true.”

The economic data hasn’t been analyzed yet by the economist collaborating on the project, but the other benefits — increased yield, decreased weed pressure, insects, and diseases — are quite clear.

In the more recent data that Tidemann has collected, from 2016 to 2019, the yield pattern changes a bit. “When we look at the final three years of yield, we start to see more of what we actually expected,” says Tidemann. The biggest increase in yield when moving from a continuous to a one-in-two rotation, and you still get an increase in yield, albeit smaller, when you go from one-in-two to aa one-in-three rotation.

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