Free Nitrogen Or Expensive Rotation?

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Rotation research is ongoing at eight sites across the Prairies


Pulses are a great way to cut the nitrogen bill, especially if the following crop is a cereal. But do shared diseases create an additional risk if pulse land is rotated into canola?

The jury is still out, says John O’Donovan, an Agriculture Canada cropping systems agronomist who spoke at a recent field day.

“Fava beans have been researched in a limited number of studies, and have been shown to be a good fixer of nitrogen and a good contributor to the nitrogen economy of cereal crops.”

But researchers currently do not have a good database of information to explain the benefits of a rotation combining a pulse and a canola, said O’Donovan. This could be a potential risk, but there has a lack of solid evidence so far.

The study of pulse-canola rotations is being conducted at about eight Agriculture Canada research stations in Alberta, Saskatchewan and Manitoba, covering all the different soil zones. “The main focus is to look at the effect of the pulse on the nitrogen requirements of the canola the following year,” said O’Donovan.

Pulses don’t extract as much moisture from the soil as cereal crops, which could be an advantage, especially in dry years, he said. Researchers will also be studying the impact of pulses on the health of the soil, particularly as it pertains to microbial biomass and microbial diversity.

Fava beans, peas and lentils, wheat and canola are all being tested in the study. Cereals will receive fertilizer treatments but the legumes will not. Hybrid canola will also be grown during the test.

“Hybrids are really strong consumers of nitrogen so we’re really interested in looking at reducing the requirement for nitrogen in hybrid canola.”

Researchers will use five different rates of nitrogen in each of the blocks, ranging from zero to 100 kilograms per hectare.


Kelly Turkington, an Agriculture Canada plant pathologist, said a pulse/ canola rotation could create a risk of sclerotinia.

“Based on my experience, I’m ambivalent,” he said. “It could be a risk but it really depends on whether or not you had sclerotinia develop in the previous crop.”

Turkington said producers should scout for sclerotinia by looking at dockage in a harvested pulse. “If you’ve got dockage as a result of sclerotinial contamination, that serves as an indication that there’s sclerotinia there and a potential risk,” he said. “It ultimately depends on what the weather conditions are like when you’re growing your canola crop.”

There are variety of factors that affect sclerotinia risk, he said. Researchers will be examining seedling concerns and the effect of the pulse on the cereal seedlings, especially when it comes to the potential carryover of diseases such as fusarium. Crop emergence counts in canola and various treatments will be used to monitor these potential risks, said Turkington.

“We should be able to get a handle on risk in the seed and seed emergence issues.”

About the author


Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."



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