Rethink Your Canola N Rates

After a couple of years of planting hybrid varieties and producing high yields without applying the necessary amounts of nitrogen, producers will be let down by lower yields.

Average yields for canola have increased dramatically in a very short time. Five years ago growers harvested 20 or 30 bushels to the acre. Today they routinely bring in 40 or 50. John Mayko, senior agronomy specialist with the Canola Council of Canada, says key factors are hybrid varieties, herbicide tolerance that provides for better and more timely weed control, direct seeding practices that lead to higher levels of organic matter and more mineralization of nutrients, favourable moisture (except for 2009), and earlier seeding.

To sustain such heavy yields, plants require larger amounts of nitrogen. Have the recommended rates for nitrogen kept pace with the new 50-bushel reality?

Manitoba Agriculture, Food and Rural Initiatives released new nitrogen recommendations in May 2009 when it published a reworked “Nitrogen Rate Calculator for Wheat, Barley and Canola.” To try the Excel-based calculator yourself, go to enter “Nitrogen Rate Calculator” in the search box at the top. It should be the first item that pops up.

John Mayko isn’t certain if Saskatchewan and Alberta are following suit. Both Alberta Agriculture, Food and Rural Development and Saskatchewan Ministry of Agriculture published their most recent recommendations in 2005. “It’s a continual evolution of results that come out of ongoing research and it can be hard to keep up,” Mayko says.


Manitoba’s recommendations come out of research that Westco Fertilizer performed a few years ago comparing nitrogen rates on openpollinated and hybrid varieties, Mayko says. Data from Westco’s research indicated that for hybrid varieties to reach economic maximum, nitrogen application rates had to be higher than for openpollinated varieties. With moderate nitrogen application, hybrid varieties will still yield more but they will not hit peak yield potential. Unless farmers fertilize more (when moisture conditions are favourable), they risk leaving yield on the table.

Jeff Schoenau, prof in the Department of Soil Science at the University of Saskatchewan, calls it a matter of balancing inputs. He compares hybrids to having a race car: “If instead of putting premium gas in it, you put in poor quality fuel, it’s not going to go to its potential.”


Some farmers might not feel it’s necessary to up their applied rate of nitrogen because they’ve produced 50-bushel and higher canola yields with relatively modest nitrogen applications. Mayko says these initial high yields didn’t come from nothing. They will have resulted partly from the high level of organic matter in the soil (if the grower direct seeds) and partly from a pre-existing high level of nitrogen in the soil due to (1) the dryer conditions in years past since nitrogen is not taken up effectively by plants when it’s dry but remains in the soil to be used in the future when the moisture is good, and (2) the grower may have previously grown open-pollinated canola varieties, which don’t extract nutrients from the soil as efficiently as the hybrid varieties do.

After a couple of years of planting hybrid varieties and producing high yields without applying the necessary amounts of nitrogen, producers will be let down by lower yields. They will definitely need to

replenish that nitrogen at increased levels if they want to continue to produce those high yields.

Mayko is also concerned that “most growers are probably a bit conservative with nitrogen rates because of the perceived risks of applying it and not getting it back in terms of a yield response.” With last year’s spike in fertilizer prices, many growers may have cut back their rate of application. The good news is that prices for nitrogen have come down at least at the wholesale level. Mayko urges producers to lock in their prices and not to be shy applying more of it.


Farmers who feel skeptical don’t have to run out and apply a higher nitrogen rate to the whole farm. Mayko suggests farmers first check it out for themselves by putting in a few test strips with higher nitrogen application rates and then seeing if the crop responds. Mayko notes that in this day and age, it’s easy to do on-farm trialing since combines now have yield monitors on them allowing growers to quickly gauge how the yields in the test strips compare to the rest of the field. Once growers see the difference for themselves, they can make an informed choice.

Mayko’s biggest piece of advice for farmers is to get their soil tested properly so they have a good benchmark to start. A basic soil test that only measures nutrients is inadequate. Farmers also need to identify the levels of organic materials in their soil. Then you can estimate the amount of nitrogen released by the soil over the growing season given the anticipated moisture levels. From there, farmers can work with their ag-retailers to determine the amount of nitrogen to apply given the yields they expect.

Mayko and Schoenau both note that whether or not the provincial agriculture departments have revised their nitrogen recommendations, ag-retailers, agronomists, crop nutrition planners and lab technicians are accessing the updated data right now and are making recommendations to individual farmers based on them.

Stay tuned, because with the speedy turnover in varieties — new ones are coming on to the market all the time, others are going off — Mayko is pretty certain that down the road, there will be further revisions to the “new” nitrogen recommendations, too.

Patty Milligan lives on a farm near Bon Accord, Alta.

About the author


Patty Milligan is a freelance writer based at Bon Accord, Alta.

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