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September 19, 2022

Get Sulphur Right to Maximize Canola Yield

Canola Field with sunny sky
Canola field with wind turbines in background

Ensure sufficient levels season-long to make the most of your crop’s potential

What’s a top under-the-radar factor for canola performance? Look no further than sulphur, say leading experts.

“Consistent high-level canola production needs to include a strong emphasis on ensuring ample levels of sulphur fertilizer – no question,” says Warren Ward, agronomy specialist and crop nutrition lead with the Canola Council of Canada.

Today more than ever it’s critical to not overlook sulphur, he says. “Our growers in Western Canada have the vast majority of production practices down to a fine science. But sulphur requirements are one aspect that our studies show can easily be miscalculated or taken for granted.”

This can put an unnecessary limit on the crop’s potential – holding back yield, quality, and plant health, Ward says. “Our most updated knowledge shows this is one area where you don’t want to skimp or cut back and take the risk of deficiency. In fact, you should make it a high priority to ensure adequate sulphur levels to eliminate that risk.”

Fueling success from seed to harvest

Even if the deficiency is small enough to not show strong visual cues, the loss of full crop potential added up acre after acre can make a big dent in profitability, Ward notes. “It can be a hidden cost where you don’t know how much yield and other advantages were left on the table.”

The uptake and removal rates Ward uses for sulphur in canola across Canadian production are approximately 0.7 lbs of sulphur taken up by the crop for every bushel produced. Of that, 0.3 lbs/bu is removed from the harvested seed.

With today’s options there is a lot of flexibility to find the best solution and approach for every operation, he says. “The right knowledge and advice from your agronomist and dealer can help optimize sulphur management and contribute to yield and profitability.”

Tackling the challenge of variability

As a quick refresher, Ward points out that canola has the highest sulphur demand of any crop grown in Western Canada – significantly higher than cereals.

Sulphur fuels overall plant growth including everything from early-stage development to pod fill. It is also critical for optimum nitrogen uptake, so ample availability is needed to get full value from nitrogen application.

“When there’s a sulphur deficiency, the damage and limitations come a lot quicker in canola than they do in other crops,” says Ward.

Studies have increasingly shown sulphur levels vary greatly in the landscape, which can make soil testing unreliable, says Ward. “With the traditional soil testing method of doing a composite sample for a field, you can easily hit a couple of pockets of high sulphur that will skew the results even when there may be many other areas that are deficient.”

“Normally when it comes to nutrient management we try to rely on testing, but because of the variability with sulphur it’s typically recommended to apply an adequate amount to meet canola yield expectations.

“It won’t hurt the high sulphur pockets and it will make sure you address the deficiencies that by now we know are going to be there. Another approach is to manage production zones within a field, including more intense sampling, to understand the landscape variability leading to applying the right rate of sulphur in each management zone.”

Recommended levels on the rise

Soils that are sandy, low in organic matter, and found in upper- to mid-slope field positions are particularly prone to sulphur deficiency, he says. Many production areas in Western Canada come with an inherent high deficiency risk.

Leaching is another key factor, as sulphur is mobile and can easily shift away from the root zone from topsoil to subsoil. This is a key reason why sulphur levels require ongoing replenishing through fertilizer application.

Canola typically needs 0.5 to 0.7 pounds of sulphur per bushel of yield, he notes. It follows that a 50 bushel per acre canola crop needs 25-35 pounds per acre of available sulphur.

Taking into account typical soil reserves, the previous general recommendation for Western Canada was to apply at least 10 lb./ac. of sulphur to every canola acre, every year, no matter the soil test result. Growers were advised to apply higher rates when necessary to meet soil test recommendations, especially when soil test results showed low sulphur.

Today, due to a better understanding of testing limitations and the costly impact of deficiencies, Ward and colleagues believe that is on the low end. At least 20 lb./ac and a typical range 20 lb./ac to 30 lb./ac is now recommended. As always, talk to your agronomist and dealer to make sure you apply the correct amount specific to your farm/fields and product of choice.

“Canola typically needs 0.5 to 0.7 pounds of sulphur per bushel of yield.” Taking into account typical soil reserves… a range 20 lb./ac to 30 lb./ac is now recommended.” said Ward.

Top fertilizer options

Different fertilizer approaches can get the job done, says Ward, but each has different advantages and requirements.

Spring application of ammonium sulphate has traditionally been the most common approach. It provides a source readily available for crop uptake and is generally applied in a band or broadcast. (It’s not recommended to be placed with the seed as it can cause damage if too close.)

Elemental sulphur (primarily sold in a sulphur-bentonite pastille) can provide an economical, season-long source of sulphur that is highly compatible with various fertilizer blends. For maximum benefit, elemental sulphur is typically broadcast in the fall at the latest. This provides logistical and performance benefits, as the winter weather helps disintegrate pastilles more thoroughly – setting up the sulphur for more efficient conversion into plant-available sulphate in the upcoming growing season.

Elemental sulphur is typically not a good choice for in-crop application since its slow conversion means it may not be available to the crop soon enough. However, it’s an excellent option when applied in the fall and overall has greater advantages for long-term maintenance.

“More producers are shifting towards this approach every year,” notes Ward.

“A long-term elemental sulphur strategy includes these applications every year to consistently allow enough time for the elemental sulphur to become plant available. It’s something you can do in the fall or year prior to growing canola to ensure your sulphur levels will be kept topped up and to reduce your workload the following spring.”


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