Nitrogen Decisions for Canola

Thursday, June 18, 2026

Turning research findings into on farm choices that support yield & cut losses

By Mary Loggan

Nitrogen underpins canola yield, quality and profitability across the Prairies, but it is also one of the hardest nutrients to manage well. Soil behaviour, weather, timing and placement all influence how much of the fertilizer growers pay for reaches the crop.

For Mario Tenuta, professor and acting head of the Department of Soil Science at the University of Manitoba, the key is to align nitrogen supply with canola’s potential while managing the risk of loss under highly variable Prairie conditions.

Why nitrogen matters

“Nitrogen is the nutrient that most strongly drives canola yield,” Tenuta says.

“Canola produces a large amount of above ground biomass (8,000–13,500 lb/ac), and much of the nitrogen in that biomass is transferred into the oilseed, where a 50 bushel/ac crop can take up a total of 120 lb N/ac.

“That removal is high because canola seed is roughly one quarter protein, and the meal left after crushing can contain up to 40 per cent protein.”

Regional systems shape that demand.

“Western Canada is dominated by spring canola, where yields reach about 55 bushels/ac or typically less, compared with higher yielding winter canola in Eastern regions.

“As a result, spring canola usually removes around 80 to 90 lb N/ac with the oilseed, while high yield winter canola can remove closer to 135 lb N/ac.”

Nitrogen is important throughout the spring canola season.

“Early on, it supports leaf and canopy development so the crop can capture sunlight efficiently.

“Later, it supports branching, flowering and pod formation, all of which determine final yield.”

Spring canola has a relatively short growing season, so Tenuta emphasizes that nitrogen must be available quickly after planting to hit yield potential.

Benefits of proper management

“When nitrogen is managed well, growers see higher and more consistent yields because the crop has access to nitrogen during critical growth stages such as branching, flowering and pod filling,” Tenuta says.

Better management also improves nitrogen use efficiency, so a greater share of the applied fertilizer is taken up by the crop rather than being lost.

“That helps maximize return on fertilizer investment and reduce environmental losses such as nitrate leaching and nitrous oxide emissions.”

Tenuta stresses that sulphur must be part of the fertility plan.

“I’d be remiss not to mention sulphur. It's also very important to consider sulphur availability; the crop won’t respond adequately to nitrogen.

“Canola is a high sulphur demand crop with a particularly high need from rosette to bolting.”

Sulphur is important for seed protein and oil and is needed for glucosinolate production, he notes.

“Sulphur deficiency is easy to spot because, unlike nitrogen deficiency, it is the young leaves that are pale yellow in colour. Leaves may seem to be ‘cupped’ and have purple edges as well.

“Ammonium sulphate (21 0 0 24S) is the most readily available fertilizer form for sulphur.”

As benchmarks, Tenuta suggests around 30 lb S/ac for spring canola and about 40 lb S/ac for winter canola, with the nitrogen in ammonium sulphate counted toward total N rates.

Why is nitrogen challenging in canola?

“Managing nitrogen is challenging because nitrogen is highly dynamic in soil and is affected strongly by weather conditions,” Tenuta explains.

Nitrogen can be lost through ammonia volatilization, nitrate leaching and denitrification.

“For spring canola, the availability of nitrogen from planting to rosette is important,” he says.

Applying nitrogen too early can increase the risk of loss if conditions are wet and warm before the crop takes it up.

Applying too late can limit early growth and yield potential, especially when seeding is delayed and the season is compressed, he notes.

When nitrogen is insufficient, the symptoms are clear.

“Canola shows reduced canopy growth, fewer branches and pods, smaller seeds and lower yield. Nitrogen deficient plants are stunted and spindly with an open, airy canopy.

“Leaves yellow from the margins, and lower leaves can brown and die. A thin canopy collects less sunlight and allows weeds to outcompete the crop, hurting yield and possibly creating weed issues in the following years.”

Start with the soil test

For Tenuta, the first step in managing risk is knowing what is already in the soil.

“Soil testing is the best way to determine how much nitrogen is present for the crop to use.”

He says on the Prairies, late fall or early spring sampling to two feet is usually sufficient to understand what is available for spring canola.

“As a rule of thumb, a 50 bushel/ac spring canola crop needs about 140–150 lb/ac of total nitrogen, combining soil test N and fertilizer N.”

Lessons from research

Tenuta’s research in Manitoba illustrates how timing and moisture interact.

“Our laboratory has tested split application of fertilizer nitrogen to spring canola in Manitoba from 2019 to 2021 for a total of six trial locations.”

In these trials, 60 per cent of the fertilizer nitrogen was applied at seeding as urea and 40 per cent at rosette as UAN (28 0 0).

Results depended heavily on rainfall.

“When rains followed the split application, yields were comparable to applying all nitrogen at planting. When it remained dry after the in season application, yields were about five bushels/ac lower with the split.

“This really shows the risk of stranding in season applied nitrogen at the surface with a lack of rain,” Tenuta notes.

He also points to seed safety as a firm limit on the amount of seed placed nitrogen.

The Prairie Agricultural Machinery Institute (PAMI) conducted extensive studies in Alberta and Saskatchewan in the 1990s.

“Maximum seed safety rates were 10 to 50 lb N/ac in furrow applied urea, depending on soil texture, row spacing and seed bed utilization,” he says.

“The Canola Council of Canada later recommended even lower seed placed rates for Manitoba, from 0–30 lb N/ac of urea, in higher pH soils because of a greater risk of ammonia toxicity.”

Tenuta stresses that canola has a very low tolerance for seed placed nitrogen, so keep it to a minimum and use sidebanding or mid row banding instead.

Placement, timing & product choice

Placement decisions strongly affect nitrogen losses.

“The placement method of fertilizer nitrogen can reduce losses of applied nitrogen to canola,” Tenuta says.

Although direct measurements of ammonia loss in canola are limited, it is reasonable to expect surface applied urea or UAN in spring to lose around five to 10 per cent of the ammoniacal nitrogen if rains don’t wash the products into the soil.

“The easiest way to prevent ammonia loss is subsurface placement banding to a depth of three inches.”

In practice, deep side banding can be difficult where canola is shallow-seeded or where equipment is limited.

“Where surface placement is a must, urea inhibitors will protect ammonia loss from the ammoniacal nitrogen in fertilizer nitrogen.”

Tenuta strongly cautions against surface applied fall urea for spring canola.

“Manitoba trial work showed that urea left on the surface in late October, even with urease or dual inhibitors, produced yields about 13 bushel/ac lower than surface applied urea at planting.

“Over five fields from 2014–2016, mid row banding of urea at planting to depths of one-and three-inches increased yields over surface placement by 2.5 and 3.0 bushel/ac, respectively.”

Earlier Prairie work by Tenuta’s colleagues Don Flaten and Kevin Tiessen also shows how drainage interacts with timing.

“Banded urea in low spots in commercial fields was about 20 per cent less efficient when banded early in the fall compared with spring banding.”

On higher, better drained positions, late fall banded urea performed similarly to spring banded urea.

“I believe avoiding early fall application of nitrogen to poor drained soils is a useful tip for spring canola in Western Canada as well,” Tenuta says.

Product choice can help bridge the gap between staffing and weather.

“The timing of soil nitrogen availability and canola demand can be improved by considering the use of enhanced efficiency fertilizer (EEF) nitrogen products such as nitrogen stabilizers containing urease inhibitors, nitrification inhibitors, or both (dual inhibited), or polymer coated urea,” he explains.

These products reduce losses when soils are wet and warm or when fertilizer must be applied well before crop uptake.

However, Tenuta cautions that yield benefits are not guaranteed.

“We have rarely found a yield benefit for spring canola with EEF products applied at planting and in season in Manitoba.”

He notes their main value is as risk management tools when conditions or workload force less than ideal timing. Polymer-coated urea can increase seed safety rates as well.

Planning ahead

For Tenuta, the principle is to match nitrogen supply to crop potential while managing the risk of loss.

“With good soil moisture and solid agronomy, the potential for strong spring canola yields is there.

“Growers should set realistic yield targets, use soil tests to understand existing N, and then choose rates, timing, placement and products to support that potential.

For producers planting spring canola, banded nitrogen at or before seeding combined with soil testing and realistic yield targets remains one of the most reliable strategies, he says.

“Ultimately, successful nitrogen management comes down to ensuring that nitrogen is available when the crop needs it most, particularly from rosette to flowering when yield potential is determined.” BF