Post-Harvest Sulphur Management: Building Nutrient Reserves for 2026

As combines finish their final passes and harvest wraps up, attention shifts to next year’s plans. Fall is a good time to evaluate how well your fertility program kept up with crop demand—especially for nutrients that move easily in the soil, like sulphur. For many Prairie growers, choosing the right sulphur fertilizer source after harvest is one of the most impactful decisions influencing next season’s yield potential.

Sulphur is essential in Prairie fertility programs, especially for high-yield crops like canola. When it runs short, canola yield, oil content, and stand uniformity all take a hit—and by the time symptoms appear, it can be too late to recover.

Across Western Canada, sulphur deficiency is increasingly common. Studies show up to 40% of Prairie soils now lack adequate sulphur. Many traditional fertilizer sources are either too short-lived or too slow to release when crops need them most.

Understanding the Challenge of Sulphur Deficiency in Prairie Crops

Why is sulphur important for canola?

Sulphur drives protein synthesis, chlorophyll formation, and oil production—key to yield and quality. Deficiency first shows as pale new growth, delayed maturity, or patchy stands, but by then yield potential has already slipped.

Managing sulphur is tricky because sulfate, the plant-available form, leaches easily—especially in sandy fields or wet conditions. Elemental sulphur must oxidize before becoming available, a process dependent on microbial activity, temperature, and moisture. In short, it’s unpredictable.

That’s why the question isn’t just how much sulphur to apply, but how reliably it will be available when your crop needs it.

Introducing Polysulphate® as a Long-Term Sulphur Fertilizer Solution

What Makes Polysulphate® Different as a Sulphur Source?

Polysulphate® is a unique multi-nutrient fertilizer that redefines sulphur replenishment. It’s a natural mineral fertilizer containing sulphur, potassium, calcium, and magnesium in sulfate form, mined from under the North Sea and simply crushed—no chemical processing or additives.

How Does Polysulphate® Release Sulphur Gradually to Match Crop Demand?

Each granule delivers sulphur (S), potassium (K), calcium (Ca), and magnesium (Mg) in readily available sulfate form. Unlike other sulfate sulfur, the crystalline form of Polysulphate must break down before the sulfate becomes available. This process is limited by the solubility of the calcium sulfate component in the polyhalite mineral. As a result of the slower dissolution, the sulfate in Polysulphate is released gently and over an extended period (up to 50 days), not all at once. This provides a sustained supply of nutrients that better matches a crop’s uptake requirements throughout the growing season.

• Sulphur is released gradually to match crop demand.
• Potassium strengthens stems and water regulation.
• Calcium builds cell walls and root resilience.
• Magnesium fuels chlorophyll production.

With a low salt index and neutral pH, Polysulphate is gentle on seedlings and soil microbes. It fits easily into fall or spring applications, offering flexibility for different systems and weather windows.

Polysulphate® vs. AMS, Elemental Sulphur, and SOP: How Do They Compare?

Each sulphur source has strengths—and limits:

• Ammonium Sulfate (AMS) releases sulphur immediately but leaches quickly and has a high salt index.
• Elemental sulphur provides a long-term reserve but is slow and weather-dependent.
• SOP (Sulphate of Potash) supplies K and S, but both release rapidly, leaving little residual benefit.

Polysulphate bridges the gap with both immediate and sustained sulphur release—plus Ca, Mg, and K for balanced nutrition and improved soil health. It is increasingly evaluated as an alternative to AMS, SOP, and elemental sulphur in Prairie fertility planning.

Field Trials Demonstrate Yield Gains with Polysulphate®

What trials show Polysulphate performance is proven?

In Western Canada canola trials, Polysulphate increased stand counts by around 10% and yield by up to 25% compared to traditional sulphur sources. AMS or KCl near the seed often reduces emergence due to salt stress, while Polysulphate, due to it’s low salt index, supports uniform stands and seed safety.

We see the same across other crops including:

• Alfalfa: +6.8% total yield, including a 25% boost in fourth cut, with higher protein and improved feed quality.
• Oats: Adding Polysulphate to Urea + MAP increased yield by roughly 32 bu/ac compared to the same blend without it.

The trend is clear: balanced nutrition, low salt load, and gradual nutrient release translate to stronger stands and higher yields.

How Polysulphate® Improves Soil Health and Nutrient Efficiency

Beyond yield, Polysulphate enhances soil structure and microbial activity. As a natural mineral with neutral pH, it supports soil balance rather than disrupting it. Its gradual release improves nutrient use efficiency and reduces leaching—a win for both productivity and sustainability.

With options like Polysulphate Premium and ICL PKpluS, growers can choose formulations tailored for Prairie conditions, blendability, and air seeder compatibility.

Key Takeaways for Planning 2026 Fertility Programs

Sulphur deficiency is widespread—and costly, but the solution doesn’t have to be complicated. By choosing a source that provides sustained release, multi-nutrient synergy, and proven field performance, growers can safeguard both yield and soil health.

For growers comparing sulphur fertilizer options for canola, Polysulphate provides a sustainable, multi-nutrient solution that reduces loss and improves availability during the peak uptake window.

As you plan your fertility strategy for 2026, ask yourself—is your sulphur program keeping pace with what your crops are taking away? With Polysulphate®, you can replenish sulphur and more—naturally, efficiently, and sustainably.

Contact your local ICL representative or retailer to discuss rates and availability in your region.

Frequently Asked Questions

1. What is the best sulphur fertilizer source after harvest?
The best source depends on how quickly the sulphur becomes available and how long it remains in the soil. Multi-nutrient products, like polyhalite (sold as Polysulphate), provide both immediate and gradual release of sulphur-based S, K, Ca and Mg, improving nutrient efficiency in the short and long-term.

2. How does Polysulphate compare to ammonium sulfate (AMS)?
AMS releases sulphur rapidly but can leach quickly in sandy or wet soils. Polysulphate provides a longer release profile, delivering steady sulphur availability over several weeks (plus it has the added benefit of being low-salt, and multi-nutrient).

3. Can Polysulphate be applied in fall ahead of canola?
Yes. With a low salt index and gradual release curve, Polysulphate is well suited to fall applications where it can mineralize and support early crop demand.

4. Does Polysulphate improve soil health?
Because it is a natural mineral with neutral pH, low-chloride K and low salt load, Polysulphate supports soil structure, microbial activity, and improved nutrient use efficiency over time.