Harnessing Polysulphate®: Fall-Applied & Post-Harvest Nutrition

Explore the benefits of fall-applied Polysulphate® for optimizing nutrient availability, improving crop yields, and supporting sustainable farming practices.

July 12, 2024
4 mins
Dr. Jason Haegele
North American Agronomy Lead, ICL Growing Solutions

The Importance of Fall-Applied Nutrients

As the harvest season approaches, farmers face critical decisions that can significantly impact the success of future crops. One such decision revolves around nutrient management, particularly the timing of fertilizer applications. Fall application of nutrients, including products like Polysulphate®, offers distinct advantages in preparing fields for optimal spring planting and crop growth.

Why Fall Application of Nutrients Matters

Understanding why fall applications matter and how to make the most of the nutrients we put down is essential for sustainably maximizing agricultural productivity. Fall is an opportune time to apply nutrients for several compelling reasons:

  • Soil Preparation: In many areas, fall tends to be drier compared to spring and post-harvest fields are accessible to application equipment. In addition, the warm, dry days of fall are an ideal time to complete tillage and nutrient incorporation operations, making for more manageable and efficient nutrient application. This preparation sets the stage for robust root development and nutrient uptake in the upcoming growing season.
  • Nutrient Availability: Applying fertilizers in the fall allows nutrients to integrate into the soil, making them readily available for plants as they begin active growth in the spring. This early availability can enhance early-season vigor and yield potential.

Pros and Cons of Fall Application


  • Optimized Soil Conditions: Fall applications capitalize on favorable soil conditions, such as adequate moisture and moderate temperatures, conducive to nutrient absorption and root development.
  • Enhanced Plant Health: Nutrients applied in the fall can provide early nutrient availability to support vigorous plant establishment, stress tolerance, and overall crop health, potentially leading to higher yields. Adequate nutrient availability in the fall is especially important for permanent crops as they are assimilating nutrients and forming buds for next year’s flowers and fruits or nuts that follow.
  • Workload Distribution: Spreading fertilizer application across seasons reduces the pressure during critical spring planting periods, allowing for more efficient farm management.


  • Weather Dependency: Timing fall applications is crucial and weather dependent. Unfavorable weather conditions can delay operations or affect nutrient effectiveness.
  • Nutrient Loss & Economic Risk: Improperly managed fall applications can lead to nutrient loss through leaching or volatilization, impacting cost-effectiveness and environmental sustainability. We must try to ensure that the nutrients we put down in the fall are available in the spring.

Polysulphate® Fall Applied, Spring Approved

What is Polysulphate®?

Polysulphate® is a multi-nutrient fertilizer derived from polyhalite, a natural mineral containing potassium, sulfur, calcium, and magnesium. Mined exclusively by ICL, Polysulphate® offers gradual nutrient release, ensuring sustained availability throughout the crop’s growth cycle. It is soluble, plant-accessible, and renowned for its low-salt, low-chloride, and pH-balanced composition, making it suitable for various crops, including fruits, almonds, cotton, corn, soy, and potatoes.

Why Choose Polysulphate® for Fall and Post-Harvest Applications

  • Nutrient Efficiency: Unlike ammonium sulfate which is prone to leaching, and elemental S which unpredictably oxidizes and becomes plant-available, Polysulphate’s gradual release minimizes nutrient loss, enhancing nutrient uptake efficiency and crop utilization. Don’t underestimate the importance of sulfur and secondary macros on yield.
  • Crop Safety: Its low-chloride K, low salt index, and pH-balanced source of nutrients make it safe for sensitive crops, supporting healthy plant growth without adverse effects.
  • Environmental Stewardship: OMRI-approved and boasting a reduced carbon footprint, Polysulphate® aligns with sustainable farming practices, promoting soil health and ecosystem resilience.
  • Ease Spring Workload Sustainably: By spreading the workload between fall and spring, farmers can manage time and resources more effectively while minimizing environmental impact and reducing pressure during spring planting.

Release of Various Sulfur Fertilizers

Polysulphate has a prolonged sulfur release pattern, which reduces losses by leaching.

Featured Trials: Polysulphate® in Action

Almonds: Boosting Orchard Resilience & Yield

A recent trial in Parlier, California, demonstrated significant benefits of fall-applied Polysulphate® on almond yields. By applying 750 lb/a of Polysulphate Standard alongside MAP and SOP post-harvest, growers achieved a 4.8% increase in kernel yield compared to conventional practices. This approach improved economic returns and enhanced soil quality and nutrient use efficiency.

Corn: Enhancing Sulfur Uptake and Yield

A recent trial at the University of Minnesota’s Waseca, MN research site highlighted the effectiveness of fall-applied Polysulphate® on corn production. Farmers applied Polysulphate® post-harvest and observed significant improvements in sulfur uptake and overall crop yield in the following season. Compared to conventional methods and sources of sulfur used for both spring and fall applications, notable increases in corn yield were achieved with Polysulphate. Polysulphate® also enhanced nutrient absorption and utilization in plant tissue and grain, demonstrating its reliability across different application timings.

🔗 Explore More Trials and Resources

Application Tips from Agronomists

To maximize the effectiveness of fall applications, consider these expert tips:

  • Flexibility: Adapt application timing based on local weather conditions and harvest schedules to optimize nutrient uptake. If you miss the fall application window, save your nutrients until spring!
  • Soil Testing: Essential for precise fall fertilization plans, soil testing provides a baseline for effective nutrient strategies. Tailor Polysulphate® application rates and ensure precise nutrient management according to crop needs.
  • Adjust Application Rates: Incorporate Polysulphate® into a balanced fertilizer program, adjusting application rates (typically 150-350 lb/a) to meet specific crop and soil requirements.
  • Community Engagement: Collaborate with local agronomists and agricultural communities to exchange knowledge and refine nutrient management strategies for enhanced crop performance. We love to talk about soil!

The Bottom Line

As agriculture continues to refine sustainable nutrient management practices, fall-applied and post-harvest nutrition becomes increasingly important. It’s not just when we apply but also what we use, in what form, and how much of it that also matters. Polysulphate® emerges as a reliable solution, offering growers a dependable means to apply nutrients still available in the spring. The goal here is not only cost-effectively improving yields but also enhancing soil fertility, optimizing crop health, and supporting environmental stewardship. By integrating Polysulphate® into fall nutrient management strategies, we can make spring plant that little bit easier.