Osmocote 101: the story and science

More than 50 years ago, Osmocote launched as the world’s first coated fertilizer. The decades since that pioneering achievement have seen remarkable advances in fertilizer technology. But ICL’s Osmocote remains horticulture’s leading controlled release fertilizer (CRF) worldwide. From Osmocote’s foundational technology to ICL innovations that drive it today, professional growers trust the Osmocote way.

What are controlled release fertilizers?

Controlled release or coated fertilizers are similar to long-acting prescription or over-the-counter medicines that release slowly over time. The technology behind those slow-release tablets on drug store shelves was pioneered in the early 1950s—a little more than a decade before Osmocote arrived on the scene.

In pharmaceuticals, one or several layers of materials applied to the outside of the tablet control the release of the active ingredients inside. Once a slow-release tablet is in your system, the outer layers slowly dissolve and release the ingredients gradually over a set time.

Coated fertilizers like Osmocote are designed in much the same way. Special coatings applied to fertilizer particles regulate the rate of nutrient release. Coating material and thickness, moisture content, and soil temperature all have a role. Controlled nutrient release offers multiple benefits, including improved plant health and yield, reduced environmental impact, reduced labor costs, and increased profits.

With controlled release fertilizers, a one-time application can optimize nutrition throughout the plant’s growth cycle. And because different CRF products are designed to release nutrients over different lengths of time—what we call longevity—it’s possible to fertilize on cycles ranging from six weeks to eighteen months.

So how does Osmocote actually work?

The key to understanding how Osmocote works is in its name. As you might have guessed, the word Osmocote came from two words: osmosis and coating. Osmosis is what happens when water moves from an area of higher concentration to an area of lower concentration, through a membrane or coating of some kind. The force behind the movement is called osmotic pressure.

If you’ve ever seen a raisin go from shriveled to plump when soaked in water, you’ve seen osmosis at work. That same principle is what regulates both the movement of water into Osmocote granules and the movement of nutrients out of Osmocote into your growing media.

The patented organic resin coating covering each Osmocote fertilizer granule regulates daily nutrient release. The granule’s inner core contains Nitrogen (N), Phosphorus (P), Potassium (K), and all essential trace elements. Varying the thickness of Osmocote’s coating modifies nutrient release, so you can choose CRF longevities to match the requirements of the plant materials you grow.

With Osmocote incorporated in your plants’ growing media, irrigation water penetrates the granule coating. That starts a process that dissolves the nutrients inside. Osmotic pressure goes to work, and released nutrients move through the coating and into your media. For all Osmocote longevities, nutrients release at constant and controlled rates. When longevity is complete and all nutrients are released, the resin coating breaks down and disintegrates.

What are the advantages of Osmocote CRFs?

The most important part of Osmocote controlled release fertilizers is the coating itself. Differences in coating thickness and type directly affect nutrient availability to your plants. Unlike some CRFs, Osmocote controlled release fertilizers aren’t affected by salinity, pH, microbial activity, water quality, or rain. Beyond coating type and thickness, only soil temperature influences the controlled release of Osmocote nutrients.

Osmocote’s continuous and uniform availability of nutrients translates to better plant growth. Plus, the coating surrounding Osmocote CRF granules minimizes nutrient leaching and loss, bringing your growing operation greater sustainability, too. And because plants grow evenly and gradually with Osmocote coated fertilizers, your crops are less susceptible to damage and disease. Greener, stronger, and more resilient plants mean higher production, higher quality, and higher returns.

More than 50 years after Osmocote pioneered a new age of fertilizers, ICL continues to innovate and leverage the latest scientific knowledge in the horticulture field. We’re determined to keep bringing you the best, most sustainable coated fertilizers in the world—and merit your trust every day, every season.

For expert advice on Osmocote controlled release fertilizers—or anything else you need—reach out to your local ICL Territory Manager. Their feet are on the ground where you grow and live. We’re here to help you achieve success—and we’re here every step of the way. So, give us a call and let us help you grow with Osmocote today.