Using Controlled-Release Fertilizers

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Water soluble fertilizers

There’s no question growers could be more efficient in their use of fertilizers in the greenhouse. Some fertilizer is lost as runoff while other fertilizer is used to feed plants when they don’t necessarily need it.

Every grower’s goal should be to use fertilizer as efficiently and as effectively as possible to achieve high-quality growth. Fred Hulme, the director of technical services at Everris (formerly Scotts Professional), discussed ways growers could achieve this goal Tuesday in an educational session about using controlled-release fertilizers (CRFs) in the greenhouse.

One key to using CRFs is to have good control of the greenhouse environment, particularly temperature. Some of the benefits of using CRFs include:

- Easier application into the soil
–The ability to vary the rate application in the same growing space for different crops
–A slow, constant feeding–even when water cannot be applied
–Reduced nutrient runoff
–Post-production nutrition

“I see big commercial growers converting over to CRF,” Hulme says. “They’re doing it because of economics, labor, etc.”

CRFs do have a few negatives, though. For example, it’s critical growers select the correct product and rate with CRFs. Additionally, growers can’t store growing media with a CRF incorporated into it for too long because a higher temperature will expedite nutrient release.

“I’m fully confident you can grow a variety of greenhouse crops using controlled-release fertilizer as a primary fertilizer source, or with a water-soluble fertilizer,” Hulme says.

In additions to CRFs, Hulme discussed water-soluble fertilizers (WSFs) and how a number of growers are still confused about how to use them most effectively.

“There’s still a lot of confusion about how to use these products based on the number of phone calls and eMails we get from growers,” Hulme says. “Water-soluble fertilizers are great if you can control your leaching fraction. Converting to drip is a good idea, but even then there’s still going to be a lot of loss with drip.”

Learn more about Everris online at

Kevin Yanik is the former managing editor of Greenhouse Grower.

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