HOW DOES CONTROLLED-RELEASE FERTILIZER WORK?
Nov 02, 2016

CONTROLLED-RELEASE FERTILIZERS

Controlled-release fertilizers are traditional fertilizers encapsulated in a shell that degrades at a specified rate. Sulfur is a typical encapsulation material. Other coated products use thermoplastics (and sometimes ethylene-vinyl acetate and surfactants, etc.) to produce diffusion-controlled release of urea or other fertilizers. "Reactive Layer Coating" can produce thinner, hence cheaper, membrane coatings by applying reactive monomers simultaneously to the soluble particles. 

How does controlled-release fertilizer work?

Controlled-release fertilizers are made of soluble fertilizer granules, encapsulated in a thin polymeric coating. This coating acts as a semi-permeable barrier that allows measured diffusion of nutrients when the fertilizer granules are applied to the soil. 

Following application, Controlled-release fertilizer granules start absorbing moisture that dissolves the nutrients inside the granules. The dissolved nutrients then diffuse, slowly and continuously, into the root zone.

The rate of diffusion – the actual release rate - depends upon and is dictated solely by the soil temperature. The release rate increases as temperature rises, just as happens with plant uptake rates.

Other factors, such as soil type, humidity, pH, and microbial activity do not affect the release rate.

The special benefits of growing palnt with controlled-release fertilizers

  • Continuous nutrition –  fertilizers granules release nutrients slowly and constantly over several months.

  • Labor saving – only single application per season is required to provide the plants with the nutrition required for healthy growth. As availability of manpower in plantation areas may be limited, saving on application labor is a significant advantage.

  • Reduced leaching of nutrients nutrients are protected from immediate dissolution, so even frequent rainfall will not leach the fertilizer from the root zone. As a result, nutrients are consumed more efficiently, and environmental pollution is avoided.