CONTROLLED RELEASE FERTILIZERS: RECENT NURSERY TRIALS IN SWEDEN^©

The development of controlled release fertilizers (CRF) parallels the progress of container growing with most of the advances being made in the 1980s and 1990s. The first CRF sources to become commercially available were only nitrogen (N) but the technology has expanded to include potassium (K), phosphorus (P), and other nutrients, including micronutrients.
Controlled release fertilizers use several mechanisms to limit the amount of nutrient made available at any one time. In the first types, nutrient prills were coated with materials as molten sulphur, clay, and wax. The problem with these materials was that cracks in the coating meant the release-rate was not uniform. Today this problem has been overcome by using other materials. For example, Osmocote^® uses a resin coating of an alkyd-type, while Multicote^® and Plantacote^® use a polyurethane-like coating and Ficote® uses thermoplastic resins. All these materials allow a controlled release of nutrients by osmosis, where the thickness of the coating determines release timing and rate.
Today CRF fertilisers are widely used in container production of nursery stock all over the western world and in Japan. Growers in Sweden started to use them in the early 1970s. At that time the only available product was Osmocote. Today we also use Multicote, Plantacote, Ficote and Basacote^®.