A controlled-release fertiliser is a granulated fertiliser that releases nutrients gradually into the soil. The slowness of the release is determined by the low solubility of the chemical compounds in the soil moisture. Since conventional fertilisers are soluble in water, the nutrients can disperse quickly as the fertiliser dissolves. Because controlled-release fertilisers are not water-soluble, their nutrients disperse into the soil more slowly. The fertiliser granules may have an insoluble substrate or a semi-permeable jacket that prevents dissolution while allowing nutrients to flow outward.
Definitions
The Association of American Plant Food Control Officials has published the following general definitions :
Slow- or controlled-release fertilizer: A fertilizer containing a plant nutrient in a form which delays its availability for plant uptake and use after application, or which extends its availability to the plant significantly longer than a reference ‘rapidly available nutrient fertilizer’ such as ammonium nitrate or urea, ammonium phosphate or potassium chloride. Such delay of initial availability or extended time of continued availability may occur by a variety of mechanisms. These include controlled water solubility of the material by semi-permeable coatings, occlusion, protein materials, or other chemical forms, by slow hydrolysis of water-soluble low molecular weight compounds, or by other unknown means.
Stabilized nitrogen fertilizer: A fertilizer to which a nitrogen stabilizer has been added. A nitrogen stabilizer is a substance added to a fertilizer which extends the time the nitrogen component of the fertilizer remains in the soil in the urea-N or ammoniacal-N form.
Nitrification inhibitor: A substance that inhibits the biological oxidation of ammoniacal-N to nitrate-N.
Urease inhibitor: A substance that inhibits hydrolytic action on urea by the enzyme urease.
Implementation
The fertiliser is administered either by topdressing the soil, or by mixing the fertiliser into the soil before sowing. One of the advantages of CRF is reduced incidence of fertiliser burn and dissolution of fertiliser in rainwater. Other important advantages are economic: the need for fewer applications and the use of less fertiliser overall. The results is in most cases improved by > 10%.
Manufacturers and distributors of slow- and controlled- release fertilizers
In North America, the leading producers and/or suppliers of slow- and controlled- release fertilizers are: Agrium Inc., Koch Agronomic Services, Georgia-Pacific, Growth Products, Helena Chemicals, Kugler Company, Lebanon Seaboard Corp., Lesco Inc., Tessenderlo Kerley and The Scotts Company.
The leading manufacturers and/or suppliers in Western Europe are: ICL-Specialty Fertilizers, Mivena Specialty Fertilizers, Ekompany Agro B.V., Aglukon, BASF, COMPO EXPERT, Puccioni and Sadepan Chimica.
In Israel the leading manufacturer and supplier is Haifa Chemicals.
The leading manufacturers and/or suppliers in Japan are: Central Union Fertilizer, Chissoasahi Fertilizer11, Co-op Chemical, Katakura Chikkarin, Mitsubishi Chemical, Sumitomo Chemical, Taki Chemical and Ube Agri-Materials.
In Vietnam, the leading manufacturer and supplier is RYNAN Smart Fertilizers.
Synonyms
Controlled-release fertilizer is also known as controlled-availability fertilizer, delayed-release fertilizer, metered-release fertilizer, or slow-acting fertilizer.
