A controlled-release fertiliser (CRF) is an insoluble, granulated fertiliser that releases nutrients gradually into the soil (i.e., with a controlled release period).
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.
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.
Controlled-release fertilizer is also known as controlled-availability fertilizer, delayed-release fertilizer, metered-release fertilizer, or slow-acting fertilizer.[1]