Controlled Release Fertiliser
Encyclopedia
A Controlled Release Fertilizer (CRF) is a solid form fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

, usually in powder or small granules that are either sprinkled on top of the soil (top dressed) or dug into the soil before planting. The outer layer is insoluble but permeable so nutrients are released slowly in a controlled way over a set period. Other names for controlled release fertilizers are "metered-release fertilizers" and "slow-acting fertilizers".
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