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Slow release vs. fast release fertilizers
Garden Tips Newsletter - July 16, 2001

With so many fertilizers available it is important to recognize the pros and cons of different types, specifically slow and fast release fertilizers.

Fast release fertilizers are useful because their nutrients are immediately available to plants and have an immediate response. Fast release fertilizers, however are subject to rapid depletion from the soil due to leaching. If fast release fertilizers are applied too heavily, the plant can be damaged usually by burning.

The other type of fertilizer is a slow release fertilizer. Two types of slow release fertilizers are available. The first type is an organic fertilizer. Organic fertilizers are made up of organic materials that must first be broken down by microbial activity before the nutrients are available to the plants. In general, organic fertilizers take a long time to release nutrients and these nutrients may not be available when the plant needs them. For organic fertilizers to be effective the soil needs to be moist and warm enough to promote soil organism activity. The other types of slow-release fertilizers are those that are slowly soluble or coated. Soluble and coated fertilizers (typically in pellet or spike form) depend on soil moisture and temperature to release nutrients. Nutrients are released over a period of time, sometimes lasting up to 12 months. Fewer applications are needed with slow release fertilizers, but nutrients may not be available when the plant needs them.

These archived newsletters were written by Dr. Lelia Scott Kelly. Kelly is a Horticulture Specialist with the Mississippi State University Extension Service. Her office is in the North Mississippi Research & Extension Center, Verona.