To choose the best slow release fertilizer, gardeners may wish to use a blended formula that contains 30% to 50% non-soluble nitrogen. A blended mixture uses both slow release and standard soluble plant food pellets together in one bag, which may be applied to flower beds or the lawn simultaneously. This type of product will feed young plants immediately, providing them with the nutrient boost they need following initial planting, and will continue to feed them slowly for the duration of the growing season.
A plant's root system can only absorb a certain amount of food following being watered and fed. Standard manufactured granual fertilizers contain large doses of nitrogen, phosphorous, and potassium which are activated when water is applied to the surrounding soil. Many times, the plants are unable to absorb all of the nutrients found in these products at once, and they are merely leached away into the soil. A slow release fertilizer breaks down over time instead of releasing immediately, encouraging the gradual uptake of minerals and vitamins into the plant's root structure.
A blended fertilizer will feed the garden both initially and throughout the growing season. A slow release fertilizer contains a certain percentage of non-soluble nutrients, which means they are not easily absorbed in water. These food pellets are typically broken down by microbe activity in the soil, or by diffusion through a manufactured pellet coating. This type of plant food will not provide initial nutrients to young plants as it requires a certain amount of time before pellet degradation begins. Blended fertilizers combine both non-soluble and soluble nutrients together in one product so that plants have the benefit of receiving immediate nutrition upon first application of the product, and sustained food throughout the growing season.
The amount of slow release nitrogen contained in the blended fertilizer should be between 30% and 50% for optimum growing results. The product must contain at least 15% of its nitrogen in a non-soluble form to be considered a slow releasing formula at all. The three numbers located on the outside of the bag indicate how much nitrogen, phosphorous, and potassium are present within the mixture respectively. Beneath this ratio on a bag of slow release fertilizer is an additional statement which indicates how much of the enclosed nitrogen is available as a slow release product. This number should be divided by the total percentage of nitrogen contained in the bag, and then multiplied by 100 to obtain an accurate measurement.