Granular or dry fertilizer is a type of fertilizer which comes in a dry pelleted form, as opposed to spikes, a liquid, or powder. Most garden stores carry several different types of granular fertilizer, along with an array of formulations which are designed to address specific soil conditions. This type of fertilizer has both advantages and disadvantages which gardeners have to consider before use.
Some companies make synthetic granular fertilizer, in which various chemicals are used to create the desired balance of nutrients. This type of fertilizer tends to have a very precise balance, and a very predictable behavior once it is applied. Others make their fertilizer from natural materials, by gathering things like compost, manure, and so forth and pelletizing them for gardening convenience. These fertilizers are tested before sale, but they may not always have the exact balance of nutrients one finds with synthetic fertilizers.
One of the best ways to use this type of fertilizer is as a soil preparation prior to planting, in which the fertilizer is worked into the soil to provide nutrients to the plants which will be established there. Granular fertilizer can also be applied to existing plants, in which case it will need to be watered in so that it settles around the root system of the plants. Watering in will also prevent nutrient burns to the plants.
The key advantage to granular fertilizer is that it acts as a time release capsule, allowing nutrients to flow out over time, rather than flooding the plants with nutrients like liquid fertilizers do. However, the fertilizer can also lose or leach nutrients in heavy rainfall, or in poor drainage conditions, in which case the plants may not get the full benefit of the fertilizer. Granular fertilizer can also be difficult to manage in an established garden, as it needs to be applied with care to avoid damage to the plants.
Gardening organizations strongly recommend that people test their soil before applying fertilizer. Many universities with agriculture programs offer soil testing to gardeners, and it is also possible to send samples in to firms which specialize in soil tests. The test results will provide information about the balance of nutrients needed in the soil, and the best type of fertilizer to use. Gardeners should also remember that the character of the plants is important, as plants have different nutrient and pH requirements which need to be addressed.