Fertilizers release essential nutrients in the soil that help plants grow and stay healthy. The three essential components in all fertilizers are nitrogen (N), phosphorus (P) and potassium (K), while they can also contain boron, zinc, iron, sulfur, copper, calcium among other elements. Fertilizers are broadly classified into two groups: organic and inorganic.
Organic fertilizers are derived from living animal or plant sources such as animal manures, meat and bone scraps, cottonseed, seaweed and fish. Sewage sludge, or waste recycled by a sewage plant is also another type of organic fertilizer. Some types of organic fertilizers are more expensive than others; they offer several advantages such as insulating the ground, promoting microbial activity and being environmental friendly. Although organic fertilizers offer valuable nutrients to garden or container soil, a gardener has to add other material to meet plant needs.
Inorganic (Chemical) Fertilizers
Inorganic or chemical fertilizers are manufactured or mixed in a laboratory and comprise of synthetic or chemical sources. These fertilizers are synthesized to produce ammonia as an end product, which is then used to create urea. There are many types of chemical fertilizers that are custom made to meet specific plant requirements, allowing gardeners to select the appropriate one according to their plant needs. Unlike organic fertilizers, chemical ones kill microorganisms in the soil. Excess amounts of chemical fertilizers containing urea severely damage foliage, so make sure you follow label directions for application rates.
Slow and Fast Release Fertilizers
Slow release fertilizers are characterized by a slow rate at which they release nutrients such as nitrogen at a consistent rate in the soil. They also have a low burn potential, causing little or no damage to foliage if excess amounts are accidentally poured, and they remain active in the ground for a long time. Fast release fertilizers, on the other hand, can cause root burn if over applied. Although cheaper than slow release counterparts, they have to be reapplied frequently because they dissolve sooner. There are organic and inorganic varieties of slow and fast release fertilizers available.
Liquid and Dry Fertilizers
Organic and inorganic fertilizers come in liquid and dry forms. Liquid fertilizers are applied directly to the plants and act immediately. They can be added to a drip irrigation system for an even distribution, and may required more frequent reapplication than dry fertilizers. Dry fertilizers are in granular forms and must be mixed with water so they penetrate the soil.