How Many Types of Fertilizers Are There?

Slow Versus Quick Release

• Fertilizers are usually labeled as either slow or quick release. The nutrients in a slow-release fertilizer are broken down gradually by microorganisms in the soil. Slow-release products are often more expensive than fast-release fertilizers and need to be applied in advance if possible to see results. Fast-release fertilizers work much more quickly, although the results may not last as long. They also tend to be inexpensive, although frequent application may compensate for any initial savings. Fast-release fertilizers are more likely to burn plants and should always be applied with extra caution.

Nutrient Content

• Fertilizers also provide nutrients in many combinations. The most common fertilizer nutrients are nitrogen, potassium and phosphorus. These are also known as macronutrients and are some of the most important plant nutrients. You may notice that fertilizer labels usually have three numbers on them. These numbers tell you how much nitrogen, phosphorus and potassium is in the product measured by percentage of volume. Some fertilizers may contain additional nutrients. These are usually labeled as secondary nutrients and trace elements and include calcium, magnesium and sulfur.

Organic and Synthetic

• Fertilizers can also be distinguished based on whether they are organic or inorganic. Organic fertilizers come from animal or plant sources and include animal manure, processed sewage sludge and bone meal. They tend to release nutrients very slowly and may be more expensive than inorganic products. Inorganic fertilizers, also known as chemical or synthetic fertilizers, may be either industrial byproducts or chemically manufactured. They are usually quick release and tend to be much less expensive than organic fertilizers.

Specialized Products

• Some fertilizers are formulated to provide maximum benefits for certain kinds of plants. Flower fertilizers, for example, tend to be water soluble and may contain more phosphorus than standard products. Vegetable fertilizers are usually granular and tend to be slow release. They may last several months and usually contain all three macronutrients. Other kinds of plants that may benefit from specialized fertilizer products include houseplants, cacti and succulents, roses and tomatoes.