Chemical Fertilizers

• Chemical fertilizers are also known as synthetic or non-organic fertilizers. They are either manufactured or derived from mineral sources. Types of chemical fertilizers include ammonium sulfate, ammonium phosphate, potassium nitrate, super- phosphate, potassium chloride and potassium sulfate. Chemical fertilizers are usually less expensive than organic products and tend to provide quick results. Use caution when applying chemical products, since most contain very concentrated amounts of plant nutrients that are detrimental when overapplied.
  
  

Organic Fertilizers

• Organic fertilizers are derived from plant or animal sources. Examples include bone meal, blood meal, cottonseed meal, sewage sludge, manure, compost and fish emulsion. Unlike chemical fertilizers, organic products usually contain a wide variety of nutrients in small amounts and must be broken down by soil organisms before they are available to plants. This makes them ideal for long-term soil amendment, although they may not be as immediately effective as chemical products.
  
  

Nutrients and Release Rate

• Both organic and chemical fertilizers are further divided based on the nutrients they contain and the rate at which they release them. Complete fertilizers contain the three essential plant nutrients nitrogen (N), phosphorus (P) and potassium (K). Incomplete fertilizers contain only one or two of these nutrients. Fast-release fertilizers have an immediate effect on plants and are usually chemical products. Most organic fertilizers are slow-release, since they must be broken down by soil organisms in order to become available to plants. Some chemical products are also slow-release and may take up to a year to be assimilated into soils.
  
  

Special Purpose Fertilizers

• Some plants have very specific nutrient or pH requirements. Azaleas, for example, require very acidic soils, and roses require regular high-nitrogen, slow-release feedings. Certain special purpose fertilizers are specifically formulated to meet the needs of certain plant groups. Examples include azalea food, rose food or citrus food. There are also products formulated for houseplants, flowers or vegetables.