• Fertilizers replace nutrients your plants need to look beautiful.garden flowers 1 image by michael luckett from Fotolia.com
  
  Any material that supplies essential nutrients to a plant is a fertilizer. Plants need 16 nutrients for optimal growth, according to the North Carolina State University. The nutrients that are in the soil often get used up and have to be replaced with fertilizers. There are a variety of fertilizers, which can be classified into two categories: organic, which are living or once-living material such as animal wastes; and inorganic, which are non-living sources such as commercial fertilizers.
  
  

Composts

• Compost is an organic fertilizer and is the "Cadillac" of fertilizers, according to Bob Vila. Composts have a wide spectrum of nutrients, are rich in humus and have a good balance. This fertilizer can be homemade or commercially purchased. Commercial compost is made from lawn/garden waste and animal manure. If you are looking for a way to recycle yard waste and want to save money from buying compost, try making your own.
  
  

Bonemeal

• Bonemeal is an inorganic fertilizer that can be used raw or steamed. The raw bonemeal does not contain as much nitrogen and is slow-acting. Steamed bonemeal fertilizer has all the cartilage, fats and greases removed when it is steamed. This makes it easier to grind into a powder form, which is better for plants. Bonemeal fertilizer works best when mixed with the soil and not just used as a top-layer fertilizer.
  
  

Plant Substances

• Some plant substance fertilizers are corn gluten meal, cottonseed meal and alfalfa meal, which are often rich in nitrogen. These are considered renewable resources, but when using this type of fertilizer you will have to take in consideration the resources used to grow or transport them.
  
  

Rock Phosphate

• Rock Phosphate is an inorganic fertilizer and has both advantages and disadvantages. The advantages of using rock phosphate are that with the right amount of rainfall this fertilizer can enhance plants. The disadvantage is that it will need to be crushed up to a powder form before using in garden soil.
  
  

Special Purpose

• Special Purpose fertilizers are formulated for use with specific plants and lawns. These fertilizers target certain plant requirements or certain soil deficiencies. An example is a straight fertilizer that is made up of one nutrient specifically for the lawn. These types of fertilizers can be inorganic or organic.