Nitrogen

• Nitrogen is the most important component of lawn fertilizers.grass,lawn image by Greg Pickens from Fotolia.com
  
  Nitrogen plays a vital role in a healthy, vibrant lawn. Many soils lack sufficient nitrogen to satisfy the requirements of a lawn. Nitrogen deficiency causes slow or sparse growth, yellowness, susceptibility to disease and increased weed growth. However, over-fertilizing with nitrogen causes the grass to grow too quickly, reducing root growth, nutrient reserves and tolerance to environmental stress. If used improperly, a fast-release nitrogen fertilizer may cause chemical burns to a lawn.
  
  

Phosphorus

• Phosphorus is necessary for your lawn to establish a healthy root system, but it also poses environmental risks.lawn,grass image by Greg Pickens from Fotolia.com
  
  Lawns require phosphorus for healthy root growth. Unlike nitrogen, phosphorus often exists in sufficient levels for lawns in most soils. If a soil is deficient, this should be corrected, if possible, before seeding the lawn. This is easily determined with a simple soil test. Many county and university extension services offer soil testing as a free service. There are environmental concerns related to the use of phosphorus as a fertilizer, and some states--such as Minnesota--place limitations and restrictions on how and where it can be used.
  
  

Potassium

• Lawns in areas with sandy soils are more likely to be deficient in potassium.green lawn image by Vladimir Koshkarov from Fotolia.com
  
  Potassium plays an important role in the regulation of many of a lawn's life processes, including the use of nitrogen. In many areas, soils will have sufficient natural supplies of potassium. Sandy soils tend to lose potassium at the root level. As with phosphorus, a simple soil test can determine the level of potassium that your lawn requires.
  
  

Considerations

• After determining the particular requirements of your soil, choose a fertilizer that reflects its particular needs. For example, if testing indicates that your soil has sufficient phosphorus, look for a fertilizer with a 0 value for phosphorus. Many fertilizers feature a blend of fast- and slow-release forms of nitrogen. The fast-release form offers immediate visual results while the slow-release form maintains the results over several weeks.
  
  

Warnings

• Phosphorus run-off into gutters and storm drains presents a serious environmental risk. This run-off eventually ends up in lakes, rivers and streams, where it causes increased algae growth, decreased oxygen levels for fish and increased ammonia levels. These risks to the environment can be controlled by the responsible use of phosphorus, including using it only when testing indicates that it is necessary.