Soil Composition

• When considering the best fertilizer options, first have the soil analyzed to determine the current nutrient levels of the macronutrients nitrogen, phosphorus and potassium, as well as calcium and magnesium. For example, nitrogen is necessary for healthy dark-green leaves, but too much nitrogen results in overgrown plants with little fruit or vegetable production.
  
  

Plant Requirements

• The specific requirements of different plants must be considered when selecting fertilizers. For example, if you are fertilizing a lawn, a fertilizer high in nitrogen would be best to promote lush leafy growth. However, if the same fertilizer was used for tomato plants, the result would be large plants with copious foliage but few tomatoes.
  
  

Organic Versus Conventional

• Another consideration is whether to use organic or conventional fertilizers. Both types can be valuable to gardeners, depending on your priority. Commercial fertilizers are fast acting and often cheaper. Organic fertilizers, on the other hand, help to build a strong soil base but take longer than commercial fertilizers to release their nutrients.