The best fertilizer to use on a lawn depends on a number of factors, including which nutrients, if any, the lawn lacks and the type of grass being used, according to the University of Minnesota. The age of the lawn is another factor to consider.
Testing the soil is the first step in determining the nutrients a lawn needs, notes the University of Minnesota. Deficiencies in nitrogen, phosphorus and potassium are common since high quantities of these nutrients are not made available through natural soil processes. High-maintenance grasses, such as improved Kentucky bluegrass, require more nitrogen per square foot to grow and require supplementation. If a lawn is new, a fertilizers high in phosphorus and potassium are recommended, as these nutrients promote early root growth.