Healthy lawns depend on many factors including adequate water for cell enlargement and evaporative cooling, sunlight and carbon dioxide for energy production, and oxygen for respiration. Lawn growth also depends on nutrients or essential elements absorbed by roots from the soil. When natural soil processes do not provide adequate supplies of these essential elements, fertilizer can be applied to maintain optimum turfgrass growth. The purpose of fertilizing a lawn is to add the necessary nutrients in the required amounts and at the proper time to achieve desirable lawn qualities and healthy turfgrass plants. This publication will help to develop a fertilizer program to promote a healthy lawn.