Once your lawn has sprouted after about six weeks, an additional feeding of starter fertilizer is appropriate. Starters release slowly with successive watering nutrients to feed young emerging lawn grass. This application should be in an amount indicated for your square footage as recommended by your local extension agent or on the bag by the manufacturer.
Avoid homemade fertilizers or hand broadcasting for direct application. An overdose can burn or kill your young grass plants. Use a liquid solution diluted to the proper specifications with a lawn hose spay system or a lawn spreader to equally distribute your dry fertilizer granules over your lawn. Dry granules must then be watered in, so that the nutrients can reach the roots. Fertilizers are salts and should not be applied in the hottest part of the day. The sun's heat will concentrate the fertilizer and increase the potential for an adverse burn out condition to occur. If you are in doubt, less is better, not more. The growth rate and condition of your lawn will be your prime indicator.
Additional soil tests can be performed, if lawn growth results are proving to be unsatisfactory. If the soil test nutrients are balanced within the acceptable ranges indicated, you will need to look at your soil drainage or for grubs in your root structure, or lawn diseases prevalent in your area and consult with your government extension agent.