If you have a newly planted lawn, you should not use any type of fertilizer for the first 60 days after the sod is planted. During the first 2 months, the root system is so short that the grass will not be able to absorb many nutrients. If you fertilize during this time the nutrients may leach past the roots of the grass and throughout the soil.
Most sod will be fertilized before it is harvested from the sod farm. During the establishment time, it will not typically need to be fertilized. If you can, ask the person that grew the sod when it was last fertilized.
When it comes time to fertilize the sod you should first conduct a soil test. This test will show what nutrients are already in the ground ready for the sod to uptake. You should look for a fertilizer that has some of the first number from the test. This number represents nitrogen and it should come in a slow release form to be most effective. The fertilizer may be labeled as coated, controlled release, sulfur coated, or polymer coated. The slow release of nitrogen allows the sod to take up the nitrogen over a longer time period.
The fertilizer should be applied at a rate of a pound of nitrogen for each 1000 sq. ft. of lawn. No more than this should be applied.
After you fertilize the sod for the first time you should follow the guidelines that are set for annual lawn fertilization for your location and the species of grass that you have had planted. Many people tend to over fertilize their lawns. One of the best ways to determine what type of fertilizer your sod needs is to simply conduct a soil test first. This can help you determine what nutrients your lawn needs so that you avoid over fertilization.