Late July is the optimum time to make that final application of nitrogen fertilizer to the lawn. Since nitrogen typically lasts 8 to 10 weeks in the soil, this would allow enough time for depletion of the nitrogen before the arrival of cooler temperatures in the fall.
The benefit of nitrogen is best realized when applied at the right time and in the right amount. The amount of nitrogen to apply should equal 1 pound of actual nitrogen per 1000 square foot area.
Nitrogen can be supplied to the lawn by using ammonium nitrate or a blended lawn fertilizer. If using ammonium nitrate, apply 3 pounds per 1000 square feet of lawn area. If using a blended lawn fertilizer such as an 18-0-18 or 24-6-18, or a 28-6-16, just to name a few, select one that has little to no phosphorus as excessive phosphorus can result in a decline in turf grass quality over time, especially in Centipede grass. Each bag of lawn fertilizer will provide a statement that gives that amount of coverage such as 5000 square feet. If your lawn area is 5000 feet and you apply the whole bag, you will have applied 1 actual pound of nitrogen per 1000 square foot area. Once you know what the bag designates as coverage you can determine how much of the bag to put down based on your total square foot area to give you the 1 pound of actual nitrogen per 1000 square feet.
If using a common blended fertilizer such as an 8-8-8 or 10-10-10 or a 13-13-13 for example, you may not find a designation of coverage on the bag.
Therefore, you would need to calculate how much of the material would be needed to provide the 1 actual pound of nitrogen per 1000 square feet. To calculate the amount of a particular fertilizer to supply 1 actual pound per 1000 square feet, simply divide the first number of the analysis into 100. For example, using an 8-8-8 blend the calculation would be 100 divided by 8 which would equal 12.5 pounds. This amount of 12.5 pounds would provide 1 actual pound of nitrogen per 1000 square feet of lawn area.