Before the next lawn growing season begins, you’d be wise to know the following.
Know square footage of your lawn. Most people overdo it when fertilizing their lawn as a result of not knowing the size of their lawn. Fertilizer and lawn pesticides, including herbicides, are applied based on square footage. Take time to accurately measure your lawn, record and save the measurement before spring. Doing so will allow you to purchase and use the correct amount of fertilizer and pesticides.
Know how to fertilize your lawn. In the absence of a soil test, choose a lawn fertilizer with equal amounts of nitrogen and potassium and low phosphorus. Look for lawn fertilizers with numbers such as 8-0-8, 10-0-10, 12-2-14 or some similar analysis. The three numbers on a fertilizer bag tell you the percentage of nitrogen (N), phosphorus (P) and potassium (K) and always in that order (N-P-K).
In North Florida, your first lawn fertilization should not be made until mid April. Fertilizing while the root area is too cool, wastes fertilizer and may injure your lawn. A second fertilizer application may be made during summer but not after mid September. Calibrate you fertilizer spreader. A UF/IFAS Extension publication is available online at http://edis.ifas.ufl.edu/lh024 to help you with this.
Know how to water your lawn. To determine how long to run your sprinkler system to apply the correct amount of water, set out small, straight-sided cans randomly within an irrigation zone and see how long it takes to fill them to the desired depth of ½ - ¾ inch. Tuna fish or cat food cans work well for this calibration exercise. Repeat this process for each irrigation zone in your lawn. Large differences in water amounts between cans within the same zone will let you know that your coverage is not uniform and your system needs to be inspected further. The goal is to uniformly apply ½ to ¾ inch of water to the lawn only when the grass needs it. When the grass needs water, leaf blades fold - like a book closing, footprints remain in the lawn long after being made and the lawn turns grayish in spots. When 30% to 40% of the lawn begins to show these signs of water need, it’s time to apply ½ to ¾ inch of water. Don't water again until the lawn begins to show these signs of water need. Publications on irrigating a Florida lawn are available at http://edis.ifas.ufl.edu/topic_lawn_watering.
Larry Williams, UF/IFAS Extension Agent, Okaloosa County, February 22, 2012