This whole issue of how much to water in Central Florida can be a bit confusing. I saw one watering regiment from the University of Florida (
Lawn Care and Irrigation- Living Green - Institute of Food and Agricultural Sciences - Extension- University of Florida) that recommended a different watering time for each month of the year. Another University of Florida publication (
ENH9/LH025: Watering Your Florida Lawn) recommends watering to a depth of 8" and watering less often as the temperatures moderate (I like this suggestion). It is very important that both St Augustine and Zoysia grasses get watered less often in the fall to prevent fungal disease problems.