Most of us are familiar with irrigation/cultural practices of turf grass. It's been pounded in our heads every other post on this forum for quite a while. But there's always been a question in my mind about heat-stressed irrigation in summer, because I've tried to keep my grass watered and yet still get fungus attacks too.

Well, I asked Dr. Brunneau at NCSU about high-heat stressed irrigation in the summer and I thought I'd pass this on to whomever is interested:

Much of the water used to irrigate lawns is improperly applied. Only apply water to the lawn when it shows signs of water stress. A dark, bluish color; footprints that remain for some time after walking; and wilted, folded or curled leaves are indications that it is time to irrigate. Delay in watering at first signs of wilt can result in permanent damage. The best time to water is in the early morning hours (4 or 5 am if you have an automatic system). This reduces the risk of disease and loss of water from evaporation and is done at a time when there is a low demand for water. If evening is the most practical time, water in early evening to allow the foliage to dry before nightfall. This lessens the chance of disease. Avoid mid-afternoon watering to reduce loss from evaporation. Leaf burn is an old wives tail.

Water to a depth of 4-6 inches to encourage deep rooting. Probing with a screwdriver can help determine moisture depth. This may take more than 1 inch of water. It takes 640 gallons to apply 1 inch of water/1000 sq ft. Clay or heavy soils accept water slowly requiring the metering of water to prevent wasteful runoff. Water clay soils until runoff occurs, wait until water is absorbed and then repeat if necessary. This same technique can be used on slopes. Mowing TF at 3 inches will enhance rooting depth.

Hope this helps.