Answer: Deep watering twice a week will be fine for your fescue, but I wouldn't count on a 15 minute schedule. How long you need to keep the water on depends upon flow, soil type, and even the temperature. Fescue turf needs one inch of water per week and you can deliver half of this amount every 3-4 days. Set some empty cat food or tuna cans out on your lawn and water as usual. Then check to see how much water has collected in the cans. If it is less than a half inch, you'll you can adjust the amount of time you run your sprinklers.
Top dressing a lawn with peat moss or compost can help improve your soil. Use a thin layer, though. As the peat or compost works its way down to the soil and decomposes it can add nutrients to the soil, which will benefit the roots of the grass.
Good luck with your landscape!
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