Skipster must have an irrigation license because his numbers are straight from the book. In some areas, Golf course Greens keepers are give tight water budgets in ACRE INCHES. They must budget those inches of water through out the year. If you think Skipster is crunching number, You would go crazy budgeting a years worth of acre inches on a golf course. In Edit: When I use Pre Emerge I insist it is watered in the first 24 hours. However there are two schools of thought on Pre emerge and CHEMICAL ROOT PRUINING. I am of the NO PRE EMERGE school. A thick health Lawn is the best method of weed control bar none. .