I don't use pre-ems on turf but am not organic either. No fertilizer in April unless it is my first year on the property and nothing was done the previous September or October. Usually no fertilizer after first week in June and prefer to finish before June 1. No fertilizers in July and if I feel forced to use any before August 15 (plus or minus a few days for weather), then I use organic and make it clear they are not getting off the hook for Labor Day week fertilizer and another sometime 4 to 6 weeks later. Three fertilizer applications a year is typical for my places, four would be high end. I am still figuring out what I think has happened to optimum results without P.