When I was a kid I knew an old timer that grew vegetables and he would collect clippings from neighbors and bury large amounts of them in the ground a few months before he would plant in the same spot.
I have used clippings for mulch in my organic veg garden many times. If they are put on thick, like a 4 or 5 inches, it works great. If any weeds geminate they will be in the top and they are easy to pull out. I never turned the grass untill it got turned into the soil at the end of the season.