looking for advice on putting down some weed and feed . sod that was put down at the local school sprouted a bumper crop of weeds...typical broadleaf variety...dandelion,chickweed ,plantain,etc....has anybody used weed and feed for this?.....several different brands of weed/feed on market.......dont want to burn up the grass but they asked if i would try to get rid of weeds......grass is centipede......my experience with weeds so far has been spot spraying but this is a 4 acre area that needs treated.....thanks