Got about 100 plants in ground, I just got my hands on some free compost and was wondering if it's ok to just throw it over my already planted and flowering- watermelons, onions, peppers, and, beans. or should I save it for when I plant more later in year and till it in? only reason I want to use it now is my yard is this gray filler sand that won't hold water just forms puddles never gets more than 1 inch under surface unless I go crazy with water was thinking maybe a layer of compost on top might help retain water?