We live in an area with a lot of rocks so after hours of digging to plant some blueberry plants we decided we would plant four blackberry plants and two blueberry bushes in a raised garden bed four ft by 16 ft and about 15 inches tall. My question is about what to use to fill the beds besides soil and compose from our local nursery. We have wood chips, leaves, grass clippings. Could I fill the first five inches with that before getting soil and compost from the local nursery to save money? Any other ideas? We are starting to compost all organic material but only started about a month ago. Thanks for any suggestions.