Right now, there's nothing under the tarp. What was under the tarp was 5 yards of sweet peet and 5 yards of municipal yard waste compost. The yard compost doesn't hold water like sweet peet so we used it to make, what should be, our last planting area. We say this every year, but this year we really mean it. We have run out of room. By using sweet peet, we have eliminated the use of chemical fertilizers. I guess that makes us organic gardeners. Yippee.