This stuff will be better than any chemically forced soil you can purchase from a hardware store. Get it, layer it in, wet it down well, and let it work into the soil. If you can till it in that's even better, but not the end of the world if you can't. With time you'll invite beneficial earth worms. And grass will grow in it.

The older piles are most likely well composted at this point so those will be the best.

thanks for your reply don't think I explained properly

when I dig out the stone, there will be no soil under it I have done a test dig to check and its just hardcore about 1 foot down so I wont have any soil to mix it with

will the oldest manure I can get be good enough for grass or will it cause problems

frant,

Plants do sprout and grow in 'pure' compost, so the short answer is yes, you can use horse manure as a medium for growing things.

But soil has a minerals in it that plants need. Also, soil, like clay soil, is a medium that holds water well. It sounds like your rocky ground had its soil washed away. You might want to make plans to bring in some topsoil.

Compost is not an ideal medium on a stand-alone basis for any sort of planting. It just doesn't offer the long term durability that a mineral based soil does, plus it will continue to breakdown and decompose, resulting in shrinkage and uneven ground.

The short answer is compost is NOT soil. And while it is fine (even advised) to add to an existing soil, you need more than just compost for long term success. The recommendation above to import some topsoil or other garden planting mix is highly advised. A good healthy lawn needs a good healthy base and that means at least 6-8 inches of a friable, fertile and well-draining soil.

thanks all for the help looks like ill have to ask my mate if I can dig some soil out of his fields instead

as you can probably tell im new to gardening

thanks all

All the comments make lots of sense. Our garden spot was 2" of topsoil over gravel. We used 1/2 topsoil from the fields and 1/2 OLD compost to bring the soil level up. That was 20 years ago. Now after adding 3 - 4" of compost every few years the soil is about 15" deep. It is was too fertile though. I got some composted bark to topdress a few beds with and I think / hope that will balance things out a bit. In Montana the product is called soil pep.

Get soil AND manure and mix them.