Check and see when Norman is starting to release the compost they have. It is free if you haul it.

Welcome to the forum! Like Carmen says, you can check with your local municipality to see if they have free compost - I think you have to have a Norman utility bill to get into Norman, but since you are in NE OK, there might be somewhere else.

What kind of dirt is under the river rock? If your bed is one foot deep, you will probably want to work slowly at digging in your new garden soil with whatever your native soil is, and that would guide you on any other amendments to add. If it's clay, you would add things to lighten it up, maybe sand or compost. If it's sandy it probably drains too easily, so you would want to add things that will help it hold water in our droughty conditions. I am by no means the soil expert but I'm sure some of them will chime in with good suggestions.

Personally, we had terrible red clay on a sloping hill. I brought in purchased garden soil to start my veggie garden last year, and I have maybe one third of the area dug and turned over to a depth of about 6 inches down below the clay. I mixed the clay in with the new soil and redistributed it. Eventually I will do more as time allows. I ended up with mounded garden dirt of a depth about a foot in a raised row situation, and dug the paths out, and only walk on the paths to keep the top soil fluffy and easy to plant in. I like to add compost or black kow manure or chopped leaves as I can, and I will be adding more eucalyptus mulch this year, plus cardboard in several thick layers in the pathways. I cannot say about the horse manure, there are certain manures that have pathogens unsafe for food (dog and cat and human are no-nos for sure) but there is some way of "cooking" the manure, during the hot summer I think, that makes it "rotted" and safe for use in the garden. Not sure if that's applicable to horse manure, but I expect a more knowledgeable person will be along to help!

NE Oklahoma is a big area. Do you care to mention what towns are near you, or at least narrow it down a little.

You could leave some of your river rock, make raised beds four feet wide and 6 or 8 feet long out of wood, remove the rocks from the bed areas and have nice walkways between beds. It would take less soil to fill the beds than to cover the whole area. There is building in my area because of a tornado and I have been getting wood scrapes. Most aren't that long but you'd be surprised what they waste.

Here is a link that might be useful: p allen smith pictures

soonergrandmom , we are just north of Owasso. Norman is a bit far but they make compost? I can get wood chips for free from Tulsa, I'm thinking of at least spreading that. As far as the soil below the grave, I think its somewhat clay.

Wood chips will keep things from growing; they are good for paths and mulch but I don't like them too close to the house. Is the issue that you don't like the look of the area as it is or that you really want a garden there. The horse manure and straw in a pile would turn into something useful pretty soon; the wood chips would take a long time to help your soil. You could transform your area a small part at a time like Mia is doing and start slow improving a small area and growing a few things that you really like. Vines could trail over the rocky area if their roots were in an improved area.