I've had very good luck using mushroom dirt and sand for a vegetable garden. Our local sand and gravel place sells it for $30.00 for a pickup truck load, but a mushroom plant sells it for $14.00 for any size load. I took an 18 ft. equipment trailer to the plant and they filled it about 4 ft. high and asked if I wanted my truck filled also.

Last spring I dug a trench 1 foot deep and 1 ft wide and put 3-4' of pine needles in the bottom, then 4' of mushroom dirt, then seed potatoes on the mushroom dirt the piled sand about 4' above the surrounding surface. All summer we had the best potatoes we have ever tasted. For our winter herb garden I am trying a bed of mushroom dirt about 6' deep by 4ft wide by 30ft long. I will then cover this with newspapers, then 3'-4' of mushroom dirt mixed with leaves and pine needles. Our winter vegetable is now well established so I will throw about 2' of mushroom dirt on that.

Here is a link that might be useful: Home Improvement