I also wonder what you you mean by "native sand". You can purchase builder's sand at any garden store or quarry. This is the sand to use in gardens, one that drains well. Peat moss is a valid amendment when adding organic matter and far from being non-renewable....I wish these people would tell us what they use instead of oil and gasoline in their autos...peat moss is renewed in as little as 10 years. Tell us Kimm how oil is put back into the ground. I suggest you not use too much mushroom compost...it can be the carrier of fungal diseases which may explain why your vegies do so poorly. These fungi are prevalent where moist soil is a constant thing. Let the soil dry down some to defeat these fungi. The spores die in short order. Instead find a more organic compost--you can buy sheep or cow manure at any garden center. I wouldn't use leaves that have fallen onto your lawn if your grass is in poor shape. Diseases abound in soil where leaves have lain for long periods. Instead rake them up, throw in the compost or garbage and count on raking new fallen leaves.

This article should answer a lot of your questions. The book covers them in more detail as well. http://www.squarefootgardening.com/html/body_mix_full.html

You will find a lot of disagreement about whether sod needs to be removed or not, but if you plan on putting a raised bed, 6 plus inches, over the sod there is no need to remove it since the raised bed will smother the grass. On the other hand I have created numerous ground level planting beds simply by covering the existing sod with newspaper/cardboard and covering that with shredded leaves and that has killed the grass growing there and left the soil in a very good workable condition. There is nothing wrong with clay that adequate amounts of organic matter will not help, in time. Texas A & M does a good job of soil testing, and you have the added benefit of having a resource readily available to answer questions from both the horticulturist and maybe Master Gardeners. Visit the campus and you will find there are demonstration and trail gardens, not just farm studies. In addition to the soil tests done by Texas A & M you might want to dig in with these simple soil tests, 1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top. 2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drainsâ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up. 3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart. 4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell, to9 a point. Too much organic matter can be bad as well. 5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy. to see what your soil looks like.

You need almost a cubic yard of soil per bed. That's a significant investment if you are going with some custom soil mix. But it is really not necessary to get too carried away with what you fill the beds with. All you need is soil - like ordinary garden soil - and some organic amendments like compost or composted manures. If you don't have excess soil sitting around at home - and who has 6 yards of soil going begging for a home?? - then search out some bulk soil suppliers in your area. Most will carry something like a "garden" or "landscape" mix that will suffice nicely, often being an OM enriched product straight from the supplier. Even plain old topsoil (whatever they choose to sell under that vague designation), as long as not filled with rocks and roots, will work perfectly well for a raised bed as long as you incorporate a fair amount of OM in the mix. Focus on the bulk suppliers - bulk soils are far less expensive than bagged product and you would need a ton of bagged stuff to arrive at 6cy. For a raised bed soil, you don't need peat moss and you don't need vermiculite. Peat moss will increase soil acidity, which may not be desirable, and can retain excess moisture. Vermiculite is not advised for any inground (or even container) plantings as once it becomes saturated with water, it collapses and impedes good drainage. And it is an unnecessarily expensive additive as well. Just plain ole "dirt" and a good quantity of OM - 10-15% of the mix - will provide a very successful start to a raised bed garden.