Hi greenthumbnick, I'm in the situation of gardening on sand as well. I decided not to bother too much with digging and batteling the sand/nematodes so I have been gathering as much organic matter as I can find. This includes cardboard boxes, newspapers, lawn clippings, leaves, any wood chips that the tree services want to dump at my place. I have paid a little money to have mushroom compost delivered (like $20 for a huge trailer load.) I get the free compost from our county whenever they have it available. My first season I didn't have much time to get a "garden" ready so I simply took cardboard produce boxes, plunked them down on a bed of wood chips, filled em with compost from the county, and planted in them. It worked in a pinch. That was this past spring. This fall's garden has several different types of beds going but I think my favorite was simply laying down some cardboard, piling fresh mushroom compost on it (mushroom compost here is horse manure mixed with straw that has been used to grow mushrooms but now they are done with it, it is usually still quite hot), covering the compost with wood chips and planting. The cucurbits planted that way are doing very well so far. Now I'm starting to think about prepping beds for the cooler weather crops and realizing I'm running out of compost so I may have to do lasagna beds with a variety of materials for layers, I'm hoping it isn't a problem that they won't get to sit long before I plant in them. I definitely think gardening with materials you can find rater than paying for dirt is the way to go. Does your local have yard waste pick up? If so you can just go around the evening before they collect the bags of grass clippings ad leaves and get lots of great stuff. Also, if they do collect such things, they probably compost them. Check with your county to see if they offer free compost to residents. Check to see if there are any mushroom farms in the area, they might give away or sell for cheep their compost. We get sawdust pretty cheep from a sawmill in the area. I also tell any tree services I see working in our neighborhood that they can dump the chips in front of my house if the need. They are usually happy to leave the chips unless the person paying for the work wants them. I've gotten three big piles this way. This last time there were lots of palm fronds in one of the loads and that stuff is making great cover material for the compost bin. More, more, I need more organic material!!!! : ) One thing I did learn about making raised beds. Extend the weed barrier (cardboard or newspaper layers) beyond the actual planting area and cover with mulch. This gives nice walkways that help keep the weeds further from the planting beds. I've found it is difficult to mow right up to the beds and can wind up just flinging the weed seeds right into the planting area!

Turf grasses can send roots down 6 inches with no problem in a good healthy soil, however a good healthy oil is more than just some "black top soil" laid down on clay. Clay can be a good soil, if it is well amended with adequate amounts of organic matter which is what makes any soil into a good healthy soil. Look for some organic material, what you put down, that will become organic matter in the soil, the residual organic material, and helps feed the plants you are trying to grow. A good healthy soil will contain about 6 to 8 percent organic matter. Have a good soil test done for soil pH and major nutrient levels and maybe use these simple soil tests to see what is there now and what you need to do to get to that good healthy soil. 1) Soil test for organic material. 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 drains’ 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, to 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.

Neither of those is really a good choice but if that is all the choice you have use the least expensive. What is your base soil? Putting a soil mix that drains very well on a clay base that does not can present problems not easily cure. As you have indicated the 50/50 soil/compost mix will shrink as the Soil Food Web digests that compost and your level lawn will no longer be level. A good soil will have about 5 to 8 percent organic matter in it which might be what that screened "topsoil" may have. Keep in miond that "topsoil" is quite simply the top 4 to 12 inches of soi from someplace and it might be something worth the price or it may not be worth anything.

If you could untill the ground and remove the peat you'd be ahead of the game. Where do you live? Is the area shaded or sunny most of the day? We need that info to help you more. Your zone doesn't matter, we need the location. Most people who think they have clay have other stuff going on. If they try to fix it like it was clay then they are doing the wrong thing. There is a test called the jar test which can help you decide if you need further testing. Get a straight sided jar, fill it half way with soil, and measure the amount of soil with a ruler next to the glass (TAKE A PICTURE). Fill the jar with water and a short squirt of shampoo or dish soap. Cap the jar and shake it until all the soil is dissolved. Set the jar down, hold the ruler up and take another picture. After 2 minutes take another picture with the ruler. After 2 hours take another picture. After 2 days take another picture. What you will see is settling of sand/gravel (2 minutes), silt (2 hours), and clay (2 days). If you can see through the water on top of the soil after 2 days you don't have very much clay. Clay particles remain suspended for days and days to cloud the water. You can divide the sand by the total to get percentage of sand. Subtract the sand from the 2-hour picture settling and divide by the total to get the silt percentage. The rest will be clay. When you discover that you don't have any clay at all, then you might want to get a soil chemistry test to see what is the problem. Likely it is an imbalance of salts in the soil with too much magnesium being a possible problem.