A good mix to use would be something akin to loam, a soil made up of about 45 percent sand, 25 percent silt, 25 percent clay and 5 percent organic matter.

kimmq is kimmsr

very interesting, that's a lot of sand. I would have thought it should have a larger amount of organic (compost) matter. I would think it would drain well.

wonder if I could replace the vermiculite in Mel's mix with Loam? that would be 1/3 each of compost, peat moss and loam ..

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.

I have access to cheap ($15 per yard) leaf type compost from the county. Would it be bad to use a 50/50 blend of top soil and compost ? The compost is PH adjusted to 7.0. Top soil (sifted) is around $40 per yard so compost is actually cheaper for me. My calculation is I need roughly 4.5 yards so not that bad (each bed is 20 cu ft).

The soil mix described above is basically Loam, the soil most gardeners wish they had. "Topsoil" probably will not be the same thing and it can be whatever the seller wants it to be. Keep in mind that the only definition of "topsoil" is the top soil from someplace and it can be anything from the top 4 to 12 inches of soil. This article may be of some interest.

http://www.ncagr.gov/agronomi/pdffiles/sfn14.pdf

Too much organic matter in a soil will present as many problems as too little. Too much organic material in soil can hold too much water which will exclude the air plant roots need to survive just as the top growth does.

Strive for a soil mix that is about 6 to 8 percent organic matter.

kimmq is kimmsr

Is loam something large nurseries carry? In buffalo none of the nurseries open until 4/1 so I can't even check availability.....

Nursery just responded to an email, they are recommending 50/50 top soil/ compost or even higher on the compost. Didn't inquire about loam yet.