You can use more compost than recommended but I'm not sure about the sand. Vermiculite is for water retention and (I think) volume, and it doesn't seem as if sand would meet that need.

When you build your beds remember that SFG is a method, not a chemical equation. There are lots of widebed & intensive planting methods, SFG is is just a subset. They key bits are wide beds, rich soil, don't walk on the beds, and close planting. The rest helps but leaving something out (such as vermiculate or peat moss) won't inevitably lead to failure.

Harimad

Hi!

I agree with Harimad. I don't think the formula for the mix is sacred, it is just "recommended". If you are a beginner, it is sometimes easier (and rather reassuring) to stick with a formula. However, I am an "intermediate" and somewhat haphazard gardener and just threw together a soil mix based on what looked and felt right, and what I could obtain at a decent price.

SO, for my first beds I put thick, wet newpaper over the grass, which covered the rocky clay. Then I added 4x4 foot frames of 2x10 inch untreated lumber held together with decking screws. I filled them with a mix of free leaf mold (decomposed leaves--about 40%), mostly decomposed mushroom compost (about 40%), and purchased topsoil (about 20%).

Oh, and when I say "mix", it doesn't mean that it needs to be thoroughly mixed from the start. My ingredients were just layered in the bed and mixed as I (and/or Mother Nature) had the time. In addition to SFG, I am also a firm proponent of "lasagna gardening" (just do a search on that term within Gardenweb).

My (old-school organic gardening/farming) father helped me with most of this and when we were finished he declared that "you could get rocks to grow from this soil".

He wasn't literally correct, but my original beds did produce incredible amounts of leaf lettuce, broccoli (raab and regular), kolhrabi, swiss chard, spinach, snap peas, scallions, eggplant, peppers, tomatoes, herbs, and nasturtiums with little additional work on my end (aside from picking the bounty).

Hope this helps!

--Orena