Native soil amendment approach

If you have decent native soil (loamy, not heavy clay or pure sand), you can amend it in place rather than importing an entirely new mix. Remove the top 6-8 inches of native soil, screen out rocks and roots, then mix it 50/50 with quality compost. Add perlite (10% by volume) if the native soil has any clay content. Return the amended mix to the bed and top with 2-3 inches of pure compost. This is the cheapest approach since you are reusing existing soil. It works best for beds placed directly on the ground (not on hardscape) where roots can penetrate deeper native soil below. The native soil brings beneficial microbial communities already adapted to your local conditions. Not suitable if your native soil is contaminated (near old buildings with lead paint, former industrial sites), extremely heavy clay, or very sandy. Get a soil test ($15-30 through your county extension service) before using native soil in food production to check for heavy metals and nutrient levels.