Q: I plan to build four raised beds for vegetable gardens in the spring. I need to purchase garden soil to fill these beds. What kind of soil should I use in raised beds? What do I look for when shopping for garden soil?
A: Try to locate a landscaping business or garden nursery that sells a compost-topsoil mixture. If you purchase topsoil with no added compost, plan on working in at least two inches of compost.
Maryland does not have regulations that set standards for topsoil sales. Go to a reputable nursery or topsoil dealer. Ask questions about where the soil comes from, what kind of soiling testing is performed, what the pH is, and whether anything has been added to it. Examine the soil before purchasing it.
Topsoil should be dark and crumbly with an earthy smell. Do not purchase soil that is foul smelling, mottled gray, or chalky in texture. Examine the soil again before it is unloaded at your home.
Learn more about soils and compost on the Home and Garden Information Center website.
By Ellen Nibali, Horticulturist, University of Maryland Extension Home and Garden Information Center. Ellen writes the Garden Q&A for The Baltimore Sun.
Lots of good suggestions there, but it was wrong to suggest 2″ of compost since it was not in context of the bed’s depth. If +/- 4″ (with a 6″ board), that would be too rich, and there was no mention of the crops although some do better and worse in leaner soil.
You are correct that we do not know the precise depth of the planned beds. The recommendation to add at least 2 inches of compost is fairly conservative. Raised beds that are 20-50% plant-based organic matter (by volume) typically produce healthy vegetable gardens.
In some cases, large amounts of organic matter (especially animal manures) can elevate soil pH, increase the risk of nitrogen and phosphorous run-off, and “burn” plants via excess soluble salts.