Building a raised vegetable garden
I am building a raised bed vegetable garden that is 4ft x 4ft and about 8 inches deep. I have been reading on the Internet to find advice on how to best fill it and find lots of variety. In general, there seem to be variations on two formulas. One common formula is 60% top soil, 30% compost, 10% potting soil. The other is evenly divided amounts of peat moss, vermiculite, compost. These seem quite different. Can you advise on a good starting mix and what is needed to maintain it in future years?
If you need to fill your beds, you can call around to topsoil/mulch suppliers for commercially available mixtures of topsoil and leaf compost. This makes an excellent media for raised beds - blended topsoil (70%) and leaf compost (30%). Can be purchased by the cubic yard. If you purchase topsoil with no added compost you should plan on adding at least 2-inches of compost. Thereafter, It is a good idea to add about an inch of compost to your garden on an annual basis in the fall or spring.
The other products like peat moss, vermiculite, etc. are costly and not generally recommended unless your soil is set on an impervious surface. In that case, a 50:50 mixture of a good soilless growing medium and compost is recommended
Whenever buying topsoil or organic matter in MD, it basically is 'buyer beware'. As far as compost, the only way to know exactly what you are putting in your veggie garden is to make it yourself. http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG%2035%20Backyard%2...
Also, look at our Vegetable website and 'Preparing the Soil' for more information http://extension.umd.edu/growit/food-gardening-101/step-3-prepare-your-soil