To choose the best method of setting up a home Garden, consider the type of soil in the Garden plot. Native top soils in the west can range from light, sandy soils to heavier clays, or to adobe types that dry like concrete. These soils are commonly found in new housing developments, where all the topsoil often has been removed, leaving only the clay subsoil.
If the soil falls somewhere between a loose, sandy soil and a rich, deep loam soil, planting a Garden in rows can be simple, inexpensive and quick. Water row Gardens by flood irrigation in furrows, or use sprinklers or drip irrigation.
To improve any soil for planting, mix three to four inches of organic material into the soil to one and one-half feet. Known as double digging, this process can quickly improve drainage, encourage plant roots to grow deeper and improve soil aeration. Organic material will hold moisture and, as it is broken down in the soil, release nitrogen which helps beneficial organisms that live in soil.
For heavy, clay soils, or soils with poor drainage, raised beds are the answer. Raised beds save space, drain faster, heat up earlier in the spring, and save water by keeping it where the plants are growing. Also, because Gardeners walk around rather than on the raised beds, the soils are kept loose.
Raised beds offer other advantages. They are more comfortable to work on than row plantings and can be designed to be accessible from a wheelchair. Raised beds can offer a solution to Gardeners with small yards and limited spaces.
For more information, see the following Colorado State Extension fact sheet(s).
http://www.ext.colostate.edu/ptlk/1812.html