Plant roots need air, water and food to thrive. The effort you put into preparing your soil at the beginning will pay off all season with easier maintenance, better harvests and more nutritious vegetables and fruits.
The amount of sand or clay in your soil will determine how much effort is needed to loosen and fluff up the soil: sandy soil is easy to loosen, but requires more compost and frequent, shallow watering; heavy clay soils need more effort to loosen and compost to help break them up and provide good drainage. The best garden soils are somewhere in between and are known as ‘loamy’ soils.
When your soil has dried out enough to work easily, prepare your beds by working the soil as deeply as possible (12-18 inches) while trying to maintain its natural layering (keep the topsoil on top and the subsoil below). If your soil is dry and compacted, soaking the area a couple of days prior to digging can help.
Using a digging fork, work mature compost, an all-purpose organic fertilizer and other organic amendments as needed into the top 4-6 inches of the soil. Level the surface of the bed and rake it smooth. These steps should be sufficient for transplants.
A more thorough finishing step is required for direct seeding. Rake out the top two inches of soil until it is free of any debris or clods. Keep the beds as level as possible to prevent water and nutrients from running off. This will provide an optimum environment for germination and allow your seedlings to emerge unimpeded.
(Two different popular approaches to soil preparation - Double Digging and Permaculture - are covered in more detail at the end of this article.)