Plants grow best in a fertile, well-drained soil with a thick and rich texture. Sandy rich soils, well-supplied with organic matter, are easily worked and are quite productive. Although many gardens do not contain such soils.
Coarse soils dry out rapidly and are hard to maintain at a high level of fertility. Clay soils are difficult to work and usually remain wet until late in the spring. These types of soil are often yellow or dark brown and sticky when wet; or grayish in color where drainage is poor. Clay soils tend to form a hard crust after a heavy rain and become so compacted that the plant's root system is deprived of essential oxygen required for growth. Clay and sandy soils must be modified for successful vegetable gardening.
For more extensive information on soil composition take a few moments to read "Good Soil Composition." Basic things to consider for optimum soil conditions see "Soil Basics." You will find six things to consider for good soil: water drainage, moisture condition at the time of working, erosion, texture and structure, fertility, and pH details.