Air-filled pore space: Oxygen, which circulates through fissures and cavities in the soil, is essential for the existence of soil bacteria and for the respiration of plant roots. The process of exchange of air between soil and the atmosphere, called aeration.
Ten to fifteen percent of your soil mix should be air. Materials like Perlite and shredded bark are coarse enough to create air space allowing the roots to breathe even though the soil may be moist.
Certain soils and soil mixtures are able to hold onto nutrients better than others. Farm manure has very good nutrient holding capacity.
The three most important nutrients gleaned from the soil are nitrogen, phosphorous and potassium. Plants use large amounts of these three nutrients and all fertilizers contain amounts of one or more of these nutrients. Along with magnesium, sulphur and calcium.
Is how well soil is penetrated by water and how well it holds water. Sandy soils have loose particles and have high water permeability but do not retain moisture very well . Clay soils on the other hand have low permeability but retain water well. Loam soils(Loam soil is a soil characterized by roughly equal amounts of clay, silt and sand) have medium permeability and absorption, and silt soils have low permeability and high retention.
These are a good idea when you are in a wind blown area or are not able to water as often as you would like or if you are using a mix of more than fifty percent sphagum peatmoss .
The Human influence:
The planting medium you choose, planter type and size and how you garden will all affect your soil and how your plants grow.
In general terms though most of the commercial planting mediums will work well for your plants.