Soil pH is most important parameter for good plant growth. Acidic soil causes the stunted of the plant and many fungus may attack the plant leaves.

Some parameters or indicators for soil quality can be physical, chemical or biological.

Physical: texture, porosity, infiltration and bulk density, available water capacity, aggregate stability

Chemicals: organic matter, pH, conductivity eleéctrica, removable NPK, cation exchange capacity

Biological: microbial diversity, diversity of macrofauna (earthworms), microbial biomass, respiration rates

Dear Dr. Zaman,

As indicated in previous answers: physical, chemical and biological soil properties will afect the plant growth. From the physical point of view the easiest parameter that can be used to infer about the soil quality is its bulk density. You can also utilize the soil porosity derived from the soil bulk and particle density. Another interesting tool is the soil water retention curve, which can give you interesting indirect information about the soil structure. If you have acess to modern techniques such as computerized tomography it is possible to have information about the soil pore size distribution, shape, continuity, tortuosity, etc. These parameters affect the soil water retention and, consequently, the root development. Other parameter that has been used by the soil physicists is the least limiting water range.

Regards.

Organic carbon, available nutrients (macro and micro), soil pH and microbial CFU decides the quality of soil. 

Dear Dr. Zaman,

Labile pools have been used as sensitive indicators of changes in response to land use management  and soil quality (Blair et al., 2001; Chan et al., 2001; Weil et al., 2003; Lutzow et al., 2007; Oyonarte et al., 2007; Partyka, Hamkalo, 2010).  See our publications in File.

Regards,

Zenon Hamkalo

Of the point of practical view, you can get with a routin analysis (easy and cheap): texture, pH, % organic carbon, microbial diversity, removable NPK.

Thnxs to all