In the case of assessment of soil quality in San Joaquin
Valley’s in California (USA); Andrews et al. (2003) considered as
potential soil quality indicators: pH, WSA (wet aggregate stability),
OM (organic matter), Olsen-P, PMN (potentially mineralizable
nitrogen), EC (electrical conductivity), and SAR (sodium
absorption ratio). These indicators may vary according to
agricultural practices, vegetation type and determine soil
productivity or soil fertility.