ABSTRACT
Soil is a key natural resource and soil quality is one of the most important properties that determines cropproductivityandsustainability.Goodsoilqualitynotonlyproducesgoodcropyieldsbut alsomaintainsenvironmentalqualityandconsequentlyplant,animal,andhumanhealth(Fageria, 2002).One of many uses and roles of soil is its function as a ˜lter. Soils can sequester large amounts of pollutantsbeforetheythreatenbiologicalorganismsorthehealthfulnessoffood(Cook and Hendersot, 1996; Oliver, 1997; Sojka and Upchurch, 1999). Soil is a dynamic, living resource whoseconditionisvitalbothtotheproductionoffoodand˜berandtotheecosystemfunctionor, inessence,tothesustainabilityoflifeonearth(Doranet al.,1996).Soilisthebaseuponwhich societyisbuilt(SingerandWarkentin,1996).Goodsoilisacriticalresourceforcivilization,asit makespossibletheshiftfromnomadicsocietiestostablecommunities(SmithandLee,2003).In the early days, soil productivity was totally dependent on natural resources, and there was a sound ecologicalequilibriumamongsoils,plants,animals,andhumans.However,thesituationbeganto changewiththeadvancementofagriculturalscienceandtechnology.Useofagriculturalmachinery, irrigation,fertilizers,pesticides,goodqualityseeds,andintensivecultivationcreateddisequilibria betweensoilandplantecosystems,andsoilqualitystarteddeclining.Asigni˜cantdeclineinsoil quality has occurred worldwide, creating a need to develop criteria to evaluate soil quality and to take corrective actions (Fageria, 2002).
