3.2 - Five Soil Forming Factors
|Active Factors||Passive Factors|
Soils are often defined in terms of these factors as “dynamic natural bodies having properties derived from the combined effect of climate and biotic activities (organisms), as modified by topography, acting on parent materials over periods of time” (Brady and Weil, 2007). Soil scientists identify climate and organisms as “active” factors of soil formation because their influence over soil development can be directly observed. For example, rain, heat, cold, wind, microorganisms (algae, fungi), earthworms, and burrowing animals can be directly observed influencing soil development. Time, topography, and parent material are noted as “passive” factors because their effects are not immediately observed. The passive factors can, however, control how climate and organisms affect soil development and formation.
Brady, and R.R. Weil. 2007. The Nature and Properties of Soils. Fourteenth Edition. Prentice Hall, Inc. Upper Saddly River, NJ. 980 pp.