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Soil Genesis and Development, Lesson 3 - Soil Forming Factors

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3.2 - Five Soil Forming Factors


Active Factors Passive Factors
Climate Time
Organisms Topography
  Parent Material

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.

Question 1: Think about this....are water tables, which fluctuate up and down, considered an active or passive factor?‏

A. Active
B. Passive



Question 2: Think about fire across the Great Plains considered an active or passive factor?‏

A. Active
B. Passive


Question 3: Think about the human manipulation of soils considered an active or passive factor?‏

A. Active
B. Passive

Brady, and R.R. Weil. 2007. The Nature and Properties of Soils. Fourteenth Edition. Prentice Hall, Inc. Upper Saddly River, NJ. 980 pp.


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