3.2 - Five Soil Forming Factors | Soil Genesis and Development, Lesson 3 - 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.

Quiz

Question

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

A. Active

Correct: Fluctuating water tables may be considered an active factor of soil formation. Water tables generally fluctuate up and down seasonally and thus the effect can be readily observed by change in soil color associated with water-logged conditions.

B. Passive

Incorrect: Can the fluctuating water table be observed?

Looks Good! Correct: Fluctuating water tables may be considered an active factor of soil formation. Water tables generally fluctuate up and down seasonally and thus the effect can be readily observed by change in soil color associated with water-logged conditions.

Question

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

A. Active

Correct: Fire may be considered an active factor of soil formation. Although fire has been suppressed across the Great Plains by humans, when it does occur its effect can be readily observed by the release of nutrients back into the soil.

B. Passive

Incorrect: Can the effects of fire be seen?

Looks Good! Correct: Fire may be considered an active factor of soil formation. Although fire has been suppressed across the Great Plains by humans, when it does occur its effect can be readily observed by the release of nutrients back into the soil.

Question

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

A. Active

Correct: Human manipulation is an active factor of soil formation. Humans constantly disturb soils via urbanization of our environment.

B. Passive

Incorrect: Can we observe human manipulation of soils?

Looks Good! Correct: Human manipulation is an active factor of soil formation. Humans constantly disturb soils via urbanization of our environment.

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