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Department of Soil Science
University of Saskatchewan
51 Campus Drive, Saskatoon SK S7N 5A8

Soil formation: factors

Hans Jenny suggested a slightly different way of considering the factors of soil formation and their effects, in his 1941 book "Factors of Soil Formation". Jenny's model (idea) is consistent with others in that it indicates five factors of soil formation: (1) climate (cl); (2) organisms (o); (3) topography (r); (4) parent material (p); and (5) time (t). Because the factors define the state and the history of soil systems, they are referred to as state factors, and the whole idea is called the state factor approach. Jenny considered that soil systems could be described mathematically by the following expression:

S = f (cl, o, r, p, t....)

where the....(dots) are additional unspecified factors that may be unique to a particular soil, S= a measureable soil property, and f means "is a factor of".

Later, Jenny suggests that the model is best used in a conceptual way to understand and study soil formation by considering that changes in the soil system that are the result of regular variations in one factor, with all other factors more or less constant. For example, the effect of topography can be evaluated by studying related groups of soils where topography varies, as in a hillslope, and the other variables (parent material, organisms, climate and time) are similar.

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