Branches of Soil Science?

Submitted by dig on Wed, 2007-07-11 20:22.

Wed 11 JULY, 2007

I visited Wikipedia recently to contribute and was surprised to discover that Edaphology described as a main branch of soil science. I believe that this is a misconception of what pedology is.

First, Buol et al. (1997) states that "pedology is a collective term used to refer to the combination of the two phases [of soil science] - soil genesis and classification. It has also been used to refer to the combination of the the entire subfield of soil genesis and classification, morphology, survey and interpretations." This authority then lists the following subareas of pedology:

  • Soil Genesis
  • Soil Classification
  • Soil Morphology
  • Soil Survey
  • Soil Geomorphology
  • Soil Characterization and Analysis
  • Soil Interpretation

Wikipedia states that Edaphology "is concerned with the influence of soils on living things, particularly plants. The term is also applied to the study of how soil influences man's overall use of the land." I contend that this Wikipedia statement is a misconception of what pedology encompasses. I state this because organisms have an intimate continuing interaction with the soil (Jenny, 1994). Plants, as the most pronounced expression of organisms interaction with soils, should be viewed as a soil forming factor and a subset of pedology; Soil Genesis, Soil Characterization and Analysis, and Soil Interpretation. Plants alter the soil by removing inorganics, contributing to the dissolution of soil minerals by exuding protons and organic acids. Plants also exude other organic compounds to chelate inorganics either for uptake or to sequester them to avoid or mediate uptake. Soil influence on man's overall use is covered in Soil Interpretation, and the Soil Survey is a product that does just that.

Pedology is integrative of other soil science disciplines. A pedologist must be conversant with other sub-disciplines of Soil Science such as Soil Chemistry, Soil Physics, and Soil Biology (sometimes referred to as Soil Microbiology or Soil Ecology). The intensity of study within these sub-disciplines often precludes the time, resources, and understanding of other soil sub-disciplines that is necessary to link the findings of their investagations to the soilscape. However, these sub-disciplines are marked by being allied to one or more of the subareas of pedology, but, again, they often do not rely on the integration if the findings into an understanding of the soilscape for acceptance of the findings by the scientific community. Pedological results always link back to the soilscape.



Buol, Stanley W., F,D. Hole and R.W. McCracken. 1997. Soil Genesis and Classification, 4th ed. Iowa State Univ. Press, Ames ISBN 0-8138-2873-2

Jenny, Hans. 1994. Factors of Soil Formation - A System of Quantitive Pedology, Dover Pub. Mineola, N.Y. ISBN 0-486-68128-9

About Donald G McGahan


As a UC-educated pedologist steeped in soil taxonomy, I can appreciate this line of thinking, and even subscribed to it until about 10 years ago. I believe strongly that a grounding in pedology is the most prized skill set to have for practicing edaphology. Pedology is integrative of the other disciplines of soil science, including edaphology. However, this integrative relationship doesn't require edaphology to abdicate equal branch standing. The integrative position is the same logic that is used to dismiss soil science's equal standing with geology, or to characterize the pedosphere as a layer of the lithosphere.

  • Pedology is the study of soil in a natural setting.
  • Edaphology is the study of soil effects on (and from) plants, animals and man. Edaphic effects are not predicated on a natural setting.

There is considerable overlap between the two disciplines, but it is not complete. Equal branch standing is necessary to allow soil science to cover the study of soil that exists outside of a natural context. Without this standing, the core of agricultural soil science becomes solely a subdiscipline of the agricultural sciences, with a parallel fate for environmental soil science. That was certainly the situation with Wikipedia in 2004. Soil science articles were categorized as agriculture, engineering, geography, and/or geology. Now both soil and soil science enjoy their own categorical hierarchies. The soil science hierarchy enjoys equal standing with geology as one of the earth science.

It has been particularly useful to maintain edaphology as a sister of pedology within the categorization structure of Wikipedia. Pedology, as distinct from edaphology, is categorized as a sub-discipline of both soil science and physical geography, a placement that has a long and substantial history to it. It is also a placement that edaphology does not share.

Vasily Dokuchaev, the father of modern soil science, was a geographer. What existed before Dokuchaev was soil science sans pedology, and was termed agricultural geology. Soil-science-sans-pedology continues to thrive, especially outside of the United State. It will not conform to sub-discipline standing under pedology.

Philip Small, User Paleorthid, WikiProject Soil