Eric, over at Dynamic Earth is blogging on about soil science.
Soils are a lot like pornography: you know em when you see em, but everyone has a hard time agreeing on a definition.
True that. Eric's posts are a pretty quick study (its a blog after all) of a complex subject, and he does an admirable job of organizing the popular understanding of soil. I shouldn't expect, but I always look for, even the briefest nod to including energy as fascinatingly important to the understanding of soil, at least as equally fascinating as the physical, chemical, and biological characteristics.
Soil classification is only a beginning in pursuing a deeper understanding of the more dynamic characteristics of the soil resource. Nikiforoff's 1959 definition of soil as the "excited skin of the sub aerial part of the earth's crust". (ref) speaks to that energy. We all recognize that soil involves energy but we have been slow to engage in an understanding of that energy as a component of the dynamic earth.
Most of what has been studied regarding energy in soil is in relation to remediation of contaminants, preventing corrosion, waste treatment, and wetland chemistry: small but practical subsets of the knowledge we need. And we do use energy states and gradients to characterize soil (redox, pE), so it is not like energy is ignored. It is just that the labels we present it under do not communicate energy. Wetland chemistry, bioremediation, phytoremediation, geobiochemistry, soil ecology: these are not terms that alerts one to the fact that energy is the fundamental driver. That our soil projects are nonetheless successful points to the simplicity of the soil problems we have been addressing up until now. As we are challenged to better understand the energy dynamics of the earth, this is certain to change.
ref: C. C. Nikiforoff. 1959. "Reappraisal of the soil: Pedogenesis consists of transactions in matter and energy between the soil and its surroundings". Science 129: 186-196.