Historical development of key concepts in pedology

As a subdiscipline of soil science, pedology consists of an accepted body of laws and theories that cover a range of related ideas and concepts. We have traced the history of these concepts as they pertain to the definition of the soil; soil horizons, profiles, and pedons; soil-forming factors; pedogenic processes; soil classification; soil geography and mapping, and soil-landscape relationships. The presented concepts have proven to be useful in our careers and are offered here to generate discussion in the pedology community. Because of space limitations, we have not attempted to critique these concepts. The concepts identified here are useful not only for understanding the development of pedology, but also for identifying future areas of research and providing a frame of reference from which pedologists can evaluate potential scientific contributions to a rapidly changing world.