A new look at soil phenoforms - Definition, identification, mapping

The soil genoform vs. soil phenoform distinction was suggested twenty years ago by Droogers and Bouma to recognize management-induced differences among pedons with the same long-term pedogenesis and included in the same soil map unit, these changes being sufficient to cause important and persistent differences in soil functions. To support the recent increased interest in soil change and soil health, we propose conceptual and operational definitions of soil genoforms and soil phenoforms, and suggest techniques to identify and map them. We define soil genoforms as soil classes as identified by the soil classification system used as the basis for detailed soil mapping in a given area. This avoids the difficulty of defining when human intervention has been sufficient to create new genoforms - by definition this is when new lowest-level classes are recognized in the classification system, based on diagnostic horizons and properties. We then define soil phenoforms as persistent variants of a genoform with sufficient physical or chemical differences to substantially affect soil functions. Soil phenoforms must be persistent enough that substantial management interventions are necessary to change them, thus seasonal and rotational variants are excluded from the concept. Soil phenoforms can be identified by measurements of indicator soil properties at locations within a soil genoform with different management and investigating if these are different enough to affect soil functions, notably soil hydrology and crop yield. Digital mapping of soil phenoforms will likely use maps of current and historical management as predictors. In areas with intensive or changed management, mapping should be repeated every few years to identify areas of changed soil phenoforms and new genoforms.