The Master V Horizon for Soil Horizons Dominated By Vesicular Porosity.

Surface or near surface horizons dominated by vesicular porosity are extensive in arid and semi-arid soils worldwide.  Vesicular horizons form by a unique process and are distinctly different from other master horizons.  Vesicular horizons are exceptionally important because they severely restrict infiltration and have high rates of dust emission when disturbed by human activities (e.g., off-road vehicles, construction). The master V horizon provides scientists working in arid and semi-arid lands with a simple way to indicate the presence of a vesicular horizon.  The master V horizon was proposed to the NCSS Standards Committee, discussed at regional and national meetings, and finally approved for use in NRCS publications and databases.  The master V horizon is a morphologic horizon and does not affect the taxonomic classification of soils.  V horizons are defined as: “Mineral horizons that have formed at the soil surface, or below a layer of rock fragments (e.g., desert pavement) or a physical or biological crust.  They are characterized by the predominance of vesicular pores.”  This new morphologic horizon will help to improve communication among soil scientists, ecologists, geomorphologists, range scientists, land managers, and others working in arid and semi-arid lands, where the presence of vesicular porosity is an important indication of soil properties that affect hydrology and air quality.