Technically, soil
forms the pedosphere: the interface between the lithosphere (rocky
part of the planet) and the biosphere, atmosphere, and hydrosphere.
More generally, soil is a three phase system comprised of various
combinations of naturally- derived solids including fine to
coarse-grained rocks and minerals, organic matter, ice, weathered
rock and precipitates, liquids primarily water solutions, and
gases. The liquid phase is typically primarily water, and is also
known as the 'soil solution'; plants take their nutrients from this
phase. The gaseous phase is important for supplying oxygen to plant
roots for respiration. Soil formation, or pedogenesis, is the
combined effect of physical, chemical, biological, and
anthropogenic processes on soil parent material resulting in the
formation of soil horizons. Dependence on and curiosity about soil,
exploring the diversity and dynamic of this resource continues to
yield fresh discoveries and insights. New avenues of soil research
are compelled by our need to understand soil in the context of
climate change, greenhouse gases, and carbon sequestration. Our
interest in maintaining the planet's biodiversity and in exploring
past cultures has also stimulated renewed interest in achieving a
more refined understanding of soil.
