Soil science is the study of soil as a natural resource on the surface of the Earth including
soil formation, classification and mapping; physical, chemical, biological, and fertility
properties of soils; and these properties in relation to the use and management of soils.Sometimes
terms which refer to branches of soil science, such as pedology (formation, chemistry, morphology,
and classification of soil) and edaphology (how soils interact with living things, especially
plants), are used as if synonymous with soil science.
The diversity of names associated with this discipline is related to the various associations
concerned.
Indeed, engineers, agronomists, chemists, geologists, physical geographers, ecologists,
biologists, microbiologists, silviculturists, sanitarians, archaeologists, and specialists
in regional planning, all contribute to further knowledge of soils and the advancement of
the soil sciences.
Soil scientists have raised concerns about how to preserve soil and arable land in a
world with a growing population, possible future water crisis, increasing per capita
food consumption, and land degradation.
== Fields of study == Soil occupies the pedosphere, one of Earth's
spheres that the geosciences use to organize the Earth conceptually.
This is the conceptual perspective of pedology and edaphology, the two main branches of soil
science.
Pedology is the study of soil in its natural setting.
Edaphology is the study of soil in relation to soil-dependent uses.
Both branches apply a combination of soil physics, soil chemistry, and soil biology.
Due to the numerous interactions between the biosphere, atmosphere and hydrosphere that
are hosted within the pedosphere, more integrated, less soil-centric concepts are also valuable.
Many concepts essential to understanding soil come from individuals not identifiable strictly
as soil scientists.
This highlights the interdisciplinary nature of soil concepts.
== Research == Dependence on and curiosity about soil, exploring
the diversity and dynamics of this resource continues to yield fresh discoveries and insights.
New avenues of soil research are compelled by a need to understand soil in the context
of climate change, greenhouse gases, and carbon sequestration.
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.
== Mapping ==
Most empirical knowledge of soil in nature comes from soil survey efforts.
Soil survey, or soil mapping, is the process of determining the soil types or other properties
of the soil cover over a landscape, and mapping them for others to understand and use.
It relies heavily on distinguishing the individual influences of the five classic soil forming
factors.
This effort draws upon geomorphology, physical geography, and analysis of vegetation and
land-use patterns.
Primary data for the soil survey are acquired by field sampling and supported by remote
sensing.
== Classification ==
As of 2006, the World Reference Base for Soil Resources, via its Land & Water Development
division, is the pre-eminent soil classification system.
It replaces the previous FAO soil classification.
The WRB borrows from modern soil classification concepts, including USDA soil taxonomy.
The classification is based mainly on soil morphology as an expression pedogenesis.
A major difference with USDA soil taxonomy is that soil climate is not part of the system,
except insofar as climate influences soil profile characteristics.
Many other classification schemes exist, including vernacular systems.
The structure in vernacular systems are either nominal, giving unique names to soils or landscapes,
or descriptive, naming soils by their characteristics such as red, hot, fat, or sandy.
Soils are distinguished by obvious characteristics, such as physical appearance (e.g., color,
texture, landscape position), performance (e.g., production capability, flooding), and
accompanying vegetation.
A vernacular distinction familiar to many is classifying texture as heavy or light.
Light soil content and better structure, take less effort to turn and cultivate.
Contrary to popular belief, light soils do not weigh less than heavy soils on an air
dry basis nor do they have more porosity.
== History == Contemporaries Friedrich Albert Fallou, the
German founder of modern soil science, and Vasily Dokuchaev, the Russian founder of modern
soil science, are both credited with being among the first to identify soil as a resource
whose distinctness and complexity deserved to be separated conceptually from geology
and crop production and treated as a whole.
As a founding father of soil science Fallou has primacy in time.
Fallou was working on the origins of soil before Dokuchaev was born, however Dokuchaev's
work was more extensive and is considered to be the more significant to modern soil
theory than Fallou's.
Previously, soil had been considered a product of chemical transformations of rocks, a dead
substrate from which plants derive nutritious elements.
Soil and bedrock were in fact equated.
Dokuchaev considers the soil as a natural body having its own genesis and its own history
of development, a body with complex and multiform processes taking place within it.
The soil is considered as different from bedrock.
The latter becomes soil under the influence of a series of soil-formation factors (climate,
vegetation, country, relief and age).
According to him, soil should be called the "daily" or outward horizons of rocks regardless
of the type; they are changed naturally by the common effect of water, air and various
kinds of living and dead organisms.
A 1914 encyclopedic definition: "the different forms of earth on the surface of the rocks,
formed by the breaking down or weathering of rocks".
serves to illustrate the historic view of soil which persisted from the 19th century.
Dokuchaev's late 19th century soil concept developed in the 20th century to one of soil
as earthy material that has been altered by living processes.
A corollary concept is that soil without a living component is simply a part of earth's
outer layer.
Further refinement of the soil concept is occurring in view of an appreciation of energy
transport and transformation within soil.
The term is popularly applied to the material on the surface of the Earth's moon and Mars,
a usage acceptable within a portion of the scientific community.
Accurate to this modern understanding of soil is Nikiforoff's 1959 definition of soil as
the "excited skin of the sub aerial part of the earth's crust".
== Areas of practice == Academically, soil scientists tend to be drawn
to one of five areas of specialization: microbiology, pedology, edaphology, physics, or chemistry.
Yet the work specifics are very much dictated by the challenges facing our civilization's
desire to sustain the land that supports it, and the distinctions between the sub-disciplines
of soil science often blur in the process.
Soil science professionals commonly stay current in soil chemistry, soil physics, soil microbiology,
pedology, and applied soil science in related disciplines
One interesting effort drawing in soil scientists in the USA as of 2004 is the Soil Quality
Initiative.
Central to the Soil Quality Initiative is developing indices of soil health and then
monitoring them in a way that gives us long term (decade-to-decade) feedback on our performance
as stewards of the planet.
The effort includes understanding the functions of soil microbiotic crusts and exploring the
potential to sequester atmospheric carbon in soil organic matter.
The concept of soil quality, however, has not been without its share of controversy
and criticism, including critiques by Nobel Laureate Norman Borlaug and World Food Prize
Winner Pedro Sanchez.
A more traditional role for soil scientists has been to map soils.
Most every area in the United States now has a published soil survey, which includes interpretive
tables as to how soil properties support or limit activities and uses.
An internationally accepted soil taxonomy allows uniform communication of soil characteristics
and soil functions.
National and international soil survey efforts have given the profession unique insights
into landscape scale functions.
The landscape functions that soil scientists are called upon to address in the field seem
to fall roughly into six areas:
Land-based treatment of wastes Septic system
Manure Municipal biosolids
Food and fiber processing waste Identification and protection of environmentally
critical areas Sensitive and unstable soils
Wetlands Unique soil situations that support valuable
habitat, and ecosystem diversity Management for optimum land productivity
Silviculture Agronomy
Nutrient management Water management
Native vegetation Grazing
Management for optimum water quality Stormwater management
Sediment and erosion control Remediation and restoration of damaged lands
Mine reclamation Flood and storm damage
Contamination Sustainability of desired uses
Soil conservationThere are also practical applications of soil science that might not
be apparent from looking at a published soil survey.
Radiometric dating: specifically a knowledge of local pedology is used to date prior activity
at the site Stratification (archeology) where soil formation
processes and preservative qualities can inform the study of archaeological sites
Geological phenomena Landslides
Active faults Altering soils to achieve new uses
Vitrification to contain radioactive wastes Enhancing soil microbial capabilities in degrading
contaminants (bioremediation).
Carbon sequestration Environmental soil science
Pedology Soil genesis
Pedometrics Soil morphology
Soil micromorphology Soil classification
USDA soil taxonomy Soil biology
Soil microbiology Soil chemistry
Soil biochemistry Soil mineralogy
Soil physics Pedotransfer function
Soil mechanics and engineering Soil hydrology, hydropedology
=== Fields of application in soil science ===
Climate change Ecosystem studies
Pedotransfer function Soil fertility / Nutrient management
Soil management Soil survey
Standard methods of analysis Watershed and wetland studies
=== Related disciplines ===
Agricultural sciences Agricultural soil science
Agrophysics science Irrigation management
Anthropology archaeological stratigraphy
Environmental science Landscape ecology
Physical geography Geomorphology
Geology Biogeochemistry
Geomicrobiology Hydrology
Hydrogeology Waste management
Wetland science
== Depression storage capacity ==
Depression storage capacity, in soil science, is the ability of a particular area of land
to retain water in its pits and depressions, thus preventing it from flowing.
Depression storage capacity, along with infiltration capacity, is one of the main factors involved
in Horton overland flow, whereby water volume surpasses both infiltration and depression
storage capacity and begins to flow horizontally across land, possibly leading to flooding
and soil erosion.
The study of land's depression storage capacity is important in the fields of geology, ecology,
and especially hydrology.
== See also