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 and
edaphology, 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,
sylviculturists, 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, performance, 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
Vasily Dokuchaev, a Russian geologist, geographer and early soil scientist, is
credited with identifying soil as a resource whose distinctness and
complexity deserved to be separated conceptually from geology and crop
production and treated as a whole. 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. 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 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 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 conservation
There 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 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. 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
See also Agrology
Agrophysics Australian Society of Soil Science
Incorporated International Soil Reference and
Information Centre International Union of Soil Sciences
Liming List of Russian Earth scientists
List of State Soil Science Associations List of State Soil Science Licensing
Boards List of Universities with Soil Science
Curriculum National Society of Consulting Soil
Scientists Soil Science Society of America
Soil value World Congress of Soil Science
References Soil Survey Staff. Soil Survey: Early
Concepts of Soil. Soil Survey Manual USDA Handbook 18, Soil Conservation
Service. U.S. Department of Agriculture. URL accessed on 2004-11-30.
External links United States Department of Agriculture
Natural Resources Conservation Service - Information on US Soils
Certified Professional Soil Scientist SoilScience.info
ISRIC - World Soil Information IPSS - Institute of Professional Soil
Scientists BSSS - British Society of Soil Science
SSSA - Soil Science Society of America National Soil Resources Institute
Michigan State University Soil Fertility Lab
Michigan State University Soil and Plant Nutrient Lab