What Is Soil Science? Pedology, Methods and Funding

Soil science is the scientific study of soil as a natural body: how it forms, what it is made of, how water, nutrients, air and organisms move through it, and how it can be used, managed and protected. It sits at the junction of earth science and biology, and it supports applied work in agriculture, forestry, environmental protection, engineering and land-use planning. This guide explains what soil science studies, how its main subfields divide the work, how soils are classified, which methods and data sources researchers rely on, how the field developed, who funds it, and what training paths lead into it — including the research-administration layer that general overviews skip.

What Is Soil Science?

Soil science treats soil as more than loose dirt or a growing medium. A soil is a natural, organized body at the land surface, built from weathered mineral material, organic matter, water, air and living organisms, and arranged in layers that record how it formed. Soil scientists ask two broad kinds of questions. The first is about the soil itself: why does a given soil have the properties it has, and how do those properties vary across a landscape? The second is about function: how does a soil store and supply water and nutrients to plants, filter or release contaminants, hold carbon, support buildings and roads, and respond to tillage, fertilizer, grazing, fire or climate change?

Because soil underlies food production, water quality and ecosystem function, soil science is both a basic and an applied science. A pedologist mapping soils in a watershed, a soil physicist modelling infiltration, and a soil fertility specialist advising on nutrient management are all doing soil science, but they are asking different questions with different tools.

Soil Science, Pedology and Edaphology

Two older terms are still used for the two halves of the field, and they are worth separating because they are often confused:

• Pedology studies soil as a natural body in its own right: its formation (pedogenesis), morphology, distribution across landscapes and classification. A pedologist describes soil profiles in the field, maps soil types and explains why one soil differs from its neighbor.
• Edaphology studies soil mainly as it relates to living things, especially how soil properties influence plant growth and land use. Soil fertility, crop nutrition and soil management for production fall here.

In practice the two overlap constantly, and most working scientists move between them. “Soil science” is the umbrella term that covers both, together with the physical, chemical and biological subfields described below.

How Soils Form: The Five Soil-Forming Factors

A core idea in pedology is that soil properties are not random: they result from a small set of controlling factors. The Swiss-born soil scientist Hans Jenny formalized this in his 1941 book Factors of Soil Formation: A System of Quantitative Pedology, which built on the earlier work of the Russian geologist Vasily Dokuchaev, whose study Russian Chernozem (1883) is widely credited with establishing soil as a natural body worth studying in its own right. Jenny expressed the state of a soil as a function of five interrelated factors:

• Climate — temperature and precipitation drive weathering, leaching and biological activity.
• Organisms — vegetation, soil animals and microbes add organic matter, mix the soil and cycle nutrients.
• Relief (topography) — slope and landscape position control drainage, erosion and deposition.
• Parent material — the mineral or organic material the soil develops from.
• Time — how long the other factors have been acting.

This framework underlies much of soil survey and classification: if you know the factors at a site, you can often predict the kind of soil that will be found there, and if you find an unexpected soil, the factors help explain why.

The Major Subfields of Soil Science

Professional soil science is usually divided into subfields that mirror the way its main society has organized its work since its founding. The boundaries are porous, and many projects cross several.

Soil Physics

Soil physics studies the physical properties of soil and the movement of water, air and heat through it. Core topics include soil texture (the proportions of sand, silt and clay), structure and aggregation, bulk density and porosity, water retention and infiltration, hydraulic conductivity, and the unsaturated zone between the surface and the water table. Soil physics supplies the quantitative basis for irrigation and drainage design, erosion prediction, compaction research and models of how water and solutes reach groundwater. It connects closely to hydrology and to physics more broadly.

Soil Chemistry and Fertility

Soil chemistry examines the chemical composition and reactions of soil: pH and acidity, the electrical charge on clay and organic surfaces, cation exchange capacity, the solubility and availability of plant nutrients, salinity, and the behavior of metals and organic contaminants. Soil fertility is the applied branch concerned with whether a soil can supply the nutrients crops need and how fertilizers, lime and organic amendments change that supply. Soil chemists also study how pollutants bind to or leach from soil, which links the field to environmental remediation. See What Is Chemistry? for the wider discipline.

Soil Biology and Biochemistry

Soil biology studies the organisms that live in soil — bacteria, archaea, fungi, protists, nematodes, arthropods, earthworms and plant roots — and the processes they drive: decomposition, nutrient mineralization, nitrogen transformations, formation of soil organic matter and aggregates, and interactions with plant roots such as mycorrhizal associations. Molecular methods have expanded the field by allowing researchers to characterize soil communities without culturing each organism. It draws on microbiology and ecology.

Soil Genesis, Morphology and Classification

This is the pedology core of the field: describing soil profiles and horizons, explaining how soils form, and sorting them into classes so that knowledge about one soil can be applied to similar soils elsewhere. Classification is covered in the next section.

Soil Survey, Land Use and Conservation

Soil survey maps the kinds of soil across a landscape and interprets those maps for uses such as farming, forestry, septic systems, roads and conservation planning. Soil conservation addresses erosion, compaction, salinization, loss of organic matter and degradation. Climate-related work asks how much carbon soils store and how management and warming change it.

Other Applied Areas

Soil science also feeds forensic analysis, archaeology, geotechnical engineering, wetland science, mine-land reclamation and urban soils research. Where the focus is crop production, it merges into the wider field covered in What Is Agricultural Science?; where the focus is the weathering and surface processes of the Earth, it merges into What Is Geology?.

Soil Classification

Soils are classified so that scientists, farmers, engineers and planners can communicate about them consistently. Two systems are most widely referenced.

• USDA Soil Taxonomy. Developed in the United States and maintained by the USDA Natural Resources Conservation Service within the National Cooperative Soil Survey, Soil Taxonomy is a hierarchical system organized in six categories: order, suborder, great group, subgroup, family and series. At the top level there are twelve soil orders: Alfisols, Andisols, Aridisols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols and Vertisols. All order names end in “-sol.” The orders are defined by diagnostic horizons and properties rather than by climate or vegetation alone. For example, Histosols are organic soils, Gelisols are soils with permafrost, and Vertisols are clay-rich soils that shrink and swell. NRCS publishes the working document, Keys to Soil Taxonomy, for assigning a soil to its class.
• World Reference Base for Soil Resources (WRB). The international classification system, edited by a working group of the International Union of Soil Sciences (IUSS). The currently valid version is the fourth edition (2022). It recognizes 32 Reference Soil Groups at the highest level and then adds qualifiers to name soils more precisely.

The two systems are not identical and their classes do not map one-to-one, so a soil name should always be reported with the system and edition used. National systems also exist in many countries, so literature from different regions may use different terminology for similar soils.

Methods and Data Sources

• Field description and sampling. Digging a pit or taking a core, describing horizons by color, texture, structure and root distribution, and collecting samples at defined depths. Sampling design matters, because soils vary strongly over short distances.
• Laboratory analysis. Particle-size analysis, pH, organic carbon, nutrient extraction, cation exchange capacity, salinity, and mineralogy, using standardised methods so results are comparable across laboratories.
• Field instrumentation. Sensors for soil moisture, temperature, redox potential and gas flux, used to follow water, heat and carbon dioxide through soil over time.
• Incubations, columns and lysimeters. Controlled experiments that isolate processes such as decomposition, leaching or nutrient transformation.
• Molecular and isotopic tools. DNA-based community analysis and isotope tracing to follow organisms, carbon and nitrogen through soil.
• Remote and proximal sensing, and spatial modelling. Geographic information systems and statistical models used to predict soil properties across landscapes, alongside process models of water, nutrient and carbon dynamics.
• Long-term experiments. Because soils change slowly, multi-year or multi-decade field trials are especially valuable, which is also why continuity of funding and data stewardship matter.

A practical resource for United States work is the NRCS Web Soil Survey, which provides soil data and maps from the National Cooperative Soil Survey, backed by the Soil Survey Geographic Database (SSURGO), generally the most detailed level of soil geographic data produced by that survey. It also gives access to Official Soil Series Descriptions. Researchers building datasets from such sources should record the version and date accessed, a habit that supports reproducibility; see this site’s entry on data management plans.

A Short History

Observations about soil and agriculture are ancient, but soil science as a discipline took shape in the nineteenth century. Dokuchaev’s Russian Chernozem (1883) presented soil as a natural body formed by climate, vegetation and topography, and he is commonly recognised as a founder of pedology. Jenny’s 1941 Factors of Soil Formation turned that idea into a quantitative framework that became central to soil genesis research in the United States and elsewhere.

In the United States, institutions grew alongside the science. Hugh Hammond Bennett, called the father of soil conservation, led the Soil Erosion Service from 1933, and Congress created the Soil Conservation Service within USDA on April 27, 1935, with Bennett as its first Chief. In 1994 Congress renamed it the Natural Resources Conservation Service to reflect its broadened scope. The Soil Science Society of America was formed in 1936 through the merger of the Soils Section of the American Society of Agronomy and the American Soil Survey Association, and was officially founded on November 18, 1936. Internationally, the IUSS brings together soil scientists worldwide and oversees the WRB.

Societies and Journals

• Soil Science Society of America (SSSA). The principal professional society for soil scientists in the United States, working alongside the American Society of Agronomy and the Crop Science Society of America. It publishes the Soil Science Society of America Journal, its main journal, and Vadose Zone Journal; it also co-sponsors the Journal of Environmental Quality and publishes Soil Survey Horizons.
• International Union of Soil Sciences (IUSS). The international body that connects national societies and maintains the WRB through its working group.
• Other national and regional societies serve soil scientists elsewhere, and many publish their own journals; researchers should check the society for their own country and subfield.

Soil research also appears in general agronomy, ecology, hydrology, geoscience and environmental journals. Citation practice and indexing therefore differ by subfield, which matters when assembling a publication record for a promotion, tenure or grant application.

Funding for Soil Research

Soil science is funded mainly through agriculture and natural-resource agencies, with additional support from general science and environmental sources. In the United States:

• USDA National Institute of Food and Agriculture (NIFA). NIFA’s Agriculture and Food Research Initiative (AFRI) is the flagship competitive grants program for food and agricultural science. Within AFRI’s Bioenergy, Natural Resources, and Environment priority area, soil health has been a designated program area (A1401), supporting foundational and applied research on soil physical and biogeochemical processes. Priority areas and program codes change between requests for applications, so applicants should read the current one. See also What Is Agricultural Science? for the wider USDA funding landscape.
• USDA Natural Resources Conservation Service (NRCS). NRCS is primarily a conservation and technical-assistance agency rather than a grant-making research funder, but it leads the National Cooperative Soil Survey and produces the soil data and classification products described above, which many research projects depend on.
• Land-grant universities and agricultural experiment stations host much of the country’s soil research and field infrastructure.
• Other federal and private sources. Soil questions also arise in projects funded by general science, environmental and energy programs and by private foundations. Funding rules differ by sponsor, so check each call for eligibility and allowable costs.

For investigators and research administrators, soil projects have some recurring practical features. Field trials and long-term plots depend on land access, site agreements and multi-year continuity. Sampling often crosses property or jurisdiction lines and may need landowner permissions. Laboratory analysis and instrumentation are common budget items, and sponsors differ on how indirect cost recovery applies. Proposal narratives for agricultural sponsors generally need to explain relevance to agriculture, food systems or natural resources explicitly.

Training and Career Paths

Most professional soil scientists start with a bachelor’s degree in soil science, agronomy, environmental science, geology, ecology, chemistry or a related field, often at a land-grant university. Graduate study (MS and PhD) specializes in a subfield such as soil physics, soil chemistry, soil microbiology, pedology or soil fertility, usually built around a thesis involving field and laboratory work. Typical employers include universities and agricultural experiment stations, federal and state agencies such as NRCS and state natural-resource departments, agribusiness and agronomy consulting, environmental consulting and remediation firms, and conservation organizations. Some roles, such as soil classification and survey work, benefit from formal professional certification; requirements vary, so consult the relevant society or employer.

Where Soil Science Sits Among Related Fields

Soil science is close to many neighboring disciplines and borrows methods from each: geology for parent materials and weathering, chemistry for reactions in the soil solution, biology and microbiology for soil life, ecology for ecosystem function, hydrology for water movement, and agricultural science for crop and land management. For how soil science fits among the major scientific fields, see the overview of the branches of science, and for the research-methods material that applies across disciplines, see the Research Methods & Statistics hub.

Frequently Asked Questions

What is soil science in simple terms?

Soil science is the study of soil: how it forms, what it is made of, how it works as a system for water, nutrients and life, and how it can be managed and protected.

What is the difference between soil science and pedology?

Pedology is one branch of soil science, concerned with how soils form, how they are described and how they are classified and mapped. Soil science also includes soil physics, chemistry, biology and fertility, which focus on soil properties and processes.

What is the difference between pedology and edaphology?

Pedology studies soil as a natural body in its own right. Edaphology studies soil mainly through its influence on plants and land use, such as fertility and crop production.

What are the main branches of soil science?

The main subfields are soil physics, soil chemistry and fertility, soil biology and biochemistry, soil genesis, morphology and classification, and soil survey, land use and conservation.

How many soil orders are there?

USDA Soil Taxonomy has twelve soil orders. The international World Reference Base for Soil Resources (2022, fourth edition) recognizes 32 Reference Soil Groups. The two systems are separate and do not map one-to-one.

What are the five factors of soil formation?

Climate, organisms, relief (topography), parent material and time, as set out in Hans Jenny’s 1941 framework.

Who funds soil research in the United States?

The main source is USDA, especially NIFA’s AFRI competitive program, which has included a soil health program area. NRCS leads the National Cooperative Soil Survey and supplies soil data. Land-grant universities, other federal programs and private foundations also contribute.

What is the Soil Science Society of America?

SSSA is the main professional society for soil scientists in the United States. It was formed in 1936 and publishes journals including the Soil Science Society of America Journal and Vadose Zone Journal.

Where can I find soil maps and data for a location in the United States?

The NRCS Web Soil Survey provides soil maps and data from the National Cooperative Soil Survey for most of the country, including Official Soil Series Descriptions.

Related Guides

Companion discipline guides in this series: What Is Agricultural Science?, What Is Geology?, What Is Hydrology?, What Is Ecology?, What Is Microbiology? and What Is Chemistry?.