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Agricultural soil science is a branch of soil science that deals with the study of edaphic conditions as they relate to the production of food and fiber. In this context, it is also a constituent of the field of agronomy and is thus also described as soil agronomy.

History[link]

Prior to the development of pedology in the 19th century, agricultural soil science (or edaphology) was the only branch of soil science. The bias of early soil science toward viewing soils only in terms of their agricultural potential continues to define the soil science profession in both academic and popular settings as of 2006^[update]. (Baveye, 2006)

Current status[link]

Agricultural soil science follows the holistic method. Soil is investigated in relation to and as integral part of terrestrial ecosystems but is also recognized as a manageable natural resource.

Agricultural soil science studies the chemical, physical, biological, and mineralogical composition of soils as they relate to agriculture. Agricultural soil scientists develop methods that will improve the use of soil and increase the production of food and fiber crops. Emphasis continues to grow on the importance of soil sustainability. Soil degradation such as erosion, compaction, lowered fertility, and contamination continue to be serious concerns.^[1] They conduct research in irrigation and drainage, tillage, soil classification, plant nutrition, soil fertility, and other areas.

Although maximizing plant (and thus animal) production is a valid goal, sometimes it may come at high cost which can be readily evident (e.g. massive crop disease stemming from monoculture) or long-term (e.g. impact of chemical fertilizers and pesticides on human health). An agricultural soil scientist may come up with a plan that can maximize production using sustainable methods and solutions, and in order to do that he must look into a number of science fields including agricultural science, physics, chemistry, biology, meteorology and geology.

Soil variables[link]

Some soil variables of special interest to agricultural soil science are:

• Soil texture or soil composition: Soils are composed of solid particles of various sizes. In decreasing order, these particles are sand, silt and clay. Every soil can be classified according to the relative percentage of sand, silt and clay it contains.

• Aeration and porosity: Atmospheric air contains elements such as oxygen, nitrogen, carbon and others. These elements are prerequisites for life on Earth. Particularly, all cells (including root cells) require oxygen to function and if conditions become anaerobic they fail to respire and metabolize. Aeration in this context refers to the mechanisms by which air is delivered to the soil. In natural ecosystems soil aeration is chiefly accomplished through the vibrant activity of the biota. Humans commonly aerate the soil by tilling and plowing, yet such practice may cause degradation. Porosity refers to the air-holding capacity of the soil. See also characterisation of pore space in soil.

• Drainage: In soils of bad drainage the water delivered through rain or irrigation may pool and stagnate. As a result prevail anaerobic conditions and plant roots suffocate. Stagnant water also favors plant-attacking water molds. In soils of excess drainage, on the other hand, plants don't get to absorb adequate water and nutrients are washed from the porous medium to end up in groundwater reserves.

• Water content: Without soil moisture there is no transpiration, no growth and plants wilt. Technically, plant cells loose their pressure (see osmotic pressure and turgor pressure). Plants contribute directly to soil moisture. For instance, they create a leafy cover that minimizes the evaporative effects of solar radiation. But even when plants or parts of plants die, the decaying plant matter produces a thick organic cover that protects the soil from evaporation, erosion and compaction. For more on this subject see mulch.

• Water potential: Water potential describes the tendency of the water to flow from one area of the soil to another. While water delivered to the soil surface normally flows downward due to gravity, at some point it meets increased pressure which causes a reverse upward flow. This effect is known as water suction.

• Horizonation: Typically found in advanced and mature soils, horizonation refers to the creation of soil layers with differing characteristics. It affects almost all soil variables.

• Fertility: A fertile soil is one rich in nutrients and organic matter. Modern agricultural methods have rendered much of the arable land infertile. In such cases, soil can no longer support on its own plants with high nutritional demand and thus needs an external source of nutrients. However there are cases were human activity is thought responsible for transforming rather normal soils into super-fertile ones (see terra preta).

• Biota and soil biota: Organisms interact with the soil and contribute to its quality in innumerable ways. Sometimes the nature of interaction may be unclear, yet a rule is becoming evident: The amount and diversity of the biota is "proportional" to the quality of the soil. Clades of interest include bacteria, fungi, nematodes, annelids and arthropods.

• Soil acidity or soil pH and cation-exchange capacity: Root cells act as hydrogen pumps and the surrounding concentration of hydrogen ions affects their ability to absorb nutrients. pH is a measure of this concentration. Each plant species achieves maximum growth in a particular pH range, yet the vast majority of edible plants can grow in soil pH between 5.0 and 7.5.

Soil Fertility[link]

Agricultural soil scientists study ways to make soils more productive. They classify soils and test them to determine whether they contain nutrients vital to plant growth. Such nutritional substances include compounds of nitrogen, phosphorus, and potassium. If a certain soil is deficient in these substances, fertilizers may provide them. Agricultural soil scientists investigate the movement of nutrients through the soil, and the amount of nutrients absorbed by a plant's roots. Agricultural soil scientists also examine the development of roots and their relation to the soil. Some agricultural soil scientists try to understand the structure and function of soils in relation to soil fertility. They grasp the structure of soil as porous solid. The solid frames of soil consist of mineral derived from the rocks and organic matter originated from the dead bodies of various organisms. The pore space of the soil is essential for the soil to become productive. Small pores serve as water reservoir supplying water to plants and other organisms in the soil during the rain-less period. The water in the small pores of soils is not pure water; they call it soil solution. In soil solution, various plant nutrients derived from minerals and organic matters in the soil are there. This is measured through the cation exchange capacity. Large pores serve as water drainage pipe to allow the excessive water pass through the soil, during the heavy rains. They also serve as air tank to supply oxygen to plant roots and other living beings in the soil. In short, agricultural soil scientists see the soil as a vessel, the most precious one for us, containing all of the substances needed by the plants and other living beings on earth.

Soil Preservation[link]

In addition, agricultural soil scientists develop methods to preserve the agricultural productivity of soil and to decrease the effects on productivity of erosion by wind and water. For example, a technique called contour plowing may be used to prevent soil erosion and conserve rainfall. Researchers in agricultural soil science also seek ways to use the soil more effectively in addressing associated challenges. Such challenges include the beneficial reuse of human and animal wastes using agricultural crops; agricultural soil management aspects of preventing water pollution and the build-up in agricultural soil of chemical pesticides.

Employment of Agricultural Soil Scientists[link]

Most agricultural soil scientists are consultants, researchers, or teachers. Many work in the developed world as farm advisors, agricultural experiment stations, federal, state or local government agencies, industrial firms, or universities. Within the USA they may be trained through the USDA's Cooperative Extension Service offices, although other countries may use universities, research instututes or research agencies. Elsewhere, agricultural soil scientists may serve in international organizations such as the Agency for International Development and the Food and Agriculture Organization of the United Nations.

Quotations[link]

The key objective of the soil science discipline is that of “finding ways to meet growing human needs for food and fiber while maintaining environmental stability and conserving resources for future generations” John W Doran, 2002 SSSA President, 2002

"Many people have the vague notion that soil science is merely a phase of agronomy and deals only with practical soil management for field crops. Whether we like it or not this is the image many have of us." Charles E. Kellog, 1961

See also[link]

• Agricultural science
• Agrogeology
• Soil science
• Agrology

References[link]

External links[link]

• The Soil Science Society of America (SSSA)
• British Society of Soil Science

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.^[1]

Sometimes terms which refer to branches of soil science, such as pedology (formation, chemistry, morphology and classification of soil) and edaphology (influence of soil on organisms, 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, 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.^[2]

Fields of study[link]

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[link]

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 a need to understand soil in the context of climate change,^[3] greenhouse gases,^[4][5] and carbon sequestration.^[6] 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[link]

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[link]

Map of global soil regions from the USDA

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.^[7] 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[link]

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 (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.^[8]

A 1914 encyclopedic definition: "the different forms of earth on the surface of the rocks, formed by the breaking down or weathering of rocks".^[9] 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.^[10] 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".^[11]

Areas of practice[link]

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^[update] 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 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 (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[link]

• Soil survey
• Soil management
• Standard methods of analysis
• Soil fertility / Nutrient management
• Ecosystem studies
• Climate change
• Watershed and wetland studies
• Pedotransfer function

Related disciplines[link]

• Agricultural sciences
  • 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[link]

• Agrology
• International Union of Soil Sciences (IUSS)
• National Society of Consulting Soil Scientists (NSCSS)
• Soil Science Society of America (SSSA)
• Australian Society of Soil Science Incorporated (ASSSI)
• World Congress of Soil Science (WCSS)
• List of Universities with Soil Science Curriculum
• List of State Soil Science Licensing Boards
• List of State Soil Science Associations
• International Soil Reference and Information Centre(ISRIC)
• Liming (soil)
• Agrophysics
• List of Russian Earth scientists

Degree programs[link]

North America[link]

• Michigan State University (Associates, B.S, M.S., and Ph.D.)
• Purdue University (BS, M.S. and Ph.D.)
• University of Idaho (B.S., M.S. and Ph.D.)
• University of Kentucky (BS, MS, Ph.D)
• University of Wisconsin - Madison (BS, MS, and Ph.D)
• University of Florida B.S., M.S., and Ph.D.

Europe[link]

• St. Petersburg State University, Bachelor and Master degrees

References[link]

• Soil Survey Staff (1993). Soil Survey: Early Concepts of Soil. (html) Soil Survey Manual USDA Handbook 18, Soil Conservation Service. U.S. Department of Agriculture. URL accessed on 2004-11-30.

External links[link]

• 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

v t e Subfields of physical geography Biogeography Climatology / Paleoclimatology Coastal geography Edaphology Geomorphology Glaciology Hydrology / Hydrography Landscape ecology Limnology Oceanography Palaeogeography Pedology/Soil science Quaternary science

This biographical article is written like a résumé. Please help improve it by revising it to be neutral and encyclopedic. (January 2012)

Elaine Ingham is an American soil biology researcher and founder of Soil Foodweb Inc. She is recognised around the world as a leader in soil microbiology and research of the soil food web. She is a key author of the USDA's Soil Biology Primer. In 2011, Ingham was named as The Rodale Institute's chief scientist.^[1]

Research[link]

Ingham obtained her PhD from the Colorado State University in 1981. Ingham’s doctorate is in Microbiology with an emphasis on soil. Elaine was offered a Post-doctoral Fellowship, along with her husband Russ (who also has a doctorate from Colorado State University in Zoology, emphasizing nematology), at the Natural Resource Ecology Lab at Colorado State University. In 1985, Ingham accepted a Research Associate Fellowship at the University of Georgia.

In 1986, Ingham moved to Oregon State University, and joined the faculty in both Forest Science and Botany and Plant Pathology. She remained on faculty until 2001.

Ingham is also an Affiliate Professor, Graduate Research, South Cross University, Lismore, NSW, Australia, 2001–present, an Affiliate Professor of Sustainable Living at Maharishi University of Management, Fairfield, Iowa,^[1] and was Program Chair, Ecological Society of America (1999–2000).^[2][3]

Books[link]

• Ingham, E.R. and M. Alms. (1999), The Compost Tea Handbook 1.1
• Ingham, E.R. (2000) The Compost Tea Brewing Manual. Sustainable Studies Institute, Eugene, OR. 60 pp.
• Ingham, E.R. (2001) The Compost Tea Brewing Manual Second Edition, Soil Foodweb Inc, Corvallis, Oregon 68pp
• Ingham, E.R. (2002) The Compost Tea Brewing Manual Third Edition, Soil Foodweb Inc, Corvallis, Oregon 78pp
• Ingham, E.R. (2003) The Compost Tea Brewing Manual Fourth Edition, Soil Foodweb Inc, Corvallis, Oregon 88pp
• Ingham, E.R. (2004), Compost Tea Quality: Light Microscope Methods, Soil Foodweb Inc, Corvallis, Oregon 47pp
• Ingham, E.R. (2004) The Field Guide for Actively Aerated Compost Tea (AACT), Soil Foodweb Inc, Corvallis, Oregon 178pp
• Ingham, E.R. (2005). The Compost Tea Brewing Manual, Edition 5, Soil Foodweb Inc, Corvallis, Oregon 79pp

Publications[link]

• Ingham, E. R. (1999). The Soil Biology Primer. Chapter 1. The Soil Foodweb. NRCS Soil Quality Institute, USDA. 48 pp.
• Ingham, E.R. (1999). The Soil Biology Primer. Chapter 2. Soil Bacteria. NRCS Soil Quality Institute, USDA.
• Ingham, E.R. (1999). The Soil Biology Primer. Chapter 3. Soil Fungi. NRCS Soil Quality Institute. USDA.
• Ingham, E.R. (1999). The Soil Biology Primer. Chapter 4. Soil Protozoa. NRCS Soil Quality Institute. USDA.
• Ingham, E.R. (1999). The Soil Biology Primer. Chapter 5. Soil Nematodes. NRCS Soil Quality Institute. USDA.
• Ingham, E.R.(2004). The Soil Foodweb: It’s Role in Ecosystems Health: The Overstory Book Cultivating Connections with Trees 2nd Edition; Editor Craig R. Elevitch.
• Ingham, E.R. and M.D. Slaughter. (2005). The Soil Foodweb–Soil and Composts As Living Ecosystems. International SoilACE Conference in Soil and Compost Eco-Biology. Leon, Spain. 1: 127-139.

References[link]

1. ^ ^{a b} "Rodale Institute Names Dr. Elaine Ingham as New Chief Scientist" (Press release). New York. January 24, 2011.. 
2. ^ Dr Ingham's background and CV
3. ^ Dr Ingham's web portal

External links[link]

• Soil Foodweb Inc
• Soil Biology Primer