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NSSH Part 624

Soil Quality

624.00  Definition and Purpose

  1. The definition of soil quality is: The capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation.
  2. Considering that soil quality is the capacity of a soil to function, specific functions of concern should be clear when applying the concept. Common examples of specific soil functions are:
    • Sustaining biological activity, diversity, and productivity;
    • Regulating and partitioning water and solute flow;
    • Filtering, buffering, degrading, immobilizing, and detoxifying organic and inorganic materials, including industrial and municipal by-products and atmospheric deposition;
    • Storing and cycling nutrients and other elements within the earth's biosphere; and
    • Providing support of socioeconomic structures (i.e. buildings, roads) and protection for archeological treasures associated with human habitation.
  3. Soil quality integrates the biological, chemical, and physical components and processes of a soil with its surroundings. Whether a research plot, field, watershed, or the earth; the concept that soil functions within a larger system remains a key consideration in assessment of soil quality.
  4. Views differ on soil quality depending on the background of individuals and their relationship to the land. Some of these views and concepts include:
    • Inherent properties of soil as determined by the soil forming factors;
    • Highly productive land, sustaining or enhancing productivity, maximizing profits, or maintaining the soil resource for future generations;
    • Plentiful, healthful, and inexpensive food for present and future generations;
    • Soil in harmony with the landscape and its surroundings; and
    • Soil functioning at its potential in an ecosystem.
  5. The concept of soil quality is also viewed from various scales of concern:
    • For the land manager, field or farm productivity and sustainability are important;
    • For members of a community, the health or the ability of the watershed to maintain a healthy neighborhood and environment is important; and
    • For national policy makers, an assessment of the overall quality and trends of the nation's soil resources are important.

624.01  Quality Concepts

Soils naturally vary in their capacity to function; therefore, an important part of the definition is the concept that quality is specific to each kind of soil (soil map unit component). The quality of a soil has two distinct but related parts, inherent and dynamic qualities.

  1. Inherent quality represents intrinsic properties (qualities) of soils; as determined by the factors of soil formation -- climate, topography, biota, parent material, and time. The inherent quality of soils is often used to compare the capabilities of one soil against another, and to evaluate the worth or suitability of soils for specific uses. For example, given all other determining properties being equal, a loam soil will have a higher water holding capacity than a sandy soil. Thus, the loam soil will have a higher inherent quality for storing water, and lower inherent quality for producing a freely drained condition.
  2. Many properties that have traditionally been recorded in the interpretive and taxonomic databases of the National Cooperative Soil Survey Program are not subject to change by commonly practiced soil use. They are use-invariant. Particle size distribution (texture) is an example of a use-invariant property. Since common land practices only disturb the soil to a depth of about 30 centimeters, the properties below this depth are normally use-invariant.
  3. Dynamic quality is determined by soil properties that are influenced by human use and management decisions. These properties are use-dependent properties and may be temporal (dynamic) of the soil. Bulk density near the surface and organic matter content are two such properties.
  4. Use-dependent properties most often manifest in surface and subsurface layers. These properties include physical, chemical, and biological properties. Certain management practices and uses of the land have a positive effect on specific soil properties such as increasing organic matter content. Other management practices may negatively impact the soil by causing compaction, erosion, or acidification. Collectively, management will either improve or reduce health of the soil. This dynamic aspect of soil quality is the focal point of the concern for assessing the state (or quality) of the soil resource.
  5. The reference condition is defined by a range of values for key soil properties (indicators) that represent conditions of the soil functioning at full capacity such as soil conditions under management systems that use Best Management Practices. Values for the reference condition can eventually be used as criteria in the Field Office Technical Guide for evaluating the soil condition (quality).
  6. Soil health can be evaluated relative to a standard or reference condition that represents the full capacity of a soil to function for a specific use. The reference condition is often based on use-invariant properties in conjunction with the dynamic properties. Soil properties are used to group soils that function similarly. Reference values are developed for the key properties of soils that reflect the capacity of the soil to function. Evaluation of soil quality or health must be tied to soil functions and the specific use of the soil.
  7. Soil health can also be evaluated by establishing a baseline condition for the use-dependent properties (indicators). After a period of years, the use-dependent properties are measured again and compared to the baseline.

624.02  Soil Quality Test Kit (Instruction Manual)

The soil quality test kit guide is available here.

624.03  Soil Quality Products and Informational Documents

A list of soil quality material and instructions for ordering is available here.

624.04  References

Pierce, F.J. and W.E. Larson. 1993. Developing criteria to evaluate sustainable land management. p. 7-14. In: J. M. Kimble (ed), Proceedings of the Eighth International Soil Management Workshop: Utilization of Soil survey Information for Sustainable Land Use, May 3, 1993. USDA Soil Conservation Service, National Soil Survey Center, Lincoln, NE.

Karlen, D.L., M. J. Mausbach, J.W. Doran, R.G. Cline, R. F. Harris, and G. E. Schuman. 1997. Soil quality: A concept, definition, and framework for evaluation. Soil Sci. Soc. Am. J. 61:4-10.

Larson, W.E. and F.J. Pierce. 1991. Conservation and enhancement of soil quality. p. 175-203. In: Evaluation for Sustainable Land Management in the Developing World, Vol. 2: Technical papers. Bangkok, Thailand: International Board for Research and Management, 1991. IBSRAM Proceedings No. 12(2).

Jenny, H. 1941. Factors of Soil Formation. McGraw-Hill, New York, NY 281 pp.

National Research Council. 1993. Soil and Water Quality: An Agenda for Agriculture. National Academy Press, Washington, DC 516 pp.

Doran, J.W. and T.B. Parkin. 1994. Defining and assessing soil quality. p. 3-21. In: J.W. Doran, D.C. Coleman, D.F. Bezdicek, and B.A. Stewart (eds.), Defining Soil Quality for a Sustainable Environment. SSSA Spec. Pub. No. 35, Soil Sci. Soc. Am., Am. Soc. Argon., Madison, WI.

Larson, W.E. and F.J. Pierce 1994. The dynamics of soil quality as a measure of sustainable management. pp. 37-51. In J.W. Doran, D.C. Coleman, D.F. Bezdicek, and B.A. Stewart (eds.), Defining Soil Quality for a Sustainable Environment. SSSA Spec. Pub. No. 35, Soil Sci. Soc. Am., Am. Soc. Argon., Madison, WI.

Harris, R.F., and D.F. Bezdicek. 1994. Descriptive aspects of soil quality/health. p. 23-35. In: J. W. Doran, D. C. Coleman, D. F. Bezdicek, and B. A. Stewart (eds.), Defining Soil Quality for a Sustainable Environment. SSSA Spec. Pub. No. 35, Soil Sci. Soc. Am., Am. Soc. Argon., Madison, WI.

Acton, D.F., and L.J. Gregorich. 1995. Understanding soil health. p. 5-10. In: D.F. Acton and L.J. Gregorich, (eds.), The Health of our Soils: Toward Sustainable Agriculture in Canada. Centre for Land and Biological Resources Research, Research Branch, Agriculture and Agri-Food Canada, Ottawa, Ont.