WHAT IS SOIL QUALITY?
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
- support human health and habitation Soil function describes what the soil does. Soil functions are: (1) sustaining biological activity, diversity, and productivity; (2) regulating and partitioning water and solute flow; (3) filtering and buffering, degrading, immobilizing, and detoxifying organic and inorganic materials, including industrial and municipal by-products and atmospheric deposition; (4) storing and cycling nutrients and other elements within the earthís biosphere; and (5) providing support of socioeconomic structures and protection for archeological treasures associated with human habitation. (Seybold et al, 1998). For the purposes of this guide, the terms soil quality, soil health, and soil condition are all interchangeable. Soils vary naturally in their capacity to function; therefore, quality is specific to each kind of soil. This concept encompasses two distinct but interconnected parts: inherent quality and dynamic quality. Characteristics, such as texture, mineralogy, etc., are innate soil properties determined by the factors of soil formationóclimate, topography, vegetation, parent material, and time. Collectively, these properties determine the inherent quality of a soil. They help compare one soil to another and evaluate
soils for specific uses. For example, all else being equal, a loamy soil will have a higher water holding capacity than a sandy soil; thus, the loamy soil has a higher inherent soil quality. This concept is generally referred to as soil capability. Map unit descriptions in soil survey reports are based on differences in the inherent properties of soils.
More recently, soil quality has come to refer to the dynamic quality of soils, defined as the changing nature of soil properties resulting from human use and management. Some management practices, such as the use of cover crops, increase organic matter and can have a positive effect on soil quality. Other management practices, such as tilling the soil when wet, adversely affect soil quality by increasing compaction.
In this guide, soil quality refers to the dynamic quality of soilóthose properties that are affected by management.
Soil quality assessments are thus used to evaluate the effects of management on the health of the soil. The guidelines in this booklet provide information for performing the most typical soil quality assessments, which include:
THE SIGNIFICANCE OF SOIL QUALITY
History
The NRCS, Agricultural Research Service (ARS), Cooperative Extension Service, and others have been working toward improving soil quality for many years by encouraging best management practices such as erosion control and nutrient management. As soil quality has emerged as a leading concept in natural resource conservation and protection, stronger emphasis is now being placed on the relationship between specific dynamic soil properties and soil performance. Enhancement of these dynamic soil properties is the goal of soil quality management.
Multiple Benefits and Applications
Conservation measures utilized by
farmers, agricultural professionals, and
public and private agencies are already
tightly linked to soil quality
management. Conservation practices,
such as conservation tillage, buffers,
nutrient and pest management, range and
pastureland management, and wetland
and stream bank restoration incorporate
soil management goals and treatments.
Achievement of water quality, air
quality, and carbon sequestration goals
rely on improving soil quality. For
example, one typical method for
improving soil quality by
increasing organic matter involves
reducing tillage, a fundamental practice
for reducing erosion. Decreasing erosion improves water quality by reducing sediment runoff. In areas subject to wind erosion, conservation tillage reduces the amount of particulate matter in the air. Thus, reducing tillage to improve soil quality also benefits erosion control, air quality, and water quality goals.
Integrated Approach
Soil quality is a useful model to evaluate and improve the soil resource as it provides an integrated method for assessing multiple aspects of the soil and their connections. By linking biological, physical, and chemical properties of soil, all of the components and interactions of a soil system are viewed together. This integrated approach leads to more comprehensive solutions as compared to assessing each soil property independently.
Familiarity Promotes Learning and
Acceptance
Soil quality management is a useful and
effective approach to resource
conservation and best management
strategies. Producers are already
familiar with many soil building
practices and many producers already
use the approach of integrated soil
management when evaluating the effects
of their practices on soil health. A
model familiar to farmers will promote
faster learning of the approaches
outlined in this guide. Joint soil quality
assessments between conservationist and
producer will facilitate the blending of
producerís knowledge and scientific
information, thus strengthening the
information base, the ability to formulate
workable solutions, and the likelihood of
adoption of best management practices.
(Romig et al, 1995).