Soil Quality Background

Development of Soil Quality Concept

Soil quality concerns are not new; evaluations of soil characteristics for crop growth appeared in the first written literature and certainly predate those records. The soil quality concept per se was introduced by Warkentin and Fletcher (1977) as an approach to facilitate better land use planning for the various functions that soil must accommodate. Early efforts to define soil quality were followed by more formalized definitions (Larson & Pearce 1991, Karlen et al. 1997), selection of indicators (Doran & Parkin 1994), and specific strategies to enhance soil quality (Doran et al. 1996).

Soil quality can be viewed in two ways:

  1. as inherent soil quality, which is regulated by the soil’s inherent properties as determined by the five soil-forming factors, and
  2. as dynamic soil quality, which involves changes in soil properties influenced by human use and management.

In both, the first consideration deals with origins of soil and processes of soil development. The inherent soil quality (together with theories of soil genesis) provides the basis for soil classification. The dynamic soil quality, is the focus of this course and will be discussed in great detail.

Source: Gene Alexander, USDA NRCS
Source: Gene Alexander, USDA NRCS

The soil quality concept is not without its critics. Recently, there have been several research editorials that recommend moving away from subjective efforts to develop an index of soil quality. Letey et al. (2003) suggest a move toward utilizing available technical information to motivate and educate farmers on management practices that optimize the combined goals of high agricultural production, low environmental degradation, and a sustained soil resource. Sojka and Upchurch (1999) reported that “quality of soil management rather than soil quality management” should be the goal of soil science. They, however, used the inherent soil quality incorrectly as a criticism toward soil quality. As Norfleet et al. (2003) pointed out, the important point to keep in mind is that the assessment of soil quality should not be done across contrasting soil types but across contrasting management practices on the same soil type.

The inherent and dynamic soil qualities follow one another (rather than mirror one another as some critics thought). A land use is chosen for a soil because of the inherent properties and/or socioeconomic needs. Subsequent management practices alter the original properties, creating change toward a new steady state for the dynamic properties. The degree of change of dynamic properties and the effect that this change has on the landscape are addressed by soil quality.