Chapter 1 Concepts of soil quality and their significance

Abstract

Although soil quality can be simply defined as a soil's “fitness for use”, it is in reality a complex concept and significantly more challenging in its assessent than air or water quality. Soil quality can basically be divided into inherent and dynamic quality. The former is a component of land quality, whereas the latter is strongly influenced by the soil manager. Measurement of soil quality involves placing a value upon soil in relation to its fitness to perform a specific function or purpose. Functions can vary in relation to both use of soil and scale. Once a function has been established, it is possible to identify and characterize soil processes and attributes that describe the function, the indicators that are related to the attribute(s), and methodologies for measuring these. This allows the development of soil quality standards and control techniques, and subsequently the design of sustainable land management systems. Overall, the following conclusions can be given in regard to the concept of soil quality: u • The concept of soil quality is not altogether new, but is undergoing development in response to the idea that soils are part of land or terrestrial ecosystems. Thus, soil quality brings together old and new ideas about soil and land. • It is important to recognize the difference between inherent and dynamic soil quality, as well as the difference between soil and land quality. Further, although soil quality describes and objective state or condition of the soil, it is also subjective or evaluated partly on the basis of personal and social determinations. • Ecosystem concepts such as function, processes, attributes, and indicators, provide a useful and robust framework to describe soil quality. This framework is also useful when it is directed towards the intensive manipulation, engineering, and/or management of the soil resource. • In the context of using soil intensively as a resource, soil quality becomes a technology or an applied science, directed towards problem solving (e.g., better soil management) and can be seen as a key to sustainable land management. • The basic idea of “fitness for use” in regard to agricultural and/or in dustrial use of soil, reflected in early attempts to classify “soil suitability” or “land capability”, is the basic premise of soil quality. If a soil is not suitable for a specific use then it is not appropriate to assign or describe quality for that specific use or function. In many cases, however, it is not possible to make a perfect match between the soil and its intended use, and quality must be built into the system. • A large range of attributes, such as chemical, physical, and biological properties, can be used to describe soil quality. Attributes need to be selected for specific soil uses. However, some attributes have a wide utility and can serve a wide range of purposes. Thus, a “minimum data set”, composed of a limited number of key attributes, is the usual approach in soil quality investigations, except for some singular situations (e.g, disturbed hydrology) in which a dominant soil response can be characterized using a single attribute. • A major impediment to the evaluation of soil quality is the lack of standardization, related to both methodology and “critical limits”. Soil quality standards are required to ensure that soil sampling, description, and analysis can set the limits for a quality soil and detect adverse changes in soil quality.