ARS | Publication request: RELATIONSHIP BETWEEN SOIL ORGANIC CARBON AND SOIL QUALITY IN CROPPED AND RANGELAND SOILS: THE IMPORTANCE OF DISTRIBUTION, COMPOSITION AND SOIL BIOLOGICAL INTEGRITY

Submitted to: Soil Processes and the Carbon Cycle
Publication Type: Book / Chapter
Publication Acceptance Date: January 15, 1997
Publication Date: N/A

Technical Abstract: A high level of soil organic carbon (SOC) is often equated with soil quality, where soil quality is defined as the capacity of a soil to perform functions which sustain biological productivity and maintain environmental quality. A plethora of evidence has demonstrated a positive relationship between SOC and soil function in a variety of ecosystems. This has led to the belief that increasing SOC nearly always leads to improved soil quality. We argue that the while this relationship holds in general, the net effect of carbon on soil quality (function) depends less on the quantity of organic carbon (organic matter) than on a combination of other factors. These factors include, (1) the spatial distribution, both horizontal and vertical, of the organic matter, (2) the composition (biochemical and physical characteristics) of the organic matter, and (3) the structure and integrity of the soil food webs, including the temporal and spatial synchrony between carbon inputs and soil faunal activity patterns. In cropped systems, decades of long-term agronomic studies have demonstrated that total SOC and the capacity of the soil to support plant growth without external inputs tend to decline together over time. Similar relationships have been identified for rangeland systems; however, in many rangelands, the relationship is complicated by changes in the structure of the vegetative community and subsequent redistributions of litter and organic matter which occur as the system degrades. In order to manage SOC to sustain soil quality in specific ecosystems, the relationships between soil functions and organic carbon distribution, composition, and the soil biological community, must be clarified.