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United States Department of Agriculture

Agricultural Research Service

Title: Soil Organic Matter Stratification As An Indicator of Soil Quality.

Author
item Franzluebbers, Alan

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 24, 2001
Publication Date: July 1, 2002
Citation: Franzluebbers, A.J. 2002. Soil organic matter stratification as an indicator of soil quality.. Soil & Tillage Research.

Interpretive Summary: Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. It is hypothesized that the degree of stratification of soil organic carbon and nitrogen pools with soil depth could indicate soil quality or soil ecosystem functioning, because surface organic matter is essential to erosion control, water infiltration, and conservation of nutrients. Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic carbon were 1.1, 1.2, and 1.9 under conventional tillage and 3.4, 2.0, and 2.1 under no tillage in Georgia, Texas, and Alberta/British Columbia, respectively. High stratification ratios of soil carbon and nitrogen pools could be good indicators of soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions.

Technical Abstract: Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic carbon (SOC) were 1.1, 1.2, and 1.9 under conventional tillage and 3.4, 2.0, and 2.1 under no tillage in Georgia, Texas, and Alberta/British Columbia, respectively. The difference in stratification ratio between conventional and no tillage within an environment was inversely proportional to the standing stock of SOC to a depth of 15-20 cm across environments. Greater stratification of SOC with the adoption of conservation tillage under inherently low SOC conditions (i.e., warmer climatic regime or coarse-textured soil) suggests that standing stock of SOC alone is a poor indication of soil quality. Stratification of biologically active soil C and nitrogen (N) pools (i.e., soil microbial biomass and potential activity) were equally or more sensitive to tillage, cropping intensity, and soil textural variables than stratification of SOC. High stratification ratios could be good indicators of soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions.

Last Modified: 12/18/2014
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