Thursday, 13 July 2006 - 4:00 PM

Depth Distribution of Soil Organic Matter and its Consequences on Soil Properties and Crop Productivity.

Alan Franzluebbers, USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center, 1420 Experiment Station Rd., Watkinsville, GA 30677

Soil organic matter is a key component of soil quality that sustains many key soil functions by providing the energy, substrates, and biological diversity to support biological activity, which affects aggregation (important for habitat space, oxygen supply, and preventing soil erosion), infiltration (important for leaching, runoff, and crop water uptake), and decomposition (important for nutrient cycling). The lack of residue cover and exposure of soil to high-intensity rainfall results in poor aggregation, reduced plant water availability, erosion, and off-site impacts of sedimentation and loss of soil nutrients to receiving water bodies. It is hypothesized that the degree of stratification of soil organic C and N pools with soil depth, expressed as a ratio, could indicate soil quality or soil ecosystem functioning (important to crop productivity). Stratification ratios would 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. Soil organic C and N fractions (i.e., total, particulate, aggregate-associated, microbial biomass, and mineralizable) were determined in a Typic Kanhapludult under two cropping systems using inversion- and no-tillage management. Relationships of soil C and N fractions to other soil properties and to crop yield will be discussed.

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Back to The 18th World Congress of Soil Science (July 9-15, 2006)