Saturday, 15 July 2006
116-22

Soil Change in Southeastern USA Ultisols.

Joey N. Shaw1, Iyassu Fesha2, D. Wayne Reeves3, C. Wesley Wood4, Yucheng Feng1, and M. Lee Norfleet5. (1) Auburn Univ, Auburn, AL 36849, (2) Ministry of Ag Res & Human Res, PO Box 4627, Asmara, Eritrea, (3) USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center, 1420 Experiment Station Rd., Watkinsville, GA 30677, (4) Dept of Agronomy and Soils, 202 Funchess Hall, Auburn Univ, Auburn, AL 36849-5412, (5) USDA NRCS RIAD, 808 E. Blackland Road, Temple, TX 76502

Soils exhibit both spatial and temporal variability. The temporal variability is due to both anthropogenic and non-anthropogenic processes, and studies documenting near surface dynamic properties related to land use are needed to develop sound soil management strategies and establish protocol for sequestering soil carbon. Documentation of soil change is also needed to improve soil survey map unit interpretations and for population of resource databases. In order to illustrate the potential magnitude of these effects, we evaluated management dependent physical, chemical, and biological soil property differences due to agronomic land use in the southeastern USA. Ultisols dominate the region, and due to their relatively high occurrence on global arable lands, further understanding of land use impacts on Ultisols is warranted. The southeastern US is a vital region for documenting soil change due to intensive cultivation and utilization of soil resources, dynamic land management related to farm policy, and a fragile soil resource with limited inherent resiliency. Research sites were located in the Appalachian Plateau (AP) and the Coastal Plain (CP) physiographic regions of Alabama, USA. Soils predominately classify as fine-loamy, siliceous, subactive, thermic Typic Hapludults at the AP site, with sandy loam textured surface horizons and 2-6% slopes. At the CP site, soils predominantly classify as coarse-loamy, siliceous, subactive, thermic Typic Paleudults, with loamy sand textured surface horizons with 0-2% slopes. Data were collected in relatively long-term (> 10 yr) conventional row crop (CT), conservation row crop (NT), hayland (HL), and woodland (WL) systems. Measured near-surface properties included bulk density, saturated hydraulic conductivity, infiltration rate, soil strength, water stable aggregates, soil water retention, water dispersible clay, extractable bases, P and Al, cation exchange capacity, base saturation, soil organic carbon, total nitrogen, soil microbial biomass C, particulate organic matter, C mineralization, and dehydrogenese activity. Differences in management dependent properties resulted from land use within soil map units, with more intensive soil cultivation resulting in reduced dynamic soil quality at both sites. Soils under conventional systems were 13 to 40% lower in water stable aggregates, 80 to 274% lower in infiltration rate, and 10 to 80% higher in water dispersible clay compared with the other land use systems. Similarly, soils under conventional tillage had lower values of soil organic carbon, soil microbial biomass carbon, and particulate organic matter than the hayland, woodland, and conservation systems. Principal component analyses of combined soil physical, biological and chemical data indicated that soil organic carbon and it's related pools were the most sensitive metric (relative to other soil properties) related to agronomic land use. Multivariate clustering indicated that land use had more of an effect on management-dependent soil properties than inherent soil properties more directly related to genetic soil differences. Pedotransfer functions were developed that reasonably estimated management dependent soil hydraulic properties within soil map units using more easily measured dynamic properties. Such an approach will allow population of management dependent soil survey databases.

Back to 1.0PW Synthesis, Modeling, and Applications of Disciplinary Soil Science Knowledge for Soil-Water-Plant-Environment Systems - Poster
Back to WCSS

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