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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #110913
Title: MINERALOGY OF ERODED SEDIMENTS DERIVED FROM HIGHLY WEATHERED SOILS

Author
item SHAW, JOEY - AUBURN UNIVERSITY
item Truman, Clinton
item Reeves, Donald

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2003
Publication Date: 2/1/2003
Citation: SHAW, J.N., TRUMAN, C.C., REEVES, D.W. MINERALOGY OF ERODED SEDIMENTS DERIVED FROM HIGHLY WEATHERED SOILS. SOIL & TILLAGE RESEARCH. 68:59-69. 2003.

Interpretive Summary: Coarse textured surface horizons are common in highly weathered, cultivated southeastern U.S. Coastal Plain soils. These soils tend to be drought prone and susceptible to erosion. They also have historically been managed under conventional tillage practices, but recent trends suggest increases in conservation tillage. Although clay contents are low in these esurface horizons, the reactive nature of this clay is important in the transport of pollutants by sediments. In addition, water dispersible clay (WDC) is correlated with sediment yield and is affected by cropping and tillage practices. Therefore, we evaluated the partitioning of clays found in original soil versus that found in runoff sediment and differences in WDC under simulated rainfall as a function of tillage practices. Plots were established on a coarse-loamy soil association in the Upper Coastal Plain of central Alabama. Tillage treatments included conventional vs. conservation tillage, with residue remaining or being removed and with or without paratilling. WDC was inversely correlated with percent organic carbon which was a function of tillage treatment. Although no differences in the clay mineralogies in the sediment were observed between tillage treatments, runoff sediments were enriched in quartz and depleted with respected to kaolinite as compared to original soils. Results help develop a mechanistic understanding of how sediments and associated nutrients and pesticides are lost from these intensively cropped soils.

Technical Abstract: Coarse textured surface horizons are common in highly weathered, cultivated southeastern U.S. Coastal Plain soils. These soils have historically been managed under conventional tillage practices, but recent trends suggest increases in conservatin tillage. Although clay contents are low in these surface horizons, the reactive nature of this fraction contributes to colloidal facilitated transport of pollutants. Because enrichment of certain minerals occur in transported sediments, we evaluated the mineralogical partitioning of clay minerals of in-situ vs. runoff sediment under simulated rainfall. In addition, because water dispersible clay (WDC) has been correlated with soil erodibility and is affected by cropping/tillage practices, we evaluated WDC differences as a function of tillage. Plots were established in the Upper Coastal Plain of central Alabama. Soils were classified as coarse-loamy, siliceous, subactive, thermic Plinthic Paleudults and Typic Hapludults. Tillage treatments, established in 1988, included conventional vs. conservation tillage treatments, with residue remaining or being removed and with or withou paratilling (noninversion subsoiling). Mineralogical analyses and quantification were conducted using thermogravimetric (TGA) and x-ray diffraction (XRD) techniques. WDC was correlated with percent organic carbon, which was a function of tillage treatment. Although no differences in clay mineralogies in the sediment were observed between tillage treatments, runoff sediments were enriched in quartz and depleted with respect to kaolinite as compared to in-situ soils. Results help develop mechanistic models to accurately predict sediment transported nutrients and pesticides from these soils.