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United States Department of Agriculture

Agricultural Research Service

Title: Clay-Humic Complexes in a Typical Agricultural Soil

Author
item Laird, David

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 1999
Publication Date: N/A

Technical Abstract: Soil management systems that encourage the formation and stabilization of clay-humic complexes will have the greatest long-term impact on C sequestration and soil quality. The objective of this study was to determine the chemical, biochemical, and mineralogical properties of clay-humic complexes isolated from a typical agricultural soil. Mineralogically significant clay humic complexes were separated from the Ap horizon of a Webster soil (Typic Haplaquoll) by an invasive sonication-centrifugation technique. The clay mineralogy was evaluated by XRD and chemical analysis, and the clay associated humic materials were characterized by GC and HPLC analyses of extractable biochemicals, solid state **13C-MAS-NMR, and scanning electron microscopy. The results revealed two distinct classes (or phases) of humic materials; (i) discrete high-density metal-humic complexes, and (ii) low-density filamentous humic films coating basal surfaces of 2:1 phyllosilicates. The two phases are chemically and functionally distinct. The impact of clay mineralogy on the formation of these materials in soils will be discussed.

Last Modified: 8/19/2014
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