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The Ultrastructure of Clay-Humic Complexes in an Iowa Mollisol

By
David A. Laird
David A. Laird
USDA, ARS, National soil Tilth Laboratory, Ames Iowa 50011 E-mail: david.laird@ars.usda.gov
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Michael L. Thompson
Michael L. Thompson
Department of Agronomy, Iowa State University, Ames Iowa 50011 E-mail: mlthomps@iastate.edu
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Published:
January 01, 2009

Abstract

The chemical and physical activity of clay minerals in soils, particularly in surface horizons, is significantly mediated by interactions with organic components. And the reactivity of soil organic matter, including its resistance to decomposition, is regulated by interactions with clay minerals. This marriage of organic and inorganic soil components has profound implications for our ability to quantitatively predict the consequences of alternative soil management practices that could improve food and energy production, protect water and air quality, or mitigate the impacts of greenhouse gases on global climate.

In this paper, we discuss observations of clay-humic complexes made by electron microscopy and other complementary techniques. By “clay,” we mean secondary layer silicate and oxide minerals that are common to soils. By “humic materials,” we mean soil organic matter that was derived from biological tissue but has been so transformed in the soil environment that it lacks any recognizable biological structures. Our definition of humic materials precludes any genetic or functional relationship with humic and fulvic acids, which are procedurally defined extracts of soil organic materials that we view as heterogeneous mixtures of hydrolyzed humic material, biological tissue, and black C. Data reported in this paper come from various analyses of a single smectite-rich Mollisol in Iowa. Because we investigated only one soil, we cannot generalize our results beyond saying that the studied soil was typical of smectite-rich Mollisols in the upper Midwest.

Interactions between soil organic matter (SOM) and soil minerals are primarily responsible for the formation and stabilization of soil structure

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Contents

Clay Minerals Society Workshop Lectures 16

Carbon Stabilization by Clays in the Environment: Process and Characterization Methods

David A. Laird
David A. Laird
USDA, ARS, National Soil Tilth Laboratory 2110 University Blvd Ames IA 50011-3120 USA
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Javiera Cervini Silva
Javiera Cervini Silva
Instituto de Geografia Universidad Nacional Autónoma de México Ciudad Universitaria, Mexico City
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Yona Chen
Yona Chen
The Hebrew University of Jerusalem, Israel
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Claire Chenu
Claire Chenu
CNRS-UPMC-INRA-AgroParisTech-ENS-ENPC, Grignon, France
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Françoise Elsass
Françoise Elsass
Centre de Géochimie de la Surface, Strasbourg, France
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Javier M. Gonzalez
Javier M. Gonzalez
USDA, ARS, NAA, AFSRC, Beaver, WV, USA
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Michael H.B. Hayes
Michael H.B. Hayes
University of Limerick, Ireland
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David A. Laird
David A. Laird
USDA, ARS, NSTL, Ames, IA, USA
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Alain Plante
Alain Plante
University of Pennsylvania, Philadelphia, PA, USA
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Andre J. Simpson
Andre J. Simpson
University of Toronto at Scarborough, Canada
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Guixue Song
Guixue Song
University of Limerick, Ireland
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Jorge Tarcjotzly
Jorge Tarcjotzly
The Hebrew University of Jerusalem
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Michael L. Thompson
Michael L. Thompson
Iowa State University, Ames IA, USA
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I. Virto
I. Virto
CNRS-UPMC-INRA-AgroParisTech-ENS-ENPC, Grignon, France
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Robert L. Wershaw
Robert L. Wershaw
U.S. Geological Survey, Denver, CO, USA
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Clay Minerals Society
ISBN electronic:
9781881208365
Publication date:
January 01, 2009

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