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Impact of soil texture on the distribution of soil organic matter in physical and chemical fractions

Plante, Alain F. , Conant, Richard T., Stewart, Catherine E. , Paustian, Keith , & Six, Johan (2006) Impact of soil texture on the distribution of soil organic matter in physical and chemical fractions. Soil Science Society of America Journal, 70(1), pp. 287-296.

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Abstract

Previous research on the protection of soil organic C from decomposition suggests that soil texture affects soil C stocks. However, different pools of soil organic matter (SOM) might be differently related to soil texture. Our objective was to examine how soil texture differentially alters the distribution of organic C within physically and chemically defined pools of unprotected and protected SOM. We collected samples from two soil texture gradients where other variables influencing soil organic C content were held constant. One texture gradient (16-60% clay) was located near Stewart Valley, Saskatchewan, Canada and the other (25-50% clay) near Cygnet, OH. Soils were physically fractionated into coarse- and fine-particulate organic matter (POM), silt- and clay-sized particles within microaggregates, and easily dispersed silt-and clay-sized particles outside of microaggregates. Whole-soil organic C concentration was positively related to silt plus clay content at both sites. We found no relationship between soil texture and unprotected C (coarse- and fine-POM C). Biochemically protected C (nonhydrolyzable C) increased with increasing clay content in whole-soil samples, but the proportion of nonhydrolyzable C within silt- and clay-sized fractions was unchanged. As the amount of silt or clay increased, the amount of C stabilized within easily dispersed and microaggregate-associated silt or clay fractions decreased. Our results suggest that for a given level of C inputs, the relationship between mineral surface area and soil organic matter varies with soil texture for physically and biochemically protected C fractions. Because soil texture acts directly and indirectly on various protection mechanisms, it may not be a universal predictor of whole-soil C content.

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ID Code: 37774
Item Type: Journal Article
Keywords: soil organic matter, SOM, Stewart Valley, Saskatchewan, microaggregates
DOI: 10.2136/sssaj2004.0363
ISSN: 1023–1035
Subjects: Australian and New Zealand Standard Research Classification > ENVIRONMENTAL SCIENCES (050000) > ECOLOGICAL APPLICATIONS (050100)
Australian and New Zealand Standard Research Classification > ENVIRONMENTAL SCIENCES (050000) > SOIL SCIENCES (050300)
Divisions: Past > Institutes > Institute for Sustainable Resources
Copyright Owner: Copyright 2006 Soil Science Society of America
Deposited On: 08 Oct 2010 11:35
Last Modified: 01 Mar 2012 00:19

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