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United States Department of Agriculture

Agricultural Research Service

Title: Particulate Organic Matter and Aggregate Formation

Authors
item Gale, William - IOWA STATE UNIVERSITY
item Cambardella, Cynthia

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1997
Publication Date: N/A

Technical Abstract: The maintenance of soil structural stability has important agricultural and environmental implications. Temporary organic binding agents such as plant roots and fungal hyphae contribute to the formation of stable aggregates, but little is known about how the decomposition of these agents affects aggregate stability. Particulate organic matter (POM) is an intermediate pool in the decay continuum between residue and soil humus. The purpose of our study is to measure changes in aggregate size distribution, stability, and C content during the decomposition of plant roots. Two wetting pretreatments were used to isolate size classes containing aggregates with different relative stability. We used 14-C labeled roots to trace the movement of C into free POM, aggregate-occluded POM, and mineral associated OM. Stable macroaggregation reached a maximum at d 180 and then declined. POM-C was nearly twice as high in stable macroaggregates compared to unstable macroaggregates. The specific activity of 14-C in microaggregates yielded by slaking increased throughout the incubation. These findings are the basis for a conceptual model describing the formation and stabilization of aggregates.

Last Modified: 7/25/2014
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