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A mechanistic approach to modeling saturation and protection mechanisms of soil organic matter

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dc.contributor.authorOlchin, Gabriel Peter, author
dc.contributor.authorPaustian, Keith, advisor
dc.date.accessioned2024-03-13T20:12:28Z
dc.date.available2024-03-13T20:12:28Z
dc.date.issued2009
dc.description.abstractSimulation models have been used extensively as a research tool in the field of soil organic matter (SOM) dynamics and should embody our best understandings of the processes and mechanisms controlling these dynamics. Our objective was to develop and evaluate a SOM model based upon measureable soil organic carbon (SOC) fractions and optimize it against long-term tillage experiments in North America. This model will include (1) soil aggregate dynamics, with direct influence from tillage events; (2); and the mechanisms of SOM stabilization; and (3) explicitly address the concept of potential SOC saturation. The major proposed mechanisms for SOM stabilization-physical occlusion, organic recalcitrance, and organo-mineral interactions-have limited explicit inclusion in current SOM models.
dc.description.abstractThe enhanced soil structure and higher SOC stocks measured under no-till (NT) management have been well documented. However, the roles of residue addition vs. aggregate disruption (i.e. tillage events) have not been compared at different depth increments. Pre-requisite to the major SOM stabilization mechanisms are the availability and continual addition of residues. Therefore, uniformly 13C-labeled wheat residues were added to incubation cores representing soils under NT and tillage management (TM) during a yearlong in situ incubation at a dryland agriculture experiment site. Residue was added directly onto the surface of NT cores, while residues were incorporated into the 0-5, 5-15, and 15-30 cm depth increments of the TM cores. Overall, our results indicate that within a plow depth of 15 cm, limiting the tillage-induced disruption of aggregates has a stronger influence than residue incorporation into the profile via tillage on the efficiency of C stabilization. However, when residues are distributed to a 30 cm depth, the negative impact of aggregate disruption through tillage appears counterbalanced with similar efficiencies of C stabilization between the NT and TM practices, possibly due to slower decomposition of residues deeper in the profile.
dc.description.abstractConventional SOM models have been defined by kinetic, rather than functional pools. Further, soil physiochemical processes (e.g. mineral surface bindings) that inhibit the breakdown of organic compounds are generally implicit in the rate constants associated with a particular pool as a rate modifying factor. SATURN, the proposed simulation model, is comprised of functional (or measureable) pools; one of the first attempts at directly 'modeling the measureable'. The model has been initially optimized for total SOC content against seven long-term (> 12 years) agroecosystem experiments; containing contrasts in tillage management (a mechanism for aggregate turnover) and different in crop rotations with a SOC gradient across sites of approximately 5-25 g C kg -1 soil. The final optimized values resulted in a root mean square error for total SOC of 1.2 g C kg-1 soil across all seven sites. This analysis is limited to the total SOC content and individual pool sizes where not optimized against which limits the degree to which we can validate the internal dynamics of the model; an added benefit of measureable pool models.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.identifierETDF_Olchin_2009_3401012.pdf
dc.identifier.urihttps://hdl.handle.net/10217/237895
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.rights.licensePer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.
dc.subjectsaturation
dc.subjectsoil aggregates
dc.subjectsoil organic matter
dc.subjectsoil sciences
dc.titleA mechanistic approach to modeling saturation and protection mechanisms of soil organic matter
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineSoil and Crop Sciences
thesis.degree.grantorColorado State University
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (Ph.D.)

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