Organic matter input determines structure development and aggregate formation in artificial soils

Ms Franziska Bucka1, Dr. Angelika Kölbl1, Dr. Daniel Uteau2, Prof. Stephan Peth2, Prof. Ingrid Kögel-Knabner1,3

1Technical University of Munich, Freising, Germany, 2University of Kassel, Witzenhausen, Germany, 3Technical University of Munich, Garching, Germany

Aggregates are formed by clustering and cohesion of mineral particles and organic matter. Up to now, little is known about the role of different organic matter types within this process complex. We developed an experimental set-up to study the influence of organic carbon (OC) derived from particulate organic matter (POM) and from dissolved organic matter (DOM) for aggregate formation under controlled laboratory conditions. We designed artificial soil microcosms with loamy texture, mimicking an arable Cambisol, and performed an incubation for 30 days under constant water tension. The microcosms received either POM as milled hay litter, DOM as solution derived from hay or no additional OC input. We analyzed aggregate size distribution and their OC content. By means of X-Ray CT, we analyzed the water retention characteristic and pore features of the recent structured soil.

We observed the formation of mostly large, water-stable macroaggregates (3000-630 µm) and some small microaggregates (<63 µm) in all treatments with OC input. Organic matter input as solid, particulate OM as well as dissolved OM solution induced aggregate formation as effect of microbial processing of the added OM. The addition and microbial decay of litter pieces led to physical occlusion of the particles into mainly large (3000-630 µm), OC-rich macroaggregates with low porosity. The addition of DOM solution also induced the formation of large macroaggregates besides small microaggregates, although the OC input was much lower. Here, we considered microbial processing of locally accumulated OC as the main process, which leads to alteration of the microbial microenvironment.

Our experimental design allows to specifically investigate selected process complexes initiated by the addition of OM in soil structure formation. It allows to differentiate between the emergent processes working together in aggregate formation and self-organization of soil structure.


2015: Bachelor of Science, Biology, University of Tübingen, Germany, Focus: Environmental ecology

2018: Master of Science, Environmental Planning and Ecological Engineering, Technical University of Munich, Germany, Focus: Soil Science, Remediation of Acid Sulfate Soils, Study project in cooperation with the University of Freiburg, Germany: Aggregate stability and dynamics controlled by a clay gradient

Since 2018: PhD candidate in Soil Science, Technical University of Munich, Germany, Supervisor: Ingrid Kögel-Knabner, Topic: Aggregate formation and dynamics and the role of organic matter

I am interested in soil structure development and aggregate formation as a consequence of organic matter turnover. I investigate relevant processes of aggregate formation in a lab approach with artificial soils, but I am also planning to expand the work towards studying initial soil development in natural soils (e.g. from post-mining areas).

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