TY - JOUR
T1 - Development of biogeochemical interfaces in an artificial soil incubation experiment; aggregation and formation of organo-mineral associations
AU - Pronk, Geertje Johanna
AU - Heister, Katja
AU - Ding, Guo Chun
AU - Smalla, Kornelia
AU - Kögel-Knabner, Ingrid
N1 - Funding Information:
The authors would like to thank Maria Greiner, Ulrike Maul, Zohre Javaheri, Samira Ravash, Zahra Kazemi and Alexander Dümig for assistance during the preparation, incubation and the characterization and density fractionation of the artificial soils. The authors thank Olivia Kreyling for the development of the density fractionation method. Furthermore, we thank Anja Miltner and Esther Cyrus of the Helmholtz Zentrum, Leipzig for the preparation of the dried manure and Holger Kirchman for supplying the soil from Ultuna used for extraction of the microbial inoculant. We are grateful to Marianne Hanzlik (Institute of Electron Microscopy, Technische Universität München, Garching) for the assistance with the SEM-EDX measurements. This project was carried out within the framework of the priority program 1315 ‘Biogeochemical Interfaces in Soil’ funded by the German Research Foundation (DFG) ( KO 1035/33-1 ) with the support of the Technische Universität München - Institute for Advanced Study, funded by the German Excellence Initiative .
PY - 2012/11
Y1 - 2012/11
N2 - Soils represent a very complex material where mineral, organic and biological components interact together to form a large 'biogeochemical interface'. In order to study this complex interface in a simplified system, a so-called 'artificial soil' incubation experiment was carried out. This experiment was used here specifically to study the effect of microbial activity and mineral interactions on the aggregation occurring during incubation. Artificial soils with different mineral composition but the same texture, were composed of well-defined model materials. The materials considered were quartz, illite, montmorillonite, ferrihydrite, boehmite and charcoal, manure as an organic matter (OM) source and a microbial inoculum extracted from a natural arable topsoil. The artificial soils were incubated for 3 to 18months in the dark, under constant temperature and water content. The pH, organic carbon (OC) and nitrogen content, extractable Fe, Al and Si of the incubated artificial soils were measured, and the amount of macroaggregates>2mm was determined by sieving. Density fractionation was performed at densities of 1.8 and 2.4gcm -3 to separate particulate OM, organo-mineral associates and the mineral fraction. The specific surface area (SSA) of the organo-mineral associate fraction and the amount of OC associated with organo-mineral associates and minerals was determined. The SSA of the model materials and the artificial soils at the start of incubation was determined by BET-N 2. The artificial soils developed quickly and CO 2 respiration occurred during the entire 18month incubation time. The actual SSA of the 'soils' was significantly lower than the sum of the SSA of the pure model materials indicating that occlusion of mineral surfaces by interaction between OM and minerals occurred almost immediately after incubation started. Macroaggregates and organo-mineral associates were formed within 3months of incubation. Macroaggregation decreased after 12months of incubation probably due to decreasing biological activity. The turnover of macroaggregates and continuing formation of organo-mineral associates was consistent with the aggregate hierarchy model. Less macroaggregation was observed in the soil where no clay mineral was present, indicating that clay minerals were important for the formation of macroaggregates. Ferrihydrite and boehmite did not affect the aggregation or formation of organo-mineral associates in this experiment. The results of density fractionation indicate that OM was mainly associated with the clay minerals, probably due to the neutral pH of the artificial soils, leading to a low or negative surface charge of the oxides. The artificial soil incubation experiment showed that interface development and the building of macroaggregates and organo-mineral associates took place within a relatively short time scale. It offers a valuable model where the formation and interactions of soil properties and processes can be studied in a well-defined system.
AB - Soils represent a very complex material where mineral, organic and biological components interact together to form a large 'biogeochemical interface'. In order to study this complex interface in a simplified system, a so-called 'artificial soil' incubation experiment was carried out. This experiment was used here specifically to study the effect of microbial activity and mineral interactions on the aggregation occurring during incubation. Artificial soils with different mineral composition but the same texture, were composed of well-defined model materials. The materials considered were quartz, illite, montmorillonite, ferrihydrite, boehmite and charcoal, manure as an organic matter (OM) source and a microbial inoculum extracted from a natural arable topsoil. The artificial soils were incubated for 3 to 18months in the dark, under constant temperature and water content. The pH, organic carbon (OC) and nitrogen content, extractable Fe, Al and Si of the incubated artificial soils were measured, and the amount of macroaggregates>2mm was determined by sieving. Density fractionation was performed at densities of 1.8 and 2.4gcm -3 to separate particulate OM, organo-mineral associates and the mineral fraction. The specific surface area (SSA) of the organo-mineral associate fraction and the amount of OC associated with organo-mineral associates and minerals was determined. The SSA of the model materials and the artificial soils at the start of incubation was determined by BET-N 2. The artificial soils developed quickly and CO 2 respiration occurred during the entire 18month incubation time. The actual SSA of the 'soils' was significantly lower than the sum of the SSA of the pure model materials indicating that occlusion of mineral surfaces by interaction between OM and minerals occurred almost immediately after incubation started. Macroaggregates and organo-mineral associates were formed within 3months of incubation. Macroaggregation decreased after 12months of incubation probably due to decreasing biological activity. The turnover of macroaggregates and continuing formation of organo-mineral associates was consistent with the aggregate hierarchy model. Less macroaggregation was observed in the soil where no clay mineral was present, indicating that clay minerals were important for the formation of macroaggregates. Ferrihydrite and boehmite did not affect the aggregation or formation of organo-mineral associates in this experiment. The results of density fractionation indicate that OM was mainly associated with the clay minerals, probably due to the neutral pH of the artificial soils, leading to a low or negative surface charge of the oxides. The artificial soil incubation experiment showed that interface development and the building of macroaggregates and organo-mineral associates took place within a relatively short time scale. It offers a valuable model where the formation and interactions of soil properties and processes can be studied in a well-defined system.
KW - Aggregate hierarchy
KW - Charcoal
KW - Clay mineral
KW - Ferrihydrite
KW - Specific surface area
UR - http://www.scopus.com/inward/record.url?scp=84865048394&partnerID=8YFLogxK
U2 - 10.1016/j.geoderma.2012.05.020
DO - 10.1016/j.geoderma.2012.05.020
M3 - Article
AN - SCOPUS:84865048394
SN - 0016-7061
VL - 189-190
SP - 585
EP - 594
JO - Geoderma
JF - Geoderma
ER -