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269 results on '"Dultz, Stefan"'

12. Landscape Settings and Mineralogy of Some Geophagic Clay Occurrences in South Africa

Author

Ekosse, Georges-I., Chistyakov, Kirill V., Rozanov, Andrei B., Bashkirova, Nadezhda N., Dultz, Stefan, Polekhovsky, Yury S., Lessovaia, Sofia N., Blondel, Philippe, Series Editor, Reitner, Joachim, Series Editor, Stüwe, Kurt, Series Editor, Trauth, Martin H., Series Editor, Yuen, David A., Series Editor, Friedman, G.M., Founding Editor, Seilacher, A., Founding Editor, Frank-Kamenetskaya, Olga V., editor, Vlasov, Dmitry Yu., editor, Panova, Elena G., editor, and Lessovaia, Sofia N., editor

Published
2020
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13. Modeling Biogenic Weathering of Rocks from Soils of Cold Environments

Author

Lessovaia, Sofia N., Gerrits, Ruben, Gorbushina, Anna A., Polekhovsky, Yury S., Dultz, Stefan, Kopitsa, Gennady G., Blondel, Philippe, Series Editor, Reitner, Joachim, Series Editor, Stüwe, Kurt, Series Editor, Trauth, Martin H., Series Editor, Yuen, David A., Series Editor, Friedman, G.M., Founding Editor, Seilacher, A., Founding Editor, Frank-Kamenetskaya, Olga V., editor, Vlasov, Dmitry Yu., editor, Panova, Elena G., editor, and Lessovaia, Sofia N., editor

Published
2020
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29. Characterization and implication of phytolith-associated potassium in rice straw and paddy soils

Author

Nguyen, Huan X., Van T. Nguyen, Tran, Chinh T., Nguyen, Anh T. Q., Nguyen-Thanh, Lan, Bui, Anh T. K., Dultz, Stefan, Wu, Ta Yeong, and N. Nguyen, Minh

Abstract

Rice straw contains up to 2.3% K in dry matter, including potassium (K) subcompartmented in phytoliths, complex siliceous structures formed in plant tissue via precipitation of Si. Rice straw is usually returned to the soil as a conventional practice to sustain soil nutrients, and therefore, the K pool accompanied with rice straw phytoliths is also cycled. Based on phytoliths obtained by ashing of rice straw at 400 °C and dissolution experiments using batch extraction in combination with physical separation of phytoliths by heavy liquid, this study evaluated the phytolith K(phytK) pool in rice straw and aged phytoliths in paddy soils. Entrapped organic matter containing K within phytolith silica cells was visualized by X-ray tomographic microscopy, and releases of this phytK pool accompanying phytolith dissolution were quantified. A 1% Na2CO3 solution, which has been commonly used to extract amorphous Si and to quantify soil phytoliths, showed obvious responses for K derived from phytolith dissolution, indicating that the Na2CO3 method can be developed for measurement of phytK. In 13 soil samples, Na2CO3-dissolvable K content assignable to phytK was 0.55 ± 0.39 g kg−1 in the puddled horizon, suggesting the phytK pool is of high significance for the management of K in paddy soils.

Published
2023
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35. Process sequence of soil aggregate formation disentangled through multi-isotope labelling

Author

Amelung, Wulf, Meyer, Nele, Rodionov, Andrey, Knief, Claudia, Aehnelt, Michaela, Bauke, Sara L., Biesgen, Danh, Dultz, Stefan, Guggenberger, Georg, Jaber, Maguy, Klumpp, Erwin, Kögel-Knabner, Ingrid, Nischwitz, Volker, Schweizer, Steffen A., Wu, Bei, Totsche, Kai U., Lehndorff, Eva, Amelung, Wulf, Meyer, Nele, Rodionov, Andrey, Knief, Claudia, Aehnelt, Michaela, Bauke, Sara L., Biesgen, Danh, Dultz, Stefan, Guggenberger, Georg, Jaber, Maguy, Klumpp, Erwin, Kögel-Knabner, Ingrid, Nischwitz, Volker, Schweizer, Steffen A., Wu, Bei, Totsche, Kai U., and Lehndorff, Eva

Abstract

Microaggregates (<250 µm) are key structural subunits of soils. However, their formation processes, rates, and transformation with time are poorly understood. We took advantage of multiple isotope labelling of potential organic gluing agents and inorganic building units to unravel their role in soil aggregation processes being initiated with and without plant growth. We added 13C-labelled extracellular polymeric substances (EPS), 15N-labelled bacteria, 57Fe-labelled goethite, and 29Si-labelled montmorillonite to fine soil <250 µm of an Ap horizon from a Stagnic Luvisol, which was planted with Festuca heteromalla or kept bare in a climate chamber. Samples were taken after 4, 12, and 30 weeks, and separated into free (f) and occluded (o) microaggregates of different sizes (<20 µm, 53–20 µm, 250–53 µm), and in stable macroaggregates (>250 µm) that resisted 60 J mL−1 ultrasonic dispersion. Afterwards, we assessed the C, N, Fe, and Si stable isotope composition in each size fraction. After four weeks we found a rapid build-up of stable macroaggregates comprising almost 50 % of soil mass in the treatment with plants and respective soil rooting, but only 5 % when plants were absent. The formation of these stable macroaggregates proceeded with time. Soil organic carbon (SOC) contents were elevated by 15 % in the large macroaggregates induced by plant growth. However, the recovery of EPS-derived 13C was below 20 % after 4 weeks, indicating rapid turnover in treatments both with and without plants. The remaining EPS-derived C was mainly found in macroaggregates when plants were present and in the occluded small microaggregates (<20 µm) when plants were absent. The excess of bacterial 15N closely followed the pattern of EPS-derived 13C (R2 = 0.72). In contrast to the organic gluing agents, the goethite-57Fe and montmorillonite-29Si were relatively equally distributed across all size fractions. Overall, microaggregates were formed within weeks. Roots enforced this process by st

Published
2022

36. Unsichtbar wirksam : Bodenmikroaggregate: kleine Strukturen mit großer Wirkung

Author

Guggenberger, Georg, Peth, Stephan, Felde, Vincent, Dultz, Stefan, Guggenberger, Georg, Peth, Stephan, Felde, Vincent, and Dultz, Stefan

Abstract

In der Bodenforschung spielen Mikroaggregate eine besondere Rolle. Sie haben eine komplexe innere Architektur in der mikrobielle, biogeochemische und physikalische Prozesse in Wechselwirkung stehen, die bisher noch sehr wenig untersucht, aber von fundamentaler Bedeutung für die Funktionsfähigkeit von Böden sind. Wissenschaftler vom Institut für Bodenkunde versuchen daher, einen Beitrag zum mechanistischen Verständnis der Bildung und Funktion von Mikroaggregaten zu leisten.

Published
2022

44. Process Sequence of Soil Aggregate Formation Disentangled Through Multi-Isotope Labelling

Author

Amelung, Wulf, primary, Meyer, Nele, additional, Rodionov, Andrey, additional, Knief, Claudia, additional, Aehnelt, Michaela, additional, Bauke, Sara L., additional, Danh, Biesgen, additional, Dultz, Stefan, additional, Guggenberger, Georg, additional, Jaber, Maguy, additional, Klumpp, Erwin, additional, Kögel-Knabner, Ingrid, additional, Nischwitz, Volker, additional, Schweizer, Steffen A., additional, Wu, Bei, additional, Totsche, Kai Uwe, additional, and Lehndorff, Eva, additional

Published
2022
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47. The regulatory role of CO2 on nutrient releases from ashed rice straw phytoliths.

Author

Nguyen, Anh T. Q., Nguyen, Anh M., Nguyen, Muu T., Nguyen, Hue T., Duong, Lim T., Dinh, Van M., Nguyen, Phuong M., Dultz, Stefan, and Nguyen, Minh N.

Subjects
RICE straw, PHYTOLITHS, UPLAND rice, SOLUTION (Chemistry), PADDY fields, WHEAT straw, RICE hulls
Abstract

Phytolith is widely known as a silica structure in numerous silicon (Si) accumulator plants, e.g., rice, and it contains various nutrients and other beneficial elements. When rice straw is returned to paddy fields, the silica structure of phytolith can be dissolved, thereby releasing its occluded nutrients. While the intrinsic characteristics and dissolution properties of phytoliths under the effect of solution chemistry have been intensively studied, the effect of gas phases, especially CO2, on phytolith stability and the implications for nutrient release are not fully known. Here, dissolution properties of phytolith ashes obtained from dry ashing of rice straw at 400, 600 and 800 °C were investigated by quantifying Si release together with other nutrients under two atmospheric conditions, i.e., without and with CO2 support (aeration). In a time span of 6 days, the releases of nutrients (K, P, Ca, Mg) showed high dependence on the overall dissolution of the phytolith ashes. CO2 significantly reduced the dissolution rate of the phytolith ashes but increased the release rates of cationic as well as anionic nutrients. The aeration of CO2 shifted the carbonate equilibrium (H2CO3, HCO3− and CO32−) towards H2CO3, reducing solution pH, thereby decreasing the dissolution rate of phytoliths. Following this, intensification of H+ exchange promoted nutrient releases from the phytolith ashes. This indicates contrasted responses of phytoliths and their occluded nutrients to CO2, and provides a better insight on the fate of soil phytoliths and the tendency of nutrient budgets from rice straw phytoliths in soils. [ABSTRACT FROM AUTHOR]

Published
2022
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