Houtermans, Miriam: Nitrogen sequestration in paddy and non-paddy soils formed from different parent materials. - Bonn, 2019. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-55501
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-55501,
author = {{Miriam Houtermans}},
title = {Nitrogen sequestration in paddy and non-paddy soils formed from different parent materials},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2019,
month = aug,

note = {Paddy soils exhibit low nitrogen (N) use efficiency. Prior research in this field suggested that paddy soils may sequester significant amounts of N in aged amino acids, microbial residues, or even in pyrogenic N. The overarching aim of my theses was to identify these bonding forms of N sequestration in different soil types, and to elucidate to what extent the properties of the parent soil rather than anthropogenic soil management controls the different N sequestration processes.
My hypothesis was that the effects of rice cultivation on N sequestration in soil depend on the mineral composition of the parent soil. My specific research questions were: (i) does paddy management lead to N sequestration in peptide bonds, (ii) do bacteria or fungi promote high microbial N sequestration in paddy soils, and (iii) to which extent can N sequestration in paddy soils be assigned to the input of charred organic matter?
To answer these research questions, I sampled paddy and adjacent non-paddy top- and subsoils from different major reference soil groups (Vertisols, Andosols, Alisols, and a Gleysol/Fluvisol pair), allocated in major paddy rice production regions in Indonesia, China and Italy. I used N biomarkers like amino sugars and amino acid enantiomers to elucidate whether N sequestration in peptides and microbial residues is stronger under paddy compared with non-paddy management. Selected samples were pre-extracted with dithionite‒citrate‒bicarbonate (DCB) to better understand the role of reactive pedogenic oxides to amino acid-N storage, origin and composition. Additionally, I analyzed charred organic matter (black carbon; BC) via the analyses of benzene polycarboxylic acids and tried to identify black N forms via X-ray photoelectron spectroscopy (XPS) in order to elucidate the contribution of pyrogenic N to total N sequestration.
The results showed that total N- and amino acid-N stocks in the topsoils were significantly larger in paddy-managed Andosols and Chinese Alisols than in their non-paddy counterparts. In other soils, however, paddy management did not lead to elevated proportions of total N and amino acid-N. The N storage in peptide-bound amino acids went along with elevated contents of bacteria-derived D-alanine and D-glutamic acid, as well as with increasing stocks of DCB extractable pedogenic oxides. In order to be able to track specifically the N sequestration into the residues of bacteria and fungi, I analyzed amino sugars as respective marker compounds. Across all soils under study, the stocks of DCB extractable oxides showed a positive correlation to stocks of microbial residue (p<0.01, R2= 0.60), whereas paddy management did not continuously led to accumulation of microbial residues. Therefore, I conclude that the mineral assemblage of soils modulates the degree at which microorganisms contribute to the N sequestration under both paddy and non-paddy management, therewith supporting the overall hypothesis of my thesis that the mineral assembly drives the overall enrichment of specific N forms in soil.
The traditional burning of straw on paddy fields led to an enrichment of BC. However, the proportion of pyrogenic organic N (black N, BN) in the soil was hardly or not detectable by XPS analysis, although a pre-test in the laboratory showed that after the combustion of rice straw the content of BN can rise to more than 50% of the total N. BC and BN did not show any correlation to soil properties such as clay content and pedogenic oxides.
Therefore, I conclude that BN from burnt crop residues does not significantly contribute to N sequestration in rice soils.
In summary, the results showed that significant amounts of N sequester in aged amino acids and microbial residues, whereas I did not find significant amounts of pyrogenic N.
The N sequestration was largely determined by the mineral assemblage of the parent material and, contrary to what was assumed, was largely independent of paddy management.},

url = {https://hdl.handle.net/20.500.11811/8000}

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