Changes in minerals and organic-mineral associations during paddy soil development Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) der Naturwissenschaftlichen Fakultät III Agrar- und Ernährungswissenschaften, Geowissenschaften und Informatik der Martin-Luther-Universität Halle-Wittenberg vorgelegt von Frau Dipl.-Geoökologin Pauline Winkler Geb. am 23.11.1984 in Finsterwalde Gutachter: Prof. Reinhold Jahn, Prof. Karsten Kalbitz, Prof. Georg Guggenberger Tag der Verteidigung: 16. November 2020 Table of Contents Table of Contents ............................................................................................................................................................... 1 List of Figures ...................................................................................................................................................................... 6 List of Tables ........................................................................................................................................................................ 8 List of Appendices .............................................................................................................................................................. 9 1 General Introduction ............................................................................................................................................ 11 1.1 Biogeochemistry of paddy soils ............................................................................................................. 11 1.2 Soil types under paddy management and their mineral properties ...................................... 14 1.2.1 Andosols ................................................................................................................................................. 15 1.2.2 Alisols ...................................................................................................................................................... 16 1.2.3 Vertisols ................................................................................................................................................. 16 1.3 Mineral-organic-carbon associations .................................................................................................. 17 1.4 Objectives ........................................................................................................................................................ 19 2 Response of Vertisols, Andosols, and Alisols to paddy management .............................................. 20 2.1 Abstract ............................................................................................................................................................ 21 2.2 Introduction ................................................................................................................................................... 22 2.3 Materials & Methods .................................................................................................................................. 24 2.3.1 Investigation area & soil sampling .............................................................................................. 24 2.3.2 Laboratory analyses of the bulk soil .......................................................................................... 24 2.4 Results & Discussion .................................................................................................................................. 26 2.4.1 Vertisols ................................................................................................................................................. 26 2.4.2 Andosols ................................................................................................................................................. 27 2.4.3 Clayey Alisols (on Java).................................................................................................................... 37 2.4.4 Sandy Alisols (in China) ................................................................................................................... 38 2.5 Implications ................................................................................................................................................... 39 2.5.1 The fate of Fe oxides under paddy management depends on initial soil properties 39 2.5.2 Accumulation of OC in paddy soils mainly depends on OM input ................................. 41 2.5.3 Desilication slowed down in Andosol-derived paddy soils .............................................. 41 2.5.4 No evidence of ferrolysis................................................................................................................. 41 2.6 Conclusions .................................................................................................................................................... 42 2.7 Acknowledgements ..................................................................................................................................... 42 3 Contrasting evolution of iron phase composition in soils exposed to redox fluctuations ...... 43 Table of Contents 3.1 Abstract ............................................................................................................................................................ 44 3.2 Introduction ................................................................................................................................................... 45 3.3 Materials & Methods .................................................................................................................................. 47 3.3.1 Field soil sampling ............................................................................................................................. 47 3.3.2 Incubation experiment .................................................................................................................... 49 3.3.3 Analytical methods ............................................................................................................................ 50 3.3.4 57Fe Mössbauer spectroscopy ....................................................................................................... 51 3.4 Results .............................................................................................................................................................. 53 3.4.1 Chemical extraction of pedogenic Fe ......................................................................................... 53 3.4.2 Fe phases identified by 57Fe Mössbauer spectroscopy ....................................................... 53 3.4.3 Fe (oxy-)hydroxide changes in soils under paddy management ................................... 56 3.4.4 Soil solution composition during incubation of non-paddy topsoils ............................ 57 3.4.5 Fe (oxy-)hydroxide changes in laboratory-incubated soils .............................................. 58 3.5 Discussion ....................................................................................................................................................... 59 3.5.1 Contrasting shifts in Fe crystallinity during redox fluctuations ..................................... 59 3.5.2 Chemical extraction vs. 57Fe Mössbauer spectroscopy....................................................... 61 3.5.3 Associations of Fe and OM in the Andosol ............................................................................... 62 3.5.4 Fe-substituted halloysite formation probable in the Andosol-derived paddy soil . 62 3.6 Conclusions .................................................................................................................................................... 63 3.7 Acknowledgements ..................................................................................................................................... 64 4 Tracing organic carbon and microbial community structure in mineralogically different soils exposed to redox fluctuations ......................................................................................................................... 65 4.1 Abstract ............................................................................................................................................................ 66 4.2 Introduction ................................................................................................................................................... 66 4.3 Materials & Methods .................................................................................................................................. 69 4.3.1 Soil selection and sampling ............................................................................................................ 69 4.3.2 Specific surface area and surface element composition of initial soils ........................ 70 4.3.3 Laboratory incubation experiment ............................................................................................ 71 4.3.4 Headspace analyses........................................................................................................................... 72 4.3.5 Soil solution analyses ....................................................................................................................... 73 4.3.6 Density fractionation of soil OM .................................................................................................