Organic matter stabilisation during paddy soil development depending on soil type
Final Report Abstract
Phase I: Redox-controlled mineral-associated organic matter stabilization in paddy soils. We investigated the soil development on calcareous marine sediments using two chronosequences with similar parent material; one used for paddy rice cultivation, the other for upland crops (nonpaddy). Within 2000 yrs of paddy and 700 yrs of non-paddy evolution, no change in clay mineral composition and mineral surface area was observed. But the soils differed in the degree of decalcification, OC accumulation and in the formation of Fe oxides. Paddy soils are characterized by specific soil-forming processes which were markedly different from those of non-paddy soils. Paddy soil management led to an enhanced decalcification and larger OC accumulation. The OC accumulation during 2000 yrs of paddy soil formation is due to strong accretion of OC in the silt-sized and coarse clay fraction, whereas the amount of OC in the S+POM fraction remains constant. This may be attributed to soil microaggregation, which seems to evolve only after more than 1000 yrs of paddy soil formation and to the retarded OC decomposition under waterlogged conditions during several months of the year might be responsible for an OC accretion. The paddy management resulted in higher OM quantities but did not affect the SOM composition during soil development. Selective enrichment of lignin-derived phenols, because of the long-term paddy rice management, could not be confirmed in the present study. Non-paddy soils have a different regime of Fe oxide formation and are characterized by higher proportions of crystalline Fe oxides. This is in contrast to paddy soils, which have higher proportions of poorly crystalline forms of Fe oxides and significant lower contents of crystalline Fe oxides compared to non-paddy topsoils. This is caused by the management-induced redox cycles, which led to a higher proportion of poorly crystalline Fe oxides. Their large SSA, added to the surface area of clay-sized minerals, provided additional options for OC coverage. Selective removal of OM by H2O2 treatment or Fe oxides by DCB showed that Fe oxides and SOM protect each other in organo-mineral associations. Only the combined treatment of H2O2 and DCB leads to completely uncovered mineral surface areas and revealed the complex association between clay minerals, iron oxides and SOM. These associations play a decisive role in OC accumulation and promote the higher organic matter coverage on mineral surfaces in paddy soils. Our findings underline the importance of fine fractions for increasing OC storage, although the process of OC accumulation in the fractions < 20 μm seems not to be complete even after 2000 yrs of paddy soil evolution. The results have major implications for the assessment of new management techniques for paddy soils such as alternating wetting and drying, as these will affect redox conditions and thus most probably also Fe oxide composition and OC storage potential. We could demonstrate for the first time that paddy soils have higher potentials for SOC accumulation compared to respective non-paddy soils, due to the different environments for Fe oxide formation. Phase II: Organic matter stabilization during paddy soil development depending on soil type. Our study is focusing on major soil types that are typically used for rice cultivation in Asia. Alisol sites of the sub-tropical monsoon climate (PR China) were compared with Andosol, Vertisol and Alisol sites (tropical climate of Java, Indonesia), as they represent a large range of soil properties to be expected in Asian paddy fields. The SOM composition revealed by solid-state 13C NMR was similar for the different soil types and was also not affected by the specific paddy soil management. The contribution of lignin-related carbon groups to total SOM was similar in the investigated paddy and non-paddy soils. A significant proportion of the total aromatic carbon in some paddy and non-paddy soils was attributed to the application of charcoal as a common management practice. The extraction of ligninderived phenols by CuO-oxidation method revealed low VSC (vanillyl, syringyl, cinnamyl) values for all investigated soils, being typical for agricultural soils. An accumulation of CuO-lignin-derived phenols due to paddy management was not found. Higher organic carbon contents for some of the paddy soils cannot be explained by lignin accumulation. Thus, paddy management does not necessarily lead to higher OC accumulation compared to their parent soil types.
Publications
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(2010) Biogeochemistry of paddy soils. Geoderma 157, 1–14
Kögel-Knabner, I., Amelung, W., Cao, Z.H., Fiedler, S., Frenzel, P., Jahn, R., Kalbitz, K., Kölbl, A., Schloter, M.
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(2010) Changes in diversity and functional gene abundances of microbial communities involved in nitrogen fixation, nitrification, and denitrification in a tidal wetland versus paddy soils cultivated for different time periods. Applied Environmental Microbiology 77, 6109–6116
Bannert, A., Kleineidam, K., Wissing, L., Mueller-Niggemann, C., Vogelsang, V., Welzl, G., Cao, Z., Schloter, M.
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(2011) Organic carbon accumulation in a 2000-year chronosequence of paddy soil evolution. Catena 87, 376–385
Wissing, L., Kölbl, A., Vogelsang, V., Fu, J., Cao, Z-H., Kögel-Knabner, I.
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(2013) Managementinduced organic carbon accumulation in paddy soils: The role of organo-mineral associations. Soil Tillage Research 126, 60–71
Wissing, L., Kölbl, A., Häusler, W., Schad, P., Cao, Z-H., Kögel-Knabner, I.
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(2013) The carbon count of 2000 years of rice cultivation. Global Change Biology, 19, 1107–1113
Kalbitz, K., Kaiser, K., Fiedler, S., Kölbl, A., Amelung, W., Bräuer, T., Cao, Z., Don, A., Grootes, P., Jahn, R., Schwark, L., Vogelsang, V., Wissing, L., Kögel-Knabner, I.
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(2014) Accelerated soil formation due to paddy management on marshlands (Zhejiang Province, China). Geoderma, 228-229, 67–89
Kölbl, A., Schad, P., Jahn, R., Amelung, W., Bannert, A., Cao, Z.-H., Fiedler, S., Kalbitz, K., Lehndorff, E., Müller-Niggemann, C., Schloter, M., Schwark, L., Vogelsang, V., Wissing, L., Kögel-Knabner, I.
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(2014) Organic carbon accumulation on soil mineral surfaces in paddy soils derived from tidal wetlands. Geoderma 228, 90-103
Wissing, L., Kölbl, A., Schad, P., Bräuer, T., Cao, Z-H., Kögel-Knabner
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(2016) Response of Vertisols, Andosols, and Alisols to paddy management. Geoderma 261, 23–25
Winkler P., Kaiser K., Kölbl A., Kühn T., Schad P., Urbanski L., Fiedler S., Lehndorff E., Kalbitz K., Utami S.R., Cao Z., Zhang G., Jahn R., Kögel-Knabner I.
