Sequestration study on mineral-organic complex of Jiangsu tea garden soil with synchrotron radiation infrared micro-imaging

【Objective】To analyze the differences between soil structures of various tea gardens in Jiangsu for finding out management methods of nutrient requirements,so as to provide scientific basis for reducing usage of chemical fertilizer while enhancing effect.【Method】To characterize structure of mineral-organic complex of tea garden soil in Jiangsu, Jiangsu tea garden soil microaggregates were sliced and analyzed with synchrotron radiation infrared micro-imaging to observe the distribution of specific components,and the distribution of mineral and organic functional groups in the samples were characterized in situ to explore mechanisms of stabilizing organic carbon in tea garden soil.【Result】Results showed that organic carbon existed in the forms of larger molecular organics(i.e. aliphatic-C, 2881 cm^-1, aromatic-C, 1620 cm^-1, and polysaccharides-C, 1100 cm^-1) and mineral element oxides Fe-O, Al-O, Si-O groups were found in all soils. The spatial distributions of each element in soil microaggregates in tea gardens were highly heterogeneous. Aliphatic carbons such as methyl and methylene C-H were adsorbed on the edge of soil microaggregates(a small amount of minerals was also found there),while functional groups such as Al-O and Fe-O of iron and aluminum minerals gathered at the core of microaggregates,and a small amount of organic material was also absorbed on the surface of microaggregates. Clay minerals (3620 cm^-1) had the highest correlation with aliphatic-C in 87.5% tea garden soil and fertilization and tea planting years affected the order of mineral organic functional group correlation. The correlation between iron oxide and polysaccharides-C was the highest in 75.0% tea garden soil and the affinity order of Fe/Al minerals and organic functional groups in each type tea garden soil was different due to the influence of altitude, pH and planting years. In summary, synchrotron-radiation-based infrared spectro microscopy is expected to be a new method to characterize soil fertility of tea garden.【Conclusion】The distribution pattern of microaggregates and organic carbon in soil from different tea gardens in Jiangsu reveals that through mineral-organic complex,organic material is kept in soil by soil microaggregates to increase content of soil organic material. In the process of tea production,different nutrient management strategies should be taken according to different situations of concrete nutrient management,tea cultivation and soil condition.