Abstract
Mineral elements in soil solutions are thought to be the precursor of the formation of reactive minerals, which play an important role in global carbon (C) cycling. However, information regarding the regulation of mineral elements release in soil is scarce. Here, we examined the long-term (i.e., 23 yrs) effects of fertilisation practices on Fe minerals in a red soil in Southern China. The results from chemical analysis and Fourier-transform infrared spectroscopy showed that long-term swine manure (M) treatment released greater amounts of minerals into soil solutions than chemical fertilisers (NPK) treatment, and Fe played a dominant role in the preservation of dissolved organic C. Furthermore, Fe K-edge X-ray absorption near-edge fine structure spectroscopy demonstrated that reactive Fe minerals were mainly composed of less crystalline ferrihydrite in the M-treated soil and more crystalline goethite in the NPK-treated soil. In conclusion, this study reported spectroscopic evidence of the improvement of reactive Femineral content in the M-treated soil colloids when compared to NPK-treated soil colloids.
Highlights
Soil organic matter (SOM) contained greater than three-fold more carbon (C) than the atmosphere and terrestrial vegetation [1]
To determine whether soluble reactive Fe played an important role in the preservation of SOC, the concentrations of mineral elements (i.e., Fe, Al, Si, Ca, and Mg) and dissolved organic C (DOC) in soil colloids were measured (Fig 1-a)
The highest concentrations of both mineral elements and DOC were found in the NPKM treatment, followed by the M treatment, with the lowest concentrations observed in the Control and NPK treatments
Summary
Soil organic matter (SOM) contained greater than three-fold more carbon (C) than the atmosphere and terrestrial vegetation [1]. The biogeochemical cycles of organic C and iron (Fe) were strongly interlinked [2,3]. Lalonde et al [2] suggested that approximately 21.5% of the organic carbon in soil or sediment was directly bound to reactive Fe minerals. Reactive Fe minerals could play an important role in the long-term storage of organic C and the dynamics of the global C cycle. A study of two-century land use changes on soil iron crystallinity and accumulation [4] suggested that land use changes (agriculture and reforestation) play an important role in transforming the iron crystallinity and its interaction with organic matter decomposition in PLOS ONE | DOI:10.1371/journal.pone.0146364. A study of two-century land use changes on soil iron crystallinity and accumulation [4] suggested that land use changes (agriculture and reforestation) play an important role in transforming the iron crystallinity and its interaction with organic matter decomposition in PLOS ONE | DOI:10.1371/journal.pone.0146364 January 11, 2016
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