Abstract
Abstract. Mineral binding is a major mechanism for soil carbon (C) stabilization. However, the submicron information about the in situ mechanisms of different fertilization practices affecting organo-mineral complexes and associated C preservation remains unclear. Here, we applied nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS) to examine differentiating effects of inorganic versus organic fertilization on interactions between highly reactive minerals and soil C preservation. To examine such interactions, soils and their extracted colloids were collected during a 24-year long-term fertilization period (1990–2014) (no fertilization, control; chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization, NPK; and NPK plus swine manure fertilization, NPKM). The results for different fertilization conditions showed a ranked soil organic matter concentration with NPKM > NPK > control. Meanwhile, oxalate-extracted Al (Alo), Fe (Feo), short-range ordered Al (Alxps), Fe (Fexps), and dissolved organic carbon (DOC) ranked with NPKM > control > NPK, but the ratios of DOC ∕ Alxps and DOC ∕ Fexps ranked with NPKM > NPK > control. Compared with the NPK treatment, the NPKM treatment enhanced the C-binding loadings of Al and Fe minerals in soil colloids at the submicron scale. Furthermore, a greater concentration of highly reactive Al and Fe minerals was presented under NPKM than under NPK. Together, these submicron-scale findings suggest that both the reactive mineral species and their associations with C are differentially affected by 24-year long-term inorganic and organic fertilization.
Highlights
Associations of organic matter (OM) with pedogenic minerals, which are termed as organo-mineral complexes, are known to be key controls in the biogeochemical processesPublished by Copernicus Publications on behalf of the European Geosciences Union.J
The oxalate-extracted Al (Alo), Fe (Feo), short-range ordered (SRO) Al (Alxps), Fe (Fexps), and DOC ranked as NPKM > control > NPK, but the DOC / Alxps and DOC / Fexps ratios ranked as NPKM > NPK > control (Table 1)
To get insight into the spatial distribution of Soil OM (SOM) associated with reactive mineral particles, we used both high-resolution transmission electron microscopy (HRTEM) and NanoSIMS to acquire in situ observations of such associations
Summary
Associations of organic matter (OM) with pedogenic minerals, which are termed as organo-mineral complexes, are known to be key controls in the biogeochemical processesJ. Soil OM (SOM) preferentially binds to rough surfaces, which provide a multitude of reactive mineral surfaces (Chen et al, 2014; Vogel et al, 2014) These reactive minerals are termed as short-range ordered (SRO) meta-stable colloidal minerals in volcanic ejecta (Torn et al, 1997), and serve as the nuclei for soil organic carbon (SOC) storage (Hochella et al, 2008; Kögel-Knabner et al, 2008; Remusat et al, 2012; Vogel et al, 2014). These reactive minerals including Al and Fe minerals in soil play a critical role in determining C stability (Solomon et al, 2012; Hernes et al, 2013)
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