Articles | Volume 13, issue 12
https://doi.org/10.5194/bg-13-3607-2016
https://doi.org/10.5194/bg-13-3607-2016
Research article
 | 
21 Jun 2016
Research article |  | 21 Jun 2016

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

Jian Xiao, Xinhua He, Jialong Hao, Ying Zhou, Lirong Zheng, Wei Ran, Qirong Shen, and Guanghui Yu

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.

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Short summary
Reactive minerals are ubiquitous in soil and are proposed as a primary driver for carbon (C) retention. However, regulation of soil reactive minerals and direct evidence in sequestrating C by them are scarce. Here we show that, compared with chemical fertilization, inorganic and organic fertilization enhanced the C-binding loadings of Al and Fe minerals in soil colloids, suggesting that reactive mineral species and their associations with C are differentially affected by fertilization practices.
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