Physical access for residue-mineral interactions controls organic carbon retention in an Oxisol soil

Abstract

Oxisol soils are widely distributed in the humid tropical and subtropical regions and are generally characterized with high contents of metal oxides. High metal oxides are believed to facilitate organic carbon (C) accumulation via mineral-organic C interactions but Oxisols often have low organic C. Yet, the causes that constrain organic C accumulation in Oxisol soil are not exactly clear. Here we report results from a microcosm experiment that evaluated how the quantity and size of crop residue fragments affect soil C retention in a typical Oxisol soil in southeast China. We found that there were significantly higher levels of dissolved organic C (DOC), microbial biomass C (MBC) and C accumulation in the heavy soil fraction in soil amended with fine-sized (<0.2 mm) compared with coarse-sized (5.0 mm) fragments. Attenuated total reflectance-Fourier transform infrared spectroscopy analysis further showed that fine-sized residues promoted stabilization of aliphatic C-H and carboxylic C=O compounds associated with mineral phases. In addition, correlation analysis revealed that the increased content of organic C in the heavy soil fraction was positively correlated with increased DOC and MBC. Together, these results suggest that enhancement of contact between organic materials and soil minerals may promote C stabilization in Oxisols.

Identifying the Molecular Signatures of Agricultural Expansion in Amazonian Headwater Streams

“…Conversion of pristine lands, such as forests, to cropland has been shown to cause substantial loss of OC from soils due to elevated erosion and decomposition (Don et al, ; Van Oost et al, ). This is particularly problematic in highly weathered soils such as the Oxisols at this study site, as these soils provide limited mineral surfaces for physical protection and stabilization of OC (Don et al, ; Ye et al, ). Multiple factors influence soil OC stocks in the Oxisols on which most new tropical cropping occurs.…”

Al/Fe Mineral Controls on Soil Organic Carbon Stock Across Tibetan Alpine Grasslands

“…They increased with Al d , Fe d , Al o , Fe o , Al p , and Fe p , with the proportions of variance explained ( r 2 ) ranging from 0.2 to 0.7 (Figure ). To examine whether the correlations of SOC and Al/Fe‐(hydr) oxides observed in Tibetan alpine grasslands are general, we collected literature data of SOC and Al/Fe‐(hydr) oxides in temperate and tropical ecosystems (Hounkpatin et al, ; Huang et al, ; Porras et al, ; Souza et al, ; Wagai & Mayer, ; Ye et al, ; Q. Zhao et al, ; J. Zhao et al, ) and found that the positive associations observed in Tibetan alpine grasslands also held true at global scale (Figures a–f). The results of partial correlation analyses further confirmed the effects of mineral variables on SOC content.…”

“…The role of Al/Fe‐(hydr) oxides in regulating SOC could be attributed to the physical and chemical properties of Al/Fe minerals. On the one hand, the charged surface of reactive Al/Fe‐(hydr) oxides and their high surface area‐to‐volume ratio (the highest could reach 800 m 2 /g in ferrihydrite, Eusterhues et al, ; Goldberg, ) enable them to adsorb the functional groups of SOC (preferentially aromatic C and carboxylic C, Chen et al, ; Eusterhues et al, ) and form humus‐clay mineral complexes (Barber et al, ; Ye et al, ). The above characters are reflected most by the complexed Al/Fe‐(hydr) oxides (Al p and Fe p ), which are more poorly crystalline among the three forms of Al/Fe‐(hydr) oxides (Keiluweit et al, ), and thus might induce high surface area‐to‐volume ratio and surface site densities (Porras et al, ).…”

“…This pattern is possibly attributed to the difference of distinct physical and chemical properties between fine‐sized and coarse‐sized particles. Silt and clay associated C can be adsorbed by Al/Fe‐(hydr) oxides more effectively, which could be due to the higher surface area‐to‐volume ratio, the more bonding sites (Ye et al, ), and the more aromatic C, carboxylic C, and aliphatic C groups in this fraction (Golchin et al, ; Six et al, ; Ye et al, ). In contrast, the particle organic matter is mainly derived from plant residues or microbial debris with high O‐alkyl content and C/N ratio, which are usually regarded as the unprotected C pool (Six et al, ).…”

Mecanismos de remoção de Cromo(VI) do solo pela interação entre matéria orgânica e Ferro(III)

“…Diversos estudos indicam a ocorrência de um complexo Fe(II)-orgânico estável (TÓMBACZ et al 2004, JIANG et al 2014, CHEN et al 2015, BHATTACHARYYA et al 2017, SODANO et al 2017, YE et al 2017. Além desse mecanismo, há a possibilidade da própria matéria orgânica dissolvida, como ácidos húmicos e fúlvicos, ser adsorvida por minerais ricos em Fe(II) e Fe(III), como hematita, magnetita e goethita (TÓMBACZ et al 2004, YE et al 2017, USMAN et al 2018. É importante ressaltar que a complexação de Fe(II)/Fe(III) com as frações orgânicas é estável e a formação desses complexos diminui a concentração iônica destes metais em solução (JIANG et al 2014).…”