Nitrogen‐rich microbial products provide new organo‐mineral associations for the stabilization of soil organic matter

Kopittke, Peter M.; Hernandez‐Soriano, Maria C.; Dalal, Ram C.; Finn, Damien; Menzies, Neal W.; Hoeschen, Carmen; Mueller, Carsten W.

doi:10.1111/gcb.14009

Cited by 148 publications

(84 citation statements)

References 44 publications

(84 reference statements)

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“…Microbial efficiency-matrix stabilization hypothesis suggests that the microbial use effectiveness is governed by the stabilization through organo-mineral associations 59 . Nitrogen rich microbial products, due to their positively charged functional groups, favorably associate with mineral surfaces compared to C-rich moieties enhancing the storage of SOM 60 . The heterogeneous and complex distribution of N-based compounds observed in the NTR thin section (100-nm) could be partly indicating microbial contribution in associating SOM with soil mineral surfaces.…”

Section: Discussionmentioning

confidence: 99%

Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates

Arachchige

Hettiarachchi

Rice

et al. 2018

Sci Rep

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Direct evidence-based approaches are vital to evaluating newly proposed theories on the persistence of soil organic carbon and establishing the contributions of abiotic and biotic controls. Our primary goal was to directly identify the mechanisms of organic carbon stabilization in native-state, free soil microaggregates without disrupting the aggregate microstructure using scanning transmission x-ray microscopy coupled with near edge x-ray absorption fine structure spectroscopy (STXM-NEXAFS). The influence of soil management practices on microaggregate associated-carbon was also assessed. Free, stable soil microaggregates were collected from a tropical agro-ecosystem in Cruz Alta, Brazil. The long-term experimental plots (>25 years) comparing two tillage systems: no-till and till with a complex crop rotation. Based on simultaneously collected multi-elemental associations and speciation, STXM-NEXAFS successfully provided submicron level information on organo-mineral associations. Simple organic carbon sources were found preserved within microaggregates; some still possessing original morphology, suggesting that their stabilization was not entirely governed by the substrate chemistry. Bulk analysis showed higher and younger organic carbon in microaggregates from no-till systems than tilled systems. These results provide direct submicron level evidence that the surrounding environment is involved in stabilizing organic carbon, thus favoring newly proposed concepts on the persistence of soil organic carbon.

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Section: Discussionmentioning

confidence: 99%

Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates

Arachchige

Hettiarachchi

Rice

et al. 2018

Sci Rep

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show abstract

“…For example, in a 365‐day incubation experiment, Kopittke et al. () reported, based on NanoSIMS, that microbial‐derived 15 N‐rich OM often adsorbed directly to mineral surfaces not previously associated with OM; but the contribution of inorganic N was not reported either. Other N compounds might only become sorbed in the subsoil as they are enriched in less sorptive hydrophilic DOM ( Kaiser and Zech , ) being disfavored from sorption in topsoil.…”

Section: Application Of the Multilayer Model In Soil Science And Relamentioning

confidence: 99%

“…The latter study shows that in subsoils 30-85% of total N were present as inorganic N. Further, the above mentioned changes in C/N ratios can also be attributed to the enrichment of N-rich microbial residuals on mineral surfaces via preferential adsorption. For example, in a 365-day incubation experiment, Kopittke et al (2018) reported, based on NanoSIMS, that microbial-derived 15 N-rich OM often adsorbed directly to mineral surfaces not previously associated with OM; but the contribution of inorganic N was not reported either. Other N compounds might only become sorbed in the subsoil as they are enriched in less sorptive hydrophilic DOM (Kaiser and Zech, 2000) being disfavored from sorption in topsoil.…”

Section: Strong Adsorption Of N-containing Compounds and Enrichment Omentioning

confidence: 99%

The multilayer model of soil mineral–organic interfaces—a review

Gao

Mikutta

Jansen

et al. 2019

J. Plant Nutr. Soil Sci.

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Association of organic matter (OM) with minerals is an important pathway in the formation of stable OM in soil. While the importance of mineral-organic associations (MOA) in regulating soil carbon cycling has been rigorously demonstrated by empirical evidence, knowledge about the molecular-scale arrangement of OM at mineral surfaces is still lacking. Such knowledge is urgently needed to disentangle the mechanisms of long-term storage of soil OM. Based on indirect observations regarding the formation, composition, and structure of MOA, a conceptual multilayer model was proposed by Kleber et al. in 2007 to foster debate and help elucidating the structure and reactivity of MOA. According to this model, the associated OM at mineral surfaces is discrete and self-organized into a multilayer structure. In this review, we aim to collect and evaluate existing studies that used this model to explain biogeochemical processes at mineral-organic interfaces, and based on this, assess the applicability of the model. The multilayer model has seen extensive adoption within soil science and related fields. In general, existing studies either support the concept of a patchy distribution of adsorbed OM on mineral surfaces or advocate that OM can be coprecipitated with nanosized poorly crystalline minerals or hydrolysable metals. However, the evidence for the patchy distribution of adsorbed OM cannot support the multilayer model on its own. There is little consensus about the role of N-rich OM in forming the contact zone according to the multilayer model but surface conditioning by different classes of organic compounds appears to be an essential factor for the overall adsorption of OM. Nevertheless, large uncertainty still remains with respect to multilayer-like organization of MOA. By taking advantage of recent developments in surface analytical sciences and computational chemistry, a rigid experimental testing of the multilayer model at the molecular level is still required and awaits to be integrated into improved concepts of MOA formation and OM stabilization.

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“…Yet, certain attributes of MAOM could make it a substantial N source. MAOM is enriched in low- Single average molecular-weight plant compounds (Haddix et al 2016) and microbial byproducts (Schmidt et al 2011;Miltner et al 2012;Kopittke et al 2017). MAOM thus possesses a low C/N ratio (Sollins et al 2006), which generally promotes N mineralization (Sollins et al 1984;Whalen et al 2000); this is in contrast to POM, which often has a relatively high C/N ratio and thus, early in its decomposition, acts as a sink for N (Whalen et al 2000;Luce et al 2011;Fornara et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Minerals in the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes

et al. 2018

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Despite decades of research progress, ecologists are still debating which pools and fluxes provide nitrogen (N) to plants and soil microbes across different ecosystems. Depolymerization of soil organic N is recognized as the rate-limiting step in the production of bioavailable N, and it is generally assumed that detrital N is the main source. However, in many mineral soils, detrital polymers constitute a minor fraction of total soil organic N. The majority of organic N is associated with clay-sized particles where physicochemical interactions may limit the accessibility of N-containing compounds. Although mineralassociated organic matter (MAOM) has historically been considered a critical, but relatively passive, reservoir of soil N, a growing body of research now points to the dynamic nature of mineral-organic associations and their potential for destabilization. Here we synthesize evidence from biogeoscience and soil ecology to demonstrate how MAOM is an important, yet overlooked, mediator of bioavailable N, especially in the rhizosphere. We highlight several biochemical strategies that enable plants and microbes /doi.org/10.1007/s10533-018-0459-5 to disrupt mineral-organic interactions and access MAOM. In particular, root-deposited low-molecularweight exudates may enhance the mobilization and solubilization of MAOM, increasing its bioavailability. However, the competitive balance between the possible fates of N monomers-bound to mineral surfaces versus dissolved and available for assimilation-will depend on the specific interaction between mineral properties, soil solution, mineral-bound organic matter, and microbes. Building off our emerging understanding of MAOM as a source of bioavailable N, we propose a revision of the Schimel and Bennett (Ecology 85:591-602, 2004) model (which emphasizes N depolymerization), by incorporating MAOM as a potential proximal mediator of bioavailable N.123 Biogeochemistry (2018) 139:103-122 https:/

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Nitrogen‐rich microbial products provide new organo‐mineral associations for the stabilization of soil organic matter

Cited by 148 publications

References 44 publications

Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates

Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates

The multilayer model of soil mineral–organic interfaces—a review

Minerals in the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes

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