Rhizosphere priming can promote mobilisation of N-rich compounds from soil organic matter

Conor J. Murphy*, Elizabeth M. Baggs, Nicholas Morley, David P. Wall, Eric Paterson

*Corresponding author for this work

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Soil organic matter (SOM) is the dominant store of nutrients required for plant growth, but the availability of these nutrients is dependent on transformations mediated by the microbial biomass. The addition of labile C to soil is known to alter SOM turnover (priming effect, PE), but understanding of this is limited, particularly with respect to impact on gross nitrogen (N) fluxes. Here we examined relationships between C and N fluxes from SOM under primed and non-primed conditions in two soils. Stable isotopes (13C and 15N) were used to measure gross C and N fluxes from SOM and to differentiate between SOM mineralised due to priming and that from basal mineralisation. 13C-glucose was added daily to simulate the effect of addition of labile C on SOM-C and -N mineralisation within the rhizosphere. Addition of glucose increased both gross N and C mineralisation from SOM. However, the C-to-N ratio of the mineralised flux from 'primed' SOM was 5:1, whereas the C-to-N ratio of the basal mineralised flux was 20:1 indicating that priming acted on specific organic matter pools. This result is consistent with the concept that priming is a distinct N-mining response of the microbial biomass, as opposed to an acceleration of the basal flux. Our data suggest that C and N fluxes are not directly linked through their gross stoichiometry in SOM. This is due to the heterogeneity and overall passiveness of OM relative to the dynamic nature of mineralisation fluxes and source pools, and in primed systems the mineralisation of N-rich compounds.

Original languageEnglish
Pages (from-to)236-243
Number of pages8
JournalSoil Biology and Biochemistry
Volume81
Early online date8 Dec 2014
DOIs
Publication statusPublished - 1 Feb 2015

Fingerprint

Rhizosphere
mobilization
soil organic matter
rhizosphere
Soil
mineralization
microbial biomass
glucose
Biomass
nutrient
nutrient reserves
biomass
Glucose
Food
stoichiometry
nutrient availability
turnover
stable isotopes
stable isotope
Isotopes

Keywords

  • Gross N mineralisation
  • Nutrient cycling
  • Priming
  • Rhizodeposition
  • Soil organic matter
  • Soil-microbe interactions

ASJC Scopus subject areas

  • Microbiology
  • Soil Science

Cite this

Rhizosphere priming can promote mobilisation of N-rich compounds from soil organic matter. / Murphy, Conor J.; Baggs, Elizabeth M.; Morley, Nicholas; Wall, David P.; Paterson, Eric.

In: Soil Biology and Biochemistry, Vol. 81, 01.02.2015, p. 236-243.

Research output: Contribution to journalArticle

Murphy, Conor J. ; Baggs, Elizabeth M. ; Morley, Nicholas ; Wall, David P. ; Paterson, Eric. / Rhizosphere priming can promote mobilisation of N-rich compounds from soil organic matter. In: Soil Biology and Biochemistry. 2015 ; Vol. 81. pp. 236-243.
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abstract = "Soil organic matter (SOM) is the dominant store of nutrients required for plant growth, but the availability of these nutrients is dependent on transformations mediated by the microbial biomass. The addition of labile C to soil is known to alter SOM turnover (priming effect, PE), but understanding of this is limited, particularly with respect to impact on gross nitrogen (N) fluxes. Here we examined relationships between C and N fluxes from SOM under primed and non-primed conditions in two soils. Stable isotopes (13C and 15N) were used to measure gross C and N fluxes from SOM and to differentiate between SOM mineralised due to priming and that from basal mineralisation. 13C-glucose was added daily to simulate the effect of addition of labile C on SOM-C and -N mineralisation within the rhizosphere. Addition of glucose increased both gross N and C mineralisation from SOM. However, the C-to-N ratio of the mineralised flux from 'primed' SOM was 5:1, whereas the C-to-N ratio of the basal mineralised flux was 20:1 indicating that priming acted on specific organic matter pools. This result is consistent with the concept that priming is a distinct N-mining response of the microbial biomass, as opposed to an acceleration of the basal flux. Our data suggest that C and N fluxes are not directly linked through their gross stoichiometry in SOM. This is due to the heterogeneity and overall passiveness of OM relative to the dynamic nature of mineralisation fluxes and source pools, and in primed systems the mineralisation of N-rich compounds.",
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N1 - Acknowledgements We acknowledge the Teagasc Walsh Fellowship Programme for PhD funding and the financial support provided by the Rural & Environmental Science & Analytical Services (RESAS) of the Scottish Government. We thank Allan Sim, Vicky Munro, Maureen Procee, Yvonne Cook, Noeleen McDonald and Chris Maddock for skilled technical support and soil collection. Finally we thank an anonymous reviewer for their comments on an earlier version of this paper.

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N2 - Soil organic matter (SOM) is the dominant store of nutrients required for plant growth, but the availability of these nutrients is dependent on transformations mediated by the microbial biomass. The addition of labile C to soil is known to alter SOM turnover (priming effect, PE), but understanding of this is limited, particularly with respect to impact on gross nitrogen (N) fluxes. Here we examined relationships between C and N fluxes from SOM under primed and non-primed conditions in two soils. Stable isotopes (13C and 15N) were used to measure gross C and N fluxes from SOM and to differentiate between SOM mineralised due to priming and that from basal mineralisation. 13C-glucose was added daily to simulate the effect of addition of labile C on SOM-C and -N mineralisation within the rhizosphere. Addition of glucose increased both gross N and C mineralisation from SOM. However, the C-to-N ratio of the mineralised flux from 'primed' SOM was 5:1, whereas the C-to-N ratio of the basal mineralised flux was 20:1 indicating that priming acted on specific organic matter pools. This result is consistent with the concept that priming is a distinct N-mining response of the microbial biomass, as opposed to an acceleration of the basal flux. Our data suggest that C and N fluxes are not directly linked through their gross stoichiometry in SOM. This is due to the heterogeneity and overall passiveness of OM relative to the dynamic nature of mineralisation fluxes and source pools, and in primed systems the mineralisation of N-rich compounds.

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