Nitrogen availability alters rhizosphere processes mediating soil organic matter mineralisation

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Background and aims: 

The intrinsic nitrogen (N) supply capacity of soil is central to understanding the productivity of natural plant communities, and essential in the context of determining optimal fertilization rates for agricultural soils. However, it is largely unknown how nutrient availability affects plant mediated priming effects driving soil organic matter mineralisation and associated N-fluxes. 


We applied continuous, steady-state 13C–CO2 labelling to Lolium perenne grown in high and low productivity grassland soils to allow quantification of SOM- and root-derived soil CO2 efflux. Nutrient treatments (N, P and K) were applied as repeated additions to soils, and impacts on source partitioned soil CO2 efflux were assessed relative to unamended planted and fallow soils. Plants were clipped to uniform height at weekly intervals. 


Increasing nutrient availability in both soils resulted in a reduction in plant-mediated SOM mineralisation and clipping of plants greatly lowered root-derived respiration but increased SOM mineralisation. Nutrient addition to fallow systems had no effect on SOM mineralisation in either soil. Plant growth stimulated SOM priming, concurrent mobilisation of N from SOM and subsequent plant N uptake in the high productivity soil. Priming was not observed in the low productivity soil due to its greater inherent organic matter stability, resulting in lowered plant-mediated and basal SOM mineralisation. 


That addition of nutrients reduced SOM mineralisation in planted systems but had no effect in fallow systems is indicative of nutrient availability specifically altering plant-mediated priming of SOM mineralisation. We suggest that plant-soil interactions mediating priming effects are an important determinant of productivity and that the magnitudes of these effects are modified by nutrient availability and soil-specific controls.

Original languageEnglish
Pages (from-to)499-510
Number of pages12
JournalPlant and Soil
Issue number1-2
Early online date16 May 2017
Publication statusPublished - Aug 2017

Bibliographical note

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 gratefully acknowledge Allan Sim, Maureen Procee, Yvonne Cook, Noeleen McDonald and Chris Maddock for skilled technical support and soil collection.


  • Defoliation
  • Nitrogen fertiliser
  • Nutrient cycling
  • Plant productivity
  • Plant-soil-microbe interactions
  • Priming
  • Rhizodeposition
  • Soil organic matter


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