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This article in SSSAJ

  1. Vol. 68 No. 5, p. 1610-1615
    Received: Nov 10, 2003

    * Corresponding author(s): Christoph.Mueller@bot2.bio.uni-giessen.de


Soil Respiratory Quotient Determined via Barometric Process Separation Combined with Nitrogen-15 Labeling

  1. Christoph Müller *a,
  2. M. Kaleem Abbasia,
  3. Claudia Kammanna,
  4. Tim J. Cloughb,
  5. Robert R. Sherlockb,
  6. R. James Stevensc and
  7. Hans-Jürgen Jägera
  1. a Dep. of Plant Ecology, Univ. of Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
    b Soil, Plant and Ecological Sciences Division, Soil and Physical Sciences Group, P.O. Box 84, Lincoln Univ., Canterbury, New Zealand
    c Agriculture, Food and Environmental Science Division, The Dep. of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK


The barometric process separation (BaPS) and 15N dilution techniques were used to determine gross nitrification rates on the same soil cores from an old grassland soil. The BaPS-technique separates the O2 consumption into that from nitrification and that from soil organic matter (SOM) respiration. The most sensitive parameter for the calculations via the BaPS technique is the respiratory quotient (RQ = ΔCO2/ΔO2) for SOM turnover (RQSOM). Combining both methods (BaPS–15N) allowed the determination of the RQSOM The RQ value determined in such a way is adjusted for the influence of nitrification and denitrification, which are both characterized by totally different RQ values. The results for the grassland soil showed that 6 to 10% of O2 was consumed by nitrification when incubated at 20°C and 0.49 g H2O g−1 soil. A set of BaPS measurements with the same soil at various temperature and moisture contents showed that up to 49% of the total O2 consumption was due to nitrification. The calculated RQSOM values via the BaPS–15N technique presented here are more closely associated with the overall SOM turnover than the usual net RQ reported in the literature. Furthermore, the RQSOM value provides an overall indication of the decomposability and chemical characteristics of the respired organic material. Hence, it has the potential to serve as a single state index for SOM quality and therefore be a useful index for SOM turnover models based on substrate quality.

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Copyright © 2004. Soil Science SocietySoil Science Society of America