Witter, Ernst
- Department of Soil Sciences, Swedish University of Agricultural Sciences
Abstract
The robustness of the assumption of equilibrium between native and added N during N-15 isotope dilution has recently been questioned by Watson et al. (Soil Biol Biochem 32 (2000) 2019-2030). We re-analyzed their raw data using equations that consider the added and native NH4+ and NO3- pools as separate state variables. Gross mineralization rates and first-order rate constants for NH4+ and NO3- consumption were obtained by combining analytical integration of the differential equations with a non-linear fitting procedure. The first-order rate constants for NH4+ consumption and NO3- immobilization for the added NH4+ and NO3- pool were used to estimate gross mineralization rates and first-order rate constants for nitrification of native NH4+. The latter were 2-4 times lower than the first-order rate constants derived from the added N pool. This discrepancy between first-order rate constants for nitrification implies that one or more process rates estimated for the added N pools cannot be applied to the native N pools. Preferential use of the added N resulted in an overestimation of the gross mineralization by 1.5-2.5-fold, emphasizing the need for critical evaluation of the assumption of equilibrium before gross mineralization rates are calculated. (C) 2004 Elsevier Ltd. All rights reserved.
Keywords
N-15 isotope dilution technique; gross mineralization; preferential use; dynamic compartmental model
Published in
Soil Biology and Biochemistry
2005, volume: 37, number: 1, pages: 183-186
Publisher: Elsevier
SLU Authors
Kätterer, Thomas
- Department of Soil Sciences, Swedish University of Agricultural Sciences
- Department of Soil Sciences, Swedish University of Agricultural Sciences
UKÄ Subject classification
Agricultural Science
Soil Science
Publication identifier
- DOI: https://doi.org/10.1016/j.soilbio.2004.06.008
Permanent link to this page (URI)
https://res.slu.se/id/publ/5483