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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 1 | Copyright
Biogeosciences, 15, 105-114, 2018
https://doi.org/10.5194/bg-15-105-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 Jan 2018

Research article | 08 Jan 2018

Soil solution phosphorus turnover: derivation, interpretation, and insights from a global compilation of isotope exchange kinetic studies

Julian Helfenstein1, Jannes Jegminat2, Timothy I. McLaren1, and Emmanuel Frossard1 Julian Helfenstein et al.
  • 1Institute of Agricultural Sciences, ETH Zurich, Lindau, 8315, Switzerland
  • 2Institute of Neuroinformatics, University of Zurich and ETH Zurich, Zurich, 8057, Switzerland

Abstract. The exchange rate of inorganic phosphorus (P) between the soil solution and solid phase, also known as soil solution P turnover, is essential for describing the kinetics of bioavailable P. While soil solution P turnover (Km) can be determined by tracing radioisotopes in a soil–solution system, few studies have done so. We believe that this is due to a lack of understanding on how to derive Km from isotopic exchange kinetic (IEK) experiments, a common form of radioisotope dilution study. Here, we provide a derivation of calculating Km using parameters obtained from IEK experiments. We then calculated Km for 217 soils from published IEK experiments in terrestrial ecosystems, and also that of 18 long-term P fertilizer field experiments. Analysis of the global compilation data set revealed a negative relationship between concentrations of soil solution P and Km. Furthermore, Km buffered isotopically exchangeable P in soils with low concentrations of soil solution P. This finding was supported by an analysis of long-term P fertilizer field experiments, which revealed a negative relationship between Km and phosphate-buffering capacity. Our study highlights the importance of calculating Km for understanding the kinetics of P between the soil solid and solution phases where it is bioavailable. We argue that our derivation can also be used to calculate soil solution turnover of other environmentally relevant and strongly sorbing elements that can be traced with radioisotopes, such as zinc, cadmium, nickel, arsenic, and uranium.

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Soil solution phosphorus (P) turnover is essential for describing the bioavailability of this important nutrient. Here, we provide a derivation of calculating soil solution P turnover using parameters obtained from isotope exchange kinetic experiments. We then calculated and analyzed soil solution P turnover for 217 soils and for 18 long-term P fertilizer field experiments worldwide. Our study thus provides important insights on P dynamics in soils.
Soil solution phosphorus (P) turnover is essential for describing the bioavailability of this...
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