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Gross phosphorus fluxes in a calcareous soil inoculated with Pseudomonas protegens CHA0 revealed by 33P isotopic dilution

Meyer, Gregor; Bünemann-König, Else; Frossard, Emmanuel; Maurhofer, Monika; Mäder, Paul and Oberson, Astrid (2017) Gross phosphorus fluxes in a calcareous soil inoculated with Pseudomonas protegens CHA0 revealed by 33P isotopic dilution. Soil Biology & Biochemistry, 104, pp. 81-94.

[thumbnail of Meyer et al 2017.pdf] PDF - Published Version - English
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Document available online at: http://www.sciencedirect.com/science/article/pii/S0038071716303261


Inoculation with phosphorus (P) solubilizing bacteria is being proposed to increase P availability for plants by mineralization and solubilization of non-available soil and fertilizer P. Solubilization of inorganic P compounds by bacterial strains has repeatedly been shown on agar plates and in liquid media. However, the effects of inoculation on P availability to plants growing in soils, either in pot or field studies, are inconsistent and do not allow to separate between direct effects on P availability and indirect effects such as improved plant health. This differentiation could be achieved using 33P isotopic labeling. We applied the 33P isotopic dilution method in a pot and in an incubation experiment to study gross P fluxes in a calcareous soil inoculated with the P solubilizing bacteria Pseudomonas protegens CHA0. We hypothesized that the inoculant dilutes the specific activity (33P/31P) in the soil solution or in the plant shoots because of P solubilization beyond the P mobilization by the endogenous microbial biomass. To this end, we conducted a plant growth experiment with Lolium multiflorum var. Gemini and an incubation experiment. In both experiments, the soil was amended or not with a calcium P rich sewage sludge ash, and both treatments were conducted with and without inoculation. The inoculant was able to solubilize P from sewage sludge ash under controlled conditions in liquid media. However, it did not enhance P release from soil or from sewage sludge ash in the incubated soil. Inoculation of the soil reduced organic P mineralization by the soil microbial biomass, which was supported by a simultaneous decrease in soil respiration. Thus, any inorganic P solubilized by the inoculant might have been offset by less basal organic P mineralization. Increased P uptake of inoculated Lolium multiflorum at first harvest was attributed to an indirect effect, since the specific activity in shoots of inoculated Lolium multiflorum was not decreased. Although sewage sludge ash contained very little water-soluble P, an increase in P availability following sewage sludge ash addition could be shown using 33P isotopic dilution, while biological processes remained unchanged. While in this study, the inoculant did not increase P availability, the approach presented here can give insight into the mechanisms underlying beneficial effects of inoculants.

EPrint Type:Journal paper
Keywords:Calcareous soil, Phosphorus, Isotopic dilution, Microbial, mobilization, Phosphorus solubilizing bacteria, Recycling fertilizer, Department of Soil Sciences
Subjects: Crop husbandry > Composting and manuring
Research affiliation: European Union > CORE Organic II > IMPROVE-P
Switzerland > ETHZ - Agrarwissenschaften
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil
Horizon Europe or H2020 Grant Agreement Number:249667
Deposited By: Meyer, Gregor
ID Code:30745
Deposited On:07 Dec 2016 11:25
Last Modified:19 May 2021 11:29
Document Language:English
Refereed:Peer-reviewed and accepted

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