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Front. Environ. Sci. | doi: 10.3389/fenvs.2019.00185

Nitrogen and phosphorus additions alter the abundance of phosphorus- solubilizing bacteria and phosphatase activity in grassland soils

  • 1University of Bayreuth, Germany
  • 2Iowa State University, United States
  • 3University of Minnesota Twin Cities, United States
  • 4Imperial College London, United Kingdom
  • 5University of KwaZulu-Natal, South Africa

Microorganisms mobilize phosphorus (P) in soil by solubilizing bound inorganic P from soil minerals and by mineralizing organic P via phosphatase enzymes. Nitrogen (N) inputs are predicted to increase through human activities and shift plants to be more P limited, increasing the importance of P mobilization processes for plant nutrition. We studied how the relative abundance of P-solubilizing bacteria (PSB), PSB community composition, and phosphatase activity respond to N and P addition (+N, +P, +NP) in grassland soils spanning large biogeographic gradients. The studied soils are located in South Africa, USA, and UK and part of a globally coordinated nutrient addition experiment. We show that the abundance of PSB in the topsoil was reduced by 18 % in the N and by 41 % in the NP treatment compared to the control. In contrast, phosphatase activity was significantly higher in the N treatment than in the control across all soils. Soil C:P ratio, sand content, pH, and water-extractable P together explained 71 % of the variance of the abundance of PSB across all study sites and all treatments. Further, the community of PSB in the N and NP addition treatment differed significantly from the control. Taken together, this study shows that N addition reduced the relative abundance of PSB, altered the PSB community, and increased phosphatase activity, whereas P addition had no impact. Increasing atmospheric N deposition may therefore increase mineralization of organic P and decrease solubilization of bound inorganic P, possibly changing P mobilization processes in grassland soils. Consequently, in ecosystems in which plant P nutrition depends on bound inorganic P, increased N inputs might diminish P supply and thus aggravate P limitation and constrain plant productivity.

Keywords: enzyme activity, nitrogen fertilization, Nutrient Network (NutNet), phosphate solubilization, phosphorus cycling, Phosphorus mineralization, Phosphorus mobilization

Received: 02 Aug 2019; Accepted: 05 Nov 2019.

Copyright: © 2019 Widdig, Schleuss, Weig, Guhr, Biederman, Borer, Crawley, Kirkman, Seabloom, Wragg and Spohn. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Marie Spohn, University of Bayreuth, Bayreuth, 95447, Bavaria, Germany, marie.spohn@uni-bayreuth.de