Das Projekt "Use of enzyme additions to characterize the nature and bioavailability of soil organic P" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Agrarwissenschaften, Pflanzenernährung durchgeführt. Short summary This project aims to further develop enzyme addition methods to characterize the nature and bioavailability of soil organic P. In combination with 31P nuclear magnetic resonance and isotopic dilution methods, factors regulating the availability of substrates for hydrolysis and P cycling are elucidated. Background The nature and bioavailability of soil organic P is not well understood, largely because of methodological limitations. Concepts and models of biogeochemical P cycling are lagging behind those of carbon and nitrogen cycling. In particular, the effects of inorganic P availability on biologically mediated P cycling and the interactions of P and carbon dynamics need clarification. In this project, new approaches to study enzymatic processes in soil P cycling will be further developed. Enzyme additions will be used to elucidate the factors regulating the availability of substrates for hydrolysis. In combination with 31P nuclear magnetic resonance (NMR) techniques, this will improve the characterization of soil organic P. In a case study on the effect of inorganic P availability on P cycling, we will use enzyme additions and NMR in combination with isotopic dilution methods using 33P labeling to measure gross P fluxes. The project will be carried out in collaboration with Dr. Ronald Smernik, University of Adelaide, Australia. National collaborators include Dr. Olivier Huguenin-Elie and Dr. Bernard Jeangros at the Agricultural Research Stations ART Reckenholz and ACW Changins. Aims The main objective is to develop methods that will contribute to a better understanding of the nature, bioavailability and cycling of organic P in soils. Enzyme additions methods will be improved and combined with solution 31P NMR spectroscopy and isotopic dilution methods to measure gross P fluxes to reveal the processes and intensity of P cycling in soils. Importance Newly developed methods and novel combinations will be used to address fundamental gaps of understanding in soil P dynamics. This knowledge is a prerequisite to increase the use of soil organic P, e.g. by selection of microbial or plant traits and by genetic modification. Since organic P is also a key component in losses of P to aquatic systems, the results will contribute to an environmentally friendly and sustainable management of P as a finite resource.