PHOSCYCLE: Turnover of organic phosphorus in soils

Phosphorus (P) is a macronutrient whose availability strongly affects many processes in terrestrial ecosystems. It is recycled through organic P (OP) decomposition, resulting in the generation of inorganic P available for plant uptake. Despite the importance of this process for P cycling and other related biogeochemical cycles, our understanding of OP decomposition is to date very poor, largely due to the lack of methods to determine the decomposition and turnover of OP in soils.

In PHOSCYCLE, a novel approach will be developed to study the decomposition and turnover of OP in soils. Marie Spohn, the project’s leader, will lead her team to develop compound-specific isotope methods to analyze the isotope signature of carbon (C) in OP compounds.

This will enable us to determine for the first time the isotope signature of all important phosphomono- and diesters present in soils. We will utilize these new methods that make use of different C isotopes to quantify the decomposition rate and turnover time of OP compounds in comparison to the soil total organic C pool and non-phosphorylated organic compounds in soils on three continents under various forms of land use, says Marie Spohn.

In addition, the project will establish how OP quality and soil minerals affect the sorption and persistence of OP in soils.

Finally, we will model the turnover of the soil total OP pool as well as the cycling of P between soil and plants in a large range of ecosystems, revealing how soil OP turnover affects P cycling in these ecosystems.

Besides leading to a step-change in the way we study and understand the P cycle in terrestrial ecosystems, PHOSCYCLE will also provide a new starting point for our comprehension of soil organic matter dynamics and interactions between element cycles in terrestrial ecosystems.