WP 1-1 P-Fixation by Al- and Fe-oxides
Brandenburg University of Technology (PI: Dirk Freese, responsible processor: Stella Gypser)

P in soil, which is immobilized e. g. by specific sorption or precipitation/complexation can be mobilized by organic matter. To increase availability of sorbed P specifically, key processes of P sorption and desorption on reactive surfaces of soil colloids have to be identified. Additionally, soil microbes will be analyzed to evaluate their potential to promote targeted P mobilization in soil.



WP 1-2 Quantum-chemical modelling of P at soil matrix
University of Rostock (PI: Oliver Kühn, responsible processor: Ashour Ahmed)

Theoretical tools will be developed and applied for the characterization of the sorption and desorption processes of P on rather contrasting mineral surfaces under the influence of low-molecular weight organic molecules. In close collaboration with the experiments in WP 1-1 the following questions will be addressed: Q1: What is the optimal quantum-chemical strategy to describe P-related processes at mineral surfaces? Q2: What are binding motifs and energies of different phosphates at mineral surfaces in the presence of water? Q3: How does the presence of organic compounds influence the surface reactions of P?
WP 1-3 Microbial P aquisition processes
TUM (PI: Michael Schloter, contact person: Martin Grafe) and
University of Rostock (PI: Christel Baum, responsible processor: Manuela Görs)

Soil microorganisms are deeply involved in P turnover, temporal P storage and transport of P from soil into the plant. Thus, an efficient P management requires knowledge on soil microbial communities, their functional redundancy and the induction of important functional traits. Metagenomic studies will be used to reconstruct the microbial P cycle to disclose the role of microorganisms in P turnover and analyses of the mycorrhizal community structure will be used to clarify the leading P transfer structures under different P supply levels in soil. Since microorganisms can act as major drivers for P transformation, some of these key players will be isolated to improve existing microbial inocula for plant growth promotion by P mobilization. Additionally, studies will be carried out on the level of metatranscriptomes to understand how the potential traits of the soil microflora related to P turnover will be induced or repressed by different management practices. In this respect mainly the questions related to interactions between P and N turnover and their response to changed carbon inputs into the soil will be evaluated. Metagenomic analyses will be done by the group of M. Schloter (TUM); the lab of C. Baum (UoR) will analyze the mycorrhizal community structure and isolate efficient P-mobilizing rhizobacteria and evaluate their potential as new inocula.

WP 1-4 Spatial heterogeneity of P in subsoil
Forschungszentrum Jülich (PI: Nina Siebers, responsible processor: Maximilian Koch)

The objective is to identify the subsoil P status and speciation for the main soil types across Germany according to the Bodenkundliche Kartieranleitung. Different forms of aged P in soil (organically, inorganically bound, fixed to minerals, enclosed in aggregates) will be analyzed and related to the P uptake and use efficiency of plants. This information is then used to develop a reliable and robust soil test for the P acquisition by plants from soil and soil amendments on the basis of the diffuse gradient in thin films method as calibrated via 33P isotope measurements.