WP 2-1 Agronomic effectiveness of P resources
TUM (PI: Urs Schmidhalter and Sabine von Tucher) and
University of Rostock (PI: Bettina Eichler-Löbermann, responsible processor: Theresa Zicker)

At plot up to farm field scale, this WP applies chemical, biological and optical sensing
techniques to achieve in-depth knowledge of P fertilizer use efficiency of different field crops
and to further evaluate soil management options for sustainable P supply. Innovative
proximal and remote sensing high-throughput technologies will be applied and adapted to
collect site-specific information on P dependent biomass production and P uptake. The aim
is to understand the reasons for differences in the agronomic response of crops to P fertilizer
application under variable field conditions by the compilation of both soil P turnover
processes and site related crop growth parameters. Results will be utilized for modelling to
develop improved P fertilizer recommendations.

As a basis, on-farm P fertilizer experiments are established over Bavaria covering
representative German soil-climate-regions. In addition, the studies further include the
multifactorial long-term field experiments in Rostock and Freising where P is supplied by
different organic and inorganic sources under diverse management practices.

The overall aims are A) to create a scientific basis for a refinement of P fertilizer
recommendations, B) to reduce the input of mineral fertilizer P to soils by applying recycling
products, C) to reduce soil P levels where possible, and D) to reduce the environmental risks
by P losses.

The project will also contribute to maintain the on-going, long-term P-fertilizer experiments
(at Rostock and Freising), and will encourage the host institutions of other long-term field
experiments to continue their labor-intensive field trials through shared soil sampling for
joint P studies and publications.
WP 2-2 Smart P-Fertilizers
Julius Kühn Institute (PI: Kerstin Panten)
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Specific objectives of this work package are the comparison of fertilizing effects of novel inorganic P recycling products (e.g. bone char, surface modified bone char, struvite, sewage sludge ash) in pot and long-term field experiments. Two newly established field experiments on different soils and with different soil management practices will be investigated to gain first insights into the fertilizing potential of such inorganic P resources during crop rotations. Chemical and biological analytical techniques will be used for the evaluation of the agronomic efficiency of P recycling fertilizers. Therefore, research conducted will contribute to close the P nutrient cycle, to maintain soil fertility and establish farming practices for newly developed fertilizers. Thus, it will extend existing fertilizer recommendations taking into account the characteristics of inorganic secondary P fertilizers.

WP 2-3 Metastudies P fertilization effects
University of Rostock (PI: Uwe Buczko, responsible processor: Michael van Laak)

Field experiments, along with literature and still unpublished (or “grey literature”) data on P fertilizer effects will be statistically evaluated in meta-analyses to strengthen the underlying, scientific basis for P fertilizer recommendations. The objective is to developnovel tools for P fertilizer recommendations by A) re-evaluations of the crop yield effects obtained with the traditional recommendation scheme on the basis of extended data mining, B) involving all relevant site and soil parameters (physical, chemical, microbial), and C) achieve an increased P utilization efficiency in agricultural practice.


WP 2-4 Redox experiments using biogeochemical microcosms
BUW (PI: Jörg Rinklebe) and
University of Rostock (resonsible processor: Karen Baumann)

The overall objective of this work package is to improve the general understanding of the geochemical behavior and availability of P under dynamic redox conditions in various arable soils in Northern Germany under conventional management. The aims are to investigate i) the impact of redox driven processes on different P-compounds, availability, and mobilization dynamics of P in top and subsurface samples of different soils, ii) the impact of equilibrium time and duration of flooding within the same redox window (oxic and anoxic) on the release kinetics of P and PO43- from soil to solution, and iii) the impact of the directions of systematic changes of redox potential (from anoxic to oxic and from oxic to anoxic) on speciation, availability, and mobilization of P in soil. Thereby, a combination of geochemical and spectroscopic approaches will be exploited to elucidate and determine the fundamental mechanisms that control the mobilization of P in water-soil systems of different arable soils under conventional agricultural land use.