WP3: Agronomic strategies and effects of plant growth promoting rhizobacteria

The complete title of WP3 is: Improved P mobilization by adapted agronomic strategies and addition of P mobilizing Plant Growth Promoting Rhizobacteria
WP-leader: Paul Mäder (FiBL-CH), Deputy: Jakob Magid (Univ. Copenhagen)

Only a minor proportion of the organic and mineral P in soils and fertilizers is immediately plant available. Nevertheless, large P fractions are potentially plant available as they can be mobilized by biotic and/or abiotic/chemical transformations. The overall aim of WP3 is to identify cultivars and crops with a high capability of mobilizing and taking-up P and to test P-mobilizing plant growth promoting rhizobacteria (PGPRs) and other organisms which can improve P efficiency of organic cropping systems that use alternative fertilizers. The objectives in detail are as follows:

1. To assess the potential of adapted cultivars of spring wheat and potatoes growing under P limiting conditions.

2. To quantify the capacity of different major crops such as L. multiflorum, T. pratense, T. aestivum and F. esculentum to take up P from scarcely available P in the soil, with or without the application of PGPRs.

3. To identify site-adapted cropping sequences using cover crops with high P mobilization potential that can enhance P uptake by subsequent crops from soil and P amendments and help reducing P losses to the environment.

4. To test PGPRs for their potential to mobilize P from APF as identified in WP2, by measuring the effects of their application on plant growth and nutrient uptake.

WP 3 comprises four different tasks as described in the following:

Task 3-1: Experiments with spring wheat cultivars with contrasting root traits, and potato cultivars with contrasting efficiency traits (Univ. Copenhagen, Univ. Newcastle)

P-efficient cultivars of spring wheat and potatoes will be tested in two different growing environments (Denmark and northern England) in long-term trials with gradients of P availability. UCPH has long term experiments in which treatments with largely varying P levels have been reached. Cultivar experiments will be laid out in treatments with moderately low P levels.

For more details please consult: Leo Rempelos and/or Yaosheng Wang.

Task 3-2: Cover-crops for P mobilization (BOKU, ETHZ)

Model cover crops like buckwheat with known capability to mobilize P from sparingly soluble P fractions will be grown and incorporated as green manure prior to cultivation of a main crop with low P mobilization efficiency. Mimicking cropping sequences in pot trials will allow for selection of compatible combinations of soils, cover crops and subsequent main crop.

For more details please consult Jürgen Friedel.

Task 3-3: Influence of Plant Growth Promoting Rhizobacteria on plant P availability in pot/greenhouse experiments using radioisotope labeling

Task 3.3 will be closely linked to the EU FP 7 project BIOFECTOR for mining multiple synergies. Soils will be supplemented with suited PGPR strains (according to results from BIOFECTOR-project). In some experiments, to calculate P uptake from soil reserves, available soil P will be labeled with ³³P according to Oberson et al. (2010). Using isotopic dilution principles, any P mobilizing effect of PGPRs on soil or fertilizer P otherwise not plant available can also be detected.

For more details on pot trials with isotopic labelling please contact Gregor Meyer and/or Astrid Oberson.

For more details on pot and field trials about the effects of PGPRs and their interaction with alternative P fertilizers please contact Iris (Minze) Wollmann.

Task 3-4: Plant Growth Promoting Rhizobacteria tested in combination with alternative P fertilizers in field experiments

Various mineral (e.g. rock phosphate, toxic elements depleted ashes or precipitation products of sewage sludge) and organic (e.g.municipal waste compost) P fertilizers will be tested in P deficient soils in field experiments with and without the use of PGPRs. Maize and red clover will be used as model plants.

For more details on the experiments carried out in Hohenheim please contact Iris (Minze) Wollmann. For more details for the experiments carried out in Switzerland please contact contact Gregor Meyer and/or Sarah Symanczik.