Research student profile: Mirja Guldner

Project title

Enhancing Phosphorus and Sulfur Nutrition with Rhizosphere Microorganisms

Project overview

Plant growth promoting rhizosphere organisms (PGPR) contribute to plant nutrition via biological nitrogen fixation, the production of plant growth promoting hormones and solubilisation of other nutrients, such as Phosphorus (P) and Sulfur (S).
For wheat, continuous field experiments have shown that N-fertiliser input can be reduced substantially when using the right combination between wheat genotype and inoculant (Azospirillum brasilense). Because plant growth depends on a balanced supply of nutrients, further research needs to be done to gain a better understanding about the effects of inoculation on overall rhizosphere microbial community and nutrient mobilisation.

In agricultural soils P and S are often either precipitated or bound in organic forms, unavailable to the plant. In order to use the biological potential of PGPR to enhance plant nutrition in the context of an integrated fertiliser management system, more knowledge about the interactions between Nitrogen-fixing microorganisms and microorganisms, responsible for cycling of other major nutrients, such as Phosphorus and Sulfur is needed.

To obtain information, which can be applied to practical agriculture, I`m investigating the effects of microbial inoculants and wheat genotypes, under different N-fertiliser managements in field experiments at the PBI in Narrabri and in Cobbitty. The field studies are backed up with in-vitro and pot experiments, where the interactions of plants and PGPR can be tested in a controlled environment. The abundance and expression of rhizosphere functional genes for nutrient mobilization and their effects on plant growth will be investigated, using molecular fingerprinting methods, such as Denaturing Gradient Gel Electrophoresis (DGGE) and Terminal Restriction Fragment Length Polymorphism (TRFPL).

Further knowledge about the interactions of microorganisms regarding N-fixation and solubilisation of Phosphorus and Sulfur will help to make more accurate predictions for an integrated fertiliser management system by defining optimized genotype x inoculum interactions. The outcomes of this project contribute to make fertiliser input more efficient, and thus increase profit margins and reduce negative impacts on environment.


I lived and studied in Germany and am living in Australia since 2009. I studied at the University of Hohenheim and have a German postgraduate degree in Agricultural Engineering, specialisation in Plant sciences (honors). After my studies I completed a Traineeship at the Ministry of Food, Rural Regions and Agriculture of Baden-Wuerttemberg, including the implementation of the agricultural law and politics of the European Union, financial consulting of farmers; agricultural administration and teaching. After completion I worked as agricultural consultant, responsible for the implementation of the EU-law about certification in Organic Farming.

I`m holder of the Australian Postgraduate Award (APA), and receive the Top-up scholarship of the Grains Research and Development corporation (GRDC).

I have received the “Herzog-Carl-Stipendium” (postgraduate award) for conduction of a field experiment in Sao Paulo, Brazil.

I participated at the 'Socrates Intensive Program' in Vienna (Academic Program of the European Union) 'ELLS Summer University 2004'.
Also presented a poster: 'Release of foliar-applied glyphosate into the rhizosphere and its possible effect on non target organisms' at the 'International Congress Rhizosphere and challenges, A tribute to Lorenz Hiltner' in Munich in September 2004.


  • Guldner, M., Yamada, T., Eker, S., Cakmak, I., Özturk, L., Kania, A., Weißhaar, C., Ye, F., Neumann, G., and Römheld, V. (2005): Release of foliar-applied glyphosate into the rhizosphere and its possible effects on non-target organisms. In: Hartmann A, Schmid M, Wenzel W, Hinsinger P, eds, Rhizosphere 2004: A Tribute to Lorenz Hiltner. GSF-Report, Munich, Neuherberg,Germany, pp. 220.
  • Römheld, V., Guldner, M., Yamada, T., Özturk, L., Cakmak, I., and Neumann, G. (2005): Relevance of glyphosate in the rhizosphere of non-target plants in orchards for plant health. In: Li CJ, Zhang FS, Dobermann A, Hinsinger P, Lambers H, Li XL, Marschner P, Maene L, McGrath S, Oenema O, Peng SB, Rengel Z, Shen QR, Welch R, v. Wirén N, Yan XL, Zhu YG (eds), Plant nutrition for food security, human health and environmental protection. Tsinghua University Press, Beijing, PR China, pp. 476-477.
  • Kania, A., Guldner, M., Szabo, B., Kazem, s., Römheld, V., Neumann, G., Morhard, J., Evers, M., and Terlouw, T. (2007): Functional characterization of the stabilized organic turf grass fertilizer “Marathon”. Rasen –Turf – Gazon 1/2007: 192-195.



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