We study nutrient cycling and dynamics at the plant scale
Background: Tropical grasslands cover approximately 1500 Mha that corresponds to 44% of the worldwide grassland area and are mainly growing on Oxisols and Ultisols. These highly weathered soils usually have low plant available phosphorus (P) contents due to the strong P sorption onto the soil solid phase. To cope with P limitation, plants develop specific strategies for acquiring P such as root system extension or root exudation enhancement, which influence plant belowground inputs. However, the resulting belowground C, N and P inputs and their effects on soil nutrient pools over time have not yet been studied.
Objectives and approach: Understand the role of P availability on the regulation and the turnover of belowground organic matter inputs (roots and rhizodeposition) from plants in highly weathered tropical soils. Along a gradient of plant available P, we will quantify and characterize belowground C, N and P input by functionally distinct plant species (grass and legume) using a 13C, 15N, 33P labeling approach applied under controlled conditions of the greenhouse. Then, we will be able to follow the incorporation of plant-derived C, N and P into soil nutrient pools over time.
Supervisors: Astrid Oberson (ETH Zurich), Emmanuel Frossard (ETH Zurich), Samuel Abiven (Soil Science and Biogeography Unit, Department of Geography, University of Zurich)
Collaboration with: Idupulapati M. Rao (International Center for Tropical Agriculture (CIAT), Cali, Colombia)
Funding source: The project is funded by the Swiss National Science Foundation (SNSF)
Professur f. Pflanzenernährung
FMG C 13.1
Eschikon 338315 Lindau
Background: Arbuscular mycorrhizal fungi (AMF) are promoted as natural plant growth enhancers mainly because of their key function in plant phosphorus (P) acquisition from soil. However, it is still not known whether non-indigenous inoculants or indigenous assemblages, or more or less, or even specific plant symbiotic partners provide the biggest plant growth and nutritional benefits. Effective use and management of soil microbiota, such as AMF, bear great potential for a resource-efficient and possibly environmentally more friendly future plant production.
Objectives and approach: In a pot experiment in the glasshouse we test whether pre-infecting seedlings with two selected inoculants, their mixture, or two entire soil AMF communities, or also their mixture, can be utilized to influence plant growth and P nutrition from living soils that already contain indigenous AMF assemblages. Fungal hypha-mediated nitrogen (N) and P accumulation in the plant are being estimated by isotopic nutrient tracing from a small root-exclusion compartment. Whole plant performance as a consequence of mycorrhizae and the rest of soil life will be assessed by a genotypic approach, which makes use of a mycorrhized wild type plant and its isogenic mycorrhiza-defective mutant line, and by measuring the shoot and root biomasses, total plant nitrogen and P nutrition, root lengths, and quantifying AMF root colonization.
Supervisor: Hannes Gamper (ETH Zurich)
Collaboration with: Muhammad Arif Ali (Department of Soil Science, Bahauddin Zakariya University Multan, Pakistan)
Funding source: Postdoctoral Excellence-Scholarship for Foreign Scholars of the Swiss State Secretariat for Education, Research and Innovation [SERI; Eidgenössische Stipendienkommission für ausländische Studierende (ESKAS)], project nr 2014.0897
Background: Long term space missions (i.e. Mars mission) or the establishment of a long-term manned base implies the development of a reliable life support system including food supply and waste management. Due to the mission duration, supplying all food oxygen and water from the Earth will result in a tremendous cost, therefore the life support system has to be generated.
Objectives and approach: The principle objective of this research proposal is to investigate plant physiological and ecological parameters that are critical to the development of a sustainable hydroponic cultivation unit for the production of food as a life support system during space missions. A final objective is to measure the effect of a given rhizosphere microbial environment nutritive quality of plant production. We are responsible for bread wheat cultivation.
Supervisor: Emmanuel Frossard (ETH Zurich)
Collaboration with: Danny Geelen (Department of Plant Production, Gent University), Stefania De Pascale (Department of Agriculture, University of Naples Federico II), Michael Dixon (Department of Environmental Biology, University of Guelph), Serge Pieters (The Paul Lambin Institute -IPL)
Funding source: The MELISSA MFC-2 project is funded by European Space Agency (ESA).
Background: An aquaponic (AP) system combines a recirculating aquaculture system (production of aquatic animals, mostly fish) with a hydroponic system (production of plants) and recycles water and nutrients between these two main components. Nutrient-rich water from the aquaculture component is directed to the hydroponic component and provides nutrients for plant growth, while nutrient-poor water is returned back to the aquaculture component. One of the key nutrients in AP is nitrogen, which is introduced into the nitrogen cycle of the system via fish feed and subsequent fish excreta. Ammonia and nitrite are both harmful to fish. The transformation between these forms as well as the production of nitrate are mediated by bacteria. Other components of the AP, such as the biofilter, solids removal unit, settler, piping, as well as their physicochemical conditions, further affect microbial community and nitrogen dynamics. The spatial distribution of microbial communities and the dynamics of the nitrogen cycle in an AP system are poorly understood.
Objectives: This project aims at quantifying nitrogen fluxes between different components of the AP system as well as quantifying the nitrogen losses from the system. In addition, microbial communities that are involved in the nitrogen cycle will be characterized.
Methods: The main forms of nitrogen in all AP system components (fish feces, fish tank, biofilter, solids removal unit, digester, sump, piping and rhizosphere) will be quantified. Bacterial community composition and function will be described with a metagenomics approach and by using quantitative PCR for specific populations of bacteria involved in N-cycling. Finally, nitrogen fluxes among system components will be traced using a 15N isotope in order to parametrize the nitrogen dynamics in the system.
Supervisors: Theo H. M. Smits and Ranka Junge (Zurich University of Applied Sciences) and Emmanuel Frossard (ETH Zurich)
Collaboration with: Institute of Natural Resource Sciences, Zurich University of Applied Sciences (Switzerland), Bioinformatics and Systems Biology Group, JLU Giessen (Germany), UrbanFarmers AG (Switzerland) and Integrated and Urban Plant Pathology Laboratory, Gembloux Agro-Bio Tech, University of Liège (Belgium).
Funding source: The project is funded by the Swiss National Science Foundation (SNF)