BSc and MSc projects

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BSc or MSc theses in collaboration with group members in Eschikon

1)    Assessing the effectiveness of different microbial inhibitors for phosphorus isotopic exchange kinetics

2)    Belowground input of carbon, nitrogen and phosphorus by a grass and a legume using isotope methods

3)    Gross sulfur mineralisation-immobilisation as determined using the isotopic (35S) dilution method in soils of the DOK long-term field experiment

4)    Gross nitrogen mineralisation-immobilisation as determined using the isotopic (15N) dilution method in soils of the DOK long-term field experiment

5)    The turnover of phosphorus in the soil solution as determined by isotopic exchange kinetics (IEK) in soils of the Rothamsted long-term field experiment (England)

6)    The chemical nature of organic phosphorus in crops using solution (1D) 31P and (2D) 31P-1H NMR spectroscopy

BSc or MSc theses in collaboration with other institutions

7)    Potential use of stable isotopes to trace organic carbon and nutrient dynamics in a field experiment with application of organic fertilizers: with FiBL

BSc or MSc theses with other institutions (not in collaboration with our group)

Availability of phosphorus and potassium in thermochemically produced mineral recycled fertilizers from sewage sludge - at FiBL

Project on reduction of nitrate losses in groundwater - at FiBL (PDF, 202 KB)

Project in Agroforestry - in collaboration with Agroscope (PDF, 1.3 MB)

Project in Mapping in Côte d'Ivoire - in collaboration with Agroscope (PDF, 213 KB)

We also announce that there is the possibility to make a stage period with CIRAD for research on yam (see here the three announcements 1 (PDF, 132 KB), 2 (PDF, 593 KB), and 3 (PDF, 580 KB)).

The group of Plant Nutrition has projects and collaborations abroad, particularly research for development. Examples are the YAMSYS project in West Africa, collaboration with CIAT South-East Asia or CIAT Colombia, and more. Contact Prof. Emmanuel Frossard and/or Astrid Oberson.

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Assessing the effectiveness of different microbial inhibitors for P isotopic exchange kinetics

Supervision: Chiara Pistocchi, Éva Mészáros, Astrid Oberson
Location: ETH research station, Eschikon
Start: By agreement
Contact:

Phosphorus (P) is an essential nutrient for all organisms. Soil P availability can be very low in some soils, and improved techniques to better understand soil P processes are still required.

A challenge in the study of phosphorus (P) cycling in soil is the quantification of P transformations, for example organic P mineralization rates.  Radioisotope techniques represent a powerful tool to assess mineralization and other transformation rates of P. However, for this approach the determination of a baseline of phosphorus isotopic exchange solely by physicochemical processes is required. This baseline is estimated by a short-term isotopic exchange kinetic (IEK) batch experiment under steady state conditions. Previous studies have shown, that in soils with very high microbial activity and low available P, the IEK can be biased by the microbial uptake of the tracer. In these cases, a microbial inhibitor, which suppresses microbial activity without eradication of the microbes and without altering the isotopic exchange processes, is required. While different substances have already been tested, an optimal microbial inhibitor has not yet been identified. The aim of this Master/Bachelor work would be to systematically test a set of preselected microbial inhibitors on a variety of different agricultural and forest soils by conducting IEK experiments and tracer uptake experiments. Within this Master/Bachelor work, the student will receive training to plan, perform and interpret a laboratory experiment independently. He/she will expand his/her knowledge on phosphorus processes in soil. Additionally, the student will gain experience on how to handle radioactive as well as biohazardous material. The work of the student will contribute to further develop methods that are crucial to better understand soil P transformations.

Belowground input of C, N and P by a grass and a legume using isotope methods

Supervision: Pierre Stevenel, Astrid Oberson
Location: ETH research station, Eschikon
Start: By agreement
Contact: or

Low phosphorus (P) availability limits crop growth on a large part of tropical soils worldwide. This feature affects the carbon (C) cycle by influencing C capture by plants, and the input of belowground C contained in roots and rhizodeposition. Moreover, low P availability influences nitrogen (N) input in soil by limiting symbiotic N2 fixation by legumes. Plants have developed strategies to cope with P deficiency, such as root system extension or exudation enhancement, which also determine belowground organic matter input. The belowground C, N and P inputs as affected by P availability and their effect on soil nutrient pools have not yet been studied. The main objective of this project is to understand the role of P availability on the regulation and the turnover of organic matter inputs from plants in highly weathered tropical soils.

Experiments will be performed with the legume Canavalia brasiliensis. Plants will be grown in a Ferralsol along a gradient of plant available P and a novel tri-isotopes (13C, 15N, 33P) labeling method will be used to quantify and study the incorporation of plant belowground input of C, N and P into soil pools over time. The experiments offer several options for BSc and MSc topics, either related to the studied element (C, N and/or P), or also related to the plant, since similar experiments are planned with a tropical grass, and we expect different responses of the legume and the grass to a gradient in available P.

Themes 3 to 6

For more information about these themes, please contact

3)    Gross sulfur mineralisation-immobilisation as determined using the isotopic (35S) dilution method in soils of the DOK long-term field experiment

4)    Gross nitrogen mineralisation-immobilisation as determined using the isotopic (15N) dilution method in soils of the DOK long-term field experiment

5)    The turnover of phosphorus in the soil solution as determined by isotopic exchange kinetics (IEK) in soils of the Rothamsted long-term field experiment (England)

6)    The chemical nature of organic phosphorus in crops using solution (1D) 31P and (2D) 31P-1H NMR spectroscopy

Potential use of stable isotopes to trace organic C and nutrient dynamics in a field experiment

Supervision: Else Bünemann, Astrid Oberson
Location: FiBL Frick, ETH research station, Eschikon
Start: By agreement
Contact:

Organic fertilizers such as compost and biogas digestates are important components of nutrient management in organic agriculture. With increasing application of digestates, concerns about the long-term effects on soil organic matter and nutrient dynamics have been raised. Likewise, the nutrient use efficiency of organic fertilizers over different time scales is not well understood. FiBL in collaboration with Agroscope is planning to install a long-term field experiment to investigate these questions.

In this BSc or MSc project, the potential use of stable isotopes to trace organic carbon and nutrient dynamics in a field experiment will be investigated. After a short review of the relevant literature, Swiss samples of organic fertilizers from different sources and different times of the year will be analyzed for natural abundance signatures of 13C, 15N, and possibly other stable isotopes. The homogeneity of the signatures in the samples will be assessed by comparing the total signatures to those of size fractions and chemical extracts. In addition, soil samples from 3-4 potential field sites will be analyzed for the same natural abundance signatures. This will allow assessing the suitability of stable isotope methods to trace organic matter and nutrient dynamics in the field experiment. If done as a MSc project, a short laboratory incubation experiment could be additionally conducted to verify the possibility to trace the fate of organic fertilizers in pools or physical fractions of soil.

Availability of P and K in thermochemically produced mineral recycled fertilizers from sewage sludge

Supervision: Else Bünemann
Location: FiBL Frick
Start: By agreement
Contact:

Phosphorus (P) is a finite resource and essential for all organisms. In Switzerland, P contained in waste streams has to be recovered from 2026 onwards. In the frame of a public-private partnership (KTI project), a thermochemical process to recover P from wastewater is being developed. Sewage sludge mixed with a potassium (K) donor is treated under reduced conditions and high temperature, with the aim to separate heavy metals and increase the availability of P in the product. The overall objective is to develop a PK-fertilizer. The process is currently being optimized at the University of Applied Sciences of Northwestern Switzerland (FHNW) in Basel, where fluidized bed experiments are conducted at laboratory scale, varying the K donor, mixing ratios and temperatures systematically. The products are then characterized chemically with respect to total element contents (ICP-OES) and structural composition (XRD). Plant uptake of P and K from the products is assessed in pot experiments conducted at the Research Institute of Organic Agriculture (FiBL) in Frick.

The main objective of this BSc or MSc thesis is to characterize the products from the experiments at FHNW with respect to plant availability of nutrients and selected toxic elements in different soils. To this end, the products are incubated in soil and the mobility of nutrients and toxic elements is quantified by extractions as well as using Diffusive Gradients in Thin Films (DGT). By relating the results to the chemical characterization of the products and to the outcome of the pot experiments, a mechanistic understanding of the potential fertilizer value and environmental effects will be reached. If done as a MSc project, the number of samples will be greater than for a BSc project, and an accompanying pot experiment with different soils could be conducted.

The experimental work will be done at the Research Institute of Organic Agriculture, Frick, under the supervision of PD Dr. Else Bünemann-König, with advice regarding the use of DGTs by Dr. Susan Tandy, Group of Soil Protection, ETH Zurich. Selected analyses (ICP-OES) may be done at FHNW (Dr. Jan Stemann). This thesis topic is foreseen for 2017 (starting date flexible).

 
 
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