Two theses are currently being offered in this project:

1) Influence of digested manure on CO₂ and N₂O emissions from organic clover-grass pastures.

The carbon stored in soils is the largest carbon store on earth. Common agricultural practices often promote the depletion of these enormous carbon stores, leading to the release of CO₂, CH₄ and N₂O into the atmosphere. In order to reduce these emissions, various land management methods are being investigated to find the best approach.

As part of the C-ArouNd project, we are investigating the carbon and nitrogen cycle on an organic dairy farm in Tingvoll (Norway). Grass-clover pastures are used to grow fodder for the farm animals. The collected manure is returned to the fields either unchanged or digested after biogas production. All the readily available carbon from the manure is lost through biogas production, leaving a nitrogen-rich material. We assume that this approach reduces CO₂ emissions. However, it is unclear whether the high nitrogen content is quickly lost as N₂O before it can be absorbed by the plants. As part of the master's thesis, gas samples are regularly taken in the field in Norway. In addition, we want to investigate the influence of digested manure on plant growth and clover grass composition by taking clover grass samples.

The main question we want to answer with your master thesis is whether digested manure releases less N₂O and CO₂ emissions from the soil than normal manure under Norwegian summer conditions.

Supervisors: Dr. Jeroen Zethof, Johanna Maria Zimmermann, Dr. Klaus Schützenmeister, Dr. Tatiana Rittl (Norsøk), Prof. Dr. Hermann Jungkunst

Contact: jeroen.zethof(at)rptu.de

2) Freeze-thaw effect on the mineralization of organic matter

Subarctic soils undergo regular freeze-thaw cycles throughout the year, which have an important influence on microbial activity in soils. It is known that thawing can release relatively large amounts of CO₂ and CH₄ through increased microbial activity, which is both an important contributor to climate change and a loss of local soil fertility. It is therefore important to better understand the underlying processes and how management practices can be adapted to reduce these losses.

As part of the C-arouNd project, we are investigating the carbon and nitrogen cycles on an organic farm in Tingvoll (Norway). Grass-clover pastures are used to grow fodder for the farm animals, with the collected manure being returned to the fields either as is or digested (after biogas production). In this work, columns are created from the collected material from the farm. Part of these columns will undergo a freeze-thaw cycle and we will regularly take gas and water samples from both the freeze-thaw columns and the control columns.

The main question we would like to answer in your work is whether the use of digested and/or undigested manure affects the release of C and N from the soil during freeze-thaw conditions.

Supervisors: Dr. Jeroen Zethof, Johanna Maria Zimmermann, Dr. Klaus Schützenmeister, Prof. Dr. Hermann Jungkunst

Contact: jeroen.zethof(at)rptu.de