SOAR is a research school. In addition to the focus on PhD students, SOAR also includes graduates, postdocs and supervisors in the activities and networks. This is important because they also constitute the research environment, in which the PhD student is under education. SOAR wants to contribute to the professional discussions with a special focus on the organic food and farming systems.
The research interests of SOAR cover a wide range of subjects within organic agriculture and food systems:
Nitrogen (N) is the most important plant nutrient for crop productivity in most agroecosystems.
Therefore the introduction of Haber-Bosch derived N fertilisers into agriculture resulted in a
sharp increase in yield per ha and a complete restructuring of agricultural management practices
especially in industrial countries. The use of fertility providing legume crops and crop rotation
practises was abandoned or reduced in favour of intensified food production. This development
resulted in a wide array of undesired side-effects like decreasing soil organic matter content and
nitrate leaching with subsequent pollution of natural ecosystems and made agriculture widely
dependent on fossil fuel reserves.
However, fertiliser prizes are predicted to rise due to increasing fossil fuel prizes and a
substitution or partly substitution of Haber-Bosch derived N fertilisers would decrease the
dependency of fossil fuels and increase food security.
Furthermore, the fossil fuel based fertilizer inputs are to a large degree responsible for the
considerable contribution to global greenhouse gas (GHG) emissions originating from the
agricultural sector. Nitrous oxide (N2O) emissions originating from the increased N input into
agroecosystems pose an additional problem due to their about 300-fold higher GHG potency
compared to carbon dioxide. Legumes have the potential to mitigate climate change in agriculture
due to the agroecosystems functions and services they provide.
Atmospheric N2 is a renewable resource and the energy that drives leguminous symbiotic
nitrogen fixation (SNF) is virtually ‘free’ and derived from photosynthesis. Yield reductions due
to energy consumption in the fixation process can be tackled by niche optimisation in the form of
intercropping. For these reasons, SNF is regarded as the most climate friendly approach to
supplying N to agro-ecosystems. Replacing fertilizer N with SNF requires the cultivation of a
legume crop before subsequent crops and the incorporated plant tissue N originating from SNF is
released via microbial decomposition for subsequent crops.
Aim
The aim of this PhD study is to optimize the Nitrogen cycle in low-input agriculture for
Increased N fixation through intercropping
Efficient N transfer from legumes plant to subsequent crop
Mitigation of climate impact due to reduction of greenhouse gas emissions and C sequestration.
