David Nimblad Svenssons halvtidsseminarium

Opponent: Professor Thomas Kätterer

Ordförande: Getachew Getahun Tiruneh

Pedagogisk granskare: Louise Malmquist

Abstract

Nitrate leaching is expected to increase in Scandinavia as a consequence of climate change, especially during years with poor harvests (low uptake of nitrogen by the main crop) followed by high precipitation and discharge during winter. Cover crops (CCs) can be grown after the harvest of the main crop to reduce N losses in autumn and winter. However, in the long-term, frequent incorporation of CC biomass may contribute to increased N mineralization in the soil and thereby also potentially increase N-losses during periods when the soil is left bare. My project aims to explore the long-term impacts of the frequent use of cover crops on crop yield, soil carbon, and nitrate leaching under present and future climates. The work is based on simulations with a soil-vegetation model (CoupModel) and data from long-term field experiments in South Sweden covering over 30 years. The calibrated model will be used to make predictions based on future climate scenarios and to optimize the use of CCs. 

During the seminar, I will present results from my first study where the model was calibrated to a fertilized and unfertilized treatment, without CCs. I will discuss the modelling approach, how the model performed, and the questions that we faced due to the unusually high C/N ratio (>20) of the soil at the field-site (Mellby) and its implications for simulations of C and N mineralization. Finally, I will also give an overview of the coming studies that will be done within my project.