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PhD defense Agro People

PhD defence: Where does the nitrogen go, when an agricultural field is artificially drained ?

During her PhD studies, Saghar K. Motarjemi researched water and nitrogen balances in artificially drained agricultural soils.

Photo: Saghar Khodadad Motarjemi

Artificial drainage is an agricultural management practice, which removes the excessive water from the root zone of crops. However, artificial drainage might elevate the risk of eutrophication of lakes and contamination of surface water bodies through facilitation of nitrogen transport from agricultural fields. Saghar K. Motarjemi studied how the quantity of drainage discharge and the installation depth of the old drainage systems affect the nitrogen cycle in sandy loam soils through number of field experiments, and with the means of both empirical and mechanistic modeling approaches. While modelling showed to be a strong tool for better understanding the complex natural interactions between the soil-water-plant-atmosphere, poor drainage conditions significantly reduced the crop dry matter yield and nitrogen uptake while increasing the risk for losses through leaching and denitrification.

The new research findings contribute to the understanding of how different drainage conditions impact the fate of nitrogen in artificially drained soils. Moreover, results of this study indicate that a combination of state-of-the-art empirical methods with mechanistic models could delineate the water and nitrogen transport pathways and contribute to future scenario analyses under the changing climate. 

The PhD study was completed at Department of Agroecology, Faculty of Technical Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Friday, 19 November 2021 at 13:00
Place: Auditorium, Foulum, Blichers Allé 20, 8830, Tjele, Aarhus University
Title of PhD thesis: Water transport and fate of nitrogen in artificially drained agricultural loamy fields located in temperate regions

Contact information: Saghar K. Motarjemi, e-mail: sa.m@agro.au.dk, tel.: +45 21810319

Members of the assessment committee:

Associate Professor Lars Elsgaard (chairman), Agroecology, Aarhus University, Denmark

Professor Per-Erik Jansson, Department of Sustainable Development, Environmental Science and Engineering (SEED), KTH Royal Institute of Technology, Sweden

Associate Professor Efstathios Diamantopoulos, Department of Plant and Environmental Sciences, University of Copenhagen, Denmark

Main supervisor:
Senior Scientist Finn Plauborg, Agroecology, Aarhus University, Denmark

Co-supervisor:
Senior Scientist Annette Elisabeth Rosenbom, Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Denmark

Associate Professor Bo Vangsø Iversen, Agroecology, Aarhus University, Denmark

Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS,Katrinebjergvej 89F, building 5132, 8200 Aarhus N.