Nitrate leaching from agricultural land is a major environmental concern affecting groundwater quality and aquatic ecosystems. In Denmark, where almost all drinking water is supplied from groundwater, protecting water resources from nitrate contamination is particularly important. Recent studies in Denmark suggest that long-term exposure to nitrate in drinking water may increase the risk of colorectal cancer. At the same time, nitrate losses from agriculture contribute to eutrophication of rivers, lakes, and coastal waters, leading to algal blooms and oxygen depletion that threaten aquatic ecosystems.

In this PhD project, Maryam Dastranj investigated how soil properties, crop management, and water movement influence nitrate leaching under Danish agricultural conditions. The research combined long-term field experiments with calibrated soil water balance modelling and nitrate measurements across forage, arable, and vegetable cropping systems.

The results show that cropping systems and soil types strongly influence nitrate losses. Perennial grass-clover systems maintained consistently low leaching, whereas annual crops and vegetable systems, particularly on sandy soils, showed substantially higher nitrate losses, mainly during autumn and winter drainage periods.

Time: 19 May 2026 at 12:00
Place: Auditorium, AU Viborg, Aarhus University, Blichers Alle 20, 8830, Tjele
Members of the assessment committee
Senior Researcher Manfred Kayser Department of Crop Sciences, Georg-August‐University Göttingen, Göttingen, Germany
Associate Professor Bjarne W. Strobel Department of Plant and Environmental Sciences, University of Copenhagen
Senior researcher Anne Grete Kongsted Department of Agroecology (chair), Aarhus University, Denmark
Main Supervisor: Senior Researcher Christen Duus Børgesen Department of Agroecology, Aarhus University, Denmark
Co-supervisors:
Professor Bo Vangsø Iversen Department of Agroecology, Aarhus University, Denmark
Professor Uffe Jørgensen Department of Agroecology, Aarhus University, Denmark

The defence is public.
The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS, Ny Munkegade 120, building 1521, 8000 Aarhus C.