Inès Chiadmi will present her thesis entitled “Regulating nitrogen pollution in agriculture: modeling policy effects and farmers’ preferences,” under the supervision of Steven Van Passel and Stephan Marette, on November 19, 2025, from Antwerp.
Nitrogen-enriched fertilizers were instrumental in driving the agricultural revolution that enabled food production to keep pace with the exponential growth of the global population in the latter half of the twentieth century. However, the widespread use of nitrogen inputs has come at a significant environmental and public health cost, primarily due to nitrogen surpluses accumulating in soil and water bodies. As such, nitrogen pollution represents a critical challenge of the agriculture-environment nexus, manifesting both as inefficiencies at farm-level input use and as societal externalities. This “double penalty” underscores the need for effective and socially acceptable regulatory frameworks. Addressing this issue requires a nuanced understanding of both policy instruments and individual decision-making.
This thesis investigates how economic policy instruments can address the regulation of nitrogen pollution from agricultural sources both from the perspective of sector-wide impacts at the EU level and of farmer decision-making within the Flemish context. The research begins by analyzing the unexpected and potentially undesired effects of nitrogen input taxation, which may compromise policy effectiveness. Spatial heterogeneity further complicates nitrogen pollution control as regions differ in their environmental vulnerability, and different regulatory approaches are of use. Through the lens of farmers’ preferences, the thesis investigates the role of information policies in the improvement of water and soil quality in Flanders through agricultural extension and advisory services. Employing a similar methodology, the study also examines the design of a voluntary, result-based agri-environmental scheme under the Flemish Manure Policy. This includes an analysis of the trade-offs farmers are willing to make between flexibility in farming calendars and a monetary incentive linked to nitrate residue monitoring results.