This paper explores the effects of a public policy that reduces by 50% the use of mineral nitrogen in European agriculture. Our results show that, for the European Union, halving mineral fertilizer use leads to: a decrease in agricultural production, a substantial increase in nitrogen use efficiency, lower use of organic fertilizer and a loss of agricultural competitiveness. At the global level, it leads to greater nitrogen consumption if no measure is taken on the demand side. Ultimately, our research highlights the critical importance of supply side adjustments, particularly in terms of cropland area expansion.