The nitrogen dilemma: Toward a novel fertilization management framework for reconciling productivity and diversity in grasslands

Abstract

Nitrogen fertilization is essential for meeting global forage demand, but consistently drives biodiversity loss in managed grasslands, creating a fundamental dilemma for sustainable agriculture. Evidence suggests that nitrogen-induced competitive hierarchies are neither instantaneous nor irreversible: diversity loss follows dose-dependent temporal trajectories that create intervention windows before dominance becomes entrenched and can be partially reversed when nitrogen inputs are reduced, a management opportunity that conventional uniform fertilization strategies fail to exploit. We propose a dynamic nutrient management framework (the PRISM framework, see below) based on systematic spatiotemporal rotation of nitrogen application rates across paddocks over time. The framework operates through alternating high-nitrogen phases (promoting productivity) with low-nitrogen phases (disrupting competitive hierarchies and creating conditions for less competitive species to thrive). By creating controlled heterogeneity in nutrient availability, this approach aims to maintain farm-scale productivity while periodically enabling legume recovery and the associated benefits of biological nitrogen fixation, reduced nitrous oxide emissions, and enhanced system resilience. We present the conceptual foundation, illustrate implementation through a hypothetical scenario, and identify critical research priorities. If validated, this framework suggests that the apparent conflict between intensification and biodiversity conservation may reflect the limitations of current management approaches rather than a fundamental ecological constraint.