There are profit neutral pathways to reduce phosphorus pollution in the face of increasing fertilizer prices: An open-source model for grass-based cattle farming

Aquatic ecosystems worldwide are being damaged by phosphorus (P) due to inefficient use in agriculture. This problematic surplus within natural systems occurs in the context of increasing vulnerability of our food system due to geo-political P supply disruptions and shocks to fertilizer prices. This dual ‘feast and famine’ nature of P challenges demands complex policy responses that enable farmers to take P stewardship action while maintaining farm profitability. This paper, provides a novel open-sourced farm-scale optimization model that allows for the identification of profit neutral policy pathways for pasture-based dairy and beef farmers to improve efficiency of P use. The model is illustrated using four hypothetical farms reflecting conditions in the United Kingdom. Widely available regulatory and management interventions are combined to reduce diffuse pollution and increase resilience in the face of rising fertilizer prices and uncertain market conditions. The model is fully open-source, allowing grassland area and quality, cattle number and performance, and other parameters to be changed, and therefore inform policy decisions more widely. Our aim is not establishing an exact policy leading to P stewardship action universally, but to evidence the existence of pathways for doing so that can be specified (with our openly available model) anywhere such livestock systems are relevant. Results demonstrate that such profit neutral pathways can be found, if differences in farm characteristics and market uncertainty are taken into account, and that farm profitability should no longer be considered as an intractable barrier to address P pressures on aquatic ecosystems.