Catchment level modelling of dairy farm adaptation to meet nitrogen loss targets and the value of including plantain as a mitigation

Abstract

Regulations addressing nutrient losses to ground and surface water bodies are increasingly applied at the catchment level, necessitating catchment-level analysis of implementing environmental mitigations. We conducted catchment-scale modelling to predict the production and economic impacts for dairy farms to achieve N (nitrogen) loss targets, using the Dairy Sector was used as a case study. The DSP model simulated a
population of dairy farms within the catchment based on real farm data, applying ‘stacked’ mitigation steps over time to meet N leaching targets. The targets required reductions in N leaching per hectare of 31% on average. The study focused on forage plantain as a key low-cost mitigation. When plantain was included, the impacts of farms achieving the final N loss targets were predicted to be substantial, including: 1,100 fewer cows farmed, 790,000 kg fewer milksolids produced annually, and $3.3 million lower annual operating profit across the 26 dairy farms in the catchment. However, without plantain, the economic impacts were even greater, with operating profit reduced by $3.8 million. Adoption of N loss mitigations for significant mandated reductions were predicted to have a large impact on the dairy farming community. Relatively low-cost mitigations such as plantain were demonstrated as valuable for softening these impacts.