Balancing water-quality threats from nutrients and production in Australian and NZ dairy farms under low profit margins

We summarise the losses of N and P from Australasian dairy farms, examine the policy drivers used for mitigating losses and evaluate the effectiveness of implementing mitigations. In 4 regions in New Zealand we found that P could be mitigated quite cheaply, but N reductions required more measures, some of which are costly. Conversely, prioritising on the basis of mitigation cost-effectiveness for a specific nutrient will lead to more rapid reductions in losses of the target nutrient, but with fewer co-benefits for non-target nutrients or pollutants, such as faecal microorganisms and sediment. This information will assist farmers in deciding how to meet a catchment target at least cost.