Managing greenhouse gas emissions in two

New Zealand dairy farms are responsible for a large proportion of this nation’s greenhouse gas emissions (GHG-e), arising mainly from enteric methane and urinary nitrogen deposition on pasture. De-intensification and the use of specific mitigation strategies can reduce GHG-e from dairy farms, but are generally costly. In this study, a farm-level model is used to analyse the cost of GHG-e mitigation strategies in medium- (10–20% imported feed) and high-input (20–40% imported feed) systems in the two major dairy regions of New Zealand (Waikato and Canterbury). Production intensity is measured solely in terms of feed importation, in accordance with standard practice in this nation. The focus of the study is to assess the cost-effectiveness of a variety of de-intensification and mitigation strategies aimed at reducing the negative impact of emissions constraints (reductions of 10, 20, and 30%) on farm profit. De-intensification options include changes in stocking rate, nitrogen fertiliser application, and supplement use. New Zealand dairy farms were found to have experience in decreasing GHG-e when GHG-e reductions were introduced. Nitrogen inhibitors were only useful for mitigation when the GHG-e reductions required were so stringent that their costs outweighed the significant costs associated with de-intensification in the high-input systems. Standard-fed and feed-based systems were found to be more profitable than those that were not already available. Overall, de-intensification of the farming system proved to be more profitable than the use of specific mitigation strategies when GHG-e was required.