Benefits and Trade offs of Dairy System

Between 2011 and 2016, small-scale farm trials were run across three dairy regions of New Zealand (Waikato, Canterbury, Otago) to compare the performance of typical regional farm systems with farm systems implementing a combination of mitigation options most suitable to the region. The trials ran for at least three consecutive years with detailed recording of milk production and input costs. Nitrate leaching per hectare of the milking platform (where lactating cows are kept) was estimated using either measurements (suction cups), models, or soil mineral nitrogen measurements. Post-trial, detailed farm information was used in the New Zealand greenhouse gas inventory methodology to calculate the emissions from all sources; dairy platform, dairy support land used for wintering non-lactating cows. Results indicated that reducing inputs of nitrogen fertiliser and purchased feed, along with lower stocking rates, resulted in less nitrate leaching. However, the implementation of wintering barns showed reduced nitrate leaching but unchanged greenhouse gas emissions due to increased manure storage. The research found that low-input systems achieved emission reductions at the cost of approximately NZ$100 per tonne CO₂-equivalent, highlighting the economic trade-offs involved.