Online appendix describing the dairy industries in the studied regions
This appendix describes the five regions studied within the paper, “Least-cost practices for reducing greenhouse gas emissions from New Zealand dairy farms”. These regions are: Canterbury, Manawatu, Northland, Southland, and Waikato.
Canterbury is the second-largest dairy region in New Zealand, with 9% of the total herds, 17% of the total cows, and around 20% of national production (LIC, 2013). In contrast to traditional regions like the Waikato, dairy area in Canterbury has expanded rapidly over the last 20 years, as irrigation has supported the conversion of less-intensive sheep farms to highly-productive dairy farms. Indeed, by 2020, 70% of the dairy land in New Zealand developed since 1996 will have been in Canterbury and Southland (PCE, 2013). The availability of large tracts of land has meant large farms are standard (mean size of 228 ha). The availability of high amounts of water for irrigation has meant that the dry summers typical of Canterbury are not a major production constraint; thus, very high levels of pasture production (15–20 t DM ha-1) are typically achieved. Nevertheless, crops and imported supplement play an important role in these systems, especially to support stock through cold winters. High production of around 1,340 kg MS ha-1 is produced, on average, each year in this region.
Manawatu has an established dairy industry, which has expanded over the last 20 years in response to higher milk prices. It contains 5% of the total herds, 5% of the total cows, and produces around 5% of national milk production (LIC, 2013). The Manawatu region is characterised by farms of low- to moderate-intensity, which are primarily pasture-based given temperate winters and reasonable pasture production (10–15 t DM ha-1). However, turnip crops are widely used to increase milk production throughout summer, especially when dry conditions constrain pasture quality and growth in late summer. Accordingly, moderate production of around 996 kg MS ha-1 is produced, on average, each year in this region.
The Northland dairy industry is well-established, though its hot, dry climate and poorer soils has constrained the establishment of highly-productive systems. It contains 8% of the total herds, 6% of the total cows, and around 5% of national production (LIC, 2013). Low rates of pasture production (8–13 t DM ha-1) and the poor digestibility of pasture, arising from the sustained droughts experienced in this area, mean most farms are of low- to moderate-intensity. Accordingly, production is low, with around 645 kg MS ha-1 being produced, on average, each year in this region, less than half of that produced in Canterbury.
The Southland dairy industry is similar to the Canterbury industry, though smaller in size. It contains 8% of the total herds, 11% of the total cows, and around 12% of national production (LIC, 2013). This area is characterised by temperate summers, but long, cold winters that constrain dairy production. Indeed, pasture production is only moderate (10–15 t DM ha-1), given depressed winter growth. As in Canterbury, the Southland industry is typified by farms of moderate- to high-intensity that use crops and high amounts of imported supplement, especially PKE and maize grain, to support stock through difficult winters. However, its level of production, around 1,051 kg MS ha-1 on average, demonstrates that its winters are a greater constraint to production than the dry summers experienced in Canterbury, to which irrigation has provided such an effective solution.
Waikato is the primary dairy region of New Zealand, with 30% of the total herds, 24% of the total cows, and around 23% of production (LIC, 2013). Systems in this region are characterised by medium to high use of supplement on farms of low to moderate size (mean size of 110 ha). Large farms are the exception, as the expansion of individual units is slowed through the presence of many historic, smaller dairy farms. The temperate climate supports high pasture production (12–17 t DM ha-1) and the use of maize silage, often grown on farm. Accordingly, moderate production of around 970 kg MS ha-1 is produced, on average, each year in this region.
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