This 18-month long plan established 12 partnership farms across New Zealand, and modelled 44 different farm systems. The aim was to improve our understanding of how changes on farm to reduce greenhouse gas emissions and nitrogen leaching may impact a farms profitability and productivity
The farms are based in Waikato, Bay of Plenty, Southland and regions such as Canterbury and Manawatu where environmental regulations from regional councils require N-loss to be reduced from now through to 2030 to meet water quality targets. The extent to which each farm must reduce N-loss depends on the catchment they are in and the farm system they are running. N-loss and GHG emissions can be reduced from dairy farms using a range of mitigation strategies, several of which address both issues.
Mitigations modelled on the partnership farms fell into three categories: farm management changes, infrastructure investment, and retiring or planting land. The best options for each farm vary depending on the farm system and the region. When selecting a package of mitigations suitable for each farm, options from all three may be chosen together.
Many of the mitigation options available are existing good management practice principles promoted through our existing projects- such as Pastoral 21 and Forages for Reduced Nitrate Leaching.
For methane focusing on efficiency of total dry matter is the key to reduction. For instance, by:
- reducing the amount of dry matter eaten per ha
- lowering stocking rates
- lowering replacement rates (improving the genetic potential of the animals)
To reduce nitrous oxide and nitrogen loss:
- minimising nitrogen surplus through better fertiliser application
- planting low-nitrogen forages or crops to reduce nitrogen excretion (eg fodder beet and plantain)
- use of low nitrogen feeds
- improving pasture quality.
These changes result in lower nitrous oxide emissions from the soils, and less nitrogen loss to water in times of drainage.
Other management changes considered included the timing of culling cows, irrigation practices, wintering practices, and using off-paddock facilities to lower nitrogen loss and nitrous oxide emissions during autumn and winter. We also looked at how farms could offset their emissions by planting trees on retired or low-productivity areas.
High level Findings
- Packages of mitigations need to be farm-specific. Opportunities are currently available on many farms to improve both profit and reduce emissions through good management practices, however there isn’t a ‘one-size-fits-all’ package of changes that every farmer can use. Packages of mitigations need to be farm-specific as not all mitigations were relevant to all farms.
- For some farms and farm systems, reducing N-loss and greenhouse gases has no impact or could have a positive impact on profitability
- The most efficient dairy farms have fewer options to improve environmental losses
- Some mitigations resulted in conflicting environmental outcomes. This was mainly around infrastructure where reduced N-loss could lead to increased greenhouse gas emissions.
- There is high correlation between reducing N-loss and emissions, this mainly focuses on reducing N-surplus.
- A lower stocking rate doesn’t necessarily mean reduced profitability, rather focusing on efficiency of farm system.
- There are limited options to reduce methane as it is closely related to total dry matter intake.
- Modelling and discussing options available to farms requires skilled professional advice and understanding in both N-loss and emissions.