The final report of the Biological Emissions Reference Group (BERG), a cumulative effort by the wider agricultural sector, estimated that biological emissions can be reduced by up to 10% for the dairy sector with currently available farm management practices. This is consistent with the Parliamentary Commission for the Environment's finding that methane emissions need to reduce by 10%-22% by 2050 to prevent any further contribution to global warming.

There is no one solution to reducing biological greenhouse gas emissions, to get up to a 10% reduction each farm will need to adopt a number of mitigations tailored to their farm and region.

Most of these mitigation measures involve good farm practices, such as feed utilisation, choice of feed type and being more selective about how and when to apply fertiliser & effluent to our land.  

The range of on-farm mitigation measures that are best suited to each farm will vary due to climatic conditions and soil type. Before you make changes to your farm system or  invest in infrastructure, you should seek advice to help determine what will work best for your situation. Contact your dairy company’s environmental advisor.  

Options to reduce methane emissions

Current options available to reduce methane emissions are limited, but managing dry matter intake is the most important. Research shows that for every additional kg of total feed eaten per hectare, total methane emissions increase proportionally. Managing dry matter intake is about increasing per cow performance for every kg of feed that is eaten.

Increasing reproductive performance of the heard to allow for reduced replacement rates will decrease your emissions as there is less dry matter requirement for young stock and less methane emissions.

• Increased animal performance can be achieved through improved breeding worth, animal health, and reproduction.
• As the performance of individual animals increases farmers can reduce their stocking rate.

Options to reduce nitrogen leaching and nitrous oxide emissions

Nitrous oxide emissions occur when bacteria in the soil remove oxygen from nitrate (NO3-). This mainly happens when the soils are in an anaerobic state (e.g. waterlogged soils). Because nitrogen is supplied to the soil from fertiliser, animal excreta, and effluent irrigation, there are a number of options to manage nitrous oxide emissions and nitrogen leaching. The mitigations options involve reducing nitrogen surplus.

Reducing nitrogen surplus

• Many of the supplementary feeds contain less nitrogen than normal pastures and can help reduce nitrous oxide emissions on farms. You can evaluate supplements used to see if there is potential to change to a lower-emissions feed.
• Evaluate existing cropping activity and the species grown. This can improve nitrogen inputs to the farm and nitrogen surplus through different types of crop and different methods in cultivation/feeding.
• Exploring the use of alternative forages in the pasture sward such as plantain to reduce nitrogen loss to water and atmosphere. These species can retain more nitrogen in the system allowing for less to be lost.

Optimising your fertiliser and effluent use

DairyNZ analysis shows that for every additional 100 kg N/ha applied via fertiliser, total greenhouse gas emissions increase by 2.6 t/ha. As well as using less nitrogen fertiliser per hectare, mitigations strategies include:

• Ensure you are applying the right type of fertiliser in the right places. Test the soil to gauge optimal levels and use precision application to ensure accurate placement.
• Avoid direct leaching and nitrous oxide emissions by not applying in winter or to waterlogged soils.
• Improve effluent management to accurately apply appropriate depths and rates to the soil so that there are less losses.
• Reduce N fertiliser applications on effluent blocks.

Paddock strategies

• Grazing cows off-paddock in the autumn months limits the build-up of nitrate in the soil when the plant growth is reduced. This build-up is then available to be lost to both water and atmosphere of the following winter and spring months. This strategy can reduce nitrogen leaching and nitrous oxide emissions if the associated effluent is well manged.
• Improve irrigation practices so that water is only applied when the soil profile has the capacity to absorb it and the plants need it and that there is no over application. This can be done by using precision water irrigation and scheduling.
• During wintering urine nitrogen leaching and nitrous oxide emissions can be reduced through appropriate paddock selection, grazing time, and grazing regime.
• Using a ‘catch crop’ to minimise the fallow period following a winter crop. This will reduce nitrogen leaching and nitrous oxide emissions during this period.

Below is an example of the cumulative effects for a future package of interventions for dairy, sheep and beef.

Planting to offset carbon dioxide

Planting trees can help ‘offset’ emissions from your farm business without impacting on production. As trees grow, they store carbon in trunks, branches, leaves, and roots. Planting will also improve water quality by helping to filter out sediment and nutrients before they enter waterways. Planting could take place in riparian areas, shelter belts, and through retiring land to forestry. Planting also helps to prevent soil erosion and increase the habitat for native wildlife. 

To more about planting see Trees on farms and Riparian planting.