Plants & GHGs

The NZAGRC’s former nitrous oxide and soil carbon work streams were combined into one programme this year. This ensures a strong overall framework, closer communication and full GHG analyses across the programme. The programme focusses on three key areas:

1. Identifying and prioritising plant traits for low GHG emissions;

2. Mitigation practices to maintain soil carbon and reduce nitrous oxide emissions at paddock scale; and

3. Defining the achievable soil carbon stabilisation capacity of New Zealand grassland soils.

Current progress and research stories

1430 Cecile de Klein, Principal Scientist (AgResearch)

Cecile provided an overview of the nitrous oxide research being conducted in New Zealand, with a focus on plant and animal interventions.

Cecile reminded the audience that animal urine is by far the largest source of nitrogen in the New Zealand farming system and that there are a number of key intervention points in the nitrogen cycle to target when trying to reduce nitrous oxide.

Nitrate leaching is also a big issue, so any technology or intervention to reduce nitrous oxide emissions needs to be win:win with respect to leaching.

Cecile outlined three options for reducing nitrous oxide:

1) reduce nitrogen excretion;
2) increase nitrogen uptake by plants; and
3) influence the plant effects on soil nitrogen processes.

Starting with number three, New Zealand researchers are investigating the effects of pasture species and cultivars on nitrous oxide emissions. They have shown variability in pot trials and larger field trials are now underway. Researchers are also studying the effects of brassicas on nitrous oxide emissions and effects of diet on animal urine composition.

For number 2, it appears that planting Italian Ryegrass, which continues to grow in the colder months of the year may have some benefits.

When looking at reducing nitrogen excretion per urination, it appears that the quantity of nitrogen applied seems to be more important that the species that it is being applied to.

The knowledge that we already have about "high risk" times for nitrous oxide emissions, urine being deposited under wet weather conditions with high pasture damage, is being incorporated into on-farm decision management tools. These may be helpful to farmers, but they will need to be able to assess the state of their paddocks easily.

With respect to irrigation, it appears that if grazing is delayed until 6 days after irrigation, nitrous oxide emissions can be reduced by ~40%.

Researchers continue to investigate win:win solutions and are working closely across organisations and programmes to achieve this.

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  1. pdf 10_DeKlein_1430_NZAGRC conference 2015_New... (2.65MB)

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