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
Investigating plantain properties
An animal feeding trial conducted in association with the Forages for Reduced Nitrate Leaching programme, investigating the ability of plantain to modify nitrogen processes in animals and soils, was a major focus this year. The aim was to assess the impact of increasing proportions of plantain in the diet on methane yield, nitrogen excretion in urine and dung, and nitrous oxide emissions.
Preliminary findings include:
- a reduction in urinary nitrous oxide concentration with increasing proportions of plantain and associated reductions in nitrous oxide emissions from urine patches.
- differences in methane per kilogram of dry matter intake between the treatment groups. However, methane emissions were unusually high for the control group so these data need careful interpretation.
- nitrous oxide emission factors reduced with increasing proportions of plantain in the sward, most likely due to an effect of plantain plants on soil processes.
To further study the effects of plantain, a sward containing 60% plantain has been established at a Waikato farm. Carbon balances and nitrous oxide emissions have been continuously measured in comparison to a ryegrass/clover sward. Experiments have commenced to compare results to traditional chamber measurements at the plot scale.
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