Increasing the quantity of carbon stored in agricultural soils has the potential to offset emissions of greenhouse gases to the atmosphere, while soil carbon losses would further add to those emissions.
However, realising this mitigation potential is technically challenging when soil carbon stocks are already high (as they are in New Zealand), potential changes in soil carbon are small and spatial variability is high.
The current NZAGRC programme has three distinct components:
(1) testing specific management practices that may increase the long term soil carbon store in field situations;
(2) developing and using models to predict how a range of management practices may influence long and short tem soil carbon storage; and
(3) identifying those factors that influence the stability of current or newly added soil carbon.
We have also supported international work to map on farm soil carbon and will participate in the international research programme CIRCASA.
Dr David Whitehead, Manaaki Whenua - Landcare Research (2010-present)
Professor Frank Kelliher, AgResearch (2010-2017)
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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