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)
Soil carbon: Modelling shows need for nitrogen when irrigating
A modeling analysis of carbon and nitrogen (input, cycling and fate) in irrigated grassland in Canterbury showed reductions in soil carbon following irrigation, due to increasing nitrogen limitation. These two co-limiters of growth interact - irrigation stimulates carbon fixation and plant growth, this leads to greater nitrogen uptake by plants, which then leads to greater removal of nitrogen in products (meat, milk). So if nitrogen input is constant, over time it leads to increasing nitrogen deficiency. Our findings suggest that using irrigation during dry periods in dry regions can greatly increase plant growth, product yields and soil carbon inputs, provided nitrogen inputs are also increased. However, evidence suggests that this may not lead to increases in stabilised carbon stocks.
- An excerpt from NZAGRC Highlights 2017 to be released shortly. Read more
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