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)
Capability building: Dr Sam McNally
Raised on a beef farm and then a kiwifruit orchard, Sam McNally enjoyed science right from primary school and had a couple of great teachers at Te Puke High School which enhanced his interest in science.
“Having grown up on farm/orchard I recognised the important role soil played in farm management but it wasn’t until the end of the end of my BSc and during my MSc that the specifics of carbon in soil started to stand out to me,” he says.
This led to his thesis for MSc having an environmental chemistry focus and his PhD on quantifying the carbon inputs to soil under a mixed-sward pasture compared to a ryegrass-clover pasture.
One of the objectives globally for addressing excess greenhouse gases in the atmosphere is to find ways to capture carbon dioxide by plants and store this carbon in the soil. Soil carbon has additional benefits for the land manager as an important part of soil quality. Making sure stored C stays in the soil was an important focus for Sam throughout his PhD and subsequent post-doctoral work.
“Some specific findings of my PhD were that there was greater root biomass and more root turnover under the mixed swards compared to a ryegrass-clover pasture which suggested that the C inputs had the potential to be greater in the mixed sward.
“However, the differences didn’t translate through when we used a stable isotope technique to trace the C through the plant-soil system. One issue was that we were confounded by a severe summer drought so the performance of both pastures was limited.”
Sam says the focus of this research is on practical applications on farms.
“Most of our research around soil C is practical so has the ability to lead to real changes on farms if successful or an outcome is significant. We are always conscious of solutions and outcomes needing to be practical on farm.
“The current research on full inversion tillage is exciting because it is a management tool that can be implemented on farms to potentially increase soil C.”
After completing his PhD Sam moved to Christchurch to start post-doctoral research with Plant and Food Research (also funded through NZAGRC) on a totally different aspect of soil C. The post-doc was just under three years and was on soil C stabilisation and defining an upper limit of soil C.
It led to his permanent scientist position with Plant and Food Research, where he is currently involved in a range of projects largely relating to soil C including ongoing soil C stabilisation work, management options to increase soil C and potential of full inversion tillage to sequester C.
Sam recognises the value of the capability building programme for his educational pathway.
“The support of the NZAGRC was very important both financially and also through providing an opportunity for specific agriculture-related projects within New Zealand.
“It would have been possible to do without the funding support but very, very difficult. The funding support for both the PhD and post-doc was vital to both the projects happening.”
Looking to the future, Sam hopes to make a significant contribution to the science community and continue to work towards the balance between production and environmental outcomes within agriculture.
“A large aspiration is to find solutions to issues we currently face, such as greenhouse gas mitigation and climate change, so that future generations can also enjoy the world that we have been fortunate to enjoy. Another aspiration is to be a strong communicator of the findings of our research to the primary industries and the farmers on the ground in most need of the outcomes of the research.”
Outside of work, sport and the outdoors has always played a large an important part in Sam’s life. He has been involved in many sports over the years, some to a representative and national level, including representing New Zealand at the Junior World Orienteering Championships.
Currently, his spare time is spent with family, competing in triathlons, cycling and running.
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