Soil Carbon Sequestration
Carbon sequestration is a biological process that takes place as part of the carbon cycle. Carbon sequestration occurs when carbon dioxide (CO2) is absorbed from the atmosphere by plants during photosynthesis. Carbon is then assimilated into its organic form and can either be respired (by plants or microbes) or stored more permanently in the terrestrial biosphere i.e. in soil or in woody biomass.
Gross carbon sequestration equates to the difference between respired and stored carbon. If the rate of ecosystem respiration is greater than storage then the ecosystem is acting as a source of CO2. Conversely, if more carbon is stored than respired, an ecosystem will act as a CO2 sink. Globally, soils and forests store vast amounts of carbon with agricultural ecosystems such as grasslands, peatlands and woodlands acting as important sinks.
In Ireland, temperate agricultural grasslands have significant potential to sequester CO2 as part of root biomass and in the soil. This could potentially aid in offsetting some of the methane and nitrous oxide emissions associated with agriculture. Therefore, enhancing carbon sequestration is vital for climate change mitigation and meeting greenhouse gas reduction targets.
There are a number of factors that influence the rate of carbon sequestration in agricultural ecosystems including:
- soil type
However, there are uncertainties surrounding the baseline soil carbon stocks and the role of certain soil types, hedgerows and management practices. This in turn, makes it difficult to measure the overall rate of carbon capture and storage.
Eddy Covariance is a micrometeorlogical technique used to directly measure the rate of CO2 exchange between the atmosphere and terrestrial ecosystems. In 2021, The National Agricultural Soil Carbon Observatory (NASCO) was funded by the Department of Agriculture, Food and the Marine (DAFM). Establishment is currently underway and will include 32 Eddy Covariance Flux Towers located on benchmark sites including agricultural grasslands, mineral soils and peatlands. The data generated will provide accurate, long-term information on the carbon dynamics of Irish agricultural systems. This will also complement the greenhouse gas research carried out as part of Teagasc Sign Post farms, Vista Milk, Terrain AI and the Agricultural Catchments Programme. Overall, NASCO will place Ireland at the forefront of international carbon research and will enable:
- Improved measurement, modelling and mapping of carbon uptake and release from agricultural land
- Accurate assessment of carbon sequestration according to climatic conditions, soil type and agricultural management practices
- Better understanding of the efficacy of mitigation measures to increase carbon sequestration
- National inventory and emission factor refinement
- Allow for participation in the EU ICOS (Integrated Carbon Observation System) network
Nasco 4 – Long term grazed grassland site with eddy covariance tower at Johnstown Castle, Co. Wexford.
Nasco 5 - Eddy covariance tower deployed on a Tillage site in the Castledockrell catchment, Co. Wexford
Signpost Programme Soil Carbon Sampling
The first phase of a national soil sampling campaign was undertaken in 2021/22 across 104 Signpost Programme farms. Extensive soil sampling was performed on each farm to inform on the general nutrient status and gather preliminary information on soil organic carbon stocks. Ten centimetre core samples were taken across all Signpost farms, with further deep soil sampling scheduled to take place in 2022. Samples have been analysed for total carbon and organic carbon as well as pH and other major nutrients and trace elements. These analyses will act in tandem with the data from eddy covariance towers to help quantify soil carbon stocks and carbon sequestration rates on Irish farms. In turn, this will allow for a greater knowledge of sustainable land use management and will allow farmers to implement emission-reducing farming systems.
Technicians taking 10cm soil samples as part of the Signpost soil sampling campaign, Co. Roscommon.
What is carbon sequestration? Researcher Gary Lanigan gives an explanation and examples of carbon sequestration. He explains by increasing carbon sequestration, farmers can increase their soil organic matter levels and help to slow the negative impacts of climate change.
One of the main management practices to increase carbon sequestration and soil organic matter build up on farms is to optimise soil fertility. Watch David Wall as he runs through 5 steps to enhancing carbon sequestration on your farm
More research is needed to understand the carbon dynamics in hedges. Farm Carbon is a research project cofunded by the Environmental Protection Agency and the Department of Agriculture, Food and the Marine. Lilian O'Sullivan, Teagasc Johnstown Castle explains more
This webinar is focused on how soil organic carbon cycling works in Irish soils. Teagasc Researchers give an insight into their research and an overview of organic carbon cycling in Irish soils and its contribution to mitigating climate change
In this webinar on Sustainable Agriculture host Pat Murphy, Head of Environment KT Teagasc was joined by Donal O'Brien, Teagasc to discuss Carbon Sequestration in Grassland.
Speaker: John Muldowney, Department of Agriculture Food and the Marine Moderater: Mark Gibson Teagasc
Find out more about the Eddy Covariance technique used to directly measure the rate of CO2 exchange between the atmosphere and terrestrial ecosystems in the videos linked below: