Thousands of farmers will struggle to reduce their carbon emissions due to the type of soil they are farming, as Climate Minister Eamon Ryan said “a lot” of rewetting of land would be required to aid Ireland in reducing its greenhouse gas emissions.
“Farmers have been told for 50 years that they have to drain land and now they are being told to wet it. That will be the case, but they will be getting paid for it because it is bringing back biodiversity as well as storing carbon,” Ryan said in the Seanad.
The Minister also signalled a “geographical divide” in relation to rewetting, adding that some farms will be doing that more than others, with “more of the north and the west getting the money, if I am truthful”.
Over 300,000ha of grassland is on peatland soil and emitting 8-9m tonnes of CO2 a year, according to Professor Gary Lanigan, Teagasc’s Principal Research Officer.
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“Mineral soils are seen as a sink of CO2 but peatlands have huge amounts of carbon in them and when they are drained for peat extraction or agricultural production, those grasslands emit a lot of Co2, on average 20t/ha/year,” he said. “While we estimate that non-peatland grassland is sequestering 1-3t CO2/ha/year, with additional management it could sequester another 1-1.5t/ha/year.
“However, 1ha of grassland on peatland or raised bog that has been receiving N,P and K is emitting the equivalent of five dairy cows per ha, without any cattle on it.
“The ideal scenario is to completely re-wet it and restore peatland or fenland, or failing that you can seasonally re-wet or raise the water table partially and gain some benefits.”
Ireland, he said, will have modelling to show how much carbon farms are emitting and sequestering by the end of 2022, with more data from 100 signpost farms coming available in 2023.
“Teagasc is measuring a lot and the main project is establishing a national agricultural soil carbon observatory.
“We are currently deploying 17 carbon flux towers around the country which will directly measure the amount of carbon being sucked up and released.
Teagasc research is focused on grassland and hedgerows, according to Lanigan, with the 100 signpost farms set to monitor soil carbon to a dept of 1m.
“We are looking at the amount of carbon in the soil and how old that carbon is. So not just what or how much, but what type of carbon is there – how much is long-lived or carbon that goes in and out of the sytsem quickly.
“We are also looking at hedgerow management and how to manage hedgerows to best manage sequestration.”
“The modelling will simulate the soil process and how much carbon is being sequestered into the soil, so we can match them up with flux tower measures and signpost farms and come up with a number for around the country.”
The modelling will allow carbon budgets to be created for fields, with the amount of carbon being emitted and sequestered through farming activities such as grass being grazed, dung, silage being cut, optimisation fertilisation and rotational grazing.
“By optimising your soil nutrient management, you can maximise the amount of carbon being captured by the sward and maximise the amount of carbon staying in there through better use of multi-species swards, or deep rooting grasses or the incorporation of straw,” said Lanigan.
“We need to maximise the amount of carbon our mineral soils can sequester and we need to plug the carbon hot spots — the peat soils.”