Soils deteriorated due to reduced lime use by farmers in 2019.
However, using less fertiliser and lime helped to reduce agriculture emissions by 3.9%.
The Environmental Protection Agency (EPA) has explained the apparent contradiction, whereby liming the soil (which the EPA says is “generally a positive thing”) leads to carbon dioxide (CO2) emissions.
A spokesperson said, “The action of applying lime to soils leads directly to CO2 emissions, however liming is generally a positive thing from a climate perspective, as liming aims to reduce soil acidity and improve plant growth, soil health and fertility.
“Maintaining soils at optimum pH and fertility status should result in significant reductions in fertiliser use which should, over time, more than offset increases in CO2 associated with the lime application itself.
“Given its role in improving soil condition, a reduction in the application of lime in 2019 is not considered to be a positive development.
“Teagasc has recommended increased action on lime usage, and it is also required under the Nitrates Regulations.
“Measures outlined in the Climate Action plan and Teagasc MACC such as switching to coated urea fertilisers, reductions in crude protein and increased uptake of low emissions slurry spreading are the preferred actions in terms of reducing agricultural greenhouse gas emissions,” said the EPA.
Adding carbonates in the form of lime leads to CO2 emissions, as the carbonates in lime dissolve and release bicarbonate, which breaks down into CO2 and water.
Farmers had been surprised when the EPA said reduced lime (and fertiliser) use on soils drove a decrease in agriculture emissions by 3.9% in 2019.
The announcement came in the same week that the Government told farmers they must apply lime, if a soil test shows it is needed, on lands with more than 170kg of organic manure nitrogen per hectare per year, equivalent to two dairy cows per hectare.
This becomes compulsory on January 1 next.
It is one of several new measures on farms which have over 170kg of organic nitrogen per hectare and which currently do not avail of the nitrates derogation.
IFA Environment Chairman Paul O’Brien urged caution after the 2019 EPA report attributed emissions reduction to a 10% decrease in nitrogen fertiliser use and 25% decrease in liming.
He said liming is proven to reduce emissions in the long-term, specifically of nitrous oxide.
He noted the benefits of lime are recognised in the Programme for Government, which outlines plans for a national liming programme to improve nitrogen fertiliser use and efficiency.
“I would be concerned that farmers are receiving very mixed messages on liming,” said Mr O’Brien.
Meanwhile, the EPA report noted that other key drivers of emissions in agriculture, such as the number of dairy cows, continued to rise in 2019, even as reduced fertiliser and lime use helped to bring down emissions.
Nevertheless, agriculture played its part in Ireland’s greenhouse gas emissions decreasing 4.5% in 2019, the largest annual reduction since 2011.
Despite this, Ireland is still not on the pathway required to meet future targets and a climate-neutral economy, said the EPA.
In 2019, energy industry emissions decreased by 11%, linked to decreased use of coal (down 69%) and peat (down 8%).
Residential emissions decreased by 7.3%, largely the result of a warmer winter.
Greenhouse gas emissions from the transport sector decreased marginally.