Agriculture accounts for about 7% of the economy and 8.5% of employment.
The real boost is in the welfare payments that farmers receive from the EU as it accounts for about 56% of farm incomes.
Output of the entire agriculture, fisheries and forestry sector was about €3.5 billion, or about 2% or modified GNI (aka GNI*) in 2017. This is pretty much what leaves the farm gate, is landed at the pier, and is cut in the forest.
The issue is that everyone involved in agriculture likes to add the output of the food processing sector (8.8bn, or 4.8% of GNI*) on top, as this makes the sector look a lot larger and more productive. In fact, much of the food processing sector has nothing at all to do with the agriculture sector!
You have to go to the UN trade database to find out, but Ireland has a lot of very obscure food exports. For example Ireland exported nearly $500m 'food preparations not elsewhere specified' in 2017. It is not at all clear what this is, but it is likely bulk ingredients or concentrates, as the value is an incredible $7 per kilo!
This is down to clever scientists in big food companies based in Ireland (some Irish-owned, some foreign-owned). For sure, Paddy down the farm is not producing anything with a wholesale price of $7 per kilo. The primary agriculture sector (everything as far as the farm gate) is deeply unproductive. It generates wages and profits of only €1 billion per year for its 100,000 employees - not counting the subsidies it receives which are nearly as much!
All of this demands a very sophisticated understanding of economic statistics. Sadly, it's something completely lacking in the Irish media, which just parrots the propaganda of the sector as it comes along.