The 2021 Ploughing Trade Exhibition and World Contest, due to take place in Co Laois in September, has been cancelled due to uncertainty over Covid-19 restrictions.
It means that the event, which had 297,000 attendees in 2019, will not go ahead for the second year in a row.
However, the National Ploughing Association said that national competitions would still go ahead.
The NPA said that site work on the event would have needed to go ahead soon, however as there is a lack of clarity around what restrictions would be in place in September "it was felt that cancelling the 1,700 trade exhibitor event was the only option."
The association said uncertainty around international travel also fed into the decision.
"Public health and safety is of paramount importance to the association and unless the NPA were confident the Trade Exhibition could go ahead without causing any risk to exhibitors, competitors & visitors it would not be feasible," it said.
"As the timeline to start site works is imminent – the NPA just could not wait any longer to make a decision."
NPA managing director Anna May McHugh described the cancellation as a "massive disappointment" and said it represented a €50m loss to the economy.
"We are very conscious of the loss of revenue for our exhibitors and the disappointment of patrons," she said. "However, the NPA is a strong establishment, we have a massively committed team behind the event, our exhibitors and our patrons have been very loyal over the years and we look forward to bringing the Exhibition back at its full potential in 2022."
The NPA confirmed that the event would return to Ratheniska, Co Laois in September 2022.
It also plans to run activities around the national ploughing competitions this year, including virtual exhibitions.