Around 150,000 people are expected to attend the National Ploughing Championships in Mogeely, Midleton, Co Cork, today.
It is the largest outdoor farming event in Europe and the largest ploughing championships in the world.
The event will be attended by President Mary McAleese, Taoiseach Bertie Ahern and other political leaders.
A traffic plan for the event will affect traffic movement within 32 kilometres of the site, and all traffic not associated with the event is advised to avoid the area.
There will be 700 exhibitors on a 20-hectare (50 acre) tented site on the grounds near Midleton, just off the N25 which links Cork and Waterford.
Sixty-five hectares of tillage land has been set aside for the 300 competitors, who come from every county in Ireland. Entries have also been received from five other countries.
Car parking space will occupy a further 81 hectares (200 acres) and the tented villages where the exhibitors will be set up will occupy an area of just over 18,580 square metres.
There will be more than €20 million worth of farm machinery on display at the site.