The National Ploughing Championships have begun in Annaharvey near Tullamore, Co Offaly.
Up to 150,000 spectators are expected on the 500-acre site over the next three days and special disinfectant facilities are in place near the livestock section as a precaution against foot and mouth disease.
Farmers are also on the alert against another livestock virus known as 'Bluetongue'.
The festival, which has been held for over 70 years, is now one of the biggest rural events in Europe.
President Mary McAleese and government ministers from both sides of the border will attend the event.
On opening the event, Mrs McAleese said farming is still the backbone of rural Ireland.
People from all over Ireland will converge to watch the ploughing competitions and to get the latest business and technical information at the 850 exhibition stands.
Gardaí have a special traffic plan in operation in the Tullamore area.
