Deputy Prime Minister Bill English has opened the 47th National Agricultural Fieldays at Mystery Creek.
People were queuing at the gates long before they opened at 8am.
Organisers were expecting about 120,000 people to attend, the same as last year.
They said that despite the downturn in the dairy sector, other areas of farming and horticulture were doing well and this was reflected in a similar number of exhibitors to last year - about 1000.
The Southern Hemisphere's largest agri event has a strong focus on innovation and education to encourage young people into careers in areas such as agri business and agri science.