The Prime Minister has opened the 47th National Agricultural Fieldays at Mystery Creek, near Hamilton.
A record 1000 exhibitors are at the four day event.
Last year Fieldays contributed just over $420 million dollars to the national economy through revenue it generated.
The President of the New Zealand National Fieldays said it was likely the downturn in the dairy industry would have some effect on sales at this year's event.
Warwick Roberts said he did not expect attendance numbers to be down this time because of the dairy slump.
"I think if I were a farmer and I was depressed about the amount of money I had to spend I would probably come along.
"Because at least I am not on the farm looking at things that need doing and can't be done, and the opportunity to actually review anything that is new, maybe the ability to reduce costs in some areas."
Mr Roberts said there was a big push this year on agricultural innovations at the Fieldays.
Last year 120,000 people attended the event and numbers were expected to be similar this week.