Questions over how rural Wales would be affected should the UK leave the European Union are likely to be a key feature at the Royal Welsh Show.
Phil Hogan, the European Commissioner responsible for farming and rural development, officially opened the event near Builth Wells, Powys.
Welsh farmers receive, on average, £13,000 every year from the EU to produce food.
Wales' deputy farming minister has said an EU exit would be "catastrophic".
As well as farmers' subsidies, Wales also gets £50m a year for rural development and other projects.
These include creating jobs in rural communities, looking after the environment or restoring village halls.
Mr Hogan will be speaking at various events as the debate about the UK's role in the EU gains pace.
Irishman Mr Hogan was unveiled as the new commissioner last September, a key role with agriculture responsible for 40% of the EU budget.
He is meeting farmers' leaders, deputy minister for farming and food, Rebecca Evans, and organisations representing the food industry.
Mr Hogan said: "We want to work together, in a European sense, 28 member states in a 500 million population market to ensure we have product opportunities for our farmers in the UK but equally that we have good quality, safe products for our consumers in the UK."
He said common agricultural policy reforms had been more market-orientated, meaning that farmers and agri-businesses could make "informed decisions about what they want to produce".
There are many questions about whether a UK government would give farmers the same level of funding they get now if the UK was to leave the EU.
Whether trade barriers or tariffs would be introduced in order to buy and sell with EU members is also of concern.
If the UK were to leave the EU, there would have to be a negotiated exit and trade agreements would be established as part of that.
Those who want the UK to leave argue it would forge its own trade links across the world. Those who want it to remain a member of the EU argue its trading position would be weakened.
Farmer Lorraine Howells, who rears Welsh black cattle in the Rhymney Valley, wants the UK to stay in the EU but said even with European money, they were just breaking even.
"We're not making enough money," she said.
"Our money goes out very quickly. For every pound in the rural economy we spend it creates jobs and makes the landscape something to be proud of - without farmers you wouldn't have the countryside that people come to.
"I firmly believe we should stay in Europe - 92% of food exports go to Europe, 170,000 are employed in that sector and we can't be without that.
"We all moan about decisions but farmers are renowned for moaning but let's reform Europe."
"We would have to compete with other sectors and we wouldn't have a hope against health and education [if farming funding was from the UK Government instead].
Meanwhile, First Minister Carwyn Jones will also visit the show in Llanelwedd, which is one of the biggest of its kind in Europe.
"Every year it continues to grow, going from strength to strength," he said.
"Its success is testament to the vibrant rural economy we have in Wales and our farming industry as a whole."