Four days of exhibitions at the UK's premier agriculture show are designed to show that Britain is "back in business" after last year's foot-and-mouth disease crisis.
The Prince paid tribute to the work of all those involved in the "horrors" of 2001.
"They were dark days for so many farmers, their families and many more in the wider community," he said.
The main thrust of his speech on Monday was aimed at looking to the future of British farming rather than dwelling on the past.
He said farmers must work together with supermarkets and if farming was to have a future, a new relationship must be built.
"I have to say that it is utterly incredible to me that farming - the basic industry of mankind - can be in such a state of crisis as it is today," the Prince said.
"The consumer needs to be made more aware that the seemingly endless desire for convenience and the lowest price has a direct impact, like it or not, on the producer.
Price matters
"There is a real cost involved in cheap food to the countryside, to those who live and work there and to animal welfare.
"Of course, I understand only too well that price matters a great deal for many families in this country.
The Prince said: "Situations can change in the world unexpectedly and there could easily come a day when the UK might be reduced to relying on its own resources again.
"So let us not sacrifice long-term security for short-term convenience."
The Prince also welcomed the shift, signalled by this year's Food and Farming Commission Report, the Curry Report, to move away from intensified food production towards quality.
"The UK may have difficulty competing with mass food producers, like the bread baskets of America and Central Europe, but what we do produce even for the mainstream market can be of a superior quality and service," he said.
"Whatever the short-term difficulties which are being faced by dairy farmers, I remain convinced that organic farming is a way forward for some farmers.
"I maintain that it is a more sustainable form of husbandry in terms of the long-term health of the soil, plants and animals.
"Supermarkets are forever saying that they cannot find sufficient quantities of organic produce to meet the demand and it seems to me utterly crazy that this food is imported when it could so easily be produced in this country."
Police expect 200,000 people to attend the show at the National Agricultural Centre at Stoneleigh Park.