Fantasize walking into your neighborhood supermarket: You find huge posters on the walls announcing the supermarket chain has decided to help the nation's farmers go organic. You push your basket to the produce aisle, once the exclusive domain of foods grown the chemical way - but today there are lush fruits and vegetables grown organically, without any artificial fertilizers or pesticides, selling at regular supermarket prices.

"This program is one of our greatest achievements," the posters proclaim, "which proves to our customers that all these agricultural products are really natural, and therefore tastier."

The fantasy seems Iudicrous here in 1978. But walk into one of the ultramodern supermarkets in Switzerland's $3-billion co-op Migros supermarket chain and that's exactly what you may find, posters and all. Ever since its customers declared overwhelmingly in a 1970 survey that they'd prefer to buy organically grown foods, the Migros chain has launched a nationwide campaign to help satisfy them.

A special team of technicians is helping teach farmers how to shift toward organic methods in the fields, and the 2,000 farmers who are participating in the special conversion program get preferential treatment over conventional chemical farmers when they go to the supermarket to sell their crops.

While some of the special produce in the supermarkets, tagged by the label, "Migros-S-Production," is already strictly organic, most of it comes from farms that are still in transition: They're cutting back on chemicals and using more organic methods, but they're not yet completely weaned from the chemical habit. "Such a conversion," says a food industry executive close to the Migros program, "needs an education of many years."

The Migros campaign is just one reflection of the growing movement for organic agriculture - across the Atlantic the term is biological agriculture - in Europe.It symbolizes the dramatic differences between the climate in Europe toward alternative methods of agriculture and that in the United States.

To Americans raised on the lessons of agribusiness, "organic" means a backyard garden or a natural food store bin full of worm-eaten tomatoes. "From a practical point of view," says USDA research administrator James Iacono, "talking about organic agriculture has no bearing on reality. We can't start turning back time and science."

But as policy-makers and scientists in Europe watch problems mounting on the farms - problems such as soaring chemical costs, environmental pollution from fertilizers and pesticides, and growing resistance of insects to potent pesticides - they are turning toward sophisticated organic methods as a potential solution.

In Holland, a government commission for Investigation of Biological Agricultural Methods declared last year that "alternative farming methods have to be seriously considered." The commission, which included top officials in the food and agriculture ministries, called for "urgent" research on the potentials of biological farming techniques.

In Germany, the state government of Bavaria recently converted a 200-acre conventional farm to an organic system, expressly to conduct research. "They think the biological system might help farmers get more out of their land," a source in the German Federal Department of Agriculture explains.

And three years ago, the Council of Europe, an official branch of NATO, unanimously passed a special resolution urging member governments to set up "pilot farms to carry out long-term experiments on the effectiveness of various farming techniques, including 'organic' farming." A "biological approach to agriculture," the council asserted, "should be introduced into the struggle to improve the quality of life."

Attribute it to accidents of history, or politics or topography, but massive chemical-intensive farms have never gobbled up the small family farms in Europe quite as voraciously as in the United States. With their Old World roots more intact, many farmers have retained, or rediscovered, a fierce commitment to a more natural system in their fields.

I visited organic farms sprinkled across Switzerland and Germany with a contigent of skeptical American farmers, agriculture extension agents and the Massachusetts state secretary of agriculture. They were storybook farms, 80 to 200 acres, with centuries-old timbered barns, alabastered houses, women baking thick-crusted, whole-grain breads in brick ovens and profusions of flowers planted in the fields.

In a competitive Common Market, organic farmers such as Germany's Hans Werner told us they were prospering with a rich blend of grains and livestock, vegetables and fruit orchards - and, Werner said, about $100,000 worth of modern equipment in the sheds. These farmers didn't go organic to earn spiritual points but to escape the mounting side effects of the chemical system: "My use of pesticides and fertilizers was increasing every year and I saw no end to it," said Werner, whose family has been farming the same land since 1890.

"Also there was a lot of bad air pollution from a factory down in the valley, and I thought the crops might be more resistant to the pollution if they were grown organically."

"I don't think I'll learn much." one U.S. agriculture extension agent scoffed as we embarked on the organic farm tour. But as they trekked from one commercial organic farm to another, the U.S. farm experts saw years of agribusiness teachings shattered before them in the fields. "I don't believe that anybody can grow any crop, I mean any crop, without pesticides and not get wiped out by diseases and insects," said University of Massachusetts extension agent Roger Harrington. But as they walked through the organic fields, the U.S. experts shook their heads in disbelief. "The thing that's amazing to me," said Winston Way, extension agent at the University of Vermont, "is that I have never seen healthier plants. I mean the plants in these organic farms are luxuriant."

And even the toughest skeptics on the trip conceded they were impressed by the organic farmers' sophisticated methods of fertilizing their crops, organically, In the U.S. use of petrochemical-based fertilizers has more than doubled on major crops in just the past dozen years, in Europe, the organic farmers grow their nitrogen fertilizer in the fields, by planting special blends of up to four different "cover" crops which suck nitrogen from the air and "fix it" in the soil."That's the biggest thing that's impressed me," said Harrington. "These farmers have really made themselves independent of the Arabs."

"These organic farms were really way beyond my expectations," said Fred Winthrop, Massachusetts secretary of agriculture and a part-time farmer. "While I'm not willing to accept everything the (organic) farmers said at face value, I do know this: It would be a mistake for those of us in the United States to miss the boat on doing basic research on biological farming."

One reason why members of the U.S. agriculture establishment have found it so easy to ignore the potentials of organic farming is because they have never seriously researched organic farming techniques - and compared them to conventional methods. "One main reason why," says James Parr, chief of the U.S. Department of Agriculture's biological waste management and soil nitrogen laboratory, "is that proponents of organic farming have been looked upon as a bunch of nuts."

But in Switzerland, the Research Institute for Biological Husbandry is conducting careful research, respected in the agricultural science community, comparing organic and conventional techniques on a 100-acre farm. Policy-makers and food industry executives take the Institute's work seriously: The researchers are fueled with grants from the Migros chain, a Swiss canton (Switzerland's version of a state) and with funds from the nation's counterpart of the National Academy of Sciences.

Preliminary studies suggest that conventionally grown crops are attacked by greater numbers of pests than their organically grown counterparts, according to Institute director Hardy Vogtmann. Researchers at the German Federal Institute for Quality Research on Plant Products and at Sweden's respected Agricultural College in Uppsala have been comparing the nutritive value of organic vs. conventionally grown crops.

USDA officials will tell you, "there is no proved, substantiated basis" for claiming that organic foods "have a greater nutrient content." But the preliminary, unconfirmed results in Germany and Sweden suggest that some organically grown crops may well have higher quality protein and other major nutrients than their chemically grown cousins.

Although three decades of U.S. agriculture research, education and government policies have promoted chemical methods on the farms, small but growing numbers of commercial farmers across the country are converting to organic systems. Researchers at the University of Washington in St. Louis, for instance, have found more than 250 commercial organic farms in the Corn Belt. There are large-scale commercial farms growing organic vegetables, grapes and citrus in other parts of the nation, too.Like the organic farmers in Europe, they abandoned chemical methods and shifted to organic systems when side effects of the chemicals started to damage their crops - and their profits.

But while the farmers are benefiting from growimg crops the organic way, most consumers are not: The produce grown by most of these farmers is not identified as organic in the stores. Most of these farmers are forced to sell their crops through conventional wholesalers, who mix them together with chemically grown foods because there is simply no organic marketing network set up in the U.S. big enough to handle the volume these organic farmers produce.

The only stores in the U.S. that sell foods labeled as organic are small health food stores. They buy from marginal farmers and sell in such uneconomically small quantities that they are forced to hike up the retail price. That's the main reason organically grown foods in the U.S. cost so much at retail. On large-scale organic farms, studies by University of Washington researchers suggest, the cost of organic crops is no more than on conventional chemical farms.

But while America's organic farmers are isolated and weak, organic farmers in Europe have built strong and supportive marketing organizations. In Switzerland, for instance, more than 600 organic farmers have joined the Bio Gemuse Cooperative, which sells $3.5 million worth of their organic produce, milk and meat to major supermarkets, as well as to health food stores, each year.

They are out to prove "that organic agriculture is possible at reasonable prices and with capitalistic profits."