FRESNO, Calif. — There was a time when Fong Tching's four children worked the fields and accompanied him to the market to help sell their strawberries, eggplants, sugar cane and 60 other crop varieties.

But one by one, the kids are leaving the family business, going to college to pursue more lucrative professions in pharmaceuticals and engineering.

"It's just me and my wife working 30 acres by ourselves," said Tching, 45, surveying a field of ripened berries.

Tching is an ethnic Hmong, a tribe from the hills of Southeast Asia with agriculture in its blood. His children are among the first generation of Hmong in the United States that are not farming.

While no one is tallying how many younger ethnic Hmong are abandoning tradition, leaders in the immigrant community and agriculture industry observers say the trend is striking.

It is a familiar pattern among immigrant farmers — the number of Japanese-American farm laborers who first came to the state in the early 1900s dwindled after World War II.

"They grew up and saw the toughness of farming, their parents working year-round, and they saw that hard labor don't necessarily pay off," said Manuel Cunha, president of Nisei Farmers League. The Fresno-based group was founded in 1971 by second-generation Japanese-American farmers, but most of its 1,000 current members have no Japanese ancestry, Cunha said.

For the Hmong, the same kind of shift means a loss of tradition that dates back centuries. The ethnic group subsisted on farming across generations of migration, until many of the men were recruited by the United States to fight communists during the Vietnam War.

After the communists won in 1975, about 44,000 Laotians, mostly Hmong, fled to camps in Thailand, according to an analysis by the Washington, D.C.-based Migration Policy Institute.

Many Hmong in Southeast Asia continue farming. Those who came to the United States have settled primarily in California, Minnesota and Wisconsin. The 2000 Census counted 102,773 Hmong, roughly 30,000 in the Fresno area.

Tching said he immediately rented farmland when he came to Fresno in 1988. The work allows freedom — "You're your own boss," he says — but requires long hours. On Fridays, he and his wife often work into the night packing vegetables, sleep for three hours, then make the three-hour drive to a farmers market in the San Francisco Bay Area.

"When I came here, I didn't have a chance to go to school. What I knew was farming, so that's what I did to raise my family," Tching said. "I don't blame them for not wanting this hard life."

Michael Yang is an example of a Hmong who came of age in the United States and didn't follow his parents into the fields. Instead Yang, who came to the country at age 9, went to college in Northern California and came back to Fresno as a farm adviser, rather than a laborer.

Hmong have struggled to learn new farming techniques and adhere to state regulations, said Yang, whose job at the University of California Cooperative Extension Service is to reach out to the roughly 1,000 Asian-owned family farms in Fresno County and help them better manage and market their crops.

The majority of Hmong who came to California's Central Valley are farming on a small scale, Yang said, growing exotic crops such as bok choy, daikon radishes, bitter melon and yard-long Chinese string beans.

There is a growing demand for such vegetables. In 2004, "Oriental vegetables" accounted for $15.7 million in sales, according to the Fresno County agricultural commissioner's office, up from $10.3 million the year before.