LOS ANGELES — Chicken farmer Lucius Adkins doesn't see how he could stay in business if Congress passes an immigration reform bill that would require immigrant workers to go home for a year.

"I can't go six months without growing a chicken. ... We'll be out of business when they come back," said Adkins, who owns one of the biggest chicken farms in Georgia and serves as president of the United Poultry Growers Association.

U.S. businesses reliant on immigrants have long pushed for reforms to address their need for labor, but many at both ends of the spectrum complain that the proposal endorsed by Senate leaders and President Bush would prove too disruptive and make it too hard for them to find the workers they need.

In Adkins' case, the poultry processing plants that buy his chickens rely on immigrant workers. And if the processing stops for even a short time, his whole operation grinds to a halt.

Nationwide, industries such as carpet manufacturing, farming, poultry processing, meatpacking, construction, restaurants and hotels depend heavily on low-skilled or unskilled illegal immigrants. Technology companies, meanwhile, increasingly look outside the U.S. to find engineers, programmers and other highly skilled workers, who are here legally, mostly on temporary work visas.

Among other things, the legislation would grant legal status to the estimated 12 million illegal immigrants already in the U.S., allowing them to seek permanent legal residency or citizenship. They would be subject to a $5,000 fee and fines, and the heads of households would have to return to their country of origin temporarily.

The reforms also call for a guest-worker program that would issue about 400,000 visas a year for largely low-skill immigrants seeking employment for two years.

Sean McHugh, spokesman for the Greeley, Colo.-based meatpacking giant Swift & Co., said he supports many of the reforms but worries that the measure will cause high turnover.

"Our needs are year-round, and we do invest substantial amount of time and money in training a new hire, so we obviously prefer to keep them on the payroll rather than lose them," he said.

Many high-tech companies that routinely face shortages of skilled workers said the reform measure could make it tougher to find workers with specific skills and experience they need.

Currently, high-tech companies recruit foreigners who possess the precise skills they need. These foreigners are issued what are called H1-B visas.

The reform measure would instead create a point system that rewards people with advanced degrees and special skills. Some high-tech companies complain that this would give them less control over the selection process. They also say that the government needs to make more H1-B visas available to highly educated professionals.

Compete America, which represents such companies as Google, Intel and Microsoft, opposes the revamped guidelines for H1-B visas.

"This could be a disaster for U.S. competitiveness," said Vivek Wadhwa, an India-born founder of two tech startups in North Carolina. "We may get more cheap labor, but we're going to lose the engineers and scientists that we need to keep our global edge."

Some businesses also are worried about a provision that would require employers to verify workers' immigration status using a new computer database.

The National Association of Home Builders, which lobbies on behalf of construction companies, called the measure "unwieldy and unworkable."

The bill "would do irreparable harm to America's small businesses, which have generated the lion's share of new job growth in the economy," said Jerry Howard, the organization's executive vice president and chief executive.