OJOCALIENTE, Mexico —
They also go to extraordinary lengths to make sure the workers go back to Mexico at the end of the season, raising criticisms that the arrangement treats them as little more than human machines.
Mexico's new President Enrique Peña Nieto said that he has told Obama that his administration is keen to "contribute" to a push for U.S. immigration reform.
Such talk would have been too politically sensitive just six years ago, when the volume of Mexican migrants crossing the border was seen as out of control and the U.S. Border Patrol was making more than a million arrests a year.
Last year, the Border Patrol made just 340,000 apprehensions, the lowest level since 1971, the result of a tighter U.S. job market, stiffer U.S. enforcement and widespread fears in Mexico of the kidnapping crews and drug gangs who roam the borderlands.
Overall, nearly as many Mexicans are now leaving the United States, whether voluntarily or as deportees, as the number who arrive, a trend that has raised alarms of labor shortages in industries such as food service and farming that are historically dependent on low-paid migrants.
"For anybody who believes that there will be a wild and endless flow of [Mexican migrants] into the future, that's just not realistic," said Craig Regelbrugge, vice president for government relations at the American Nursery and Landscape Association, a trade group.
According to industry estimates, U.S. farms hire more than 2 million workers each year, at least half of whom are thought to be in the country illegally.
Farm laborers already tend to earn minimum wage or more, experts say, so employers wouldn't necessarily have to pay higher wages to guest workers than what they currently pay illegal migrants.
Still, some U.S. farmers and other employers fear that if the illegal workforce is granted legal status or "amnestied," many of those workers will seek jobs in less arduous occupations.