The sweet potato harvest starts in mid-September and can extend as late as mid-November. Thousands of agricultural laborers trudge through the fields, filling buckets with the tubers and hauling them back to waiting trucks. Sometimes they work as few as five hours a day; sometimes, as many as 12. One full bucket earns a worker about $0.40 or $0.50. But the work — crouch to fill the bucket, run it back to the truck, repeat over and over until the day is done — is backbreaking.

Welcome to North Carolina, where the state vegetable is the sweet potato and the state minimum wage is $7.25. Nearly half of the United States’ crop hails from here, especially the coastal plain region. Any given Thanksgiving feast is likely to include at least a portion of that crop, harvested by low-wage workers under grueling conditions.

“Sweet potatoes are definitely one of the biggest labor-intensive crops in the state, second probably only to tobacco,” Justin Flores, vice president of the agricultural workers’ union FLOC (Farm Labor Organizing Committee), told Al Jazeera America.

Like tobacco pickers, sweet potato harvesters often don’t receive a standard hourly wage. Instead they’re paid a piece rate, meaning compensation is based on the volume they’re able to haul each day. The law says their hourly pay can never dip below the legal minimum wage, but employers don't always comply, said Flores.

“In sweet potatoes, you get a lot of the folks who are working for the bucket,” Flores said. “And for big chunks of the season, they’re making less than minimum wage. It really depends on the yield of the farm you’re working at.”

Exact data on wages can be hard to come by, given the casual, seasonal nature of the work and the fact that many agricultural laborers are undocumented immigrants. The most comprehensive figures in recent years were probably those from the U.S. Labor Department’s 2005 National Agricultural Workers Survey, based on 6,472 farm worker interviews conducted between October 2000 and September 2002. The survey found agricultural workers’ average income to be somewhere between $10,000 and $12,499 per year.

And low wages might not be the worst of it. Last month, the Urban Institute, a public policy think tank, released a major study on labor trafficking in the U.S. that found agriculture to be among the top industries in which trafficking occurs. Many of those trafficked workers are children.

A 2013 survey of North Carolina agriculture workers found that roughly 25 percent “reported ever experiencing a situation that may constitute trafficking.” For example, the researchers said they heard reports of "workers who reported not being able to leave the camp, being paid less than expected, and appearing fearful."

Many of the North Carolina farm workers who spend their autumns harvesting sweet potatoes wind up picking tobacco over the summer. Thousands of those tobacco pickers work on farms that have contracts with the tobacco giant R.J. Reynolds, and FLOC is currently attempting to push the company into guaranteeing a baseline for labor standards on all of those farms.

North Carolina tobacco travels around the world, including to the United Kingdom. As a result, FLOC's campaign has attracted the support of two Labour members of the UK's parliament, who earlier this month filed a report on labor conditions in North Carolina tobacco fields. The report, titled “A Smokescreen for Slavery,” was based on the testimony of FLOC President Baldemar Valesquez and the MPs' own visit to the U.S.

“We get pesticidies sprayed near us when we work and we don’t know what they are,” one agricultural worker told the MPs, according to the report. “This season, I got sick from the chemicals and one day I was sick in the bathroom and the supervisor came and told me I had to get back to work. When I couldn’t, he told me he didn’t need me anymore and that was my last day working there.”

Documenting the plight of American agricultural workers has been something of a Thanksgiving tradition ever since 1960, when CBS first aired “Harvest of Shame,” a special report featuring the legendary newscaster Edward R. Murrow.

“One farmer looked at this and said, ‘We used to own our slaves. Now we just rent them,’” Murrow said at the beginning of the report, over scenes of migrant laborers headed to work.

Bruce Goldstein, president of the nonprofit advocacy group Farmworker Justice, said there has been some substantial progress in the half-century since that report aired — but not enough.

“Conditions for most farmworkers are still pretty poor,” he said. “So the degree of improvement since 1960 is disappointing.”

Goldstein singled out U.S. immigration policy as one major factor that continues to suppress labor standards in the agricultural industry, because the undocumented workforce is particularly vulnerable to abuse.

“Conditions have either stagnated or gotten worse over the past few years because of the broken immigration system,” he said. In his eyes, the harvest of shame continues.