The labourers, many of them migrants, lived in shanty towns at Borgo Mezzanone near Foggia.
They were allegedly paid slave wages to fill 56 crates of vegetables, mostly tomatoes, in eight hours of backbreaking work, police said.
To add insult to injury, police said, they were forced to pay out five euros from their scanty wages to the gangmaster who recruited hem and brought them to the fields in his truck.
They were closely watched during their shifts, unable to take breaks and regularly insulted, police said.
Interior Minister Matteo Piantedosi said "gangmastering must be stamped out, it is a criminal phenomenon that wounds people's dignity".
Italy's foremost anti-gangmastering campaigner and only black MP, Aboubakar Soumahoro, has recently become embroiled in an alleged exploitation scandal that has hit the farm cooperatives run by his wife and mother-in-law.
ANSA
