SAMARKAND, Uzbekistan — For most of the year, Dr. Tamara Khidoyatova treats patients as a doctor at a hospital here in this picturesque, old Silk Road city. But for a few weeks every autumn, she is forced to pick cotton, for which she is paid little or nothing.

Throughout the fall, when the cotton harvest comes in, the government drafts about a million people, primarily public-sector employees and professionals, to work as cotton pickers, helping bring in the harvest for the world’s fifth-largest cotton exporting nation.

“You come to work, with all the makeup, wearing nice clothes, good shoes,” Dr. Khidoyatova, 61, said. “And the polyclinic director runs in and says, ‘I need 40 people in the field, the bus is outside, hurry, hurry!’ ”

That was just a day trip. But most people are given some notice, and then go away for a month at a time. Once in the fields, pickers loop heavy cloth sacks over their necks, stoop between the furrows and repeatedly clutch at the white puffs to gather a quota of 120 pounds of raw cotton a day. At night, they sleep on cots in the gymnasiums of village schools or in crude barracks in the fields.