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 worldΆs 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!Ά ”

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.

Until recent years, students, some as young as 7, were routinely called on to pick cotton, and some high school-age youths still do. But pressured by a boycott organized by the Cotton Campaign and the Responsible Sourcing Network, groups that have worked with major Western garment companies, Uzbekistan has mostly stopped using students in the fields. To replace them, the authorities have in effect turned to their parents.

It is one of the worldΆs more bizarre systems of agricultural labor, possible, perhaps, only in one of the worldΆs most cloistered and repressive societies. Central AsiaΆs most populous country, at 30 million, Uzbekistan since 1989 has been ruled by President Islam Karimov, first as a Soviet apparatchik and later as head of state. Human Rights Watch estimates that the country holds more political prisoners than the rest of the former Soviet Union combined.

To hear the government tell it, all these teachers, doctors, bureaucrats, employees of small businesses, engineers and architects “volunteer” for a few weeks of farm labor each year.

“The government doesnΆt invest in mechanization at all because they have cheap labor, and cotton gathered by hand is more valuable,” said Sergei V. Naumov, an Uzbekistan-based reporter for Ferghana.news, a website for Central Asian news, who has covered the harvest for a decade.

In simplest terms, it is a system of forced labor, rights groups and international labor monitors say, an old scourge of the cotton industry that has returned to life. With its monopoly on the industry, the government pays far below world prices for the cotton, reaping extortionate profits that help balance the budget. In return, it provides farmers with free labor.

Still, the international apparel industry, having tolerated forced labor of younger children in UzbekistanΆs fields and already stung from negative publicity for relying on Asian sweatshop labor, has extended its boycott here to include forced labor of any sort. So far, 136 companies, including Disney, Fruit of the Loom, Gap, H & M, LeviΆs and Walmart, have pledged to avoid knowingly buying Uzbek cotton as long as the practice continues.

That threat goes unheard here through the harvest months, from mid-September to mid-November, when more than a million people are sent from cities and villages into the sprawling fields of mud and ripe cotton plants. There, the conditions for teachers and doctors are not so different from those of the slaves of the past, but with one modern twist.

“Nobody beats you with a whip,” Muhabbat Abdullayeva, a stately, plump woman with short, dyed-red hair who teaches at an elementary school, said in a village near Samarkand.

But failing to “volunteer” can lead to being fired or arrested.

Come harvest time, office managers and school principals divide employees into two groups, then rotate them through cotton picking and ordinary duties. Those not picking work a double shift or, in the case of teachers, combine two classrooms.

In this system, your boss at work is also your boss in the fields. Cotton-picking skills become a component of annual job evaluations, skewing decisions on promotions, said Dmitri Tikhonov, a rights activist and an authority on UzbekistanΆs cotton-picking policies.

Cotton picking aggravates office politics when, for example, a promotion goes to an otherwise inept doctor or teacher who is a stalwart in the fields.

There, men with scales weigh the sacks, then unwrap them to add their contents to dirty-white heaps of cotton piling up on carts, which eventually make their way into the international cotton supply chain. The men jot a figure next to each pickerΆs name, moving them closer to the government-set quota and freedom, at least until the following year.

In June, the State Department ranked Uzbekistan in the lowest category for tolerating human trafficking and forced labor.

“What makes the situation in Uzbekistan so unusual is that the Uzbek government works as the trafficker in chief, mobilizing the population with the use of officials at all levels,” Steve Swerdlow, a Central Asia researcher with Human Rights Watch, said in an interview. “Millions of its citizens pick cotton in abusive conditions, exposed to pesticides, without potable water, with inadequate shelter, for which they receive little or no pay.”

Dr. Khidoyatova, in an interview in her kitchen, over tea and plates of raisins, almonds and lumps of brown sugar, the local delicacies, said, “Every fall for the past 22 years, all the years of Uzbek independence, I had to pick cotton, and every year things only get worse.”

The police in UzbekistanΆs Soviet-style government control the harvest with the threat of criminal prosecution of employers who fail to compel their workers to meet quotas. (The charge is usually formulated as sabotaging state property, as the cotton harvest belongs to the state purchasing monopoly, Uzkhlopkoprom.)

Yet, strangely, it is legal to hire a substitute for the season. Employees whose numbers get drawn to pick cotton often find a day laborer or homeless person to take their place.

Finding a willing family member is another way out. “If you canΆt go, you have to send your brother or sister, whomever you can,” said Sayeed, a 27-year-old doctor in Samarkand, who did not want his last name published for fear of retribution.

Every cotton harvest, meanwhile, brings more signs of dysfunction in the general economy because of absent employees. Hospitals close for all but emergencies. The social welfare system breaks down, as bureaucrats who disburse pensions are no longer at their desks.

The Uzbek government characterizes the widespread participation in the harvest as upholding tradition or patriotic service, akin to volunteering for the National Guard or a neighborhood cleanup. Pickers are paid about 3 cents a pound, a pittance even here. Sometimes, the cost of a bus ticket and food exceeds this payment, meaning laborers work for nothing or even end up owing the state.

In a speech in October, Mr. Karimov praised the citizenry, saying: “Since olden days cotton has been seen as a symbol of whiteness, of spiritual purity. And only people of pure mind and beautiful soul are capable of farming it.”

Rights advocates say they are shocked to find that their efforts are sometimes resented inside the country. “ ΅What have you accomplished?Ά ” Mr. Tikhonov, the rights activist, said Uzbeks had told him. “ ΅You wanted to eliminate child labor, so now we have to do it.Ά ”

Mansur Mirovalev reported from Samarkand, and Andrew E. Kramer from Bishkek, Kyrgyzstan.