Nosir Mamurzoda says he was detained along with a correspondent for Tajikistan's Avesta news agency.
Ther two men were then taken to a police station for questioning.
Mamurzoda says he was released after being warned to be "careful" to not report about news that could "destabilize the country."
Tajik President Imomali Rakhmonov on September 12 decreed that students and schoolchildren should not participate to this year's cotton harvesting campaign.
International organizations have been critical of Tajikistan, Uzbekistan and Turkmenistan for forcing schoolchildren and students to pick cotton for meager wages or for none at all.