WASHINGTON — A comprehensive survey of all known organic producers who are certified, exempt from certification or transitioning to become certified has been launched by the U.S. Department of Agriculture. Conducted by the department’s National Agricultural Statistics Service, the survey will explore a range of aspects of 2014 organic farming from production and marketing practices to revenues and costs. U.S.D.A. deputy secretary Krysta Harden said U.S. organic sales climbed 83% between 2007 and 2012. “As we look to the future, the important information we gather will be crucial to capturing the strong private and public sector support to sustain the continued growth of this industry,” she said.