HOLTVILLE, Calif. — It’s late when I check into the Barbara Worth Country Club, 600 miles southeast of my home in the Bay Area. Spare rooms border dark fields, a dry golf course and a web of open irrigation troughs that help make Imperial County one of the biggest agricultural producers in California. Holtville calls itself the carrot capital of the world, and even now, after this season’s harvest, stray carrot tops bolt, blooming to seed.