Here is a book; Handbook of Plant-Based Fermented Food and Beverage Technology, Second Edition
Published:May 17, 2012 by CRC Press - 821 Pages
Cannot cut and paste from there. Try to google.. pit fermentation radishes .. click on the title of above book, it shoes up about 4th from the top. Click and you should on the right page.
Here is a summary; Radish
roots in the Himalayas are put in pits 2 or 3 feet deep and 2 or 3 feet wide. After about a month of lactic acid fermentation, the radishes are sun dried a few days. Then stored in airtight containers and will last several years this way. It is called Sinki.
My note (Sounds like this would be successful in an arid climate)
Here is another book, Himalayan Fermented Foods: Microbiology, Nutrition, and Ethnic Values . It shows up on the above search and says about the about the same thing but has pictures. Aloha, Kay