Should I store root vegetables with or without the dirt? When you buy vegetables at a farmers market, often you will get root vegetables (e.g. potatoes, carrots) that are unwashed and with its dirt still clinging on them. I heard somewhere that this will prolong its shelf life. Is this true? If so, how?
Not really, the dirt's there because of:


Authenticity: dirty veggies make people think "garden-fresh"
Laziness: farmers don't want to spend much time cleaning their vegetables


Washing to remove dirt won't shorten the shelf life, but mechanically removing dirt (as in with a hard brush) might in some cases as it could remove or puncture skins or peels.