I estimate a kerb could probably consume a gallon of beer per day on earth (they're hearty), or about 1 liter on Kerbin (6 hours in a day) resulting in about 425 liters per year. A Duna year is 1.88x longer, so we could say each kerbinaut will drink 800 liters per year. At approximately 30hL of red ale produced for each malted acre of barley you could calculate that an acre (4000 sq meters) on Duna would provide beer for 3.75 kerbins. Hops also need some land, at about 1kg per 100L, 30hL will require 30kg, if you can get 1000kg of hops per acre on Duna, you could grow all the hops you need on .33 acres (1335 sq meters) per 3.75 kebals.
