Green’s Dictionary of Slang

silo n.

(US) an alcohol made of fermented vegetables.

[Aus]Bulletin (Sydney) 13 Oct. 19/3: Amongst these sinful fabrications may be mentioned [...] ‘silo,’ a vegetable alcoholic juice, madly intoxicating, but liberally swallowed in some of the farming regions of Kansas and Iowa, wherever prohibitory laws hold absolute sway.