another stab at the math. thanks @TMN
an acre is 43264 ft sq. if we calculate for the least successful amount of 5 bushels per acre. at the expected weight of 45 lbs of barley per bushel
(5/43264)*45 = 0.0052 lbs of barley per sq ft.
this seems really on the low side.
this fellow claims he got one 330ml finished beer per sq ft at the gravity he was targeting. https://brewingbeerthehardway.wordpress.com/2015/08/02/one-beer-per-square-foot/
his yield was 32 lbs in 226 sq ft.He made 4 5 gal batches at 8 lbs of grain batch. that 0.142 lbs per sq ft. 2 orders of magnitude more than the other number.