To make the numbers more meaningful, the infield of a baseball diamond is 0.19 acres (43,320ft^2/90ft/90ft) and a bushel of corn is 56 pounds of corn by definition.
A patch of his field the size of an infield produced 5000 pounds of corn.
At three thousand Calories a day, that five thousand pounds of corn would last 9.1 years. Said another way, it would produce enough corn on a patch the size of an infield to nominally feed a family of nine for a year.
|Corn yield over time. Source.|
Before hybrids and chemical fertilizers a yield of 30 bushel per acre was considered par.
|Yield per acre from a multi-state, organic corn trial. Source|
The one thing I noticed about locally grown, organic corn is that it must be planted later if it is going to have good germination and compete with the weeds. Planted early, too much seed will rot in the ground because it is not treated with fungicides. The weeds take advantage of the sparse canopy and the fact that the organic farmer cannot spray glyphosate or pre-emergence herbicides that prevent weed seeds from germinating.