Didn't read the entire article, but wouldn't such a tax disproportionately affect farmers and ranchers, i.e. rural America? And wouldn't this affect our food supply?
To the contrary. It would hurt inefficient farmers that don't utilize their land well, but this would only prod them to either a)increase their efficiency or b)sell some/all of their land to more efficient operations.
The thing to understand is that, while income and sales taxes punish and therefore discourage economic activity, land taxes(and in particular land value taxes along the Georgist model) punish economic inactivity.
Isn't it already pretty difficult for a small farmer to get by today, regardless of skill? And if a farmer sells too much of their land, I don't see how they would be better off in the long run.