That seems to make sense. Are there any cities or states that have tried that? If not, why not?
Why not? Well, it's a... let's call it a "heterodox" economic theory. It's not mainstream.
And, if a state were to do it, it would probably have negative effects on farming. (A city, not so much, unless there was significant farmland within the city limits.) Making most of the farms in your state less economically viable is probably not a formula for winning elections, so a state is probably not going to go for it.
So create a different tax system for farmland, or exempt them from taxes. It's not like giving farmers subsidies and tax relief is unprecedented.