Land is actually one of the few cases where specific performance is generally allowed, although I’m not sure it would be in that situation.
You’d have the same issue though in that situation:
How speculative are the damages? Was it so impossible to calculate what the yield from the field would be that not only did you need an LD clause, but the clause required specific performance and not a monetary payment?
It seems to be that, in your scenario, the field can reasonably be expected to yield a certain amount of crop a year, and the market rate for that crop is $XXXX. So “X” is when your damages.
I don’t think it requires specific performance, and im not sure it even requires an LD clause.