But farmers are inclined to switch to where the money is and may go into things like cheese and ice cream. There seems to be some sort of allowance for industrial buildings.
Assuming high value land with high performing yield, based on the numbers already posted. The farmer would be short 50% of the tax bill at the end of the 10 years. I've already done these figures..
Your tax bill is X, you pay X+Y, Y sits there until you claim the overpayment, if you don't they keep it. There are a few days delay in synchronising payments with self assessment due. The obligation is on you to claim it back.
I've been caught out before, since I sometimes do my tax returns in two goes (within the time limit). You pay the balance due and when you update with the second wave of calculations it doesn't account for the payment made, so it tells you, you owe more than you do. A week later it balances out and you are in credit.