Can I gift a property to my wife so that she uses up her 20% tax band?

It depends totally on the facts of each individual case. Most family farms are jointly owned between spouses, typically with the husband farming full time and the wife working off farm. When a full time farmer retires and lets out his farm (as is typical when there is no obvious successor within the family) essentially replacing his farming income with farm letting income, it would be peculiar if half of the latter had to be automatically treated as his wife's income.
 
That about sums up the position - thank you!
 
What is the advantage if both husband and wife are jointly assessed for tax purposes?
Tax individualisation. Joint assessment only goes part of the way in terms of allowances and standard rate band. Transferring income producing asset allows use of spouse's self-employed tax credit, full standard rate band AND lower rate USC bands. Well worth doing. €thousands saved.
 
You have to have earned income to avail of it.

It won't apply in the scenario being discussed in this thread.

This tax credit is not available against tax payable on passive (rental) income.
My apologies. I'd always thought that it applied to all forms of income when the old PAYE credit was gradually extended to self-employed. Wrong end of the stick - mea culpa.