I'm going by what we do. I have farms in MN and Iowa. My Father-in-law is an accountant and knows taxes to the point of annoyance.
We write off interest on the land loan, improvements, property taxes, maintenance such as CRP mowing. Mileage to and from the farm for maintenance, and that can be be a decent chunk if it's 4-7 hour drive.
It all adds up!! I believe timber/timber income should be in same category.