Do we file the sale of a tractor under Rentals, Royalities and Farm?

I assume you mean you report farm income on your tax return and you have a farm tractor that you sold. If so, you would edit that asset entry and report it as being sold during the year. It would be reported as a sale of business property on form 4797.

Edit the asset by using the Update option next to Assets depreciated on your Farm business page, under Farm Assets:

Edit the tractor asset entry and indicate that the tractor was sold:

Later, in the same section you will see an option to report the sale of the tractor:

The sale will end up on Form 4794, sale of business property.