There's another alternative that will allow you to correctly classify the asset, and still depreciate over 5 years instead of 7.
On the screen for "Describe this Asset" select Intangibles, Other Property and continue.
Then select Other Asset Type and continue.
Now enter the property description (something like off-the-road tractor I would presume) along with it's cost and the purchase date, and continue.
Now select "purchased new" and "used 100% for business" (I presume that to be correct) , enter the date you started using the tractor in your farming business, and continue.
Set the asset class to 5-year and continue.
Select the depreciation method and continue. ( don't know off hand the method for a tractor. I assume you do)
This if appropriate, select NO to indicate this asset does not qualify as listed property.
I think you can take it from there.
