You have to report the trade-in of your old tractor as a sale because after the TCJA (tax reform) Section 1031 now applies only to exchanges of real property and not to exchanges of personal or intangible property.
See https://www.irs.gov/businesses/small-businesses-self-employed/like-kind-exchanges-real-estate-tax-ti...
Your new tractor would then be added as a new asset subject to depreciation with the basis for depreciation being whatever you received for the old tractor (which sounds like an even trade).
