S.D. Codified Laws § 10-46E-3
An excise tax is imposed at the same rate as imposed by § 10-46E-1 on the privilege of the use, storage, or consumption in this state of farm machinery, attachment units, and irrigation equipment used exclusively for agricultural purposes not originally purchased for use in this state, but thereafter used, stored, or consumed in this state, at the same rate as provided in § 10-46E-1 and imposed on the fair market value of the property at the time it is brought into this state. However, if any trade-in or exchange of used farm machinery, attachment units, and irrigation equipment is involved in the transaction, the excise tax is only due and may only be collected on the cash difference. The use, storage, or consumption of farm machinery, attachment units, and irrigation equipment used exclusively for agricultural purposes that is more than seven years old at the time it is brought into the state by the person who purchased such property for use in another state is exempt from the tax imposed by this chapter.
SDCL 10-46E-3