Tenn. Code Ann. § 55-1-119: "Farm truck" defined

(a) "Farm truck" means any truck motor vehicle used by the owner in connection with the agricultural pursuits usual and normal to the owner's farming operations, such as the transportation of products of the soil, livestock, poultry, seed, or any materials to be used by the owner in the production, cultivation, growing, or harvesting of agricultural commodities; also for uses incidental to farming as the transportation of the farm laborers or bringing to the farm products or materials that may be used for its improvement or promote its operation.

(b) "Farm truck" shall not be so construed as to permit the vehicle's use either part time or incidentally in the conduct of any commercial enterprise, or for the transportation of farm products after such commodities have entered the "channels of commerce," as for example in the "house to house" delivery of milk.