Mo. Rev. Stat. § 144.063

In addition to the exemptions granted under this chapter, there shall also be specifically exempted from state and local sales and use taxes defined, levied, or calculated under section 32.085, sections 144.010 to 144.525, sections 144.600 to 144.761, or section 238.235, all sales of fencing materials used for agricultural purposes, and the purchase of motor fuel, as defined in section 142.800, therefor which is used for agricultural purposes.