Multiple use farm buildings use a 20 year useful life, 150% DB, section 179 does not apply.
Single use farm buildings (greenhouse, hay shed) use 10 year useful life, 150% DB, section 179 does apply.
TurboTax will select the right MACRS convention for you.
They are entered in the Farm Asset entry section under Farm Equipment, Animals, Agriculture.
Please see the attached page snips below;