Other mistake: In the opening sequence Oliver stops the tractor in front of the house by pulling a lever. This lever is not a brake but is to engage a wheel to put a belt around to operate a threshing machine.
Plot hole: Oliver and Lisa are in a truck, taking a load of apples to the Farmers Market in the state capital. Oliver says it's a "15-hour drive." Driving 30 miles an hour, that would be 450 miles. Driving 40 miles an hour, that would be 600 miles. It was never specified where Green Acres is located but only Alaska, Texas and California extend for such a distance north-to-south and/or east-to-west.