You do it the MUCH easier way... have a harvest golem with the order upgrade (this will make it harvest and replant)
Then instead of setting the golem to do EVERY farmland, you just need to have it know where the patch is, so if you have a layout like this:
XXXXXXXXXX
XFFFFXFFFX
XXXXXXXXXX
With X being any non-farmland block and F being farmland
You will only need to tell the golem to go to one of the F's in each set eg. FFF* with *being where the golem is being told to go, instead of F*F*F* like you have it
Doing it this way will mean you could have 2 of each crop type, and never run low on any, as you could have Potato, Spice Leaf, Soybean, and Carrot, all in one patch, and the golem will work with them all separately