Find or build the following vehicle parts: a plough, seed drill, and a reaper. Two of each if you can. Then put them on a vehicle shaped something like this:
o o
DPs>R
DPs>R
o o
that’s four wheels, each pair offset to the side, with two reapers up front, followed be engines and seating, and then plows and drills (in that order) in the back. You’ll be able to drive down a row of crops ready to harvest, reap them, collect the seeds and produce, plow fresh ground, and plant new seeds in a single pass.