I like the idea, but once the batteries are full the solar cells would just sit there doing nothing. I think it would be better to have the solar panels stationary and charge the batteries via plug. That way you could have enough surface area to charge at a meaningful speed and could use the panels to power the house when not recharging the tractor. Or, you could just say it powers the house, including recharging your tractor and maybe even your electric car.
2 hours of "tractoring" at a time is plenty for most hobby grade tractor owners. It wouldn't be the end of the world if you also owned a noisy tractor for when you need to do more work.