So you need to find a Formular regarding speed, energy and weight to lift in correlation to the overall weight and tire size.
I'm curious when you will do those tests what the outcome is.
At least when I look at it it feels that the energy limit and tire size might be a problem but of course this depends highly on the size.of the field.
How much energy do you currently use when moving with things? Or while doing things?
My assumption when weeding is that you drag something heavy around or do it with laser.
Water I would not use dripping due to micro plastics and cost.
I would also fertilize to a certain degree. Even organic has to fertilize.