The space isn't what is used efficiently by industrialized agriculture (for the most part). The efficiency comes from saving time by having large machines. Space is used most efficiently when you have people actively involved on small plots.
Wouldn't the area needed for the active involvement of people require more space than commercial agriculture, where large machines can do a lot on a small footprint? A sprayer with 12 inch tires and a 120 foot boom can effectively 'weed' 118 feet of growing area with just two feet required for the tires. I'm not so sure a person with a hoe can beat that.
And s sprayer only spray, it does not harvest anything. They actually make UAV sprayer, though...
A traditional seed drill, for crops that can be suitably planted with one, plants rows 7.5 inches apart and spacing within the row is even closer. There is really no room for a human to comfortably exist within that space without tramping the crop. I'm not sure I understand how a hexagonal pattern opens up space for a person in that circumstance without reducing the growth area?
> And s sprayer only spray, it does not harvest anything.
For many crops you're not concerned about, even desire, wiping out the entire plant.
> They actually make UAV sprayer, though...
Certainly. Crop dusting has been a thing for as long as flying has been a viable human achievement. Although with larger and larger machines on the ground able to have a smaller and smaller footprint relative to the working area (and precision technology ensuring that the machine obeys an exact footprint), the practice seems to be going out of favour.