"micky" wrote in message
news
When big circle watering of farm crops is used, does the plowing,
seeding, and fertilizing apply to the whole surrounding square, or only
to the circle as best they can.

Only to the circle as best they can and that's one of the reasons
that so many are now not bit circles, usually called lateral moves.
https://en.wikipedia.org/wiki/Irriga...ne,_wheelmove)[36][37]

Somone on the radio says that it's the square, but I've assumed that
farmers, especially those with GPS-equipped tractors, but also those
without (since cirular watering long preceded GPS), do as little excess
as the farmer's abiltity to see where the circle is while driving the
tractor,
and as the width of the plow, seeder, fertilizer can make happen.

Yeah, particularly with the planting and harvesting.

If I can get a good answer here, I'll be happy, but if not, I'll
stop the car and check next time I'm near one of thes things.

Not easy to time the stop right and there is plenty spelt out on the web.