I have 65 fields, with one farmer each, and produced 65 500 food last year, 25 300 used. After the harvest in early winter 67 800, so maybe 70 000 in year 30.
The combination of beans and wheat is very convenient to micromanage. So unless the barns are really overfull or there is a very nasty wheather, I manage to harvest all there is.
I start in early summer:
looking at the beans, at 95% growth, the harvest is started manually,
in late summer most beans are working and the wheat harvest could start, again at 95%,
at the same time, the first bean fields are done, the farmer is sent to a close wheat field, where the harvest has started and there's plenty of wheat left,
I go on this way until the temperature gets close to the freezing point or I see that everything will be harvested anyway,
if I am short of stones, I send the spare farmers to the quarry during the winter (I built a second quarry close to my main farming area to make this easier)
and of cause; reset all the fields to one farmer,
in late winter all farmers are sent back from the quarry,
So from early summer to late winter this takes almost all my time. Some new fields, a lot of new barns and a few houses are planned in the time between.