Exactly this. For instance after sugar beet has been harvested, the land needs 5-10 years to regenerate back to proper nutrient levels and may not yield anything.
You must be describing some unique situation. Sugar beets don't do well if they are planted year after year, but they are included in crop rotations with no fallow years, never mind 5 or 10.
I am describing common knowledge in Balkan agriculture - in Vojvodina, Serbia, it is widely known that after harvesting sugar beets you simply can't have a solid harvest no matter what you plant for the next 5 or more years, and our land is mainly
https://en.wikipedia.org/wiki/Chernozem . Usually you plant garlic/onion/phacelia or something similar in the subsequent years to "reset" the land.
Not saying there is a fallow, but that sugar beets take a lot of nutrients from the land, at least in this area.
Sorry for the lack of proper terminology, agriculture is not my primary occupation.
