Everybody recognized that if you tried to grow a crop year after year, in the same place, pretty soon the land got worn out. You'd see smaller and smaller crops, until pretty soon you got nothing. The old answer to this was to let the land lie fallow on a regular basis. Some time later on, the idea of crop rotation took hold. People would plant corn for a year or two, and then beans or clover, which would restore the balance to the soil.
Some farmers still do that.
Our practice, today, is often to pump up the soil with artificial fertilizers, and maximize the crop with the highest profit potential, year after year after year. We know that's wrong, but we do it anyway. A lot of people who farm today make their living balanced on a knife edge, testing and analyzing, fertilizing and correcting. It's a very stressful way to make a living. By analogy, many of us do the same thing in our own lives.