But modern farmers, soils scientists, and ag engineers do. It's just that not all farmers practice the proper methods as they sometimes don't pay as much in the short term.
What did they grow down there in the present rainforest wasteland? Habaneros, corn, tobacco, and potatoes would be my guess, none of which were avalaible in Asia or Europe or Africa until the time of Phoenicians.
Have to have some beans or other crop that hosts nitrogen fixing bacteria, maybe peanuts? I'm not real up on crop rotation practices, but they often involve at least 3 different crops and a fallow period. My father in law's farm does corn, soy beans, alfalfa and the fallow year. Course it helps that his father was the first in the county to do contour plowing and one of the first, if not the first, to put in terraces. His land didn't blow away in the '30s like so many others' did. He, my wife's grandpa, learned all that at Ag College, where he got a 4 year degree in something like 1918. He was a real rarity in those days, a farmer with a 4 year college degree. He taught at an Ag school, 1 and 2 year programs plus short courses, before returning to take over the farm from his father.
You beat me to it!
The first thing I thought of after reading that ecologists don't know how to improve soil was "crop rotation."
Yes, but this appears to be a newer and quicker means to do so.
"Have to have some beans or other crop that hosts nitrogen fixing bacteria, maybe peanuts?"
Not necessarily. These soils "could" host soil microbes that accomplish the same thing.
It's an area that definitely needs more thorough research.