This description of farming in the Incan empire in 1539 was written by Garcilasco de la Vega. He was the son of an Incan princess and a Spanish explorer.
As soon as the Incan ruler had conquered any kingdom and set up his
government, he ordered that the farmland used to grow corn be extended.
For this purpose, he ordered irrigation channels to be constructed. The
engineers showed great cleverness and skill in supplying water for the crops,
since only scattered sections of the land could grow corn. For this reason,
they endeavored to increase its fertility as much as possible.
What engineering technique did de la Vega describe?