Llanos de Moxos region (Amazonian food plains of the Moxos). Over time, the canals also were used to farm edible fish, and the resulting canal sludge was dredged for fertilizer. The fields grew to cover nearly the entire surface of the lakeand although they were not uniform in size or shape, all had the same primary function.
Though labor-intensive, suka kollus produce impressive yields. While traditional agriculture in the region typically yields 2.4 metric tons of potatoes per hectare, and modern agriculture (with artificial fertilizers and pesticides) yields about 14.5 metric tons per hectare, suka kollu agriculture yields an average of 21 tons per hectare.
Significantly, the experimental fields recreated in the 1980s by University of Chicago�s Alan Kolata and Oswaldo Rivera suffered only a 10% decrease in production following a 1988 freeze that killed 70-90% of the rest of the region's production. This kind of protection against killing frosts in an agrarian civilization is an invaluable asset. For these reasons, the importance of suka kollus cannot be overstated.
As the population grew, occupational niches were created where each member of the society knew how to do their job and relied on the elites of the empire to provide all of the commoners with all the resources that would fulfill their needs. Some occupations include agriculturists, herders, pastoralists, etc. Along with this separation of occupations, there was also a hierarchal stratification within the empire. The elites of Tiwanaku lived inside four walls that were surrounded by a moat. This moat, some believe, was to create the image of a sacred island. Inside the walls there were many images of human origin that only the elites were privileged to, despite the fact that images represent the beginning of all humans not only the elite. Commoners may have only ever entered this structure for ceremonial purposes since it was home to the holiest of shrines
