Whatever the origin, the Incan empire quickly spread from its center in Cuzco in all directions under the rule of two consecutively aggressive emperors during the fifteenth century, eventually stretching from the northern border of modern Ecuador to the Maule River in mid-Chile, and as far east as Paraguay: an area of 380,000 square miles--on a European scale, this is the area of the Low Countries, France, Switzerland, and Italy combined (Metraux, 56). Within the "Four Quarters" of this huge kingdom were contained the "radically disparate conditions and dissimilar resources" of the Andean Cordillera, all connected by some 35,000 kilometers of well engineered roadways, pivotal to the consolidation of an empire of this size (Moseley, 25). Together, these dissimilar areas prospered when the resources of each were shared amongst the others, thus creating a highly successful and wealthy empire. However, there were many climactic and geographic difficulties to be overcome before each of these areas could successfully contribute.
Of these "Four Quarters," Antisuyu, located on the eastern rim of the Cuzco Basin, is the area where the Incan culture was truly based, including most important religious sites, such as Machu Picchu, as well as governmental posts (Moseley, 32). The steep mountainsides and deep canyons of this area, all above the jungles at 1500 meters, provided very little fertile ground, but at the same time a great variety of agricultural possibilities for those willing to work on the carved terraces which lined the mountainsides, like level topographical lines on a map (Moseley, 32). The most prodigious of these staple crops was the potato, actually changed into the tuber we know today by the Indians' careful selection from over 700 varieties found in the area and a key part in high-altitude agriculture due to its ability to grow at altitudes of up to 12,000 feet (Metraux, 66). On the lower plateaus nearer to the jungle floor would be grown tropical fruits, such as guavas and avocados, thus providing a full array of fruits and vegetables (Moseley, 32). Also grown at lower altitudes was the important coca plant, chewed upon by the farmers to stimulate and combat altitude fatigue, as well as providing calcium and Vitamin B (Moseley, 44). The final important crop in Antisuyu was maize, the only food considered worthy of offering to the Gods and a enduring cereal due to its ability to grow on poor soil (Metraux, 66).
Also very important to this region was the furry, camel-like animal, the llama. Although these "beasts of burden" for the Incas do not carry a load of more than 55 pounds or travel more than 10 miles a day, their abundance in the region, as well as their ability to travel several days without food or water, made them the pack-animal of choice (Baudin, 23). Another redeeming factor was the fur of the llama, which provided excellent warm clothing for the extreme conditions of the Andes, as well as a key trading commodity. Lastly, these animals provided critical fertilizer for crops when grazing on the stubble of harvested fields in the pastures at above 12,000 feet, thus creating a replenishing cycle for the fields (Moseley, 31).
Although the Incas placed their greatest efforts on the development of the Antisuyu region, the other areas also each contributed uniquely to the livelihood and technology of the Incan empire. Foremost among these were the densely populated coastal communities, where fishing was plentiful due to the Humboldt current which runs along the Peruvian coast, bringing cold water rich with plankton (Metraux, 23). Furthermore, advanced methods of irrigation, with canals sometimes as long as nine miles, turned local desert plains into fertile ground on which low altitude crops could be grown using the small amount of westerly mountain runoff from the Andes (Baudin, 220). However, perhaps the most important and unlikely of commodities which the coastal communities possessed was the abundance of guano from the seabirds. So important was this fertilizer to the agriculture of the kingdom that the birds which produced it were protected by Incan law under the penalty of death (Metraux, 69).
Finally, the vast mineral deposits in the Andes provided the Incas with an plentiful source for tools, such as the bronze chisel and copper ax, as well as fine metals for the famous Incan idols and other art forms (Baudin, 229). With these tools, the workmen could shape the gigantic stones which were then used to construct monumental cities with astonishing durability and precision.
Although the reign of the Incan empire was cut short by the Spanish inquisition in 1523, many of its agricultural contributions, such as the potato, survive today just as their monumental cities.
From Josh Marcy's, Topher Wilkins' and Adam Tarnoff's ID1 paper.