Agriculture in the prehistoric Southwest
After the Hohokam disappeared, Spanish explorers of the 16th century noted the use of canal irrigation in only two areas of the Southwest: eastern Sonora, primarily practiced by the Opata and Lower Pima, and among the Pueblos of northern New Mexico. Irrigation by the Opata and Pueblos had different objectives. In Sonora, with a long growing season, two crops of maize a year were grown in river valleys. The spring crop during the dry season was dependent upon irrigation; the summer and fall crop during the rainy season utilized irrigation to supplement rainfall. The necessity of irrigation probably required a high level of social organization. In New Mexico, with only one crop of maize per year possible, irrigation was supplemental and the lesser dependence on irrigation implies less social organization than in Sonora.
Agriculture in the prehistoric Southwest
Floodplain cultivation was possible under the most extreme conditions. The Sand Papago (Hia C-eḍ O'odham) were mainly hunter-gatherers but practiced floodplain cultivation when it was possible for them to do so. In 1912, ethnographer Carl Lumholtz found small cultivated fields primarily of Tepary beans in the Pinacate Peaks area of Sonora. In the Pinacate, with an average annual precipitation of three inches (75mm) and temperatures up to 118F (48C), Papago and Mexican farmers utilized runoff from sparse rains to grow crops. In the 1980s author Gary Paul Nabhan visited this area, and found one farm family taking advantage of the first large rain in six years, planting seeds in the wet ground and harvesting a crop two months later. The most successful crops were Tepary beans and a drought-adapted squash. Nabhan calculated that the Pinacate is the most arid area in the world where rain-fed agriculture is practiced.