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
In their effort to attain food security, Southwestern Indians cultivated the floodplains of rivers and ephemeral streams. Crops were planted on floodplains and islands to take advantage of high water when the river or stream overflowed, saturated the land with water and enriched the soil with silt. This method was most effective when floods came at predictable times. Floodplain cultivation was used instead of canal irrigation by the La Junta Indians (often called Jumano) along the Rio Grande in western Texas and was also employed by other peoples.