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 Spain
Grains covered about 10 percent of Spain's cultivated lands, and about 10 percent of that area was irrigated. Wheat and barley were generally grown in the dry areas because corn tends to crowd such crops out of areas with more abundant rainfall or irrigation. Although most of the wheat was grown in dry upland areas, some of it also was grown on valuable irrigated land. Rice was dependent on plentiful water supplies and, accordingly, was produced in the irrigated areas of the Levante, in Andalusia, and at the mouth of the Rio Ebro. Spanish farmers also grew rye, oats, and sorghum.