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.
Mezquital Valley
Since the latter 20th century, the valley has become an important agricultural center for the state of Hidalgo, growing corn, beans, wheat, onions, tomatoes, cactus fruit, and peaches; the valley also produces one-quarter of all green chili peppers grown in Mexico. It also produces alfalfa, principally used to feed the area's cattle. A small but important quantity of lettuce, cabbage, cilantro, radishes, carrots, spinach, and parsley is grown. There are also a number of fish farms, especially in Tezontepec de Aldama. About 61% of the population works in agriculture, which has been made possible by the diversion of wastewater from the neighboring Valley of Mexico through the Tula River. Sixty percent of the farmland is irrigated with wastewater. Thirty nine percent of the farmland is dependent on clean water sources such as wells and rain, and only 0.38 percent is irrigated with treated water. The areas most dependent on wastewater are: Actopan, Ajacuba, Alfajayucan, Atitalaquía, Atotonilco de Tula, Francisco I. Madero, Chilcuautla, Mixquihuala, San Salvador, Tasquillo, Tetepango, Tezontepec, Tlahuelilpan, and Tlaxcoapan. The areas that use wastewater are more productive, as the water contains phosphorus and nitrogen, but the products are more likely to have problems with contaminants. These contaminants also pose a risk to farm workers and their families.