SOIL SURVF.Y OF THE MIDDLE GILA VALLEY, ARIZONA. 11 



corded at the Maricopa station is 8^ F., though temperatures as low- 

 as 25° are unusual, and even crops sensitive to cold can be success- 

 fully grown. 



The prevailing wind direction is from the west. Hot, drying winds 

 are frequent during the summer months. Snow very seldom falls, 

 and hail is of local occurrence and unimportant. 



The growing season for the more hardy crops extends throughout 

 the year, but frosts occur during December, January, and February. 

 The average date of the last killing frost in the spring is about 

 March 7, while that of the earliest in the fall is about November 27. 

 The latest killing frost recorded in the spring at the Maricopa sta- 

 tion occurred April 4, while the earliest in the fall was recorded by 

 the same station on October 22. 



AGRICULTURE. 



Agriculture has not reached a very high state of development in 

 the Middle Gila Valley area, although there is abundant evidence 

 that irrigation fanning was carried on by the prehistoric races and 

 Indians for centuries preceding settlement by the whites. The lack 

 of game and wild food plants on the arid plains and treele&s moun- 

 tains forced the early peoples to turn their attention to agriculture, 

 and the river bottoms and adjoining higher lands that could easily 

 be irrigated from the Gila River were made to produce. The Pima 

 Indians have no traditions of the prehistoric race or races that 

 carried on agriculture in this valley;, but the ruins of their dwellings 

 and canals indicate that they had reached a rather high state of 

 culture. Before the advent of the white man, in the latter part of 

 the sixteenth century, American Indians were irrigating land and 

 producing food crops. These Indians were not concerned mainly 

 Avith warfare, but they were continually called upon to protect their 

 stores of grain and their families from other tribes. The small farms 

 along the Gila Eiver were irrigated with the silty waters of the 

 stream by means of small ditches, which carried the flood waters a 

 short distance to the cultivated land. Overflows either stimulated 

 the yields or destroyed the crops, depending upon the time and 

 manner of occurrence. The grain was harvested in the crudest 

 fashion and thrashed with a flail or by trampling with horses. This 

 method of harvesting and thrashing grain has changed little among 

 the Indians, their hard-earth thrashing grounds being everywhere 

 in evidence. The farming of desert land lying outside the river 

 bottoms was not looked upon with much favor by the white settlers, 

 and little of the desert slopes is cidtivated to-day. Extremely h>ng 

 droughts and low average rainfall have forced settlers to abandon 

 some areas formely cultivated. 



