112 AGRICULTURAL ENGINEERING 



during the part of the growing season when the tubers or 

 ears are forming, require a large amount of plant food and 

 moisture. At this time the plants have a wonderful root 

 development, absorbing a great amount of soil moisture; and 

 if maximum yields are to be secured, sufficient moisture must 

 be supplied. 



History of Irrigation. The practice of irrigation runs 

 back even before the time history began to be written. 

 There is evidence that irrigation was practiced along the 

 Nile and the Euphrates rivers more than 2000 years B. c. 

 There were also large irrigation works in Baluchistan and 

 India before the Christian era. Many of these ancient works 

 have been abandoned, yet not a few have been maintained 

 and are still in use. In the Western Hemisphere, irrigation 

 was practiced at a very early date in Peru, in South America, 

 an,d by the Aztec civilization in North America. The 

 remains of ancient irrigation works are to be found in parts 

 of Arizona and New Mexico. 



Settlers in the vicinity of San Antonio, Texas, began to 

 practice irrigation as early as 1715. When the Mormons 

 settled in the Salt Lake Valley in 1847, they soon began to 

 give attention to the matter of irrigation, and much credit 

 for the development of irrigation methods should be given 

 to these pioneers. As early as 1870, a colony known as the 

 Greely Union Colony was established in northern Colorado, 

 and began the construction of works for irrigation. Since 

 that time irrigation has grown by bounds in the United 

 States. 



Dr. Elwood Meade, former Chief of Irrigation Investiga- 

 tions, U. S. Department of Agriculture, has estimated that 

 the area now under irrigation in countries from which it is 

 possible to secure reliable statistics, aggregates 85,000,000 

 acres. Taking into account countries which do not have 



