CROP ROTATION AND IRRIGATION 111 



alkali previous to 1864. Water containing over 1,000 parts of 

 salt in a million has been used without injury. Most of the 

 artesian wells of Dakota have a salt content much higher than 

 this, and the effects of irrigating three or four years with this 

 water rendered wheat lands of the Red river valley almost 

 wholly unsuited to raise current crops. 1 The most effective 

 method of removing alkali from land is by underdrainage and 

 flooding. 



The Cost of Irrigation in the United States as shown by the 

 eleventh and twelfth census is as follows: 



Average values per acre 

 1889 1899 



Irrigated land $83.28 $42.53 



Water right 26.00 



Annual cost 1.07 0.38 



First cost of water rights 8.15 7.80 



A rise in values would be expected, instead of a fall, as good 

 lands with water supply were scarce in 1899, and those lands 

 were first irrigated which required least labor and capital. It 

 has been estimated that a perpetual water right in a grain 

 country is worth from $25 to $50 per acre. The cost of irri- 

 gation from many of the original ditches was as low as $2 to 

 $5 per acre. 2 



The Semi-Arid Region of the United States. There are men 

 still living who knew the Mississippi valley as a wilderness. 

 For several generations a popular American slogan has been 

 " westward the course of empire takes its way/' and the rapid- 

 ity with which the fertile lands of the great river valleys were 

 brought under cultivation has been almost incredible. As this 

 huge wave of immigration swept across the prairie to the great 

 plains, it encountered the subhumid belt as a buffer between the 

 humid and the arid regions. Gradually the settlements pro- 

 ceeded westward from the abundantly watered Mississippi and 

 lower Missouri valleys, and pushed into the well defined sub- 

 humid slope which rises progressively toward the Rockies. 

 These virgin lands, bordering upon the greatest wheat raising 

 region of the world, and fully as fertile, since they were not 

 washed by frequent rains, were a continual temptation to 



1 Mon. TT. S. Geol. Sur., 25:546-547. 



2 Indus. Com., 10:xxxii. 



