CHAPTER XVI 
IRRIGATION AND DRY-FARMING 
IrRIGATION-farming and dry-farming are both 
systems of agriculture devised for the reclamation of 
countries that ordinarily receive an annual rainfall 
of twenty inches or less. Irrigation-farming cannot 
of itself reclaim the arid regions of the world, for the 
available water supply of arid countries when it shall 
have been conserved in the best possible way cannot 
be made to irrigate more than one fifth of the thirsty 
land. This means that under the highest possible 
development of irrigation, at least in the: United 
States, there will be five or six acres of unirrigated 
or dry-farm land for every acre of irrigated land. 
Irrigation development cannot possibly, therefore, 
render the dry-farm movement valueless. On the 
other hand, dry-farming is furthered by the develop- 
ment of irrigation farming, for both these systems of 
agriculture are characterized by advantages that 
make irrigation and dry-farming supplementary to 
each other in the successful development of any arid 
region. 
Under irrigation, smaller areas need to be culti- 
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