SOILS AND FERTILIZERS 



97 



Reservoirs. As the flow of water in streams is at 

 some seasons of the year overabundant for irrigating 

 purposes and at other times there is a scarcity, dams and 

 reservoirs are built to hold back and save the water for a 



FIG. 36. Storage Reservoir. 



time of drought. The United States government is 

 helping in this work on a large scale by building large 

 storage reservoirs in the West. By this means thou- 

 sands of acres of desert land have been reclaimed and 

 many more will be as the work progresses. In. more 

 humid regions the damming of a small creek or river 

 might save the farmers of the vicinity much loss from 

 drought. The Wisconsin Experiment Station has done 

 more than this. Water was pumped from a depth of 

 about twenty-five feet by burning coal at five dollars 

 a ton and the added expense has been more than met 

 by the increased yield of crops. 



Limitation to the Use of Irrigation. All surface 



M. & H. AG. 7 



