IN WESTERN STATES 45 



From 20 to 40 inches 20 per cent. 



From 40 to 60 per cent 11 per cent. 



From 60 to 80 inches 9 per cent. 



From 80 to 120 inches 4 per cent. 



From 120 to 160 inches 0.5 per cent. 



Above 160 inches 0.5 per cent. 



100.0 per cent. 



It is seen from this table that the tillable portion of 

 two-thirds of the land surface of the earth receives less 

 than 30 inches of precipitation annually, and must therefore 

 be reclaimed by the best known dry-farming practise if at 

 all. What a gigantic problem for scientific agriculture ! 



Dry-farm areas of the United States. Almost half 

 of the area of the United States receives less than 30 

 inches of rainfall annually, and more than three-fifths re- 

 ceive less than 20 inches. All of this great region is 

 therefore dependent on either dry-farming or irrigation for 

 its agricultural success. 



Eighteen states, most of them of large area, comprise 

 this territory. For convenience in study they may be 

 classed in groups as follows : 



Arid to semi-arid group: Arizona, California, Colora- 

 do, Idaho, Nevada, Utah, Wyoming, and part of New 

 Mexico. 



Semi-arid to sub-humid group: Montana, western part 

 of Nebraska, New Mexico, North Dakota, Oregon and 

 Washington. 



Sub-humid to humid group : Western half of Nebraska, 

 and sections of Minnesota, Oklahoma, Texas and Kansas. 



Note: Send to the United States Department of Agri- 

 culture, Washington, D. C, and ask for Farmers' Bulle- 

 tin entitled "The Effects of Cultural Methods of Crop 



