CHAPTER III 
DRY-FARM AREAS. —— RAINFALL 
Tue annual precipitation of rain and snow deter- 
mines primarily the location of dry-farm areas. 
As the rainfall varies, the methods of dry-farming 
must be varied accordingly. Rainfall, alone, does 
not, however, furnish a complete index of the crop- 
producing possibilities of a country. 
The distribution of the rainfall, the amount of 
snow, the water-holding power of the soil, and the 
various moisture-dissipating causes, such as winds, 
high temperature, abundant sunshine, and low humid- 
ity, frequently combine to offset the benefits of a large 
annual precipitation. Nevertheless, no one climatic 
feature represents, on the average, so correctly 
dry-farming possibilities as does the annual rainfall. 
Experience has already demonstrated that wherever 
the annual precipitation is above 15 inches, there is 
no need of crop failures, if the soils are suitable and 
the methods of dry-farming are correctly employed. 
With an annual precipitation of 10 to 15 inches, 
there need be very few failures, if proper cultural 
precautions are taken. With our present methods, 
the areas that receive less than 10 inches of atmos- 
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