22 



BULLETIN 339, IT. S. DEPARTMENT OF AGRICULTURE. 



seem to prove that on an average about 1^ feet of water per acre are 

 required for the maximum yield of grain on the average soil of Idaho. 



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.,?,5" .50 .75" /<? AST /.5tf /^5" <£<? ees 230 £7S 300 325 350 



OfPTrt ^}PPL/£0 //V F££7: 



Fig. 3.— Irrigation requirement curve based on yields and amounts of water applied to 207 individual 

 fields of grain on clay loam soils in Idaho during the seasons 1910 to 1913, inclusive. 



The curve shown in figure 4 is made up from the results secured on 

 77 fields of alfalfa and clover on clay loam soil and shows marked 

 tendency toward increase in yield as the application of water is in- 



