32 



BULLETIN 339, U. S. DEPARTMENT OP AGRICULTURE. 



53.) As these were comparatively old, well-developed projects, and 

 normal in every way, there is good reason to believe that the acreages 

 of the different crops on other projects will bear practically the same 

 relationship to one another in the future. If this is the case, and 

 the normal project of the West is ultimately devoted to approximately 

 equal acreages of (1) spring and winter grains, root crops, and 

 orchards, and (2) alfalfa, clover, pastures, and crops requiring simi- 

 lar quantities of water, the requirements of the projects as a whole 

 will be found by averaging the requirements of the two classes of 

 crops. This has been done in Table XVII, each line of the table repre- 

 senting the requirement of one class during a single year of the investi- 

 gation. The average given in the table therefore shows the combined 

 requirements during each month of the irrigation season for the two 

 classes of crops during the four years of the investigation, the process 

 of averaging having neutralized and offset the eccentricities of irri- 

 gators and the individual differences of the seasons, stand of crop, 

 soils, and plots included in the investigation. 



Table XVII. — Average depths of water applied to 171 selected fields of grain and alfalfa 

 on medium clay and sandy loam soils. 



[Altitudes ranging from 2,400 to 5,000 feet.] 





Season. 



Num- 

 ber of 

 plots. 



Depth of water applied. 





Crop. 



April— 



May. 



June. 



July. 



Au- 

 gust. 



September — 



Total 



for 

 season. 





1-15 



16-30 



1-15 



16-30 





Alfalfa 



1910 

 1910 

 1911 

 1911 

 1912 

 1912 

 1913 

 1913 



15 

 31 

 13 

 30 

 11 

 25 

 13 

 33 



Foot. 

 0.06 



Foot. 

 0.02 



Foot. 



0.55 



.32 



.49 

 .03 

 .49 



Foot. 



0.74 



.60 



.29 

 .65 

 .50 

 .94 

 .23 

 .54 



Foot. 



0.65 

 .55 

 .91 



.48 

 .62 

 .66 

 .74 

 .59 



Foot. 



0.61 

 .08 

 .70 

 .01 

 .61 

 .05 

 .39 

 .23 



Foot. 

 0.07 



Feet. 



Feet. 

 2.70 





1.55 



Alfalfa 





.04 



.25 





2.68 





1.17 



Alfalfa 







.04 





2.26 









1.65 



Alfalfa 







.86 

 .21 



.02 





2.24 







.04 



1.61 

















.01 



.5 



.01 

 .5 



.37 

 18.7 



.56 

 28.3 



.65 

 32.8 



.34 

 17.2 



.04 

 2.0 





1.98 

















Table XVII is a general average of the results which have been 

 secured on the average soil of southern Idaho during the entire four 

 years' investigation, after eliminating the results secured from all 

 tracts whose yield was reduced by excessive or insufficient applica- 

 tion, and is considered by far the most important table included 

 in this report. The facts given in the table are shown graph- 

 ically in figure 9. It is in reality the meat, or final result, of the 

 entire four years' study of water investigation, and as the soil in 

 question is an average of that which is, or will be, included in at 

 least 75 per cent of Idaho's irrigation projects, and probably of as 

 large a per cent of the projects in many other States, it is believed 



