28 



BULLETIN 339;, U. S. DEPARTMENT OF AGRICULTURE. 



The curves shown in figure 8 are made up from the results secured 

 from 16 plots of potatoes grown at the Gooding experiment station 

 during five years. The curves show that potatoes require somewhat 

 more water than the grains and that there was a strong tendency for 

 the yield to increase as the supply of water was increased within the 

 limits of the experiment. Since the rate of increase in yield grows 

 smaller as the quantity of water is increased, it probably will not be 

 advisable or profitable to apply more than 2 or 2\ feet per acre to 



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F IG . 7._Yield per acre and per acre-foot of water applied from 24 plots of alfalfa at Buhl and Gooding 



during 5 years, 1910-1914. 



potatoes on clay loam soil under conditions similar to those existing 

 in the vicinity of Gooding. Here, as before, the curves indicate 

 within reasonable limits the results which may be obtained with 

 different volumes of water, and the quantity to apply in each case 

 will be determined by local economic conditions. 



IRRIGATION REQUIREMENTS AT DIFFERENT TIMES DURING -THE SEASON. 



The curves (figs. 5 and 7) do not show the proportion of the season's 

 supply required at different times. In thedesign of irrigation projects, 

 whether they be dependent upon reservoirs or direct diversion from 



