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 withia the 
limits of the experiment. Since the rate of mcrease m 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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Fic. 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 ra 
