TERTOATION EXPERIMENTS IN IDAHO. 



29 



a stream, or whether water be pumped, it is necessary to know this 

 factor. The irrigation requirements at different times throughout 

 the season are controlled by the crops grown and the climate of the 

 locality in question. Alfalfa or pasture in any arid region usually 

 requires water throughout the growing season, or from early spring 

 until late fall, while the grains require water during not to exceed 

 the first one-half or two-thirds of the season. Potatoes require 

 water throughout the season, but do not need it so early as grains. 



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Fig. 8.— Yield yer acre and per acre-foot of water applied from 16 plots of potatoes at Gooding experi- 

 ment station during 5 years, 1910 to 1914. 



Beets and orchards when well cultivated need little water in the early 

 part of the season, the greater part of their requirements occurring 

 from July to September, inclusive. 



For the purpose of throwing more light upon the total require- 

 ments during the season and showing the proportion of the whole 

 required during each month, the data secured from both the medium 

 and porous soils have been reclassified in the following manner: 

 (1) The data for each class of crop on each class of soil (for classes, 

 see p. 20) have been segregated; (2) the average depths of water ap- 

 plied to the tracts for each month and for the season have been com- 

 puted; and (3) tracts on which the yield was appreciably reduced by 



