TRRTOATION EXPERIMENTS IN IDAHO. 



23 



creased, as there is no appreciable break in the curve within the limit 

 of the experiments. This curve shows again that alfalfa and clover 

 require much larger supplies of water than grain, but the increase in 

 the yield of alfalfa is not proportional to the increase in the water 

 applied. Notwithstanding the fact shown by the curve, that the 

 yield continues to increase with increased quantities of water, other 

 considerations, such as the danger of water-logging land and the 



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Fig. 4.— Curve based on yields and amount of water applied to 77 individual fields of alfalfa on clay 

 loam soils in Idaho, during 5 seasons, 1910 to 1914. 



limitation of the acreage which can be irrigated with a given water 

 supply, would make it appear somewhat doubtful whether more than 

 3 feet per acre should ever be allotted to alf alf a on medium clay loam 

 soil. 



The alf alf a curve (fig. 4) was made up from observed data by first 

 plotting all points on the sheet, after which points representing dif- 

 ferent plots of each experiment were connected up by straight fines 

 similar to the method used with the grain curve (fig. 3). The depths 

 13653°— Bull. 339—16 4 



