148 



IRRIGATION PRACTICE 



been applied, and the yields of other crops, not given in 

 the table, likewise diminished after certain limits l\ad been 

 reached. Undoubtedly, had more water been used than 

 the maximum in the above table, or if the soil had been 

 shallower or less fertile, there would have been a strong 

 falling off in the yields of all the crops. 



In the following table the evapo-transpiration ratios 

 of the above yields under varying applications are given: 



POUNDS OF WATER REQUIRED TO PRODUCE ONE POUND OF DRY 

 M.4.TTER WITH VARYING QUANTITIES OF WATER 



(Evapo-transpiration ratio) 



Without exception, when small quantities of water 

 are applied, the water-cost is low; as larger quantities are 

 applied, the water-cost becomes greater and greater. By 

 increasing the total quantity of water throughout the 

 season, the evapo-transpiration ratio or the pounds of 

 water for one pound of dry matter increased for wheat 

 from 850 to 1,809; for corn, from 255 to 1,087; for alfalfa, 

 from 641 to 1,480; for sugar beets, from 569 to 1,186, and 

 for potatoes, from 1,136 to 3,292. While, therefore, there 

 is a distinct increase in dry matter as more water is 



