154 



IRRIGATION PRACTICE 



104. The nature of the crop. The nature of the plant 

 is a factor in the economical production of dry matter. 

 Little is as yet known as to the special properties of the 

 plant that affect the water-cost of dry matter; but, it is 

 certain that plants differ in their water requirements. A 

 number of interesting results have, indeed, been obtained, 

 as for example, Montgomery's observation that narrow- 

 leaved corn uses less water to produce a pound of dry 

 matter than does corn with wider leaves. Attempts have 

 often been made to classify crops in accordance with 

 their water needs, but seldom under irrigated conditions. 



Some crops always yield largely, others lightly. This 

 differing power is inherent in the crops, and is generally 

 beyond the farmers' control, for the variations in yield 

 due to cultural methods are within rather narrow limits. 

 The results of the Utah work has made possible the 

 arrangements of the crops in the order of their acre- 

 yield of dry matter, as in the following table: 



With light, medium and heavy irrigations, the order 

 was practically the same. Corn yielded the largest quan- 

 tity of dry matter to the acre ; Italian rye grass, the smallest. 



