184 IRRIGATION PRACTICE 



season crops, after having been planted in a soil well 

 filled with moisture, should be allowed to grow as long as 

 possible without irrigation. The early irrigation of such 

 crops is only slightly advantageous, and the results 

 seldom pay for the labor and cost of water. By post- 

 poning the first irrigation, the root-system may be more 

 fully developed, so that the best use may be made of the 

 water when it is applied. Such crops, grown for seed, 

 seldom need irrigation before the time of flowering or 

 seed-formation, when one or two moderate irrigations 

 may be applied with decided advantage. 

 At the Utah Station it was found that, when a given 

 quantity of water was used, the total weight of the crop 

 was not greatly affected by varying the time of irrigation; 

 the effects were felt in the yields of grain produced. When 

 irrigation was performed early, before flowering, more 

 straw and less seed were produced; when irrigation came 

 late, less straw and more seed resulted. The sum of straw 

 and seed was, in both cases, practically the same. That 

 is, late irrigations make possible the transfer of nutritive 

 materials from the roots and stalks to the heads, there to 

 be permanently elaborated into seed materials. 



After the seeds are well formed there is seldom any 

 advantage in irrigation. Certain varieties of grain, peas 

 and beans have an extended growing season, and to such 

 it may be necessary to apply water some time before 

 flowering, and perhaps once after seed-formation is well 

 under way. Even to the crops that mature early, it may 

 often be profitable to add water at the time the seeds 

 are forming most rapidly, for it may help fill them more 

 completely. 



116. Time of irrigating long-season crops. Sugar 

 beets, potatoes, corn and similar crops should also be 



