Frequency of Irrigation 235 



irrigations would be required for such a crop of maize 

 on the medium soil and five on the most open one, 

 making the intervals between waterings 37 and 22 days; 

 but if the yield was 100 bushels per acre instead of 

 70, the number of irrigations required would be four 

 or seven, and the intervals between waterings would be 

 27 days for the medium soil and 15 days for the most 

 open one. 



Computing for wheat on a similar basis, with a 

 yield of 40 bushels per acre, requiring 12 acre -inches 

 of water under the conditions of the highest duty, the 

 number of irrigations would have to be three or five, 

 at intervals of 33 or 20 days, according as the texture 

 of the soil was medium or very coarse; while a crop 

 of barley yielding 60 bushels per acre in a period of 

 88 days would need 12.84 acre -inches, to be applied in 

 three or five irrigations, at intervals of 29 or 18 days. 



These three cases may be taken as types of the 

 highest limits likely to be attained under the best of 

 field conditions, and they may serve as standards 

 toward which we may strive with the satisfaction of 

 knowing that extremely good and thorough work has 

 been done if they are attained. 



It will be desirable, now, to review the literature of 

 the frequency of irrigation, and see how actual practice 

 in various parts of the world corresponds with the 

 conclusions stated. 



In southern Europe, wheat is irrigated three to four 

 times; in India, five times during the hot seasons and 

 four times for the crop of the cool season. In the 

 United States, Colorado irrigates two, three and, occa- 



