Irrigation and Drainage 135 



five-inch irrigations to these various stages both singly 

 and in various combinations. The results are shown in 

 Fig. 15, which gives the average yield of roots and tops 

 for the various treatments. The lowest yield was ob- 

 tained when the land was irrigated after the seed was 

 planted and before it came up. The yield with this treat- 

 ment was decidedly less than it was when no water was 

 given. 



Comparing the various periods in which but one five- 

 inch irrigation was given, it will be seen that the third 

 period, when the beets averaged two inches in diameter, 

 was the most favorable ; the last period, when the beets 

 were nearly ripe, was the least favorable. The second 

 period was decidedly more favorable than the first. It 

 will be noted further that the yield of tops was greatest 

 with the very late irrigation. This means that the farmer 

 by looking at his beet field will doubtless be deceived into 

 thinking that the very late irrigation is increasing his 

 yield much more than it really is. 



- Upon examining the plants receiving two, three, and 

 four irrigations, the greater value of irrigation water 

 during the third stage is clearly evident. The highest 

 yield was received where a total of fifteen inches was ap- 

 plied. It will be remembered that in the weekly irri- 

 gations a higher yield was obtained for 12.8 inches than 

 for 32 inches. It seems, therefore, that the total require- 

 ment of sugar-beets for irrigation water is not large, but 

 that the period of application is important. 



The old ideas, that it is necessary to withhold water 

 until the beets suffer before giving the first irrigation and 

 that irrigation should be discontinued five or six weeks 



