174 Irrigation and Drainage 



The amounts of rainfall and of water applied by irrigation are 

 given in the table below: 



Rainfall . Watev of irrigation . 



1896 1897 1896 1897 



INCHES INCHES INCHES INCHES 



May.... 6.11 .51 May May.... 



June.... 2.25 4.03 June June 



July.... 3.42 1.79 July 10.... 2.15 July 20.... 2.45 



Aug. . . . 2.43 3.7 July 21. . . . 2.15 Aug. 18 ... 2.45 



Sept.... 3.73 1.73 Aug. 3.... 2.15 Sept. 8 . . . . 2.45 



Aug. 10... 2.15 



Sept. 3.... 2.15 



Sum. 17.94 11.76 10.75 7.35 



The distribution of the rainfall during the season can be 

 learned from the table given on page 108. It will be seen that in 

 1896 the irrigated potatoes had 10.75 inches, and in 1897 7.35 

 inches, more water than the potatoes grown under the natural 

 rainfall conditions. 



These differences in the amount of water produced differences 

 of yield, which are shown below in the table, and graphically to 

 the eye in Figs. 26, 27 and 28. To eliminate the effects of varying 

 soil conditions, the water was applied to alternate groups of 6 to 

 10 rows, with corresponding intervening groups of rows which 

 received no water. There were 16 of these plots in 1896 and 22 

 in 1897, making 38 trials in all, in which there were grown a total 

 of 555 bushels of potatoes, or 33,304.4 pounds. 



Table thawing yield per acre of potatoes irrigated and not irrigated in 

 Wisconsin 



RURAL NEW-YORKER 



BURBANK TYPE 



220 22.7 141.5 16.2 



302 16.8 184.S 19.7 



Mean 317.5 1.2 21l.e 14 



Difference . . . 105.& 1.2 



