22 



Irrigation and Drainage 



*Table showing the changes in the water content of the soil upon which corn had 

 been grown in 1890 under field conditions 



Dry weight of soil per 

 cubic foot 



PLOT I 



PLOT II 



June 7 22.66 



Sept. 16 15.75 



Loss 6.91 



June 7 24.93 



Sept. 16 18.43 



Loss 6-5 



From this table it appears that each volume of soil four feet 

 long and one square foot in section lost the amounts of water 



which follow: 



Plot I 



LBS. 



Loss of water in soil 27.67 



Rainfall from June 7 to Sept. 16 64.72 



Plot II 



LBS. 



28.84 

 64.72 



Total loss 92.39 



93.56 



17.76 inches 17.99 inches 



The amount of dry matter produced in these cases was, for 

 Plot I, 450.18 pounds; Plot II, 455.36 pounds, making a yield per 

 acre of 9,727 pounds and 9,840 pounds for the two plots respectively. 



Were it admissible to assume that the percolation of rain- 

 water below the zone of root action had been exactly equaled by 

 the rise of water into it by capillarity from the subsoil below, it 

 would follow, from the observed losses of water and yields of dry 

 matter, that the amount of water used for a pound of dry matter 

 under these field conditions was 413.7 pounds for Plot I, and 414.2 

 pounds for Plot II. 



The results of a trial similar to the one just described, and with 

 the same variety of corn, for the year 1891, gave 309 pounds of 

 water for one pound of dry matter, on ground which had been given 

 a dressing of farmyard manure, and 333 pounds of water for a 

 pound of dry matter on land which had not been manured. Here 

 we have two trials by pot culture, where everything was under 



*Eighth Annual Report Wisconsin Experiment Station, p. 123. 



