Water Used by Plants 23 



control, and there could be no percolation, which gave an aver- 

 age of -301.49 pounds of water for a pound of dry matter. We also 

 have four field trials, where there is the uncertainty of some loss 

 of water by percolation and of some gain by capillarity from 

 below, which gave a mean of 413.95 pounds for 1890, and in 1891 

 321 pounds of water for a pound of dry matter. The amount of 

 percolation during the season of 1890 was certainly greater than it 

 was during the season of 1891, and this may or may not be an 

 explanation of the difference in. the amounts of water used per 

 pound of dry matter in the two seasons. 



, In the case of oats grown under field conditions and studied 

 in the same manner as that described for the corn, the results 

 showed 519 pounds of water for a pound of dry matter in the one 

 case, and 534 pounds in another case, while the average of the 

 two pot experiments was 501.47 pounds of water for one pound 

 of dry matter. 



So, too, in the case of field studies with barley, we had an 

 observed loss of 537 pounds of water in one case on ground which 

 had been fallow, but 719 pounds on ground which had not been 

 fallow, for each pound of dry matter produced ; while the pot 

 culture gave a mean loss of only 401.74 pounds of water for a 

 pound of dry matter. 



If we count the rainfall during the growing season and the 

 difference between the amounts of water in the soil at the time 

 of planting and at harvest, in the several field cases, as the 

 amounts of water used by the crop, including surface evaporation, 

 and then compare these amounts per square foot with those added 

 to the several pots in the pot trials, we shall have results which 

 are given below: 



Table showing number of pounds of water consumed per square foot 



Oats 



In pots In field Difference 



Mean amount of water per sq. ft. Ibs 101.98 72.98 29 



Mean amount of water per sq. ft. Ibs 79.11 5865 20.46 



Mean amount of water per sq. ft. Ibs 137.3 63.8 73.5 



