RESULTS OF MEASUREMENTS. 



RESULTS OF CHECKING EVAPORATION. 



51 



The percentage of evaporation in a field sheltered by a windbreak, 

 as compared with the evaporation in the open, having been calcu- 

 lated, it will be interesting to determine what this may mean quantita- 

 tively wjiere the loss of moisture by evaporation is an important 

 item in farm economy. 



Observations l have shown that the amount of water evaporated 

 from a free water surface in the States of Kansas and Nebraska is 

 between 40 and 50 inches per annum, or about 45 inches for the central 



WINDWAffO 



DIAGRAM -2. Protective efficiency of open osage orange hedge. For wind velocities of 5, 10, 15, and 

 20 miles per hour. Height, 23 feet; 275 readings. 



portion of those States. The amount evaporating during the growing 

 period for corn, May to October inclusive, is about 73 per cent of the 

 total, or 33 inches. It has also been computed that the evaporation 

 from a field of grain is about 1.7 times as great as that from a free 

 w<i(er surface, 2 or, in the case in question, 56 inches. This probably 

 represents the demands of the air for moisture in a region where the 



1 Kimball, H. H., "Evaporation Observations in the United States." Monthly Weather Review, Vol. 

 XXXII (1904), No. 12. 



2 Ebennayer, E., "Die gesamnite Lehre der Waldstrev," 1876. 



