Capillary Movements of Soil Moisture. 1G1 



CAPILLARY MOVEMENTS OF SOIL MOISTUKE. 



The capillary movements of soil moisture are relatively 

 slow, when compared with those of percolation, and are 

 slower in dry than in wet soil. 



The general tendency of capillarity is to bring water to 

 the surface from varying depths, but its movements may 

 occur in any other direction, the flow being always from a 

 soil where the water films are relatively thick toward those 

 where they are thinner, or from the wetter toward the 

 dryer soils. 



If the roots of plants have made the soil dryer in their 

 immediate neighborhood capillarity may carry water to 

 them from below, above or from either side. When heavy 

 rains follow a dry spell then capillarity will assist gravity 

 in carrying the water more deeply into the ground; and 

 when water is applied by the furrow method in irrigation 

 capillarity carries it laterally away from the furrows. 



191. The Else of Water in Capillary Tubes. When a 

 clean glass tube whose bore is small and wet is held verti- 

 cally in water the liquid rises to a certain height above the 

 level outside, the amount varying with the diameter of the 

 tube, as given in the table below : 



In a tube 1. inch in diameter the water raises .054 inches. 

 In a tube .1 inch in diameter the water raises .545 inches. 

 In a tube .01 inch in diameter the water raises 5.456 inches. 

 In a tube .001 inch in diameter the water raises 54.56 inches. 



That is to say, reducing the diameter of the tube one-half 

 doubles the height the water may be raised by capillarity, 

 and reducing the diameter to one-hundredth enables the 

 water to rise 100 times as high. The results in the table 

 above will be true only when the walls of the tube are very 

 clean, the water pure and the temperature 32 ~E\ 



192. Cause of the Variation in Height to Which Water Is 

 Raised in Capillary Tubes. The reason for the differences 



