228 SOILS: PROPERTIES AND MANAGEMENT 



with the fluctuations of the ground water of a soil held 

 in a large cylindrical tank. He found that with a lower- 

 ing of temperature the ground water was lowered, due 

 to the increased capillary capacity of the soil generated 

 by a higher surface tension. A consequent upward move- 

 ment of water took place. When the temperature was 

 raised, however, there was a reverse movement, due to a 

 change of capillary water to free water brought about by 

 a lowered surface tension. 



The surface tension may also be varied by materials in 

 solutions, most salts tending to cause increased tension. 

 The addition of soluble fertilizer salts to a soil would 

 therefore be expected to exert some influence. It must 

 be remembered in this connection that all soils contain a 

 certain amount of oily substances, produced during the 

 processes of organic decay. It is probable that the lower- 

 ing effect of such material would largely overbalance 

 any marked influence from fertilizer salts. Moreover, 

 as such salts are strongly adsorbed by the soil particles, 

 their effect on the concentration of the surface film would 

 probably be light even if undisturbed by the soil resins. 

 Wollny l has shown that adsorbed salts produce little 

 effect on capillarity, while non-adsorbed salts cause a 

 depression increasing with concentration. 



Briggs and Lapham 2 found that with Sea Island soil 

 dissolved salts in dilute solution had no appreciable effect 

 except in the case of sodium carbonate. The increased 

 rise in this case they ascribe to the saponification of the 



1 Wollny, E. Untersuchungen iiber die Kapillare Leitung 

 des Wassers. Forsch. a. d. Gebiete d. Agri.-Physik, Band 7, 

 Seite 269-308. 1884. 



2 Briggs, J. B., and Lapham, M. H. Capillary Studies. 

 U. S. D. A., Bur. Soils, Bui. 19, pp. 5-18. 1902. 



