EFFECT ON SOIL MOISTURE OF CHANGES IN THE SUR- 

 FACE TENSION OF THE SOIE SOLUTION BROUGHT 

 ABOUT BY THE ADDITION OF SOLUBLE SALTS 



[a preliminary report] 



By P. E. Karraker, 

 Assistant Professor of Soils, Kentucky State Univetsity 



While temporary research assistant in soils in the Michigan Experiment 

 Station the writer had occasion to do laboratory work in which informa- 

 tion was sought as to how far the effect of fertilizer or soil-amendment 

 materials in altering the moisture condition of soil is dependent upon 

 changes produced in the surface tension of the soil solution. 



The effect of the materials on the surface tension when in dilute water 

 solutions was taken as an indication of their effect on the surface tension 

 of the soil solution. The surface tension of the dilute solutions, together 

 with their viscosity, specific gravity, and resistance in ohms, is shown in 

 Table I. For comparison like expressions for pure water and for two 

 soil percolates are also introduced. 



Table l.^Effect of salts on certain physical properties of the solutions 



Solution. 



Specific 

 viscosity. 



Water 



NaNOs 



(NH,)2S04 



Manure extract 



NaCl 



KCl 



K2SO4 



CaH^CPOJj 



NazCOg 



Sandy -loam percolate 

 Clay-loam percolate. . 



0000 

 0049 

 0163 

 0992 

 0200 

 001 1 

 0132 

 0207 

 0464 



059s 

 0677 



" Approximately. 



The solutions of the single salts were made by dissolving 10 gm. of 

 Kalbaum's chemically pure salts in 1,000 c. c. of pure water. The 

 changes brought about here in the physical properties of the solutions 

 very probably were greater than those which result in the soil solution 

 from average field application of the salts. The manure extract was 

 obtained by forcing out the liquid contents of approximately equal 

 ■ parts of fresh solid and liquid horse manure and then diluting to about 



Journal of Agricultural Research, 

 Dcpt. of Agriculture, Washington, D. C. 



(187) 



Vol. IV, No. i 

 May IS. 191S 

 Ky.— I 



