1 88 Journal of Agricultural Research voi. iv, no. 2 



the resistance of the sodium-nitrate solution. The soil percolates were 

 obtained by taking the first small portions of solutions percolated through 

 500 gm. of previously air-dried soil in a percolator tube. The first 15 

 c. c. were used from sandy-loam soil and the first 20 c. c. from the clay- 

 loam soil. These portions were the densest percolates it was possible 

 to obtain. 



All the single salts increased the surface tension to some extent, but 

 in no case was this action marked.^ The viscosity was also increased in 

 all cases. Changes in the viscosity of the soil solution, while theoretically 

 not affecting the final distribution of moisture reached, should, never- 

 theless, alter the time required for this state to be gained. The small 

 increases in surface tension noted above could hardly be expected to exert 

 any appreciable effect on the moisture content of, or the moisture move- 

 ment in, soil. In this connection the work of Whitney ^ in determining 

 the effect of soluble salts on the surface tension of solutions, which has 

 been used to show that fertilizer salts may exert a significant effect on 

 the soil-moisture content or movement through changes in the surface 

 tension, seemingly has been allowed more weight than it merits. The 

 solutions used by Whitney were either very dense or else saturated, 

 and as such gave changes in the surface tension that would not be com- 

 parable with those arising from the field application of fertilizer salts. 

 The surface tension of the manure extract was much lower than that of 

 water. It is interesting to note that the surface tension of the soil 

 percolates was but little lower than that of water. 



Information as to the effect of the materials on the soil-moisture con- 

 tent and movement was secured through the following experimental work. 

 Samples of the sandy-loam and the clay-loam soils from which samples 

 for the soil percolates were obtained were weighed out. The sandy-loam 

 samples weighed 660 gm. each, and the clay-loam samples, 580 gm. each. 

 Fifty c. c. of the dilute water solutions above described, omitting the 

 two soil percolates, were added to each sample. This is at the rate of i ,000 

 pounds per acre of surface, with the exception of the manure extract. 

 The treated samples were air-dried, mixed, and put into glass tubes 

 6 cm. in diameter and 20.32 cm. in height. In each case the samples 

 were packed into a volume of 505 c. c, making a soil column approxi- 



i Values for the surface tension and also for the viscosity of these salts in some cases of densities not far 

 removed from that employed here have been determined by a number of investigators in pure physico- 

 chemical lines. (See Castell-Evans, John. Physico-Chemical Tables for the Use of Analysts, Physicists, 

 Chemical Manufacturers, and Scientific Chemists ... v. 2, p. 756. London, 1911.) The results given 

 here are not presented as affording any essentially new information along this line. The work was done 

 largely for the purpose of establishing the accuracy of the work to follow on soil percolates and manure 

 extract solutions. 



The drop method was used in the surface-tension work, employing the dropping pipette (stalagmometer) • 

 of Traube. (See Abderhalden, Emil. Handbuch der biochemischen Arbeitsmethoden. Bd. 5, T. 2. p. 

 1358. Berlin, Wien, 1912.) 



- WTiitney. Milton. Some physical properties of soils in their relation to moisture and crop distribution. 

 U. S. Dept. Agr. Weather Bur. Bui. 4. 90 P- 1892. 



