Apr. 9,1917 
Water-Retaining Capacity of Soil 
53 
Table XVIII.— Ratio of final water content to the hygroscopic coefficient 74 to 715 days 
after water had been applied to the base of the soil column 
Final ratio of— 
Soil No. 
Water 
added. 
Initial 
ratio.** 
24 tO 22 
inches. 
21 tO 19 
inches. 
18 to 16 
inches. 
IS to 13 
inches. 
12 tO 10 
inches. 
9 to 7 
inches. 
6 to 4 
inches. 
3 to I 
inches. 
A. 
Inches . 
2. II 
1. 0 
2. 0 
I * 9 
1.8 
1-5 
I. I 
I. O 
0.9 
0.8 
B. 
2. 12 
1. 0 
1.9 
Zm 9 
1.8 
1. 6 
1-5 
1-3 
1. 0 
C. 
I. 21 
1. 1 
2. 1 
2. O 
1.9 
x -7 
1.4 
I. 2 
1. 1 
1. 0 
D. 
.90 
1-3 
2-3 
2. I 
1.8 
i -5 
*•3 
I. 2 
1. 1 
1. 0 
E. 
I. 42 
1. 0 
1.9 
1.9 
1.8 
i -7 
I. I 
I. 0 
.8 
G. 
x. 58 
1. 0 
2. I 
2. I 
2. 0 
1.8 
x -7 
1.6 
x -3 
1. 0 
H. 
I. 28 
1. 2 
2. 2 
2. 2 
2. 1 
1.9 
x. 7 
1.4 
1. 2 
1. 0 
I. 
. 60 
1. 2 
2. I 
2. O 
1.8 
x. 5 
i *3 
1. 2 
1. 1 
1. 0 
L . 
.89 
1. 0 
2. I 
I.Q 
1.8 
x. 7 
1.4 
1. 1 
•9 
•9 
K. 
•33 
i -3 
2. 2 
2. I 
1. 8 
1. 6 
x. 5 
x -3 
x -3 
1. 2 
L . 
.27 
i -3 
1.9 
x. 7 
1. 6 
1.4 
x -3 
1. 2 
1. 1 
•9 
M.. . 
•33 
x -3 
2.4 
2. 2 
x. 7 
1.4 
1.4 
x -3 
1. 1 
1. 0 
a In the 1- to 3-inch section, and, in some of the soils, also in the next section, the initial moisture content 
was somewhat lower than this value. 
The initial moisture content in the above parallel experiments is 
similar to that found in the subsoil traversed by the plant roots when 
the plants have just died or have begun to die from lack of moisture 
(2, p. 122). From these experiments it would appear safe to conclude 
that the water from any soil layer in which the ratio is not above 1.7 
will not appreciably affect the moisture content of the soil at a distance 
of 12 inches or more, even during a period of three months. Even the 
maximum that remains in a subsoil in contact with the earth’s soil mass 
after downward movement has ceased appears able to affect the moisture 
content to but a slightly greater distance during such a period. It would 
appear that with loam soils, such as those employed, the maximum 
ratio to be expected near the point of application, several months after 
the water had been added, would be between 1.6 and 2.5. 
Under field conditions evaporation might prevent this ratio being 
found close to the surface, except for short periods following rain or irri¬ 
gation, but at a distance of a foot or two it is to be expected, and, if not 
disturbed by the invasion of plant roots, may long persist. 
When the ratio lies much below 1.0, the more moist soil seems to exert 
an influence upon the drier soil through a greater distance, which is to 
be attributed not to a movement of water along the surface of the soil 
grains but to evaporation of moisture into the air from the soil having 
a ratio in excess of 1.0 and its absorption from the resulting saturated 
atmosphere by the soil with a ratio below 1.0 (3, p. 259). 
EXCEPTIONAL CONDUCT OF DUNE SAND 
The distribution of water in coarse sands takes place quite differently 
from that in the loams above dealt with. Using the dune sand Q, with 
an initial content of 0.2 per cent of water, we added 0.50 inch in the case 
of five cylinders and 1.0 inch in the case of five others. All had been 
