Apr. 9 ,1917 
Water-Retaining Capacity of Soil 
57 
scopic coefficient, unless it has been reduced by transpiration or evapora¬ 
tion. As capillarity in sands elevates water but a very short distance, 
the proportion of the rainfall available for transpiration by deep-rooted 
plants may be surprisingly large, as during the growing season the run¬ 
off is likely to be negligible, most of the water quickly penetrating beyond 
the influence of surface evaporation; and finally the further penetration 
to any great depth is much delayed, thus allowing time for its withdrawal 
by the roots. 
Table XXI .—Ratio of water content to hygroscopic coefficient in sandy soils and subsoil 
in an abandoned orchard near Palm Springs , Cal., on October 10, IQ12 
PERCENTAGE OF TOTAL WATER 
Depth. 
Pit I. 
Pit II. 
Pit III. 
i to 12 inches.. 
Per cent. 
6.3 
8.6 
7.0 
6.4 
1. 1 
Per cent. 
5*4 
6. 0 
6. 1 
•7 
•7 
Per cent . 
4-7 
4.9 
4.0 
•7 
i -3 
Second foot.. 
Third foot... 
Fourth foot. 
Fifth foot. 
HYGROSCOPIC COEFFICIENT 
2 to 12 inches... 
0.6 
0.7 
. 7 
©•7 
• 0 
Second foot... 
.6 
Third foot. 
. 7 
. 7 
W 
♦ « 
Fourth foot. 
* r 
.6 
* r 
. 7 
• C 
Fifth foot... 
.6 
.6 
. 7 
r 
RATIO OF TOTAL WATER TO HYGROSCOPIC COEFFICIENT 
2 to 12 inches... 
10. s 
14.3 
10.0 
7. 7 
6.7 
5 - 4 
0* 2 
Second foot.. 
8.6 
Third foot. 
8.7 
1.0 
Fourth foot. 
xo. 7 
1.8 
V 
1. 4 
Fifth foot. 
1. 2 
i *9 
B.— Finer-textured soils. —Data from a field study in the summer of 
1912 permit a close comparison with the data from the laboratory experi¬ 
ments on soils A and D. A was a bulk composite from the fourth to 
fifth foot taken from an excavation being made for a new building on the 
Experiment Station grounds. Three hundred yards away a considerable 
area of subsoil had recently been exposed in preparing a railroad grade, 
3 or 4 feet of surface material having been removed. Throughout the 
season we kept this exposed subsoil free of weeds, and at frequent inter¬ 
vals took samples for the determination of moisture in the different inch 
sections of the surface foot and less frequently in the foot sections to a 
depth of 6 feet. The samples employed in the case of the inch sections 
were from duplicate borings, 10 to 20 feet apart, using a soil auger 4 
inches in diameter. D was a bulk sample of the surface 6 inches of soil 
taken from one side of a long cultivated field adjacent to the exposed 
