Apr. 9,1917 
Water-Retaining Capacity of Soil 
29 
Leather (13, p. 105-106), from a study of the moisture in a fallow field 
at Pusa, India, during the dry season of 1906, conduded that— 
during a dry period water moves upward toward the surface from a limited depth 
only; this limited depth increases with the period. Below this depth the water is 
stationary or possibly still draining downward. 
In the Pusa soil he found the maximum distance that water moved 
upward during the period to be somewhat more than 3 feet and that 
eventually it was about 7 feet. While he did not determine the hygrosco- 
pidty of his soils or recognize in this a means of estimating the relative 
surfaces of the solid particles, he concluded that— 
the relative water-retaining power of a soil after drainage has ceased is closely related 
to the total surface possessed by the solid particles, and it is probable that from a 
determination of the latter the water-holding capacity of soils may be ascertained. 
Extreme views of the importance of the upward capillary movement 
have been expressed by Cameron (10) and McGee (16, 17). The former, 
mentioning that in humid areas the larger part of the water from rains 
returns to the surface, states that it sometimes does so “through distances 
of many feet” (10, p. 23). He assumes the upward capillary movement 
to be sufficient to bring to the surface annually more than sufficient 
potash and phosphoric acid to replace the amounts that would be 
removed by— 
one ton per acre of dry crop containing one per cent, potash and 0.6 per cent, phos¬ 
phoric acid (io, p. 77). 
McGee has estimated that in the Great Plains of the United States the 
quantity of water which the deeper subsoil contributes to the growth of 
crops is not less than 6 inches annually and that by supplementing the 
local rainfall it suffices— 
to render the land productive and habitable over a vast area which would otherwise 
be unproductive (17, p. 40); that it will move during the course of a year from a depth 
of say 10 feet; and that under favorable conditions of subsoil texture it will move 
during a term of years and progressively equalize the distribution of subsoil water 
through a depth of 30 or 35 feet (16, p. 11). 
Widtsoe and McLaughlin (25, p. 230) have suggested the term “lento 
capillary point” to designate the moisture content of a soil at which 
capillary movements become very sluggish. They consider that it can 
not be defined with precision. In a field study of a soil very uniform in 
texture to a depth of 8 feet they found the moisture content to vary be¬ 
tween about 10 and 18 per cent and the lento capillary point to lie between 
12 and 13 per cent. 
From experiments with crop plants grown in cylinders 6 feet deep, in 
which the hygroscopic coefficients of all the soils used were determined, 
one of the authors concluded that the stored moisture in the different 
depths of subsoil in the case of ordinary dry lands becomes available to 
