28 
Journal of Agricultural Research 
Vol. IX, No. a 
determined by plant-house experiments, in which crop plants were grown 
in 6-foot cylinders and left unwatered until they matured or died of lack 
of water (2), appears to be practically coincident with the hygroscopic 
coefficient. Up to the present a method of estimating the water reten¬ 
tiveness in the field from one of the physical constants of the soil has not 
been developed. The laboratory experiments and field studies of the 
authors make it appear that, in the case of soils with hygroscopic coeffi¬ 
cients between 14 and 3, this bears a rather simple relation to the hygro¬ 
scopic coefficient, and that, in coarser soils, while it bears a much less 
simple relation, this is still one that may be experimentally determined. 
As the great majority of the tillable soils of dry-land regions fall within 
the limits of hygroscopicity mentioned, it would appear that, through 
the determination of the moisture content and the hygroscopic coeffi¬ 
cient in the case of samples of the deeper subsoil, we could learn both the 
percentage of the physiologically important water and the departure of 
this from the maximum which the particular subsoil could retain. 
The hygroscopic coefficient may be determined directly or more 
conveniently by one of the indirect methods that have been proposed 
(8, p. 73 J 5 >P- 4 io; 4 . P- 530 - 
HISTORICAL REVIEW 
The authors who maintain the theory “that water can rise to the 
surface from the deep layers by capillary action” are, as Rotmistrov 
has stated (23, p. 16), too numerous to name, but few of them offer any 
experimental evidence in support of the theory. 
From field observations during unusually prolonged summer droughts 
Hall concluded that in certain soils the capillary rise of water might be 
as much as 200 feet (11, p. 94). 
Mitscherlich, who has calculated the maximum possible elevation of 
water to be as high as 2 or 3 km. in heavy clays and loams (19, p. 192), 
considers this of no practical importance, on account of its extreme slow¬ 
ness of movement. From experiments with “the most varied soils” 
exposed for a 3-month period, during which they became appreciably 
altered by algae, he observed no rise exceeding 0.8 meter and concluded 
that 1.5 meters from ground water may be regarded as the practical 
limit, so far as plants are concerned (20, p. 136). 
In the case of one soil Tulaikow (24, p. 665) observed a rise of 135 cm. 
in 513 days, and the maximum had not yet been -reached; while with 
three finer-textured soils the rise at the end of a year and a half had 
become stationary at 60 to 70 cm. 
From field studies in Saskatchewan in 1904 and 1905 one of the authors 
concluded that in semiarid regions the roots go to the stored water in the 
subsoil instead of the latter being elevated to the surface foot by capil¬ 
larity and that but comparatively little water which has once passed 
below the first foot is lost by evaporation (i, p. 42). 
