16 
Research Bulletin Xo. 3 
PREVIOUS STUDIES BY THE WRITER. 
In 11)04 and 1905, while examining into conditions in the 
Canadian Northwest 1 for an explanation of the remarkably high 
vie his of small grains obtained on summer- fallowed land, the 
writer took several sets of soil samples to a depth of 6 feet at 
the Indian Head Experimental Farm and determined the total 
water in these. Finding that the percentages of total water did 
not at all correspond with the field notes, which had been re- 
corded as the samples were taken foot by foot, the hygroscopic 
coefficients of all the samples were determined, following the 
example of Loughridge referred to above. The resulting data on 
the free water were in satisfactory accord with the field notes. 
In a single experiment, using some surface soil from Indian 
Head, barley plants were grown in a glass cylinder 10 inches 
deep. At the end of six weeks water was withheld. After the 
plants died, 2 the soil at all depths below 2 inches contained 18 
to 19 per cent total water. The hygroscopic coefficient, as de- 
termined, was found to be 12. 
It was concluded that : a. In such moisture studies in the 
field the depth to which moisture determinations should be made 
depends upon the limit of the root penetration of the crop, being 
4 to 5 feet for wheat and oats and 6 to 7 feet for grasses at 
Indian Head. b. Unless the soil under consideration is very 
uniform a determination of the hygroscopic coefficient of each 
sample is indispensable, and the determination of this value is 
extremely important even where the soil is uniform, c. A better 
idea of the moisture condition of the soil at Indian Head could 
be obtained by a casual exnmination in the field, using a soil 
auger, than by drying and weighing samples unless the hygro- 
scopic coefficient of each sample was determined, d. The stor- 
age capacity for available water of the two soil types studied 
amounted to from 5 to 7 inches of rainfall for wheat and oat 
crops, e. Comparatively little water is lost by direct evapora- 
tion from the subsoil below the surface 12 inches of soil. f. In 
semiarid regions roots penetrate to the stored water and the lat- 
^Alway, F. J. Studies on the Soils of the Northern Portion of the 
Great Plains Region — The Second Steppe. American Chemical Journal, 
1906, vol. 31, p. 580. — Some Soil Studies in Dry Land Regions — A pauer read 
at rhe Second Annual Meeting of the Cooperative Experiment Association 
of the Great Plains Area, held at Manhattan, Kansas, June, 1907, and pub- 
lished in Bui. 130, Bureau of Plant Industry, U. S. Dept. of Agriculture, 
1908, p. 42. — Studies of Soil Moisture in the Great Plains Region. Journal 
of Agricultural Science, 1908, vol. 2, p. 333. 
2 Briggs, L. J., and Shantz, H. L., have incorrectly referred to this as 
tho the moisture had been determined when the plants wilted. The Wilt- 
ing Coefficient for Different Plants and its Indirect Determination, Bul- 
letin 230, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1912, p. 66. 
