278 REPORTS ON THE STATE OF SCIENCE.—1914. 
show no tendency to send new roots into soil in which the moisture- 
content is reduced to the wilting coefficient. (See fig. 6, 1911.) 
An example of the application of the wilting coefficient to the inter- 
pretation of moisture determinations is shown in the accompanying 
measurements by W. M. Osborne *° at Akron, Colorado (fig. 5). The 
change in moisture during the season in each foot-section to a depth of 
6 feet is shown graphically by the solid lines. The dotted lines 
represent the wilting coefficient for each foot-section. The first chart 
(1911) represents the moisture conditions under a crop of spring wheat 
during a dry season, the crop being practically a failure. It will be 
seen that in the spring there was available moisture in small amounts 
to a depth of 6 feet, the greater part being in the upper 3 feet. 
The crop had removed the growth-water from the first foot by June 1; 
from the second and third feet by June 15; from the fourth foot by 
July 15; while the fifth and sixth feet still contained a limited amount 
of growth-water at harvest time, although the moisture had been 
reduced in each case. 
The second chart (1912) shows the moisture conditions in the 
same plat during the next summer while the land was in fallow. At 
the time the spring samples were taken the moisture-content of the 
surface foot of soil was practically up to the field-carrying capacity of 
this soil. With the advent of the seasonal rains the surface foot began 
to deliver to the section below. It will be noted that the change in 
moisture-content does not take place simultaneously through the soil- 
mass, but is progressive from foot to foot, each section delivering water 
to the section below as it rises to its field-carrying capacity. When 
the moisture supply is below a certain percentage, dependent upon 
the soil in question, capillary adjustment in that soil is very slow. 
_Plants in order to avail themselves of all the growth-water must 
consequently develop a root-system which permeates the soil-mass 
from which water is being drawn. In other words, when the moisture 
supply is limited the capillary distribution becomes so slow as to be 
effective only through very small distances. Plants having a coarse 
root-system, such as maize, when used as indicator-plants, might be 
expected to give a somewhat higher wilting coefficient than plants 
with fine root-systems like the small grains, and this has been observed 
to be the case.?? 
The first chart in fig. 6 represents the moisture conditions as 
measured by J. C. Thysell?* in a barley plat at Dickinson, North 
Dakota, during the dry season of 1911. This plat is normally seeded 
to barley each year. Inspection of the chart will show that at the 
beginning of the season the moisture-content of the second and third 
feet was at the wilting coefficient, to which it had been reduced by 
the preceding crop. A good supply of growth-water was present in 
the fourth, fifth, and sixth feet of the soil, but the roots were unable 
6 Office of Dry-Land Agriculture in Co-operation with the Office of Biophysical 
Investigations. 
27 Briggs and Shantz, op. cit. 
8 Office of Dry-Land Agriculture in Co-operation with the Office of Biophysical 
Investigations. 
