10 
BULLETIN 1465, U. S. DEPARTMENT OF AGRICULTURE 
A - 
CHARACTER OF SOIL 
The soil used throughout the experiment was taken from the fields 
of the Colorado Potato Experiment Station. This soil is classified 
by the Bureau of Soils, United States Department of Agriculture, as 
a Billings loam. It 
contains some sand 
and enough clay to 
cause it to adhere 
strongly in large lumps 
when slowly dried. It 
is free from gravel ex- 
cept for traces of fine 
gravel found irregu- 
larly. The color va- 
ries with the quantity 
of moisture present 
from brown to dark 
gray. The soil below 
the customary depth 
of plowing is of a 
lighter color and has 
more nearly the con- 
sistency of clay. The 
soil used for the exper- 
i m e n t a 1 work was 
taken from the top 8 
inches. It was free from 
stones and gravel and 
contained some hu- 
mus. Several hundred 
cubic feet of this soil 
was taken from the 
field and shoveled over 
from pile to pile until 
it was thoroughly and 
uniformly mixed. No 
other type of soil was 
used. 
METHODS AND TECH- 
NIQUE 
The methods and 
technique were devel- 
oped and improved 
with time and expe- 
rience. The method 
of conducting the 
experiment can be ex- 
plained, but the ac- 
tual technique of ma- 
nipulation can be but 
poorly described. Many failures led to changes in the methods, and 
greater skill improved the technique. It is intended to discuss here 
only the system ultimately used. 
Fig. 5.— Diagrammatic representation of a top view of a filled soil 
can, showing the water shield and wooden block in place; also a 
vertical cross section of the can on the line A-B 
