Sept. 1918 Deep Tilling and Dynamiting in the Great Plains 485 
or to a total depth of 14 to 16 inches. The variation from this depth 
is hardly more than 2 inches either way. In general, subsoiling is 
done for two years in succession, and then is omitted for two years. 
The present outline 
calls for subsoiling at 
all stations in the fall of 
1915, 1918, and 1919. 
The ground may be 
worked down in the 
fall or left rough over 
the winter. In the early 
years of the work these 
plots were harrowed im¬ 
mediately after plowing 
and kept cultivated 
during the fall, but the 
tendency has been more 
and more to leave them 
rough over the winter. 
This is considered the 
better practice both for 
catching snow and pre¬ 
venting run-off and soil 
blowing, and at the 
same time it reduces 
the expense of crop pro¬ 
duction. 
In some cases where 
it has been impossible 
to plow as early as de¬ 
sired, the stubble has 
been disked and the 
plowing done later. 
In the spring the 
ground is finally pre¬ 
pared for seeding by the 
necessary use of the disk 
or smoothing harrow, or 
both. 
Seeding is done with standard farm machinery at what is believed 
to be the best date and rate per acre. 
The plots are 2 by 8 rods, or 0.1 acre in size. The B and E plots of 
any one crop are separated on their long dimension by the C and D plots, 
or an interval of 78 feet. The different crops may be more widely sepa¬ 
rated, but all are within a field of approximately 20 acres at each station. 
Fig. x—Map of the Great Plains area, which includes parts of io 
States and consists of about 400,000 square miles of territory. Its 
western boundary is indicated by a 5,000-foot contour. The loca¬ 
tion of each held station within the area is shown by a dot within 
a circle (0). 
70393°—18 - 3 
