512 Journal of A gricidtural Research voi. xiv. no. « 
years the two center tiers of plots running east and west are dynamited. 
In the odd years the two north tiers of plots are cropped to wheat and the 
two south tiers to corn. In the even years the two east tiers of plots are 
cropped to wheat and the two west tiers are cropped to com. The size 
of each plot is % acre. 
Eight plots were dynamited late in September, 1912. The charges 
of powder were placed 15 feet apart in each direction, X pound of 20 per 
cent powder being used in each charge. The charges were fired at a 
depth of 30 inches, which is as deep as is practicable to place them in 
this soil when it is dry. The soil on which this experiment is located is 
of the heaviest clay of 
the type commonly 
known as gumbo. Ap¬ 
parently it is almost 
impervious to water 
under some condi¬ 
tions, and samples 
taken to a depth of 10 
feet reveal no change 
in its character. Af¬ 
ter the explosive had 
been used, an exami¬ 
nation of the soil 
showed that it had 
not been in the least 
affected at a distance 
greater than 5 feet 
from the location of 
the charge. In many 
cases the soil was not 
disturbed beyond a 
distance of 3 feet from the charge. This was when the soil was very dry. 
When the soil is at all moist, the powder exerts a packing rather than a 
disrupting effect. 
After the first year the powder company withdrew its active coopera¬ 
tion, but the experiment has been continued by the Department, and the 
blasting done each year as provided for in the original outline. 
Each fall, after the dynamiting is completed, the entire 16 plots are 
plowed to a depth of 7 or 8 inches. They are left rough to overwinter, 
the object being to leave them in condition to catch and retain the 
maximum amount of snow and rainfall. In the spring the plots are 
given the necessary tillage with a disk and a harrow to put them in proper 
conditions for seeding. m 
In 1913 good stands of both corn and wheat were obtained. This land 
had produced a crop of sorghum in 1912, and consequently contained no 
water in storage. The season of 1913 was very dry, particularly during 
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Fig. 4 . —Diagram of plots in dynamiting experiment at Ardmore, 
S. Dak. 
