520 
Journal of Agricultural Research 
Vol. XIV, No. II 
SUMMARY 
Subsoiling, deep tilling, and soil dynamiting are all operations that 
increase the expense of production over that on ordinary plowing. They 
also increase the amount of labor expended on a given area, or reduce 
the acreage that can be prepared by a given working unit. Subsoiling 
is as laborious and expensive an operation as plowing, but must be done 
in addition to it and at the same time. Plowing with a special deep- 
tillage machine to a depth of 12 to 14 inches requires considerably more 
than double the labor, time, and expense of ordinary plowing. The use 
of dynamite in the least quantity that might be effective involves an 
added expense for material and labor of more than $20 per acre. Conse¬ 
quently, in order to justify their use, these practices should show 
increases in yields sufficient to pay for the extra expense involved. 
In any year a combination of conditions favorable to subsoiling may 
occur at any station. At some stations the average results of a series 
of years shows no measurable effect on crop yields as a result of sub¬ 
soiling. At other stations the effect has clearly been to decrease yields. 
At still other stations, particularly at Hays, Kans., subsoiling appears 
to have resulted in significant increases in crop yields. With some of 
the crops showing increases, however, the yields from either method 
have been too small to be profitable. 
Recognizing the fact that there may be times and places giving results 
favorable to subsoiling or other methods of deep tilling, the average 
yields obtained in the extensive experiments here reported seem to war¬ 
rant the conclusion that as a general practice for the Great Plains as a 
whole no increase of yields or amelioration of conditions can be expected 
from the practice. 
In their relative response to deep tillage there is no marked difference 
to be observed between crops. 
Subsoiling and deep tilling have been of no value in overcoming 
drouth. The effect, on the contrary, apparently has been to reduce the 
yields in those seasons that are below the average in production. 
Experiments have been conducted with the subsoil plow, the Spalding 
deep-tillage machine, and dynamite. The effect or lack of effect of 
deep tillage appears to be essentially the same, irrespective of the means 
by which it is accomplished. 
These conclusions are the result of extensive experiments covering a 
wide range of crops, soils, and conditions in the Great Plains. Experi¬ 
ments conducted in the Great Basin under semiarid conditions with the 
greater part of the precipitation occurring in the winter; under humid 
conditions in the States of Illinois, Pennsylvania, amd Mississippi; under 
semiarid conditions at San Antonio, Tex.; and under semiarid condi¬ 
tions on the black soil of southern Russia have all led to the same con- 
