26 
BULLETIN 174, U. S. DEPARTMENT OF AGBICULTUBE. 
DEPTH OF PLOWING. 
In order to ascertain whether plowing is usually deeper when 
done by tractor than when done by horses, Tables XVI and XVII 
were prepared. Table XVI shows the average depths of tractor 
plowing in nine States for the number of seasons for which reliable 
averages could be obtained. While the variations seem to be slight, 
they are greater than would appear at first glance. Each depth 
shown represents an average of a large number of reports, most of 
which are, of course, close to the final average; therefore, in order 
to increase or diminish the final average even one-tenth of an inch 
requires a general increase or decrease in the individual reports. 
Table XVI. — Average depth of tractor plowing on farms in various States. 
Average depths reported (inches). 
State. 
Average depths reported(inches). 
State. 
First 
season. 
Second 
season. 
Third 
season. 
Fourth 
season. 
First 
season. 
Second 
season. 
Third 
season. 
Fourth 
season. 
6.18 
6.30 
6.21 
6.19 
58 
6. 44 
6.47 
5.87 
0.17 
6.14 
6.57 
5. 55 
6.09 
6.11 
Iowa 
6.35 
6.85 
6.71 
6.19 
6.42 
6.77 
6.02 
South Dakota. . . 
California 
Nebraska 
Texas 
The distribution of the individual reports for all States west of 
the Mississippi River is shown in Table XVII. The concentration 
of the reports on the 5, 6, and 7 inch depths will be seen. The 
reports for the second season show a decided decrease in the percent- 
age reporting 7 inches or more, with a corresponding increase for 
6 inches or less. In the third and fourth seasons there appears to 
be a gradual return to the greater depths, but in connection there- 
with it must be borne in mind that the men who have used tractors 
for three or four seasons have been the most efficient operators; in 
fact, they are the survival of the fittest, for the first two seasons 
serve to eliminate many of the inefficient operators, as well as many 
of the defective outfits. 
Table XVII. — Percentage of tractor plowing done at various depths on farms in all States 
west of the Mississippi River. 
Depth of plow- 
ing. 
First 
season. 
Second 
season. 
Third 
season. 
Fourth 
and 
subse- 
quent 
seasons. 
Depth of plowing. 
First 
season. 
Second 
season. 
Third 
season. 
Fourth 
and 
subse- 
quent 
seasons. 
4 inches 
3.84 
16.85 
37.22 
24.32 
4.94 
23.51 
41.66 
18.72 
5.17 
20.34 
36.55 
20.34 
5.94 
14.61 
41.10 
21.46 
8 inches 
11. 54 
7.84 
11.72 
3.45 
8.22 
2. 72 1. 60 
.91 
10 inches 
2.04 
5.94 
7 inches 
