EXPERIMENTS WITH FALLOW IN MONTANA 
11 
The annual and average yields of the three crops on fallow plowed 
to different depths for the seven years, 1917 to 1923, inclusive, are 
given in Table 7 and shown graphically in Figure 6. 
Table 7. — Annual and average yields of oats, barley, and winter wheat on fallow 
plowed at different depths, 1917 to 1923, inclusive 
Depth of 
plowing 
Yields per acre (bushels) 
Crop 
1917 
1918 
1919 
1920 
1921 
1922 
1923 
Average 
Oats 
[4 inches 
<8 inches 
1.18 inches. 
(4inches 
finches 
[18 inches 
21.6 
23.1 
24.1 
16.3 
18.8 
21.9 
7.5 
10.3 
13.4 
6.0 
9.4 
12.1 
7.7 
10.8 
10.5 
1.6 
1.6 
1.7 
1.8 
2.1 
1.7 
1.0 
. 7 
.7 
20.3 
26.9 
34.1 
18.8 
17.1 
17.3 
4.3 
6.7 
8.0 
34.1 
43.8 
46.6 
22.7 
34.8 
33.3 
12.3 
14.8 
11.8 
21.6 
26.3 
27.8 
19.2 
20.2 
19.0 
9.7 
12.0 
13.8 
30.3 
40.0 
39.7 
20.2 
25.0 
20.2 



19.6 
24.6 
Barley 
26.8 
15.0 
18.2 
17.9 
5.8 
Winter wheat x 
7.5 
1.18 inches 
7.5 
1 Winter wheat winterkilled in 1920 and 1922 and was reseeded to Marquis, 
in 1923 and was reseeded to Marquis, but it was too weedy to harvest. 
It partly winterkilled 
The yield of oats was generally increased by increasing the depth 
of plowing, with the difference between the 4-inch and the 8-inch 
plowing much more pronounced 
than that between the latter 
depth and subsoiling to 18 inches. 
The average yield from 4-inch 
plowing for fallow was 19.6 
bushels per acre and from 8-inch 
plowing 24.6 bushels, an increase 
of 5 bushels on the greater depth. 
The average yield on subsoiling 
to a depth of 18 inches in plow- 
ing for fallow was 26.8 bushels, 
an increase of 2.2 bushels over 
8-inch plowing. This increase in 
yield was not sufficient to pay 
for the greater cost of the sub- 
soiling. 
Barley was not as consistent 
as oats in its response to the 
different depths of plowing. 
During the first two years of the 
experiment subsoiling showed the highest yields; in 1920 the 4-inch 
plowing gave the highest yield, and in the other tour years the 8-inch 
plowing resulted in the largest returns. The averages for the period 
show an increase of 3.2 bushels per acre for the 8-inch plowing over the 
average of 15 bushels for the 4-inch plowing. The average yield 
from the subsoiling was 0.3 bushel less than from the 8-inch plowing. 
The winter-wheat yields have not been satisfactory in that this 
crop winterkilled in 1920, 1922, and 1923. The thin stand in other 
years and in the reseeded crop in these years allowed Russianthistles 
to grow profusely. The heavy growth of thistles decreased the 
yields very noticeably in all years. 
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Fig. 6.— Average yields of oats, barley, and winter 
wheat on 4-inch plowing, 8-inch plowing, and 
subsoiling to a depth of 18 inches for the 7-year 
period from 1917 to 1923, inclusive 
