4 BULLETIN 625, U. S. DEPARTMENT OF AGRICULTURE. 
also shows that in this case the variation in profits for the farm 
groups was not due to the difference in the percentage of rotation 
area in summer fallow. 
It will be seen from the two foregoing tables that any cropping 
system which either will increase yields or reduce the amount of land 
devoted to summer fallow without decreasing the crop yields will 
materially increase farm profits on these farms. It will, therefore, 
be the purpose of the following pages to present methods of crop 
improvement through the use of proper cropping systems, and also 
to show how the percentage of rotation area in summer fallow may 
be reduced without materially affecting the yields. 
METHODS OF INCREASING FARM PROFITS. 
The effect on crop yields of eliminating summer fallow from the 
rotation was shown in a farm survey on the silt loam soil farms of 
the Willamette Valley, Oregon. For more than 40 years this section 
grew wheat and oats by the summer fallow system. The farm prac- 
tice followed during this period was almost identical with that of 
eastern Washington, eastern Oregon, and northern Idaho at the 
present time. The crop yields gradually decreased from year to 
year until farming became so unprofitable that a change had to be 
made in the cropping sys terns. Legumes were introduced into the 
crop rotation and the amount of land devoted to summer fallow was 
decreased until in 1912 only 2.7 per cent of the rotation area was 
idle. 
Table III. — Relation of summer fallow to crop yields on 144 silt loam soil farms in the 
Willamette Valley, Oreg. 
Item. 
Number of farms 
Average yields per acre 
Potatoes (bushels). 
Wheat (bushels) . . 
Oats (bushels) 
Hay (tons) 
Crop index 
Farms 
without 
summer 
fallow. 
127 
155.9 
21.9 
37.9 
1.94 
101 
Farms 
with 
summer 
fallow. 
17 
98.4 
23.5 
36.5 
1.76 
In Table III is given a comparison of per-acre yields between 
farms having summer fallow and those having none in the Willa- 
mette Valley. It will be seen that farmers on the silt loam soil in 
the Willamette Valley eliminated summer fallow from their rotation 
without reducing the average cr<^p yield. Wheat was the only crop 
which produced more per acre on farms with summer fallow than on 
those without. These results were accomplished through the intro- 
duction of legumes, principally clover, into the rotation. 
