MANAGEMENT OF GENERAL FARMS IN OREGON. 
17 
On 61 farms no clover was grown; 45 farms devoted less than 20 
per cent and 38 farms over 20 per cent of the field-crop area to clover. 
It will be observed from this table that the yields of potatoes, wheat, 
and oats steadily increased when the percentage of the field-crop area 
in clover increased. The yield of hay, also, was approximately one- 
fourth of a ton per acre greater on farms growing clover than on those 
having no clover. The crop index ranged from 92 for the group of 
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PERCENTAGE OF FIELD CROP AREA UN CLOVEF 
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Fig. 5.— Percentage of increase in crop yields with increase in field-crop area in 
clover on 144 silt loam farms in Marion and Polk Counties, Oreg. (1912). 
farms that grew no clover to 113 for the group having over 20 per cent 
of the field-crop area in clover. 
Figure 5 shows the percentage of increase in the yields of potatoes, 
wheat, and oats for the two groups of farms in Table XII which grew 
clover, as compared with the yields of these crops for the group of 61 
farms having no clover. The average yields of wheat, potatoes, and 
oats for the group of 45 farms having 11.1 per cent of the field-crop 
area in clover were 8 per cent, 13 per cent, and 12 per cent higher, 
respectively, than the yields of these crops for the group of 61 farms 
