20 
BULLETIN 705, U. S. DEPARTMENT OF AGRICULTURE. 
of these farms was not due to the lack of capital or usable land on 
the part of the clay farms. Neither was it due to the difference in 
the valuation of real estate on the two types of soil, for Table I 
shows land was worth $89 per acre on the clay farms and $112 on 
the silt loam farms. 
CAUSES OF THE DIFFERENCE IN EFFICIENCY. 
(1) An average of 73.6 per cent of the farm area of the silt loam 
farm, as shown by Table I, was improved land, as compared with 
71.2 per cent for the clay farms. Thus the silt loam farms have 
available a slightly higher percentage of improved land. 
(2) The silt loam farms produced clover seed, whereas the clay 
farms produced none. As shown in Table VIII, clover seed in 1912 
was a very profitable crop. This contributed materially to the dif- 
ference in the efficiency of the farms on the two types of soil. 
Table XV. — Relation of types of soil to income per productive animal unit and to crop 
yield on 212 farms in Marion and Polk Counties, Oreg. (1912). 
Item. 
Number of farms 
Average income per productive animal unit per farm. 
Average productive animal units per farm 
Crop yields per acre: 
Potatoes (bushels) 
Oats (bushels) 
Wheat (bushels) 
Hay (tons) 
Crop index a 
Salem 
Salem 
clay. 
silt loam. 
68 
144 
$51 
$55 
13.87 
13.19 
187.7 
150.2 
30.8 
37.7 
25.2 
22.0 
2.0 
1.9 
96 
102 
a Crop index of this table is based upon the 212 records. 
(3) Table XV shows the number of productive animal units per 
farm, the income per productive animal, and the crop yields on the 
two types of soil. It will be seen that the clay farms had an average 
of 13.87 productive animal units per farm, as compared with 13.19 
for the silt loam farms; and that the income per productive animal 
unit was $4 greater on the silt loam farms than on the clay farms. 
This would give the silt loam farms an income approximately $55 
per farm greater than that of the clay farms. 
(4) From Table XV it will also be seen that potatoes, wheat, and 
hay, three of the four leading crops upon which crop index in this 
table is based, gave higher yields on the clay farms than on the silt 
loam farms. Oats, on the other hand, gave the highest yield on the 
silt loam farms. However, the crop index of the clay farms was 96 
as compared with 102 for the silt loam farms. The difference in 
the yield of oats on the two types of soil and the large percentage of 
the rotation area devoted to that crop (see fig. 1) are the causes of 
the clay farms having the lower crop index. Hence, the difference 
in the percentage farm income is of capital on the two types of soil 
