Nature of Soil Losses on Cropland 
Soil Erosion 
Soil erosion has forced the abandonment for cultivation of an 
estimated 25 million acres of land that was originally suitable 
for crop prodiction. For the base period the rate of such loss 
was 500,000 acres per year. In addition, perhaps 75 million 
acres once cultivated but not originally well suited to cultiva= 
tion have been rendered unfit even for occasional cultivation. 
On the remaining cropland, erosion continues t take its toll of 
productivity. 
The effects of physical soil loss upon crop yield vary widely 
with soil type, the kind of crop grown, and the nature and amount 
of other inputs. Clearly, a loss of several inches of topsoil 
from a shallow stony soil with the resultant exposure of bare 
rock would be agriculturally disastreus. On the other hand, a 
similar loss from a deep, fertile grassland or alluvial soil 
might result in decreased yield and land value but probably not 
in abandonment. 
Of the 450 million acres used for crops and retation pasture 
in the base period, about 80 percent were subject to erosion. 
An estimated hl percent included deep, fairly uniform soils, 
which could withstand considerable erosion while, with increasing 
inputs, continuing in cultivation. About 8 percent were deep 
soils with heavy subsoils, which, if eroded, would require shifts 
to much longer rotations, or to permanent pasture or woodland 
use. The remaining 11 percent were shallow soils over rock, 
hardpan, and claypan, upon which any considerable erosion would 
mean the virtual end of their use for cultivated creps. 
To illustrate the effects of erosion on crop yield, Tables 30 
and 31 indicate the relationship as it exists on some Corn Belt 
soils. 
Table 30. Relation of Corn Yield to Depth of Surface Soil, 
Tllinois 1/ 
ne silt ace unt 
mypert silt loam 
opt eld Y: epu 
TE eee tan ee vee a en) (oka) (Begnela) 
2c6 933 13.3 79.8 13.0 70.4 14.0 561 
10.6 75.8 11.0 88,8 9.5 68.8 10.0 lho? 
8,0 71.6 8.5 77.0 Tol 57.5 6.5 29 of 
/ O'Dell, Ro T. 1950. A study of sampling methods used in 
determining the productivity of Mlincis soils. Jour. Agr. 2(7):17. 
| i653 
