22 BULLETIN" 180, U. S. DEPARTMENT OF AGRICULTURE. 
humus, although rye has no bad effect. If corn or other exhaustive 
crop precedes tobacco, the legume humus does not injure the tobacco. 
The presence of large quantities of humus in a soil tends to produce 
weedy cotton and to retard its maturity. It is thus apparent that 
the rotation worked out and the means employed in reducing erosion 
must be adapted to the crops desired and the soils on which they are 
to be grown. 
The loss in productiveness alone should make it worth while to 
prevent erosion, not to mention the rapid depreciation of the money 
value of eroding lands. The amount of material removed from hilly 
land by erosion is enormous. The amount of solid material carried 
to the sea by the Potomac River is estimated 1 at 400 pounds per 
annum to every acre drained by it. The James Kiver, with a flood 
of 10-foot crest, is said to remove an average of 275,000 to 300,000 
cubic yards of solid material within each 24 hours, and to remove 
annually 3,000,000 or 4,000,000 cubic yards from the region above 
Richmond, in Virginia. 2 The loss from erosion on moderate slopes 
in the Piedmont region of North Carolina is said to amount to about 
$3 an acre yearly in decrease in crop value alone, making the total 
annual loss in this region over $2,000,000. 3 Since there are many 
hilly farms on which excessive erosion is effectually prevented, the 
eroded areas must far exceed this estimate in actual loss. 
ECONOMIC LOSSES. 
' The losses resulting in depreciation of the land from erosion are 
only part of the total losses occurring from this cause. Large 
amounts are annually expended in removing from stream channels 
and storage reservoirs sediment brought down by rivers. In many 
places the sediment collects so rapidly that it has been found prac- 
tically impossible to maintain the reservoirs, and the method of 
simply keeping a channel open has been adopted. This, of course, 
entails great losses in water power and in navigation. Many river 
bottoms fill so rapidly that it requires continual dredging to maintain 
channels for purposes of navigation. In the rivers of the Southern 
States the sediment carried is one of the great difficulties in devel- 
oping power sites. Because of the peculiar soil conditions and the 
fact that practically all of the precipitation in both the valleys and 
the headwaters of the streams is in the form of rain, the rivers carry 
a great burden of sediment. In testimony before the Agricultural 
Committee of the House of Representatives in 1908, W. S. Lee 
stated that the capacity of the reservoirs of the Southern Power Co. 
on the Catawba and Broad Rivers in South Carolina was so reduced 
that in a few years only the flow of the rivers would be available. 
i U. S. Geol. Sur. Bui. 192. 
2 Rept. Chief of Engineers, U. S. Army, 1885, pt. 2, p. 847. 
3 Bui. 17, N. C Geol. Sur. 
