22 BULLETIN" 180, U. S. DEPARTMENT OF AGEICULTUEE. 



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 ^ at 400 pounds per 

 annum to every acre drained by it. The James River, with a flood 

 of 10-foot crest, is said to remove an average of 275,000 to 300,000 

 cubic yards of soHd 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.^ 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.^ Since there are many 

 hUly 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. 



1 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. 



