1512 A NATIONAL PLAN FOE AMERICAN FORESTRY 



grazing, and cultivation has often not only prevented soil building 

 but diminished the fertility of the existing soil and impaired its ability 

 to produce cover of the original type. This condition is illustrated 

 by data from an area in Mississippi studied by the Southern Forest 

 Experiment Station where 23 tons of topsoil per acre were lost from 

 cultivated land as compared to only a trace of soil lost from forest 

 land. Erosion cannot be completely stopped, but by restoring forest 

 or other vegetative cover on the steeper and more critical areas the 

 process can be retarded to a rate less than that at which fertility is 

 added to the soil. 



In each of the major drainage basins, bad conditions of stream flow 

 and erosion now exist. On an immense area the forest cover has been 

 reduced or removed by fire and improper cutting. The vegetative 

 cover has too often been depleted by improper grazing methods, and 

 the fertile topsoil has been washed from millions of acres of agricul- 

 tural lands. The result of this land treatment has been higher and 

 more frequent floods, silted reservoirs and stream channels, accen- 

 tuated difficulties during periods of low water, and reduced produc- 

 tivity of the land. 



KELATION OF OWNERSHIP TO WATERSHED CONDITIONS 



Land ownership, more than any other one factor, has determined 

 the differences in present watershed conditions. The degree to which 

 watershed requirements have been met on land in various types of 

 ownership and the sort of action necessary to establish satisfactory 

 watershed management in each of these types are substantially as 

 follows: 



PRIVATE 



AGRICULTURAL LAND 



In the eastern half of the United States the most acute stream-flow 

 and erosion problems exist on land now classed as agricultural. On 

 such land, according to rough calculations, perhaps 70 percent of the 

 erosion takes place and 40 percent of the water troubles originate. 

 As has been pointed out in the section of this report entitled " Agri- 

 cultural Land Available for Forestry", more -than 50 million acres of 

 agricultural land in the United States is now abandoned or idle, and 

 present trends indicate the abandonment of an additional 25 or 30 

 million acres in the next 20 years. Largely because of removal of 

 fertile topsoil, often through sheet erosion, the productivity of nearly 

 all the land now abandoned was reduced below the point at which the 

 land could be used economically for crop production. 



Sheet and gully erosion on agricultural land are by no means con- 

 fined to abandoned land and land approaching abandonment. Under 

 present cropping methods erosion is the usual condition, and unless 

 present practices are remedied more and more of the fertile soil from 

 farm lands generally will be added to the silt load of our streams and 

 rivers. On land suited for agricultural use, the problem is one to be 

 solved by agriculture rather than by forestry. The Bureau of 

 Chemistry and Soils and the Bureau of Agricultural Engineering, 

 individually, in cooperation with States, are working on the agricul- 

 tural land phases of the erosion problem. Further reference here to 

 the control of erosion on agricultural land will be omitted. 



