THE CONTROL OF SOIL-MOISTURE 205 



uplands by running water, erosion is no insignificant factor 

 in soil management considerations. 



Two types of erosion are generally recognized, sheet and 

 gully. In the former, soil is removed more or less uniformly 

 from every part of the slope. Gullying occurs where the vol- 

 ume of water is concentrated, resulting in the formation of 

 ravines by undermining and downward cutting. Both types 

 of erosion are serious. 



A number of different methods for the effective prevention 

 and control of erosion may be utilized. Anything that will 

 increase the absorptive capacity of the soil, such as deep plow- 

 ing, surface tillage, and increase of organic matter, will lessen 

 the run-off over the surface. On steep slopes, however, such 

 influence is of little importance, since during heavy rainfall 

 absorption is too slow to lessen materially the surface losses. 

 In cultivating corn and similar crops, it is important that the 

 last cultivation be across the slope rather than with it. On 

 long slopes subject to erosion, the fields may be laid out in long 

 narrow strips across the incline, alternating the tilled crops, 

 such as corn and potatoes, with hay and grain. The grassed 

 areas tend to check the surface flow of water. Where the 

 slopes are subject to very serious erosion, they should either be 

 reforested or kept in permanent pasture, guarding always 

 against incipient gullying. 



About the only effective means of controlling sheet erosion 

 is by terracing of some kind. Strong prejudice exists in many 

 communities against terraces, since they usually waste land, 

 are often unsightly and are a serious obstacle to harvesting 

 machinery. The Mangum terrace * however, is worthy of es- 

 pecial attention, since it obviates the really serious objections 

 to the ordinary terrace while maintaining the desired water 

 control. The Mangum terrace is generally a broad bank 

 of earth with gently sloping sides, contouring the field at a 



1 First constructed by P. H. Mangum of Wake County, North Caro- 

 lina. 



