8 MISC. PUBLICATION 6 5 6, U. S. DEPT. OF AGRICULTURE 



ranged from 2 percent to 18 percent, but were, for the most part, 

 from 6 to 8 percent. Positive values were obtained from the use of 

 a wide variety of well-known erosion-control practices on these tobacco 

 lands. The studies also showed that no single practice when operated 

 alone could be depended on to give adequate protection against ero- 

 sion. In nearly all cases there was need for coordinated use of mul- 

 tiple practices. As the erosion hazard increased with the slope and 

 with shallower soils, a greater number of practices was required. 



In these early studies erosion-control practices found to have spe- 

 cial value on tobacco lands included the following : 



Sodded water diversion channels that were well protected on the 

 uphill side by a grassed buffer strip 10 to 15 feet in width ; channel- 

 type terraces properly laid out with spacings, grades, and lengths 

 adapted to topography, soil, and slope; well-developed and well- 

 maintained grassed waterways capable of carrying off surplus rain 

 water from crop rows, terraces, and fields ; early fall seeding of winter 

 cover crops on land that otherwise would remain bare over winter; 

 crop rotations, and strip cropping that include a year or more of un- 

 broken sod ; vigorous sod-mixture growth in all field depressions that 

 were not smoothed out by plowing or other methods. 



Faulty Row Systems 



These early studies also showed that much of the erosion occurring 

 in tobacco fields was due to the row systems commonly used by farm- 

 ers. Throughout the flue-cured areas tobacco is generally grown on 

 strongly ridged rows. The desire of farmers in this area to provide 

 free row drainage, particularly on slowly permeable soils, has caused 

 them to lay out crop rows down slope or with excessive grades. This 

 practice intensifies the effect of slope and greatly accelerates runoff 

 and soil loss. Many farmers prefer straight rows and will take such 

 row direction across fields as will give them the straightest rows. 

 This usually results in excessive grades with serious erosion in some 

 places and poor drainage in others. 



In some tobacco areas, particularly in the flue-cured middle belt, 

 crop rows are generally run straight across terraces (fig. 5). It was 

 found that as a result of this practice excessive amounts of soil moved 

 down the row middles and lodged in the terraces. The capacity of 

 the terrace channels was also reduced by this practice and terrace 

 maintenance was correspondingly increased. 



Preliminary observations in the Maryland tobacco belt showed 

 that farmers generally were using flat culture and straight rows with- 

 out regard to slope (fig. 6 ) . In this belt where there is somewhat larger 

 acreage of tobacco soil available than is used every year, little effort 

 had been made to protect tobacco fields against erosion other than by 

 various crop rotations, winter cover crops, and land rest in weed 

 growth. 



RESEARCH ON CORRECTIVE MEASURES 



Observation and knowledge of the widespread erosion resulting 

 from the crop-row systems used by farmers of the flue-cured belt led 

 in 1940 to specialized research on this and related phases of erosion. 



