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MISC. PUBLICATION 



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DEPT. OF AGRICULTURE 



row furrows apparently reduced runoff to some extent but never 

 caused poor drainage because the extra water was absorbed quickly. 

 As the grade of the row middles increased to 30 inches, these depres- 

 sions usually filled with soil and the row middles became smooth 

 channels. 



As the grade increased the water flowed faster and moved more 

 soil as indicated by the increasing amount of sand along each furrow. 

 In this erosion process on sandy land the soil tends to separate. The 

 silt and finer material stays in suspension and goes with the water, 

 while the sand and coarser material moves along the channel floor 

 where much of it is deposited in slight depressions as shown in figure 8. 



Figure 8.— Supplemental row-grade studies at the Soil Conservation Experiment 

 Station near Raleigh, N. C, illustrate the effect of flowing water on row channels 

 with different grades. Grades shown are (A) 6. (B) 18, (C) 30. and (D) 42 

 inches per 100 feet. Note that as the grade increases a greater amount of the 

 fine material is washed away, leaving heavy sand particles in the bottom of 

 the furrow. One cubic foot of water per minute entered the rows for 30 

 minutes. 



In row-grade tobacco plots there was little evidence of scouring on 

 the 30-inch grade, even though the rate of soil loss had greatly 

 increased. This explains how much of our topsoil may be removed 

 before farmers realize that erosion is taking place. 



Row Grades ox Maryland Tobacco Soils 



The experiments with row grades in Maryland were mainly to 

 test the yield and quality of tobacco grown on ridged rows laid out 

 on different grades, and to evaluate the erosion-control features of 

 this method of tobacco culture in the Maryland belt. On one area, 

 ridge rows on contour and on 5-percent grade were tested in compari- 

 son with up-and-down-hill flat rows as checks. On another area 1- 

 percent grade ridge rows were compared with up-and-down-hill flat 

 rows. All grades for across-slope cultivation (contour. 1 percent. 

 or 5 percent) were established by first laying out guide rows which 



