CONSERVATION PRACTICES FOR TOBACCO LANDS 13 



were 11 full rows apart at the steepest part of the slope. Thus five 

 full rows could be laid out above and below each guide line, and short 

 rows were used to fill in any wide places that occurred. Continuous 

 tobacco cropping with winter covers of wheat and vetch has been 

 practiced on the areas used. The plots were laid out on a Sunnyside 

 fine sandy loam soil, on slopes ranging from 8 to 14 percent. All 

 treatments except row grade and tillage were the same. 



In the first season all tobacco was planted on relatively flat rows 

 and the plan was to gradually develop ridges on the across-slope crop 

 rows with cultivation. 



However, rains immediately following planting caused heavy soil 

 losses from all plots. The plots cultivated across slope were severely 

 damaged by cross washing and rilling. This thoroughly demonstrated 

 the need for developing strong ridges before planting. Since this 

 first season, all across-slope rows at Beltsville have been bedded before 

 planting to leave a furrow 8 or 9 inches deep. This ridge row main- 

 tained during the tobacco-growing season has prevented cross wash in 

 all except contour plots (fig. 9). 



Where ridge rows on the contour were compared to flat rows up and 

 down a 10-percent slope, heavy soil loss occurred on the up-and-down- 

 hill area during a severe rainstorm in July. Less than 7 tons per acre 

 of soil were washed from the contoured area, whereas the rows that 

 ran up-and-down-hill lost an estimated 70 tons per acre (fig. 10). 

 Even with the best treatment more weight of soil than of tobacco was 

 removed. 



Rills measuring up to 8 inches in depth were eroded in the up-and- 

 down-hill plots whereas the relatively slight erosion on the contour 

 plot resulted from a break in the row system which affected only a 

 small part of the plot. With the exception of the break in the con- 

 tour area, practically no soil moved off the field. In the plot with 5- 

 percent row grades, no cross wash occurred, but there was severe 

 scouring between the rows resulting in deep V-shaped rills, increas- 

 ing in depth toward the end of the rows. 



This and other observations made during the course of this study 

 showed rapid rates of soil destruction by both the up-and-downhiil 

 culture and the 5-percent ridge-row culture. 



On land with 8- to 10-percent slope, ridged rows with 1-percent 

 grade were compared with flat rows up and down hill. At the end 

 of 7 years' cropping to tobacco, the depth of topsoil on the 1-percent 

 grade-row area had remained relatively unchanged, whereas on the 

 up-and-down-hill row area the soil surface on a plot 150 feet long 

 had been lowered by approximately 6 inches. The loss of topsoil 

 varied from approximately 1 inch at the upper half of the plot to 

 about 10 inches at the lower half of the plot. 



The Effect of Row Grade on Crop Yield 



Early in the present studies it was recognized that ridge rows 

 properly laid out across slope represented an effective measure for 

 controlling erosion during the crop season. Accordingly, yield tests 

 at the Raleigh station have dealt with tobacco grown on ridge rows 

 with all conditions as nearly identical as possible, except row grades. 



