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



Land Slope 



The greatest single factor contributing to erosion on tobacco land 

 is the slope of the fields on which tobacco is grown. Musgrave (1£) 

 points out that for a given soil type the erosion rate increases greatly 

 with the steepness of slope. Except for parts of the Coastal Plain, 

 most of the tobacco is grown on gently sloping to rolling land with 

 some slopes of 15 to 20 percent. Relatively little of the good tobacco 

 soil in these belts is flat enough to be unaffected by erosion. 



Rainfall Pattern 



With tobacco as with other row crops high-intensity rainfall is one 

 of the principal causes of soil erosion (#, 5, #, H). The distribution 

 of intense rains is shown in relation to tobacco seasons in figure 4, A. 



In the flue-cured and Maryland tobacco belts the erosion hazard is 

 intensified because the tobacco-growing season occurs within the period 

 of the year with highest rainfall intensity. High-intensity storms 

 occur more frequently in June, July, and August than in any other 

 months. 



Results of experiments on cultivated tobacco land at Raleigh, N. C, 

 show a significant relationship between season and erosion. Under 

 the conditions of the studies at Raleigh about 80 percent of the erosion 

 occurred in the 3 months of June, July, and August, whereas only 6 

 percent occurred in the 7-month period from September to March. 



Observations on many tobacco fields likewise indicate that most 

 of the erosion losses take place during high-intensity rainstorms occur- 

 ring in the 5-month tobacco season. Results obtained by others (14, 

 2, 5, 6) show a similar relationship between summer rainfall and the 

 erosion of farm land in widely different parts of the country. 



The important relationship of seasonal rainfall to erosion is graph- 

 ically ilustrated in figure 4, B, which serves to emphasize the follow- 

 ing important points : The erosion hazard in tobacco fields reaches its 

 peak during the 5 -month period from April to August. This in- 

 creased erosion hazard is due to the interlocking influences of the 

 greater amount of rainfall, more intense rains, and increased dis- 

 turbance of the soil by cultivation. From the time land is plowed in 

 spring until the soil is again stabilized after the crop season, there is 

 great need for intensifying the use of erosion-control practices. 



EARLY STUDIES OF EROSION CONTROL ON TOBACCO LANDS 



The serious nature and widespread extent of erosion on tobacco 

 lands was recognized by conservationists early in the development of 

 soil-conservation programs in the flue-cured and Maryland bright- 

 tobacco belts. Immediate steps were taken to test and evaluate all 

 standard soil-defense practices thought to be applicable to the soils 

 in tobacco production. 



Field trials were begun in 1937 in the flue-cured tobacco areas of 

 Virginia and North Carolina. From 1937 to 1939 operations and re- 

 search workers of the Soil Conservation Service, cooperating with 



