CONTROL OP TOBACCO WILT IN THE FLUE-CURED DISTRICT. 11 



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Fig. l.-^Plan of the experiment field at Crcedmoor, N. C, showing details of the crop- 

 ping system on each plat. Plats B, C, D, B, and F were planted to tobacco in 1916. 



tobacco, corn, cotton, peanuts, wheat, sweet potatoes, cowpeas, mixed 

 clovers, and grasses. Two different types of cropping were fol- 

 lowed. In the first type a single crop or group of crops was grown 

 continuously on the same plat. Thus, corn was grown continuously 

 on a quarter-acre plat for five years, with crimson clover as a winter 

 cover crop. In the same way, peanuts and sweet potatoes were each 

 grown continuously on separate plats for five years, in each case 

 with rye as a winter cover crop. Wheat, followed by cowpeas cut 

 for hay, also was grown continuously on one plat. On one plat a 

 mixture of mammoth or sapling clover, redtop, orchard grass, and 

 tall meadow oat-grass was grown each year, the plat having been 

 reseeded in 1913. A plat cropped continuously to cotton was started 

 two years later and thus far has run only three years. For com- 

 parison, tobacco was grown each year on one plat, with rye and 

 crimson clover as a winter crop. In 1916 tobacco was grown on all 

 plats to determine the effects of the other crops on the wilt. There 

 were two objects in the continuous cropping to the same crop plants 

 each year. In the first place it was not certain at the outset which 

 of the crops are immune to the wilt, and, secondly, it was desired to 

 determine by direct test the comparative values of the different 

 crops in reducing the amount of wilt. This plan was fully justified 

 by later development, for it was soon found that peanuts are quite 

 susceptible to the disease, while, on the other hand, the remaining 

 crops proved to be about equally effective in reducing the injury 

 from the wilt, thus indicating that they are immune. 



In the second type of cropping, a system of rotation including 

 corn, wheat and cowpeas, red clover and grass, and tobacco was 

 followed on a series of plats. In this series it was arranged that after 



