6 



Table II. Tests to Determine Length of Rotation. 



Name of Plot and year Crops planted in previous years 



fCorn 1911, wheat 1912, clover. 

 Rotation Plot 2A, 1914 |and mixed grasses 1913, to- 1 



Ibacco 1914. ) 



rCorn 1911, wheat 1912, corni 

 Rotation Plot 3A, 1915 i 1913, clover and mixed grasses [ 



[1914, tobacco 1915. J 



■• rCorn 1911, wheat 1912, corn^ 



1913, clover and mixed grasses 



1914, clover and mixed grasses 



1915, tobacco 1916. 

 Corn 1911, wheat 1912, clover 

 and mixed grasses 1913, corn 

 1914, wheat 1915, clover and 

 mixed grasses 1916, tobacco 

 1917 



Percentage of wilt 

 In rotation In check 



Rotation Plot 4A, 1916 



Rotation Plot 2B, 1917 



Plot 



12.6 



18.9 



10.9 



2.3 



Plot 

 53.0 



72.0 

 81.0 



97.6 



Less than 5 per cent of wilt was present in 1915 at the time when 

 the tobacco was ready to harvest and, as has previously been explained, 

 much of the wilt in Plot 4A occurred in a poorly drained corner. It 

 is, therefore, evident that a good crop of tobacco with not over 5 per cent 

 loss from wilt can be grown every fourth or fifth year even on badly 

 infested land. 



Since cotton has not been employed in any of the systems of rotation 

 reported, a test was made of the effect of planting cotton for four suc- 

 cessive years before returning the land to a crop of tobacco. The 

 results are presented in Table III. 



Table III. Condition of Tobacco in 1917 on Plot Continuously 

 Cropped with Cotton as Compared with One Continuously 



Cropped with Tobacco. 



Name of Plot Percentage of Wilt 



Plot lA. (Cotton continuously) 5.2 



Plot IB. (Tobacco continuously) 97.6 



Wilt was generally very severe in 1917 as indicated by the fact that 

 Plot IB was practically a total loss. The results of this test indicate 

 that cotton may safely and advantageously be employed in a rotation 

 system on wilt-infested lands. 



Attention should also be called to the fact that, whatever system of 

 rotation is adopted, wilt-infested land must not be left to grow -weeds 

 or to "lie out" as is the practice with some farmers. These weeds not 

 only seed the land and are thus troublesome to the succeeding tobacco 

 crop, but many of them harbor the wilt germ. It has been found that 

 both rag weeds and horse weeds, which are the most common weeds on 

 fields left to lie out, harbor the wilt germ. Other species of weeds, such as 

 jimson weed, ground cherries, croton, horse nettle, and eclipta, are more 



