870 
Journal of Agricultural Research voi. xxvn, No. n 
crop successions. There was a reduction in yield of 11.6 bushels, or 
13.9 P er cent, on the plats where corn followed scabbed wheat. Doubtless 
this was due largely to differences in fertility; but no doubt a small part 
was due also to seedling blight and com rootrot from the previous crops, 
since the resistant com was not immune, as is shown by the inoculation 
experiments with pure cultures on virgin soil, the results of which are 
given in Table X. The yields from disease-susceptible corn, on the 
other hand, showed much greater variation in yield due to the previous 
crop. There was a reduction of 18.5 bushels, or 25.4 per cent, on the 
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Fig. 2.—Diagram of experimental plats in 1920, data on which are presented in Tables VI and VII. Plat* 
A, C, and E, disease-resistant com; B, D, and F, disease-susceptible corn. 
plats previously cropped with wheat. All evidence indicates that the 
difference between the 13.9 per cent reduction in yield of resistant com 
and the 25.4 per cent reduction of susceptible corn was caused by disease- 
producing organisms in the soil which produced seedling blight, thus 
reducing the stand, as well as reducing the yield of the remaining plants. 
In reality, the loss from disease probably was even a little larger than 
this, because, as already mentioned, part of the 13.9 per cent reduction 
in yield from the resistant corn was most likely also caused by disease. 
The experimental series of 1921, the results of which are given in 
Tables VIII and IX, were conducted on virgin bluegrass sod and on an 
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Fig. 3- —Diagram of experimental plats in 1921, data on which are presented in Tables VIII and IX. Plats 
A, C, and E, disease-resistant com; B, D, and F f disease-susceptible com; intervening and marginal 
plats all planted with nearly disease-free seed com of the same variety. 
adjacent field that had grown a crop of moderately scabbed winter 
wheat during 1920, badly scabbed oats in 1919, and corn during the 
previous 6 years. Bone meal had been applied to this field so that the 
productiveness was nearly equal to that of the virgin soil. The plats, 
figure 3, were of the same size and planted in the same way as those in 
1920, but they were arranged differently. Between each two plats used 
in this experiment was a plat of com of the same size grown from nearly 
disease-free seed. Thus the disease-resistant and disease-susceptible 
com were bordered by the same kind of corn and apparently should 
have had the same opportunities. In this series all of the 40 hills in 
each plat were included in the stand count (Table VIII) and were har- 
