58 



and the total number of these insects found in each row. The follow- 

 ing- table gives the totals of all these counts. 



Infestation of Plots Plowed in Fall and in Spring 



No. of 

 plot 



Hills with 

 ants 



Hills with 

 aphids 



Total No. 

 of ants 



Total No. 

 of aphids 



50 



55 



41 



116 



31 

 31 

 20 



82 



1,125 

 1.395 

 1,215 

 4.150 



348 



310 



295 



1,419 



Fall plowing 

 Fall plowing 

 Fall plowing 

 Spring plowing 



Plots 3 and 6 differ only in the fact that 3 was fall-plowed and 

 disked owce in spring, while 6 was spring-plowed and not disked at all. 



From a comparison of the data of these plots it appears that the 

 fall plowing and single spring-disking of 3 had a decided effect to 

 reduce the ant and root-louse infestation, this being only about a fourth 

 to a third as great in Plot 3 as it was in 6. On the other hand, a com- 

 parison of the data for plots 1, 2, and 3 shows practically no increased 

 advantage due to the more thorogoing treatment of plots 1 and 2 

 as compared with 3. 



Rotation of Crops with Fall Plowing 



Advantage was taken by Mr. Sanders at Galesburg in 1908 of the 

 fact that there lay immediately beside the field used in our experi- 

 ments another field which was to be planted to corn, but which had 

 been in oats in 1907. For the four years before this it had been in corn 

 continuously, while the experimental field had all been in corn without 

 interruptior. since 1904, and a part of it since 1903. 



An experimental plot planted on this oats stubble, and treated like 

 our checks and our other experiments, would thus give us a means of 

 judgmg f>f the eft'ect upon root-aphis infestation of a change for one 

 year from corn to oats. Such a comparison was complicated in this 

 case, however, by the fact that the oats field had been all plowed in 

 the fall of 1907. while the experimental field was not plowed until the 

 spring of 1908. What was actually got by planting a plot in the oats 

 field was consec|uently a chance to observe the apparent effect of rota- 

 tion and fall plowing combined. 



This plot, like the others beside it, was 20 rows wide and 200 hills 

 long, thus containing 4,000 hills. In the fall of 1907 it was merely 

 plowed, to a depth not stated, and on the 19th of the following May it 

 was disked and harrowed. The two check plots in the experimental 



