Mar. 15, 1924 
Wheat Scab , Corn Rootrot, and Crop Successions 865 
pairs of fields were located, each pair consisting of two adjacent wheat 
fields, on the same type of soil of about the same fertility, with similar 
topography and drainage, and sown at nearly the same time with Turkey 
wheat. One field of each pair had been planted to corn the previous year 
and the other had been cropped with either wheat or oats. Numerous 
counts were made in each field, as shown in Table III. Some variation 
in the percentage of scabbed heads occurred in each field. General observa¬ 
tions in previous years indicated that scab infection generally was most 
severe at the lower field elevations. This was probably caused by the 
more succulent growth in these locations. Climatic conditions in 1921 
were such that the growth in the low areas was not very succulent. On 
the contrary, the crop was thin and poorly developed in many of these 
lower places. An attempt was made to cover all of the different condi¬ 
tions in each field so as to establish correct averages. In every case the 
land was only gently rolling and the differences in elevation were not great. 
Table III shows that in this year the percentage of wheat scab was only 
slightly affected by differences in elevation, the greater infection, if any, 
occurring on the higher ground where, in this season, the wheat had made 
the best growth. 
Table 111 .—Percentages of scab in Turkey wheat at different elevations in four pairs of 
adjacent fields (A, B, C, D), on brown silt loam with similar fertility, drainage, and 
topography, but having had different previous crops, in McLean County, III., in IQ2I 
Group. 
Field 
num¬ 
ber. 
Size 
of 
field. 
Pre¬ 
vious 
crop. 
Eleva¬ 
tion. 
Percentage scab at different locations in fields. 
Field 
aver¬ 
age. 
r 
2 
3 
4 
5 
6 
7 
8 
Aver¬ 
age. 
Per 
Per 
Per 
Per 
Per 
Per 
Per 
Per 
Per 
Per 
Acres. 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
fHigh. 
40 
31 
43 
43 
39.3 
424 
40 
Corn... 
53 
52 
14 
26 
39 
41 
37.5 
(Low 
29 
26 
9 
19 
15 
25 
20. < 
21, 6 
A 
[High. 
4 
5 
2 
5 
3 
1 
5 
6 
J 
3.9 
J*' u 
428 
60 
Wheat 
j Medium.. 
3 
4 
3 
7 
4.3 
[Low 
4 
4 
2 
2 
3 
6 
1 . 
3-8 
[High. 
9 
16 
13 
26 
. 
0 • j 
16.0 
610 
20 
Com... 
•(Medium.. 
19 
16 
14 
10 
14.8 
[Low. 
13 
13 
8 
7 
10.3 
I3. 
B 
(High. 
1 
4 
4 
4 
i 
3.3 
611 
20 
Wheat 
<Medium.. 
4 
5 
2 
4 
3.8 
[Low. 
2 
6 
3 
4 
3.8 
3* 6 
1 
[High.. .. 
22 
14 
12 
18 
. 1 
1 
16. 5 
133 
80 
Corn... 
•{Medium.. 
22 
22 
14 
12 
18 
14 
17.0 
[Low. 
6 
8 
10 
12 
16 
14 
11.0 
14.6 
C 
[High. 
8 
11 
8 
9.0 
. 132 
80 
Oats... 
{Medium.. 
3 
6 
8 
5. 7 
[Low. 
6 
6 
8 
4 
6.0 
6.8 
( 109 
20 
Com... 
/Medium.. 
[Low. 
8 
11 
4 
13 
22 
5 
18 
3 
9 j 
6 
7 
11 
10.6 
8.0 
9,8 
D 
J 
j 
(High. 
3 
c 
3 
3.5 
l 107 
40 
Oats... 
•{Medium.. 
0 
o 
A 
0 
< 
4 
4.0 
[Low. . .. 
0 
c 
H 
C 
j 
1 
5 
4.0 
3.8 
* 
D 
D 
| 
In group A the wheat was drilled in a field on which the corn was still 
standing. This left all the old cornstalks in the wheat field. In the 
other groups, the corn had been removed for silage, leaving only the corn 
stubble and a very few broken or scattered stalks that were not picked up. 
