1112 
Journal of Agricultural Research 
Vol. XXX, No. 12 
every year on the block or cropping 
unit embraced in the first five plots of 
Section A (upper lefthand corner of 
fig. 4), this cropping unit being desig¬ 
nated as A 1. Tobacco is grown in 
rotation with potatoes on Plots 6 to 
10, inclusive, of Section A, and Plots 
I to 5, inclusive, of Section B, the 
tobacco crop occupying the first- 
named plots in even years and the last- 
named plots in odd years. Tobacco is 
grown in rotation with corn on the 
cropping units embracing the last five 
plots of Section A and the first five 
plots of Section C. Similarly, potatoes 
are grown every year on the central 
block of plots in Section B, and corn 
is grown every year on the cropping 
unit embracing Plots 11 to 15, inclu¬ 
sive, of Section C. Potatoes and corn 
are grown in rotation on the third 
division of Section B, embracing Plots 
II to 15, and on the second division 
of Section C, consisting of Plots 6 to 10. 
The cropping control plots through¬ 
out the field (Plots 3, 8, and 13) are 
planted to tobacco every year The 
results on the control plots are sum¬ 
marized in Table IV. The plots are 
arranged in the table to accord with 
their actual position in the field, as 
shown in Figure 4. It appears that 
the productiveness of the field decreases 
somewhat from north to south and 
from west to east. 
perfect stands of tobacco have been 
obtained, although in some instances 
not all plants made sufficient growth to 
justify harvesting. In 1919 the num¬ 
ber of plants actually harvested con¬ 
stituted about 92 per cent of a perfect 
stand where tobacco followed tobacco, 
92 per cent where tobacco followed 
potatoes, and 90 per cent where tobacco 
followed corn. Similarly, where to¬ 
bacco followed tobacco in 1920, 92 per 
cent of a stand was harvested, and in 
1921, 80 per cent of a stand of tobacco 
was harvested after tobacco, 87 per 
cent after potatoes, and 90 per cent 
after corn. In all other cases the stand 
of tobacco harvested was 95 per cent or 
better. Practically perfect stands of 
potatoes were obtained in all instances. 
The same is true of corn, except that in 
1917 the imature ears were damaged 
approximately 10 per cent by birds 
where corn followed corn, and in 1921 
the stand on the same plots was about 
91 per cent. 
In comparing the three crops—to¬ 
bacco, potatoes, and corn—it will be 
apparent that the valuable portions 
are, respectively, the leaf, tubers, and 
grain or seed, representative of three 
different features of plant growth. In 
the case of tobacco and corn, approxi¬ 
mately the entire portion of the plant 
above ground is harvested, but this is 
not practicable for potatoes. Since no 
Table IV.— Comparative productiveness of the. cropping units of Field I as indi¬ 
cated by the average yields of tobacco on the control plots for the period 1916-1982, 
inclusive 
Location of plot 
Leaf, average yields per acre 
Stalks, average yields per acre 
Plot 13 
Plot 8 
Plot 3 
Plot 13 
Plot 8 
' Plot 3 
Section A....... 
Lbs. 
987 
997 
Lbs. 
955 
921 
738 
Lbs. 
886 
810 
822 
Lbs. 
603 
677 
462 
Lbs. 
662 
492 
393 
Lbs. 
492 
440 
468 
Section B____ 
Section C___ 
In 1916 the fertilizer materials were 
applied to the various plots at the 
standard rates, but in subsequent years 
only half the normal rates has been 
applied, as indicated in Figure 4. The 
Maryland Broadleaf type of tobacco 
has been used in these cropping tests as 
well as in those described later. The 
McCormick variety of potatoes was 
used in 1916, and in subsequent years 
the Irish Cobbler variety has been 
grown. The Boone County White 
variety of corn has been used in all the 
cropping tests of this group. Special 
effort has been made to insure satis¬ 
factory stands of the three crops on all 
plots. In practically all cases nearly 
crop effects could be produced until 
the second year of the test, the crop 
yields of 1916 are not considered in this 
discussion. The average yields for the 
years 1917 to 1922, inclusive, under the 
different cropping combinations and 
different fertilizer treatments, are sum¬ 
marized in Table V. The tobacco crop 
of 1919 is not included in the averages 
because the buds of the young plants 
were severely injured by flea beetles 
and the results are not considered 
reliable. 
The average yields of tobacco on 
the control plots in continuous culture, 
in rotation with potatoes, and in rota¬ 
tion with corn, are, respectively, 886, 
