1116 
Journal of Agricultural Research 
Vol. XXX, No. 12 
effects would be cumulative only to a 
limited degree. However, depletion of 
plant nutrients ordinarily would be 
essentially progressive over relatively 
long periods and might first become of 
importance after several years’ crop¬ 
ping. So far, the expectations just 
mentioned seem to have been realized 
in part, but there are important ex¬ 
ceptions. Certain of the crop effects 
are not influenced at all or are only 
partly overcome by the fertilizer treat¬ 
ments used and are not in accord with 
the facts as to comparative withdrawals 
of plant nutrients by the different crops. 
It will be of interest to ascertain the 
result of continued soil depletion by 
prolonged cropping for comparison with 
the more immediate crop effects which 
do not seem to be explainable by the 
plant-food theory alone. No definite 
conclusion can be reached at this time 
as to the true nature of these latter 
effects. 
TOBACCO, POTATOES, AND COEN 
IN ROTATION WITH WHEAT, 
OATS, AND EYE 
These cropping systems constitute 
the second step in testing the funda¬ 
mental value of the general type of 
rotation under study and should bring 
out the relative merits of the various 
possible combinations of these two 
groups of crops. In this series a deep- 
rooted crop regularly alternates with 
a shallow-rooted crop. Mention was 
made in the preceding series of the fact 
that tobacco and potatoes belong to 
the same family, and in the present 
tests it is well to keep in mind that 
corn is similarly related to wheat, oats, 
and rye. There is a comparatively long 
interval between the harvest of the 
small grain crops and the planting of 
the hoed crops which follow, the soil 
thus remaining unoccupied for nearly 
12 months. The small grains, on the 
other hand, are seeded almost immedi¬ 
ately after harvest of the hoed crops. 
The general plan of the cropping tests 
and the fertilizer treatments are quite 
similar to those used in the preceding 
tests, except that two fields are em¬ 
ployed instead of one in order that all 
crops may be grown each year. The 
fields are numbered II and III. Be¬ 
ginning with 1914 on Field II, tobacco, 
potatoes, and corn have been grown in 
even years, and wheat, oats, and rye in 
odd years. On Field III, beginning 
with 1915, the hoed crops have been 
grown in odd years and the small grains 
in even years. The location of the fields 
and the general characteristics of the soil 
are shown on the soil map and accom¬ 
panying report (p. 1199). The detailed 
plans of Field II, the cropping system, 
and the fertilizer treatments are shown 
in Figure 6. The plan and treatments 
of Field III are the same, except that 
the dimensions of the plots differ 
slightly from those of Field II. As in 
the experiments previously described, 
tobacco is grown on Section A, pota¬ 
toes on Section B, and corn on Sec¬ 
tion C. Following these crops, wheat 
is seeded on Division 1, embracing the 
first five plots of Sections A, B, and C. 
Similarly, oats are seeded on Division 
2 , extending across the three sections 
and embracing Plots 6, 7, 9, and 10, 
Plot 8 being a control; and rye is 
seeded on Division 3, embracing Plots 
11, 12, 14, and 15 of the three sections, 
Plot 13 being a control. 
Maryland Broadleaf tobacco, Irish 
Cobbler potatoes, and Boone County 
White corn have been used in the 
tests. For the winter small grains 
Currell’s Prolific wheat, Culberson 
oats, and local seed of winter rye have 
been used. The rates of seeding have 
been 2 bushels of oats and \}/i bushels 
of wheat and rye per acre. As indi¬ 
cated in Figure 6, the fertilizers have 
been applied to the hoed crops at the 
normal rates throughout the tests. 
The first crop of wheat, oats, and rye 
on both fields received no fertilizer, 
but all subsequent crops of small 
grains have received one-half the 
normal rates applied to the hoed crops. 
Liming has been the same as on 
Field I. There has been very little 
winter killing of rye and wheat, but 
in a few instances oats have been 
somewhat damaged by this factor, 
the injury being mostly limited to 
oats after corn where but little fall 
growth had been made. During the 
first three years of the experiments, 
considerable injury to wheat resulted 
from joint worm, but subsequently 
this has been avoided by plowing 
under the grain stubble shortly after 
harvest and removing all wheat straw 
from the farm immediately after 
threshing. 
Each year the stand of potatoes on 
both fields has been nearly perfect. 
On Field II the tobacco crop of 1922 
was practically a failure because of 
the wildfire and mosaic diseases and 
has not been included in tabulating 
the average yields. In 1916, 1918, 
and 1920 the stands of tobacco on the 
three cropping units of Field II ranged 
from 85 to 96 per cent, and the differ¬ 
ences in any year did not exceed 6 per 
cent. On Field III the stands of to¬ 
bacco have been 95 per cent or better. 
