1098 
Journal of Agricultural Research 
Vol. XXX, No. 12 
the “tobacco-tired’’ land for a period 
of years eventually came to largely 
supersede the custom of using virgin 
soil. It was found that from the stand¬ 
point of both yield and quality of prod¬ 
uct good results were obtained by grow¬ 
ing occasional crops of tobacco and 
allowing the land to lie idle during the 
intervals. This system of cropping, 
which is really a rotation of tobacco and 
weeds or other adventitious vegetation, 
is especially applicable to sections where 
the acreage of cleared land greatly ex¬ 
ceeds that needed for the tobacco crop 
and has been extensively followed in 
southern Maryland, where the present 
experiments have been conducted. A 
striking example of this practice is 
found in the culture of fine cigar-wrap- 
er tobacco in the east coast district of 
umatra. There the land is cleared for 
a single crop of tobacco, followed per¬ 
haps by a dry crop of rice, after which 
the soil is left undisturbed for seven or 
eight years. During this period the 
original jungle growth is largely re¬ 
stored. Fertilizers may be used to 
advantage in this system of resting the 
land, but fertilizers alone apparently 
can not be employed as a substitute for 
fallowing. 
There are two other important crop¬ 
ping systems in tobacco culture which 
involve more intensive methods. In 
Lancaster County, Pa., tobacco is 
grown in a rotation with wheat, grass, 
and red clover, and commonly a crop 
of corn immediately precedes tobacco 
in the rotation. The soils are strong 
naturally, and barn manure and some 
commercial fertilizer are applied to the 
tobacco crop. Under this system the 
tobacco yield is maintained at a rather 
high level (8, p. 418). This seems to 
be about the only successful rotation 
for tobacco which embodies Macaire’s 
principle of substituting useful crops for 
weeds in the cropping system. The 
Connecticut Valley method consists 
essentially of continuous tobacco cul¬ 
ture with very heavy annual applica¬ 
tions of high-grade commercial fertili¬ 
zers and liberal use of barn manure, 
with or without lime. On some soils 
this method has given very satisfactory 
results and large yields have been ob¬ 
tained. On other soils, however, the 
yield of tobacco rapidly declines. There 
are instances where one field on a farm 
continues to give excellent yields after 
continuous tobacco culture for more 
than a half century, while on another 
field the crop has become practically a 
failure after a few years, identical meth¬ 
ods being applied on the two fields. 
In some cases root rot, due to Thielavia 
basicola (B. and Br.) Zopf, seems to 
satisfactorily account for the decline 
in yield, but in other instances diligent 
search for a causal parasite has thus 
far failed. It should also be recalled 
here that decline of the crop on old 
tobacco land, as already indicated, is 
by no means confined to the Connecti¬ 
cut Valley or to the cultural methods 
employed there. 
The field tests discussed here have 
consisted of two principal features and 
have been carried out primarily to 
furnish further information as to 
(1) why attempts to apply intensive 
methods in tobacco culture, either by 
using soil-improving crops or by heavy 
fertilizing and manuring, so commonly 
result in failure; and (2) whether 
tobacco is especially injurious to soil 
productivity as compared with such 
crops as com and potatoes. The 
results of the tests seem to indicate 
that these two problems are rather 
closely interrelated. 
The experimental tract is located 
immediately south of Upper Marlboro, 
in Prince Georges County, Md., and lies 
in the Atlantic Coastal Plain. The 
first series of tests, begun in 1912, 
include tobacco in continuous culture, 
with and without winter cover crops; 
in two-year rotations with wheat and 
legumes; in a three-year rotation with 
wheat and red clover; and on rested 
land. In two of the cropping tests no 
fertilizer has been applied, but in all 
cases the soil has been limed. These 
tests furnish data for a period of years 
as to the possibility of increasing the 
yield and improving the quality of 
tobacco by use of soil-improving crops, 
with and without addition of commer¬ 
cial fertilizers. The results have been 
rather surprising in several particulars. 
The second series of tests, as origin¬ 
ally planned and begun in 1914, had 
in view simply a direct comparison 
of the effects of tobacco, potatoes, and 
corn on soil productivity as measured 
by three succeeding crops, namely, 
wheat, oats, and rye. This experi¬ 
ment consisted essentially in growing 
the three hoed crops on adjoining par¬ 
allel strips of land and then seeding the 
three small-grain crops crosswise these 
strips. Anticipating that the compara¬ 
tive effects of the hoed crops on the 
succeeding crops might be modified 
by fertilizers, the major cropping plots 
were subdivided uniformly into smaller 
plots which received different fertilizer 
treatments. The first results obtained 
were so surprising that it seemed desir¬ 
able to extend the tests. As eventually 
developed, the scheme becomes sub¬ 
stantially an effort to analyze through 
field experimentation the merits of a 
