1104 
Journal of Agricultural Research 
Vol. XXX, No. 12 
Table III .—Yields and gross values of tobacco in special cropping tests, 1912-1928 
Yields of Tobacco Leaf, Pounds pee Acre 
DISCUSSION OP RESULTS 
In analyzing the results of the tests 
it will be profitable to consider the 
averages for the period covered, the 
yearly variations, and the general trend 
under the several treatments, the latter 
being more readily presented in graphic 
form. For the whole period of the 
tests, 1912 to 1923, inclusive, where 
fertilizer was used, an average yield of 
about 1,150 pounds of tobacco per acre 
has been obtained in continuous cul¬ 
ture with vetch as a cover crop and in 
a two-year rotation of tobacco and 
wheat with cowpeas as a soiling crop. 
For the same period a yield of about 
1,100 pounds of tobacco leaf has been 
obtained in the three-year rotation of 
tobacco, wheat, and red clover. The 
last-named rotation has given the best 
quality of cured leaf. A yield of some¬ 
what less than 1,000 pounds has been 
obtained both in continuous tobacco 
culture with crimson clover as a cover 
crop and in a two-year rotation of 
tobacco and wheat with crimson clover 
as a soiling crop. The latter, however, 
has given a somewhat better quality 
of leaf. In continuous culture with 
crimson clover as a cover crop, and in 
the two-year rotation with crimson 
clover and cowpeas as a soil-improving 
crop, omission of the fertilizer has 
greatly reduced the yield and value of 
the tobacco (pi. 3, A). Under these 
conditions the tobacco after cowpeas 
and the cowpeas themselves have 
shown well-defined symptoms of pot¬ 
ash hunger, and leaf spot resembling 
wildfire and black fire of tobacco has 
been decidedly more prevalent than 
where fertilizer has been applied. 
For the period 1916 to 1923, in¬ 
clusive, continuous culture'of tobacco 
with fertilizer, but without use of any 
cover crop, has given a yield of 900 
pounds per acre and the product has 
been of good quality. With rye used 
as a cover crop there was an unexpected 
lowering of the average yield of to¬ 
bacco and the value of the crop was 
lowered to an even greater degree. 
The use of crismon clover and cowpeas 
as soiling crops, without addition of 
commercial fertilizer, has greatly re¬ 
duced the yield and value of the to¬ 
bacco as compared with a tobacco crop 
every year with fertilizer but without 
soiling crop. The three-year rotation 
of tobacco, wheat, and red clover has 
given best yields and best quality of 
