The Cook County herald. [volume] (Grand Marais, Minn.) 1893-1909, 1905-04-08
CoWpea 1 Bacteria.

ne coWpea bacteria are already
quite widely distributed IN southern
Illinois, l1l especially where this crop has
neen .a, grown for several years, but
tiney are not common In the soils Of
other parts Of the state. 1t lis doubt
1M, however, ii it Is necessary or even
worth while to- take the trouble to-
lnoculate soil for cowpeas.S'5 Some few
tuoercles almost Invariably develop
on cowpea roots the first year they
are seeded, even where they have
naVer been grown before, and If seed
eq the second year on the same land
tAe plants: are usually abundantly
provided with root tubercles. Just
why the cowpea bacteria develop so
rapidly even without special inocula-
t1on is not definitely known. 1t may
oe that the same bacteria also live
On at some other leguminous plant which:
= more or less widely distributed over
tne state, but it seems more likely
tnat the bacteria are brought with the
seed. AS matter of fact, the cowpea
harvest is usually dirty, This is an
annual plant, and consequently the
crop is srown on recently plowed land
and is sometimes cultivated during
the season. Cowpeas are commonly
harvested with moving machine and
then raked up ON the loose ground.
Wnen they are threshed more or
less dirt remains with the seed. Fur
tnermore, the seed coats are not in
frequently cracked, thus providing an
excellent place for the lodgment of
PARTICLES of soil. = =:
f.: Whether it. would be. profitable to
:moculate the land for cowpeas would
depend very largely upon the difficulty
or cost of obtaining the infected ma
ter1al. If soil thoroughly infected with
tne cowpea bacteria can be scattered
over the land at the rate of about
1,oo0 pounds to the acre at cost of
y or less per ton, it might prove
prohtable. It is doubtful if light
application Of 100 or 200 pounds would
produce any very marked effect in
tne yield the first season. After the
soil becomes well infected the: cow
peas then obtain much nitrogen from
rhe afT, and the yyIe1d of ;co,Iwlpeas Ii
likely to be largely Increased. OF
course there is no fixation of atmos-
pher1c nitrogen if there are no tuber-
cles on the roots.
In 1902 several. plots of cowpeas
were seeded on the soil experiment
field at the university. One of these
plots GOD had become thoroughly
infected with the cowpea bacteria, be-
cause Of it's being so situated that
more or less surface drainage water
flowed over it from an adjacent field
upon which cowpeas had been grown
for three successive years. Another
plot (40S), owing to slightly differ
ent situation, had not become in
fected. The two plots were seeded
in July after crop of oats had been
removed from the land. Within three
weeks after seeding, numerous root
tubercles could be found on the plants
on the infected plot. Later on, ten
average consecutive plants were taken
up as completely as possible, and 412
tubercles were found on the roots.
making an average of more than 40
tubercles to the plant. On plot 408
only an occasional plant was found in
fected, and such plants would usually
have only a single large tubercle on
their roots.-Professor G. G. Hopkins
in Bulletin of Illinois Station.