CIRCULAR No. 29 SEPTEMBER, 1914
ALABAMA
Agricultural Experiment Station
OF THE
Alabama Polytechnic Institute
AUBURN
Bur Clover Seed; Means of Hastening
Their Germination
By
J. F. DUGGAR, Director
and
H. B. TISDALE, Assistant in Agriculture
1914
PostPublishing Company
Opelika, Ala.
COMMITTEE OF TRUSTEES ON EXPERIMENT STATION.
HON. R. F. KOLB--------------------------Montgomery
HON. H. L. MARTIN--------------------------------Ozark
Hox. A. W. BELL-------------------------------_Anniston
STATION STAFF
C. C. THACHT, President of the College.
J. F. DUJGGAR, Director of Experiment Station.
DEPARTMENTAL ORGANIZATION
AGRICULTURE: BOTANY:
J. F. Duggar, Agriculturist. J. S.Cd lBo
E. F. Cauthen, Associate.
M. J. Funchess, Associate.
J. T. Williamson, Field 
Agent.
0. H. Sellers, Assistant. 
PLANT PATHOLOGY:
H. B. Tisdale, Assistant. F. A. Wolf, Path(
VETERINARY SCIENCE:
C. A. Cary, Veterinarian. HORTICULTURE:
I. S. McAdory, Assistant.
CHEMISTRY: 
Ernest Walker, H
B. B. Ross, Chemist, 
State J. C. 
C. Price, Ass
Chemist. G. 
V. Stelzenmull
J. T. Anderson, Chemist, 
Soils
and Crops.
C. L. Hare, Physiological 
Chemist. ENTOMOLOGY:
T. Bragg, First Assistant. W. E. Hinds, En
S. Adler, Assistant. J. . Rck.Assis
)tanist.
sistant.
ologist.
iorticulturist.
sociate.
ler, Field Agent..
tomologist.
Itnt.
EXTENSION: 
G. W. Ells, Field Agent.
J. F. Duggar, Director.
L. N. Duncan, 
Superintendent
Junior and Home 
EconomicsANIMAL 
INDUSTRY:
WorB. Hby soit Superin- G. S. Templeton, Animal 
Hus-
J. B. Hoby, Associ, ate C
tendent, Junior and Home 
Eco- bandman.
nomics Work. E .GroAssat
N. A. Negley, Assistant.* 
E .GroAssat
Miss Madge J. Reese, 
Assistant.* 
E. Gibbens, Assistant.
J. C. Ford, Assistant.* 
J. A. McLeod, Assistant.
*In co-operation with United 
States Department of Agri-
culture
Bur Clover Seed; Means of Hastening
Their Germination
BY
J. F. DUGGAR, Director,
and
H. B. TISDALE, Assistant in Agriculture.
The seed of the Southern species of bur clover
(Medicago Arabica or M. maculata) has heretofore ger-
minated very slowly and imperfectly. This is due to the
fact that practically all bur clover seed of the Southern
species is sowed in the unhulled condition. It is usually
found necessary to sow unhulled bur clover seed sev-
eral weeks earlier than the seed of any other winter-
growing legume, for there must usually elapse four to
eight weeks after sowing before many of the seed ger-
minate. Indeed, this delay in germination often re-
sults in very imperfect stands or in such late germina-
tion that the very young plants are destroyed by cold.
With a view to hastening the germination of bur
clover seed, experiments were begun by the Agricultu-
ral Department of the Alabama Experiment Station
last winter, and these chemical treatments were effec-
tive in hastening germination.
Later, information reached us that Mr. A. D. McNair,
Little Rock, Arkansas, had hastened the germination
of bur clover seed by "scalding." However, the wri-
ters had no information as to the temperatures or other
details employed until after our own experiments here
recorded were well under way.
At the Alabama Experiment Station germination ex-
periments were made in August, 1914, some of which
are still incomplete. But they have progressed far
enough to justify a preliminary statement and recom-
mendation, which is now issued in order to be helpful
to those who will sow bur clover this fall. Certain of
these germination tests were made by planting the burs
in the soil and others by sprouting the seed between
layers of damp cloth.
114
Percentage of Bars Containing Sprouted Seed, Ger-
minated Between Damp Cloths, August, 1914.
No. hours soaked
No. minutes soaked Temperature of
in hot water hot water "
temperature 6 Z
SERIES I
No soaking No scalding 21 6
No soaking 1 min. 1600 F. 21 11
No soaking 1 min. 1400 F. 21 13
No soaking 1 min. 2120 F. (Boiling) 21 51
SERIES III
No soaking No scalding--9 8
2ji hours 1 mi. 2120 F. (Boin) 9 53
2 hours 1 rin. 2120 F. (Boiling) 9 59
3 hours 1 min. 212 0 F. (Boiling) 9 62
4 hours 1 min. 2120 F. (Boiling) 9 76
Percentage of Bars Containing Sprouted Seed; Planted
in Soil August, 1914.
TREATMENT RESULTS
No. hours soaked
in wterat oom No. minutes soaked Temperature of
in hot water hot water
temperature 
" -C
SERIES III
No scalding---------------------- 21 4
No soaking 1 mmn. 1400? F. 21 6
No soaking 1 mmn. 1800? F. 21 10
No soaking 1 mmn. 2120 F. (Boiling) 21 52
115
It should be noted that in one experiment only 8 out
of 100 burs had germinated at the end of nine days,
where no special treatment was given; but in the same
time 76 out of 100 burs had sprouted where the burs
had been soaked for four hours in water at room tem-
perature and then kept in boiling water for one minute.
All of our other experiments point in the same direc-
tion.
Even the above figures do not represent all the bene-
fit of treatment, for it was noted that more seed sprout-
ed from each germinated bur that had been treated
than from each untreated but "germinated" bur.
Effect of Drying Out of Soaked Seed.-In all cases in
these experiments the scalded or soaked burs were
thoroughly dried (for from 30 to 40 hours) before be-
ing planted. It is easier to sow the burs while still wet,
but the burs may be sown either while wet or after be-
ing rapidly dried.
Scalding Permits Later Souing. Heretofore, it has
been considered risky to sow Southern bur clover seed
much after the middle of September in central Ala-
bama. By employing the washing and scalding pro-
cess it becomes safe to continue for several weeks lon-
ger the sowing of the burs, or up to a date as late as is
safe with the seed of crimson clover say up to
the first week in October in central Alabama.
This extension of the sowing season gives op-
portunity to select for sowing bur clover a time
when soil moisture conditions are favorable. Scalding
also affords better stands and economizes these expen-
sive seed. However, to insure a full stand we would
advise not less than three bushels even of scalded seed.
This Station has soaked and scalded a large amount
of bur clover seed in bulk, and suggests the following
procedure in thus preparing large amounts of seed:
(1.) Soak each sack of burs in water at room tempe-
rature for at least two hours, stirring them so as to
wash out as much mud as possible for later use in re-
inoculating the same seed (as under 5 below).
(2.) Then dip each sack of seed for a very few min-
utes into a barrel of very warm or hot water (say 140
to 160 degrees Fahr.) so as to avoid too great cooling
of the boiling water into which the seed are 
to be
dipped later-
(3.) In a pot of water, kept boiling, dip the still
warm seed for one minute.
(4.) Immediately dip the hot seed into cool water.
116
(5.) Now dip the cool seed in that cool 
water in
which the dry seed had first been placed 
(See No. 1
above). This is for the purpose of re-inoculating 
the
seed. To this inoculating water may also be added ei-
ther (1) soil from a field of bur clover or alfalfa, where
the plants have been healthy, or (2) pure cultures arti-
ficially prepared for inoculating bur clover,
The fifth recommendation is made on the assump-
tion that the nitrogen-fixing bacteria lodged on the
dry burs may have been killed by exposure for one
minute to boiling water. This assumption has not been
proved, but re-inoculation is advised as a matter of
safety until experiments now under way at this Sta-
tion determine whether this short exposure to boiling
water makes re-inoculation necessary.
If the amount of seed to be scalded is large, it is im-
portant either to select dry weather for this treatment,
so as to be able to dry the seed thoroughly so as to pre-
vent germination before the seed are sown; or else to
sow the seed soon after treatment while still wet, and
preferably in damp soil.
Prompt drying of the seed (except for those sown in
very damp soil) is believed to be the main precaution
nteeded.
Scalding is regarded as more important than the pre-
ceding soaking. Indeed, the soaking may be omitted;
and it probably should be omitted if there is any dan-
ger that the seed may remain undried in the air for any
considerable time after being scalded. Certainly the
seed should not be allowed to swell and soften before
planting.