The Rural Voice, 1988-06, Page 55A
FOCUS ON ALFALFA
lfalfa, Medicago sativa L.,
originated in southwest
Asia, although forms of it
can be found growing wild scattered
from central Asia into Siberia. It is
thought that alfalfa was first cultivated
in Iran. The early Roman writers,
Strabo and Pliny, recorded the intro-
duction of alfalfa into Greece as early
as 490 B.C., apparently by invading
Medes and Persians as feed for their
chariot horses and other animals. It
later spread into Italy and other Euro-
pean countries, including Spain, from
where Spanish explorers brought the
forage to Central and South America.
The importance of alfalfa (and
other leguminous plants) in agriculture
was recognized centuries ago by both
early Greek and Roman agricultural
writers who described using it as a
green manure crop. The reason for
the usefulness of these crops was not
understood, however, until the 19th
century, when root swellings (nodules)
produced by root -nodule bacteria were
discovered on leguminous plants. At-
mospheric nitrogen can be converted
(fixed) into forms available for plant
use within the nodules, making leg-
umes much less dependent on soil
nitrogen (N) than other plants.
Alfalfa's benefits to agriculture are
enormous. The air harbours huge
natural reservoirs of nitrogen, which is
accessible to us only through the N -
fixation of legumes. Growing plants
like alfalfa therefore increase soil fer-
tility (and decrease the need to provide
N fertilizer). This is true not only with
regard to the legume crop itself, but
for following crops in the rotation,
providing that the root residues are
plowed in before the stubble dries.
The first recorded attempt to
grow alfalfa in North America was in
Georgia, in 1736. About 1790, it was
grown by both Thomas Jefferson and
George Washington. Despite its pop-
ularity, it was not especially success-
ful until it was introduced to the west
by Suzanne Lovegrove
Medicago sativa L.
coast in about 1850.
During the gold rush, gold seekers
brought alfalfa seed from Chile to
California, where it grew vigorously.
In 1857 one Wendelin Grimm, from
Germany, introduced alfalfa to the
harsher conditions of Minnesota,
clearing the way for the crop's suc-
cess. After several generations of
natural selection under these more
severe climactic conditions, the
"Grimm" cultivar became an early
hardy cultivar.
Soon after, in 1871, alfalfa was
introduced to Ontario's Welland Co.
by Nathan Bethal, and has played a
leading role in Canadian agriculture
ever since. Canadian variegated
alfalfa evolved and took on world
prominence. The variegated types of
alfalfa are still among the hardiest
kinds we can grow.
Planting Alfalfa Today ...
Alfalfa establishes best when
seeded in early spring. Banding the
seed over a high phosphorus fertilizer
tends to improve the stand and vigour
of new alfalfa plants. Covering after
seeding, either by packing or with a
worn, short -toothed spike harrow, is
recommended, and harrowing is
especially advantageous on clay -like
soils that frequently crust.
Shallow seeding (about 1/2 -inch
deep) is advised, at rate of about 13
kg/ha for pure stands to be used for
high -protein stored feed. An excellent
mixture for green chop (which is ideal
for use on small acreages where fewer
animals are involved) is 11 kg alfalfa/
9 kg. bromegrass per ha. (For pastures
with drier conditions, it may be wise
to substitute 3 kg orchardgrass for the
timothy in this mixture.)
The seed should be inoculated with
the proper bacteria for N -fixation, un
less alfalfa, clovers, etc. are regularly
grown in the rotation. In such cases,
the necessary nodule bacteria usually
become established in the soil and are
available when the same plant is
grown again.
Many cases of poor yield in legu-
minous crops are due to inadequate
nodulation, so it may be advisable as
a general principle to use artificial
inoculation at seeding. The result is
often a substantial increase in yield for
a very moderate cost.
Inoculants contain living bacteria,
so follow the instructions on the label
carefully to ensure effectiveness.
Keep in the mind that leguminous
plants are arranged in groups known
as cross -inoculation groups. The
members of each group are success-
fully nodulated by one species of
bacteria, which will not, however,
nodulate members of other groups.
The alfalfa group is comprised of
alfalfa and yellow and white sweet
clover. The clover group is made up
of common clovers: alsike, red, white,
JUNE 1988 53