Burr Medic for Central and South Texas
W.R. Ocumpaugh
Texas A&M University Agricultural Research Station, Beeville, TX 78102
Forages provide 75 to 90% of the feed for the $7 billion Texas ruminant
livestock industry. Traits required in a winter annual legume are: drought
tolerance, good seedling vigor, hard seededness, and freeze tolerance. Burr
medic (Medicago polymorpha) was introduced into Texas over 75 years ago and
has become naturalized. It has all the above traits, almost to a fault, in
that it is nearly a weed in my plot areas. In 1994, we collected seed of
naturalized burr medic from eight locations in Central and South Texas with
the objective of developing a superior, persistent, winter-growing variety.
One collection was selected and two cycles of spaced-plant rouging has been
completed. In 1996, we produced sufficient seed to evaluate our selection
(BEPAS18) against three commercial annual medics from Australia ['Circle
Valley' burr medic, 'Jemalong' and 'Parabinga' barrel medic (M. truncatula)]
at 10 sites across Texas, Oklahoma, and Louisiana. BEPAS18 performed well in
the high pH soils of Central and South Texas, and has never failed to
re-establish itself in any planting in Central and South Texas. In fact, it
spreads to colonize adjacent pastures, whereas none of the commercial medics
seem to spread to adjacent pastures. Frost/freeze tolerance exceeded that of
all commercial medics, but the northern limit of adaptability is somewhere
south of Interstate 20. Total season dry matter yields of about 4000 lb/A
measured at Beeville, College Station and Yoakum, TX are comparable to those
of the commercial medics. Flowering of BEPAS18 is about a week later than
Circle Valley burr medics and about 1 month later than Parabinga barrel
medic, but about 1 week earlier than Jemalong barrel medic. Seed size
(164,000/lb) of BEPAS18 is smaller than Circle Valley burr medic and Jemalong
and Parabinga barrel medic. Seeds/burr is about four. In 1997 we established
a seed production block under center pivot irrigation near Fowlerton, TX.
This 15 acre block was established with three objectives--first to produce
Foundation Seed, second to evaluate seed production under near commercial
conditions, and third to demonstrate the utility of a Horwood Bagshaw vacuum
seed harvester. At this time we have not recleaned and weighed all the bags,
but this year's seed production is expected to be in the 900 lb/A range. We
made a lot of mistakes in land preparation, so we were not able to harvest as
much seed as we believe is possible. Hence, we believe that at least 1000 lb
of clean seed per acre is obtainable under irrigation. Seed production and
harvest costs will be in line with other annual forage legumes, as in a good
day we could harvest over 3000 lb of seed. This legume will need to be
planted only once (on sites where it is well adapted) at a seeding rate of 8
to 15 lb/A. We believe BEPAS18 burr medic will reduce overall costs of
producing forage for livestock and wildlife while improving performance. It
will reduce or eliminate the need for N-fertilizer on perennial warm-season
grass pastures. An exclusive release is anticipated this fall.
We are also evaluating other annual Medicago species that have become
naturalized in Texas, for use in other ecological zones of Texas.
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