Managing Cover Crops Profitably - Valley Crops Home

Southern Spotted Bur Medic Offers Reseeding Persistence
While annual medics, in general, are hard reseeded in a Louisiana no-till cotton field
seeded, they usually cannot tolerate winters for more than 10 years without special
north of the Gulf South. Southern spotted management to maintain it (77).
bur medic (Medicago arabica) shows
Research in the Southeast showed that if
promise as a winter legume that can reseed Southern spotted bur medic begins blooming
for several years from a single seed crop in March 23, it would form viable seed by May 2,
Hardiness Zone 7 of the Southeast.
and reach maximum seed formation by May
Once as widely grown as hairy vetch in the 12. By allowing the cover crop to grow until
mid-South region of the U.S., bur medic
40 to 50 days after first bloom and managing
persists in non-cropland areas because it is the cropping system without tillage that
well adapted to the region (265, 266). A local would bury burclover seeds too deeply,
accession collected in northern Mississippi Southern spotted burclover should
exhibits better cold hardiness and insect
successfully reseed for several years.
resistance than commercially available
Native medic seed is being increased in
(Australian) annual medics.
cooperation with the USDA-Natural Resources
In a replicated cold-hardiness trial spanning Conservation Service’s Jamie Whitten Plant
several states, spotted bur medic flowered in Materials Center, Coffeeville, Miss., for
mid-March, about two weeks after SERENA, possible accelerated release to seed growers
CIRCLE VALLEY, or SANTIAGO burclover, but two as a “source-identified” cover crop. As of late
weeks before TIBBEE crimson clover.The bur 1997, there were no commercial seed sources
medic flowered over a longer period than for Southern spotted bur medic seed.
crimson, matured seed slightly sooner than
Insect pests such as clover leaf weevil
TIBBEE but generally did not produce as much (Hypera punctata Fabricius) and the
biomass.
alfalfa weevil (Hypera postica Gyllenhal)
The big advantage of spotted bur medic preferentially attack medics over other
over crimson clover was its ability to reseed winter legume cover crops in the Southeast,
for several years from a single seed crop. In and could jeopardize seed production.These
studies in several states, the native medic insects are easily controlled with pyrethroid
successfully reseeded for at least two years insecticides when weevils are in their second
when growth was terminated two weeks after instar growth stage.While not usually needed
TIBBEE bloomed. Only balansa clover (see Upand-Coming
Cover Crops, p. 158) reseeded icides may be warranted in the seeding year
for single-season cover crop benefits, insect-
as well as spotted burclover (79). The bur to ensure a reseeding crop for years to come.
medic cultivar CIRCLE VALLEY successfully
raw seed may still be 50 percent viable (351). Bur
medic seed in the intact bur remains viable for a
longer time than hulled seed (91).
Their status as a resilient,reseeding forage makes
medics the basis for the “ley system” developed in
dry areas of Australia. Medics or subterranean
clover pastured for several years on Australian drylands
help to store moisture and build up soil productivity
for a year of small grain production before
being returned to pasture. This use requires livestock
for maximum economic benefit. GEORGE
black medic is prostrate,allowing other grasses and
forbs to become the overstory for grazing.It is wellsuited
to cold winter areas of Hardiness Zone 4,
where it can stay green much of the winter (3).
Quick starting. Black medic can germinate within
three days of planting (228). About 45 days
122 MANAGING COVER CROPS PROFITABLY