[permaculture] Up and Coming Cover Crops - Managing Cover Crops Profitably, 3rd Edition - Sustainable Agriculture Research and Education
Lawrence F. London, Jr.
venaurafarm at bellsouth.net
Fri Mar 18 01:17:32 EDT 2011
Managing Cover Crops Profitably, 3rd Edition
Opportunities in Agriculture Bulletin
UP-AND-COMING COVER CROPS
Identified as a promising new cover crop in screening trials throughout
the Southeastern U.S., balansa clover (Trifolium michelianum Savi) is a
small-seeded annual legume with superior reseeding potential compared
with other legumes, including crimson clover. Well-adapted to a wide
range of soil types, balansa performs particularly well on silty clay
soil with a pH of about 6.5. Established stands tolerate waterlogging,
moderate salinity, and soil pH from 4.5 to 8.0. It does not do well on
highly alkaline soils (30). It is considered marginal in Zone 6B.
Balansa and other reseeding legumes were screened in Zones 6, 7, and 8
(from the Gulf Coast to northern Tennessee, and from Georgia to western
Arkansas). TIBBEE crimson clover (Trifolium incarnatum) was used as a
phenological check. Growth was terminated 2 to 3 weeks after TIBBEE
bloomed at each location to identify adapted cover crops that reseed
earlier than TIBBEE. Spotted burclover (Medicago arabica) and balansa
clover were the best reseeding legumes that were hardy throughout zone
7a. Of these, only balansa clover is commercially available.
Balansa clover is open pollinated. Flowers vary from white to pink and
are attractive to bees. Ungrazed, it grows up to three feet high and
produces thick hollow stems that are palatable and of good feed value.
It becomes more prostrate when grazed.
Balansa clover was named Trifolium michelianum Savi in 1798. It is
sometimes called Trifolium balansae or Trifolium michelianum subsp.
balansae. A landrace of balansa clover collected in Turkey in 1937 was
released in 1952 by the Alabama office of NRCS with the name MIKE. Small
amounts of seed of this accession are available from the Plant
Introduction Station in Athens, Ga.
Balansa clover seed is quite small, so planting only 5 lb. /A gives a
dense stand. Seed is produced commercially only in Australia. Balansa
clover requires a relatively rare inoculant, designated “Trifolium
Special #2” by Liphatech, Inc., manufacturer of “Nitragin” brand
inoculants. Kamprath Seed Co. imports balansa seed (See Seed Suppliers).
Some seed suppliers offer coated seed that is pre-inoculated. The price
per pound of coated seed is about the same as bare seed, but 1/3 of the
weight is coating so the seeding rate for coated seed should be
increased to 8 lb./A.
PARADANA is the cultivar that has been most widely tested in the U.S. It
was released in 1985 by the South Australia Department of Agriculture.
It was derived from Turkish introductions crossed and tested at Kangaroo
Island, NSW, Australia. Seed yields over 550 lb. /A have been obtained.
BOLTA is 1-2 weeks later than PARADANA and FRONTIER is 2-3 weeks
earlier. FRONTIER, a selection out of PARADANA, has replaced its parent
in the seed trade in recent years.
While PARADANA seed matures slightly earlier than crimson clover, it
often does not produce as much biomass. Nitrogen accumulation in above
ground biomass is about 60 lb. /A at full bloom. Balansa can reseed for
several years from a single seed crop, due to its relatively high amount
of hard seed. It reseeded for four years following maturation of a seed
crop in 1993 in Senatobia, Miss., and for at least two years in no-till
systems at several other locations in Alabama, Georgia and Mississippi.
Neither TIBBEE nor AU ROBIN crimson clover reseeded for more than one
year at any location in those tests. Balansa clover does not reseed well
after tillage, probably because the small seeds are buried too deeply.
Allowing balansa clover to grow for 40 days past first bloom every 3 to
4 years will allow stands to persist indefinitely in no-till systems.
Reseeded stands are denser, bloom 5 to 7 days earlier, and are more
productive than planted stands because growth begins as soon as
conditions are favorable and seedling density is higher. However, seed
cost is minor compared to opportunity cost and risk associated with
delaying main crop planting. Waiting past the optimum planting date to
encourage reseeding is only practical in rotations that include main
crops optimally planted in May in the Southeastern U.S.
Balansa is less likely than crimson clovers to host root-knot nematodes
(Meloidogyne incognita, race 3).Gary Windham, USDA-ARS, Starkville,
Miss., found that balansa had egg mass index scores between 2.3 and 2.9.
For comparison, a very resistant white clover scored 1.5, most crimson
clovers score between 3 and 3.5 and very susceptible crops like REGAL
white clover score 5 on a scale from 1 to 5.
USDA-ARS National Sedimentation Lab
P. O. Box 1157 Oxford, MS 38655-2900
662-232-2975; sdabney at ars.usda .gov
Black oat (Avena strigosa L.) is the No. 1 cover crop on millions of
acres of conservation-tilled soybean in southern Brazil, and has
potential for use in the southern USA (Zones 8-10).
Black oat produces large amounts of biomass, similar to rye. It
maintains a narrower carbon to nitrogen (C:N) ratio than rye so it
cycles nitrogen better than rye, important for nitrogen management in
conservation tillage systems. It breaks disease cycles for wheat and
soybean and is resistant to root-knot nematodes. It is very resistant to
rusts and has exceptional allelopathic activity for weed control. It is
easy to kill mechanically.
Black oat is adapted for use as a winter cover crop in the lower Coastal
Plain of the USA, including Zones 8b-10a. It has done well in fall
plantings in Zone 8b, but winterkilled one year of six at some locations
within this zone, dependent on planting date.
Planting dates are similar to common oat. If planted too early, it is
more susceptible to winterkill and lodging. Planting in late winter
(early February) yielded good biomass and ground cover for late planted
cash crops in the lower Coastal Plain.
Seed 50-70 lb. /A for use as a cover crop, 40 lb./A for seed production.
In the Southeast, fall plantings (November) result in seed ripening in
mid May through early June. Seed yields range from 800 to 1400 lb./A.
Seed is available commercially in limited amounts.
One cultivar, SOILSAVER, was selected for increased cold tolerance and
released by Auburn University and IAPAR (Institute of Agronomy of
Paraná, Brazil). Auburn University and USDA-ARS researchers developed it
from a population of IAPAR-61-IBIPORA, a public variety from the
Institute of Agronomy of Parana, Brazil (IAPAR) and the Parananese
Commission for Evaluation of Forages (CPAF).
SOILSAVER black oat has several advantages as a cover crop. It tillers
well, producing good soil coverage in relation to total biomass
produced. It suppresses broadleaf weeds extremely well. In one study,
weed control in conservation tillage cotton (Gossypium hirsutum L.)
averaged 34% with black oat compared to 26% for rye, 19% for wheat, and
16% with no cover crop.
—D. W. Reeves
USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center
1420 Experiment Station Road
Watkinsville, Ga 30677
706-769-5631 ext. 203
Wayne.Reeves at ars.usda.gov
SoilSaver— a Black Oat Winter Cover Crop for the Lower Southeastern
Coastal Plain. 2002. USDA-ARS National Soil Dynamics Lab. Conservation
Systems Fact Sheet No. 1.
Lupins are cool-season annual legumes that provide plenty of N and can
be grown widely in the USA and southern Canada. Lupins have aggressive
taproots, especially the narrow-leaf cultivars. You can kill lupins
mechanically or with herbicides. Their hollow stems crush or break
readily, making it easy to plant cash crops using conservation tillage
White lupin (Lupinus albus L.) and blue or narrow-leaf lupin (Lupinus
angustifolius L.) species were originally named after their flower
colors, but both species now have cultivars with white, blue or magenta
/purple flowers. Blue lupin is adapted to the lower Coastal Plain and is
more readily identified by its narrow leaflets (about 0.5- inch wide)
rather than flower color.
As a fall and winter cover crop in the southeastern USA, white lupin is
the most cold-tolerant. Some cultivars overwinter as far north as the
Tennessee Valley. They typically produce 100 to 150 lb. N/A when
fall-planted and killed in early spring.
Seed spring cultivars in early April in the northern U.S. and southern
Canada. Kill in June when they’re at peak biomass (early-bloom to
For use as a cover crop, drill lupins no deeper than 1 inch at 70 lb. /A
for small-seeded blue varieties to 120 lb. /A for larger-seeded white
varieties. At $30 to $40 per acre, the seed is relatively expensive. Be
sure to inoculate lupin seed with compatible rhizobia.
Three winter-hardy lupin cultivars are readily available on a commercial
scale. TIFWHITE-78 white lupin and TIFBLUE-78 blue or narrow-leaf lupin
were both released by USDA ’s Agricultural Research Service in the
1980s. These two varieties, and other modern varieties, are “sweet”
types as opposed to “bitter” types that were widely grown in the South
prior to 1950. Sweet varieties have a low concentration of naturally
occurring alkaloids. Sweet lupin is favored by wildlife, especially
deer. Sweet lupin cover crops may act as a trap crop for thrips
(Frankliniella spp.) in cotton plantings, but this has yet to be
confirmed by research.
AU HOMER bitter white lupin is a new release by Auburn University
derived from Tifwhite-78. It was selected for increased alkaloid content
for use as a cover crop. Alkaloids make lupin seed and forage
unpalatable for livestock, but also play a major role in resistance to
disease, insects and nematodes.
Lupins are susceptible to many fungal and viral diseases and should not
be grown in the same field in successive years. Rather, rotate lupin
cover crops with a small grain cover crop, ideally in a rotation that
allows three years between lupin plantings. Lupin are intolerant to
poorly drained soils.
For information about lupins and seed sources, contact: Edzard van
Santen, Professor Crop Science, Agronomy & Soils Dept., 202 Funchess
Hall, Auburn University, Auburn, AL 36849; 334-844-3975; fax
334-887-3945 vanedza at auburn.edu
A tropical legume, sunn hemp (Crotalaria juncea L.) can produce more
than 5,000 lb. dry matter/A and 120 lb. N/A in just nine to 12 weeks. It
can fill a narrow niche between harvest of a summer crop and planting of
a fall cash or cover crop and is especially fitted to vegetable
production. Sunn hemp sown by September 1 following a corn crop in
Alabama, for example, can produce an average of 115 lb. N/A by December 1.
Sunn hemp is not winter hardy and a hard freeze easily kills it. Sow
sunn hemp a minimum of nine weeks before the average date of the first
fall freeze. Seed at 40 to 50 lb. /A, with a cowpea-type inoculant.
Sunn hemp seed is expensive, about $2.25/lb., so the cost may be
prohibitive for large-scale plantings. Seed can be produced only in
tropical areas, such as Hawaii, and currently is imported only by
specialty seed companies.
A New Alternative for South Florida Producers
A study by the NRCS Plant Materials Center (PMC) in Brooksville,
Florida, concluded that sunn hemp seed can be a viable alternative cash
crop for southern Florida growers. Sunn hemp is an annual legume that
suppresses some types of nematodes and can produce over 5,000 pounds of
biomass and 100 pounds of nitrogen per acre within a few months. Because
of its potential use in alternative pest management systems and as a
sustainable biological source of nitrogen, sunn hemp is a promising
cover crop for rotation with vegetables throughout the Southeastern U.S.
Unfortunately, its use has been limited by the high seed cost—most is
shipped from Hawaii as seed production requires a tropical climate. Two
years ago, the NRCS PMC in Brooksville initiated a study to determine
which zones in Florida could most economically produce sunn hemp seed.
Seed was distributed to 15 growers throughout Florida and although many
locations lost their crop to frost, sunn hemp stands in coastal counties
below the 27th parallel consistently produced up to 370 pounds of seed
per acre. Growers in more southern areas, such as Homestead, obtained
even higher yields. Your contact is Clarence Maura, Manager, NRCS
Brookville Plant Materials Center, at 352-796-9600 or
clarence.maura at fl.usda.gov.
A management caution: Many Crotalaria species contain alkaloids that are
poisonous to livestock. However, the sunn hemp variety TROPIC SUN,
developed jointly by the University of Hawaii and USDA-NRCS, has a very
low level of alkaloid and is suitable for use as a forage.
Research suggests that sunn hemp is resistant and/or suppressive to
root-knot (Meloidogyne spp.) and reniform (Rotylenchulus reniformis)
—D. Wayne Reeves (see Black Oats)
Mansoer, Z., D. W. Reeves and C. W. Wood. 1997. Suitability of sunn hemp
as an alternative late-summer legume cover crop. Soil Sci. Soc. Am. J.
Balkcom, K. and D. W. Reeves. 2005. Sunn hemp utilized as a legume cover
crop for corn production. Agron. J. 97:26-31.
Sunn Hemp: A Cover Crop for Southern and Tropical Farming Systems.
USDA-NRCS Soil Quality Technical Note No. 10.May 1999. Available at:
K. H. Wang and R. McSorley. Management of Nematodes and Soil Fertility
with Sunn Hemp Cover Crop. 2004. University of Florida Cooperative
Extension. Publication #ENY-717. http://edis.ifas.ufl.edu/NG043
Valenzuela, H. and J. Smith. 2002. Tropic Sun’ Sunnhemp. University of
Hawaii Cooperative Extension. Publication #SA-GM-11.
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