SORGHUM (Sorghum bicolor), SORGHUM-SUDANGRASS (S.
bicolor x S. sudanense), SORGHUM x SUDANGRASS, SUDAX, SUDEX
K. Dover, K.-H. Wang & R. McSorley
Last updated January, 2004
Contents:
Problems
and Warnings of Growing Sorghum-sudangrass
Sorghum (Sorghum bicolor (L.) Moench) and
sorghum-sudangrass (S. bicolor x S. sudanense (Piper) Stapf) are
often used as cover crops.
Sorghum-sudangrass (S. bicolor x S. sudanense),
also known as sorghum x sudangrass, sudax, or sudex, is a hybrid between
sorghum (S. bicolor) and sudangrass (S. sudanense). This cover crop has many advantages over
either one of its parents.
Fig. 1 Sorghum bicolor (picture is courtesy
of K.-H. Wang)
Sorghum, currently
classified as S. bicolor (Fig. 1), was formerly known as S. vulgare
Pers. (Purseglove, 1975). For
centuries, sorghum has been used as a grain and forage source. In the United States, sorghum is largely
used as forage. However, the grain is
used as food in many other countries (Magness et al., 1971). This grass can also be used as a source of
sugar, syrup (produced from sweet sorghum types), fiber and grain (Duke,
1983). In addition, various parts of
the plant are reported to have medicinal properties such as being a demulcent,
antiabortive, and diuretic, or it can be an intoxicant or emollient. It has been used in folk medicine against
cancer, epilepsy, and stomachache (Duke and Wain, 1981). However, it is also cyanogenic which means
that it can also be a poison.
The earliest cultivation
of sorghum was in ancient Egypt. Most
of the sorghum grown in the United States is of African origin and is most
popular in the central and southern Midwest, where its excellent drought
tolerance allowed it to flourish in the dry climate (US Grains Council,
2003).
Sorghum can be harvested
either as a grain or forage. The former is of more commercial importance in the
U.S. Approximately 7.3 million acres of
grain sorghum were harvested in 2002 (USDA-NASS, 2003). Grain sorghum (less than 6 feet tall) is
usually shorter than forage sorghum (6-15 feet), and may be planted for
food-used grain or silage, whereas forage sorghum is planted for silage only
(Southern States Cooperative, Inc., 2003).
Forage sorghum matures later in the year than grain sorghum (Sustainable
Agriculture Network, 2003). Although
forage sorghum produced more biomass than sudangrass, it is usually only
harvested once (The Small Farm Resource, 2002).
There are several
varieties of grain sorghum grown throughout the world, and each is put into one
of seven agronomic groups (Table 1).
Table 1. Seven agronomic groups of grain sorghum
(Magness et al., 1971).
|
Agronomic
Group |
Site
of Origin |
Characteristics |
|
Kafir |
South Africa |
Thick stems, large leaves; seeds are medium in size
and may be white, pink, or red; panicles are awnless and cylindrical |
|
Milo |
East Africa |
Wavy leaf blades with yellowish midrib; seeds
are large and may be pink or cream-colored; seed is bearded or awned; more
tolerant than Kafir to drought and heat |
|
Feterita |
Sudan |
Few leaves; stems are thin; seeds are large and
white |
|
Durra |
Mediterranean Area, Middle East, or Near East |
Panicles bearded or hairy, may be closed or
open; seeds are large and flattened |
|
Sballu |
India |
Tall, thin stems; seeds are white, requires a
long growing season because of their maturity |
|
Koaliang |
China, Manchuria, Japan |
Woody stems with few leaves; seeds are brown and
taste bitter |
|
Hegari |
Sudan |
Similar to Kafir, but panicles are more oval and
plants tiller profusely; seeds are chalky white |
Adapted from
Magness et al., 1971.
Sudangrass (Sorghum
sudanense, formerly classified as S. vulgare var. sudanense),
like sorghum, is a summer annual and has no winter hardiness. It has high palatability, and does not
produce toxic compounds that threaten livestock and horses (Mojtahedi et al.,
1993). Some varieties, most notably
‘Trudan 8’, also have nematicidal properties. Therefore, sudangrass can be
planted for forage and nematode management.
Sudangrass usually grows 3-8 feet high and has stems about ¼” in
diameter. It will regrow following each
harvest until cool temperature or lack of moisture (The Small Farm Resource,
2002).
Fig. 2. Sorghum-sudangrass
(S. bicolor x S. sudanense) (picture is
courtesy of R. McSorley).
Sorghum-sudangrass (Fig.
2), also commonly called sudax, sudex, or sorghum x sudangrass (Sudax® is
registered by DeKalb Genetics Corporation, De Kalb, IL) is advantageous over
either parent in that it produces larger quantities of biomass. It resembles sudangrass but is taller and
has larger stems and leaves. Like
sudangrass, the hybrid will regrow after each harvest unless restricted by
environmental conditions (The Small Farm Resource, 2002). Sorghum-sudangrass roots deeply, and may
even help to aerate compacted subsoils (Valenzuela and Smith, 2002; Sustainable
Agriculture Network, 2003). This hybrid
is able to grow in soil with a pH range of 5.5-8.3 and is sometimes used to
reclaim alkaline soil (Valenzuela and Smith, 2002). It is very drought tolerant, has high seedling vigor, and some
varieties have reduced lignin content (such as the brown midrib sorghum x
sudangrass crosses) to increase digestibility for animals and decomposition
rate (Southern States Cooperative, Inc., 2003). However, certain varieties of sorghum-sudangrass have some
disadvantages. For example, brown
midrib varieties have been found to be “environmentally sensitive,” and may
limit their growth in cooler and shorter growing seasons (Casler et al.,
2003). Some sorghum-sudangrass
varieties can be toxic to livestock and horses (Mojtahedi et al., 1993).
Due to its rapid biomass production,
sorghum-sudangrass is recommended as a cover crop to build up organic matter
content in soil. Research in Hawai’i
has determined that dry matter production can be as much as 8,000-10,000
lbs/acre/year. In addition, it generally
does not support populations of some key nematode pests, such as root-knot nematodes
(Halcomb, 2002). In addition,
sorghum-sudangrass is found to have other pest management properties listed
below.
Certain
sorghum-sudangrass varieties are not only poor hosts for root-knot nematodes,
but may also be disease and (insect) pest resistant. According to Monsanto (2003), four of their varieties are
resistant to downy mildew, one to anthracnose, two to maize dwarf mosaic virus,
one to head smut, and nine to greenbug (an aphid, Schizaphis graminum).
Sorghum or some other
crops (including barley, rye, buckwheat, sudangrass, sweet clover, and
sunflower) can be planted to suppress weed growth (Rice, 1984). These crops have traditionally been called
“smother crops” because of their ability to suppress weed growth. The weed-suppressive properties of sorghum
are attributed to competition and its vigorous growth habit. However, some believe that a combination of
competition and allelopathic effects of toxins and other inhibitory substances
produced by sorghum is a better explanation for this weed-smothering effect
(Overland, 1966).
Sorgoleone, a quinone,
is the primary allelopathic chemical found in exudates from sorghum-sudangrass
roots (Almeida Barbosa et al., 2001; Nimbal et al., 1996; Sustainable Agriculture
Network, 2003). This compound is
inhibitory to weeds such as barnyardgrass (Echinocloa crus-galli), large
crabgrass (Digitaria sanguinalis), and velvetleaf (Abutilon
theophrasti) (Nimbal et al., 1996).
In addition, five
phenolic compounds have been identified and quantified in mature plant residues
of sorghum. These compounds are p-coumaric,
syringic, vanillic, ferulic, and p-hydroxybenzoic acids, with p-coumaric
present in the highest amounts (Guenzi and McCalla, 1966). Guenzi and McCalla (1966) noted that since
these acids are mostly bound in the residues, decomposition of the sorghum
residues is necessary to release sufficient amounts of p-hydroxybenzoic
acid to achieve weed suppression. On
the other hand, Fries et al. (1997) found
that soil amendments of p-coumaric and p-hydrobenzoic acid may
even encourage populations of mycorrhizae (a beneficial root-associated fungus)
and enhance crop growth.
A cultivar of sudangrass (‘Trudan 8’) has been shown to suppress the northern
root-knot nematode Meloidogyne hapla infestation in vegetables (Widmer
and Abawi, 2002; Rehiayani and Hafez, 1998).
Sudangrass contains a compound in the cell cytoplasm call dhurrin, a
cyanoglucoside.
As ‘Trudan 8’ decomposes, an enzyme degrades the dhurrin and releases
hydrogen cyanide (Adewusi, 1990). Other
products of this degradation, such as nitriles or isothiocyanaates, may also
have nematicidal properties (Donkin et al., 1995). It is noted that soil
amended with all parts of sudangrass resulted in lower reproduction of M.
hapla on lettuce than soil amended with only roots of sudangrass (Viaene
and Abawi, 1998). In a greenhouse
study, soil incorporated with leaves of sudangrass reduced root gall on lettuce
(up to 54%) (Widmer and Abawi, 2003). There was also a correlation between
amount of free cyanide in the soil and root gall reduction. However, in the same experiment,
incorporation of white clover and flax reduced galling by 45%, and 53% respectively
(Widmer and Abawi, 2002).
In a greenhouse tests, sorghum-sudangrass ‘SX-17’ did not support
reproduction of Meloidogyne incognita (races 1 and 3), M. arenaria (race
1) or M. javanica (McSorley et al., 1994a). No egg masses were found on ‘SX-17’ in any of the tests. Another study by McSorley et al. (1994b)
suggests that sorghum-sudangrass (here, ‘SX-17’) could be a beneficial crop for
use in a rotation for the control of nematodes
(Meloidogyne spp.) and yield improvement of subsequent vegetable crops.
In an Oregon potato trial in which sudangrass and sorghum-sudangrass
residues were incorporated into the soil, the sudangrass cultivar ‘Trudan 8’
and sorghum-sudangrass hybrids ‘Sordan 79’ and ‘SS-222’ reduced populations of Meloidogyne
spp. These are poor root-knot nematode
hosts and chemicals present in the leaves were found to be nematicidal
(Mojtahedi et al., 1993).
Another experiment compared nematode populations in several varieties of
corn, a variety of sorghum (‘FS25E’), and a sorghum x sudangrass hybrid
(‘SX-17’). Both ‘FS25E’ and ‘SX-17’
maintained low populations of Meloidogyne incognita, whereas corn (which
is more susceptible) supported higher populations of the root-knot
nematode. However, no variety
significantly reduced populations of Paratrichodorus minor (stubby root
nematode), Pratylenchus scribneri (lesion nematode), or Criconemella
spp. (ring nematode) (McSorley and Gallaher, 1991).
It has been noted, however, that sudangrass can harbor large populations
of a lesion nematode (Pratylenchus penetrans) (Marks and Townshend,
1973). A more recent study conducted by
Thies et al. (1995) found that although forage sorghum, sudangrass and
sorghum-sudangrass are all hosts for P. penetrans, these crops are less
suitable hosts than are other forage crop species such as white clover, oat,
and rye. Sting nematode (Belonolaimus
spp.) populations were found to be high enough to reduce yields in
cool-season vegetables when planted after sorghum-sudangrass (Rhoades, 1980),
and populations of Meloidogyne arenaria (root-knot nematode) juveniles
in a sorghum-soybean rotation were elevated above numbers found in either a
soybean monoculture or a corn-soybean rotation (Rodriguez-Kabana et al.,
1991). Also, Paratrichodorus minor
(stubby-root nematode) populations built up when sorghum-sudangrass was used in
a rotation (McSorley et al., 1994b).
The nematode species persist in the site and nematode susceptibility of
the subsequent crop(s) should be evaluated before deciding on a sorghum or sorghum-sudangrass
cover crop.
Varieties of sorghum, sudangrass or sorghum-sudangrass suppressive to
nematodes are summarized in Table 2, whereas varieties that enhanced nematodes
are shown in Table 3. Table 4 showed
nematodes considered to be key pests of sorghum, sudangrass or
sorghum-sudangrass in several countries (Sharma and McDonald, 1990).
Table 2.
Nematode-suppressive varieties of cover crops.
|
Plant
and Variety |
Nematode
Suppressed |
Method
of Suppression |
Reference |
|
Sudangrass |
|
|
|
|
‘Trudan 8’ |
Meloidogyne hapla |
Incorporation of leaves into the soil reduced galling by 54% |
Widmer and Abawi, 2002 |
|
|
Meloidogyne chitwoodi |
Poor reproduction in roots |
Mojtahedi et al., 1993 |
|
‘Trudex 9’ |
M. chitwoodi |
Poor reproduction in roots |
Motjahedi et al., 1993 |
|
‘Piper’ |
M. chitwoodi |
Poor reproduction in roots |
Motjahedi et al., 1993 |
|
‘332’ |
M. chitwoodi |
Poor reproduction in roots |
Motjahedi et al., 1993 |
|
Sorghum-sudangrass |
|
|
|
|
‘SX-17’ |
M. incognita (Races 1 and 3), M. javanica, M. arenaria
(Race 1) |
No reproduction occurred in roots; reduction in galling |
McSorley et al., 1994a |
|
|
Meloidogyne spp. |
No reproduction occurred in roots; reduction in galling |
McSorley et al., 1994b |
|
|
Meloidogyne incognita |
Reduced populations, although reproduction did occur |
McSorley and Gallaher, 1991 |
|
‘ST6E’ |
Meloidogyne javanica |
Poor or non-host |
Sipes and Arakaki, 1997 |
|
‘Sordan 79’ |
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
|
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
‘SS-222’ |
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
|
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
‘Bravo II’ |
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
|
M. chitwoodi |
Poor reproduction in the roots |
Mojtahedi et al., 1993 |
|
Sorghum |
|
|
|
|
(No specific variety) |
Heterodera glycines |
Poor host |
Rodriguez-Kabana et al., 1991 |
|
Forage sorghum |
|
|
|
|
‘FS25E’ |
Meloidogyne incognita |
Poor host; Reduced populations, although reproduction did occur |
McSorley and Gallaher, 1991; Gallaher et al., 1991 |
|
‘BR64’ |
Meloidogyne incognita |
Poor host |
Gallaher et al., 1991 |
Table 3.
Nematode-enhancing varieties of cover crops.
|
Cover
Crop |
Nematode
Enhanced |
Method
of Enhancement |
Reference |
|
Sudangrass |
|
|
|
|
(No specific variety) |
Pratylenchus penetrans |
Good host (although less suitable as a host than other forage,
including white clover, oat and rye) |
Marks and Townshend, 1973 |
|
(No specific variety) |
Meloidogyne incognita |
Supports reproduction |
Johnson et al., 1977 |
|
‘Piper’ |
Meloidogyne chitwoodi |
Good host; reproduction occurred in roots |
Mojtahedi et al., 1993 |
|
‘332’ |
M. chitwoodi |
Good host; reproduction occurred in roots |
|
|
Sorghum-sudangrass |
Belonolaimus spp. |
Good host |
Rhoades, 1980 |
|
(No specific variety) |
Paratrichodorus minor |
Good host |
McSorley et al., 1994; McSorley and Gallaher, 1991 |
|
(No specific variety) |
Pratylenchus penetrans |
Good host (though less suitable as a host than other forage, including
white clover, oat and rye) |
Thies et al., 1995 |
|
(No specific variety) |
Pratylenchus scribneri |
Good host |
McSorley and Gallaher, 1991 |
|
(No specific variety) |
Criconemella spp. |
Good host |
McSorley and Gallaher, 1991 |
|
‘P855F’ |
M. chitwoodi |
Good host; reproduction occurred in roots |
Mojtahedi et al., 1993 |
|
‘P877F’ |
M. chitwoodi |
Good host; reproduction occurred in roots |
Mojtahedi et al., 1993 |
|
Sorghum |
|
|
|
|
(No specific variety) |
Meloidogyne arenaria |
Reproduction occurred (when used in a sorghum-soybean rotation) |
Rodrigues-Kabana et al., 1991 |
|
Forage sorghum |
|
|
|
|
(No specific variety) |
Pratylenchus penetrans |
Good host (though less suitable as a host than other forage, including
white clover, oat and rye) |
Thies et al., 1995 |
|
(No specific variety) |
Pratylenchus scribneri |
Good host |
McSorley and Gallaher, 1991 |
|
(No specific variety) |
Paratrichodorus minor |
Good host |
McSorley and Gallaher, 1991 |
|
‘FS25E’ |
Criconemella spp. |
Good host |
McSorley and Gallaher, 1991 |
|
‘BR64’ |
Criconemella spp. |
Good host |
Gallaher et al., 1991 |
Table 4. Most
important nematode pests in sorghum by country (Sharma and McDonald, 1990).
|
Country |
Nematode
Pest |
|
Australia |
Pratylenchus spp. |
|
Brazil |
P. brachyurus |
|
Egypt |
P. zeae |
|
India |
Tylenchorhynchus spp. |
|
Pakistan |
P. thornei |
|
Sudan |
Pratylenchus spp. |
|
Thailand |
P. zeae |
|
USA |
Pratylenchus spp. (P.
zeae) |
|
Zimbabwe |
P. zeae |
Sorghum-sudangrass was recommended for remediation of orchard soil with
high populations of nematodes and/or soilborne fungi (Steiner, 1998; Koehler,
ed., 2000). It is imperative that the
site be evaluated and properly prepared before investing in new trees. Not only may orchard soils harbor diseases
and other pest organisms, they may also be low in nutrients, high in residual
pesticides or herbicides, or have poor drainage. Leaving the area fallow prior to planting trees will not
eliminate the presence of diseases and pests, and may do little to improve soil
quality. Sorghum-sudangrass has been a
top choice for planting prior to orchard establishment because it rapidly
builds up soil organic matter and its deep rooting system can improve soil
structure (Valenzuela and Smith, 2002) (see Introduction).
Although
sorghum-sudangrass is a warm season crop, the Sustainable Agriculture Network (2003)
believes that it can be planted year-round in south and central Florida. However, it may still be a good practice to
plant sorghum-sudangrass in late spring or early summer. The best planting time is when soils are
warm and moist. Although sorghum-sudangrass
tolerates high pH (and moderate acidity) and low fertility, it will become
better established with good fertility (with special attention paid to
nitrogen) and near-neutral pH (Sarrantonio, 1994). Sorghum-sudangrass biomass will increase with the rate of
nitrogen applied (Iptas and Brohi, 2003).
For the best biomass accumulation, the Sustainable Agriculture Network
(2003) suggests applying 75 to 100 lbs of nitrogen per acre. The Sustainable Agriculture Network also
recommends broadcasting 40 to 50 lbs of seed per acre, or drilling 35 to 40 lbs
of seed to a depth of 2 inches. These
rates should provide a thick cover for smothering weed competition.
Sorghum-sudangrass may
be interplanted (broadcast together) with buckwheat or with legumes such as
sesbania (Sesbania exaltata), forage soybean (Glycine max), or
cowpea (Vigna unguiculata).
Buckwheat germinates very quickly and may help suppress early weeds
(Sustainable Agriculture Network, 2003).
When used as a late-season
cover crop in temperate climates, Sattell et al. (1998) advise that
sorghum-sudangrass be “frost killed” in the winter since frost increases the
cyanide content, making it more effective when incorporated into the soil. This practice, however, is best used before
planting a cold weather (early spring) crop such as potato. Mowing when stalks are 3 to 4 feet tall will
encourage the plants to root more deeply, and will keep them from getting too
woody before the frost (Sustainable Agriculture Network, 2003). Another option may be to plant
sorghum-sudangrass as early as seven weeks before the first frost which may
make mowing unnecessary and still produce adequate biomass (Mishanec, 1996;
Sarrantonio, 1994). In warmer regions
where fall crops are grown, a better option may be to mow the
sorghum-sudangrass and incorporate into the soil.
If incorporating
sorghum-sudangrass residue into the soil, it is important to break the plants
into smaller pieces so decomposition will be hastened. Disking, flail chopping or sicklebar mowing
before tillage will decrease the likelihood that residue nitrogen will be tied
up and thus be unavailable to the subsequent crop. Sudangrass has a very high C:N ratio, meaning that large amounts
of biomass will take a relatively long time to be fully decomposed by soil
microorganisms (Sattell et al., 1998).
If residues are to be left on the soil surface (as in a no-till
operation), flail chopping after the frost or using an herbicide to kill the
sorghum-sudangrass is recommended by the Sustainable Agriculture Network
(2003). However, it is important to
remember that for best nematode control sorghum-sudangrass must be incorporated
while still green. Also, immediate
tillage will give the best soilborne disease suppression (Orfanedes,
1995).
Problems and Warnings of Growing Sorghum-sudangrass
Sorghum-sudangrass contains levels of hydrocyanide
and hordenine (an alkaloid) (Morton, 1981).
Prussic acid (hydrocyanide) is
bound to sugars within the plant, and is released during frosts, decomposition,
drought stress, and mechanical damage.
If using sorghum-sudangrass as forage for cattle, Chambliss (2002)
recommends not allowing grazing until the plants are at least 24 inches tall since
prussic acid content may be higher in younger plants. Horses should never be allowed to graze on or eat hay made from
sorghum-sudangrass as it may cause inflammation of the urinary tract (cystitis
syndrome)(Chambliss, 2002; Sattell et al., 1998).
Hordenine is a compound
generated from the breakdown of certain plants (including sorghum). It may also be found in beer and certain
horse feeds. It is believed to be a
stimulant and may increase blood pressure (Feliks et al., 2000; Hapke and
Strathmann, 1995).
In terms of nematode
suppression, there is some variability in the influence of sudangrass on growth
of lettuce in the greenhouse (Viaene, 1996).
Phytotoxicity can occur if the green manure is not decomposed properly.
Viaene and Abawi (1998) planted lettuce 1 month after incorporation of
sudangrass. However, tissues of 1- or
2-month-old were more effective than 3-month-old tissue of sudangrass for
nematode suppression (Viaene and Abawi, 1998). Therefore, proper management of
the sudangrass as a cover crop is important for the best results of nematode
suppression and yield improvement.
Anonymous.
2002. The small farm
resource. http://www.farminfo.org/. August 02, 2002.
Abawi, G. S. and T. L. Widmer. 2000. Impact of
soil health management practices on soilborne pathogens, nematodes and root
diseases of vegetable crops. Applied Soil Ecology 15: 37-47.
Adewusi, S. R. A.
1990. Turnover of dhurrin in green sorghum seedlings. Plant Physiology
94: 1219-1224.
Almeida
Barbosa, L.C. de, M.L. Ferreira, A.J. Demuner, A.A. daSilva, R. deCássia
Pereira. 2001. Preparation and phytotoxicity of sorgoleone
analogues. Química Nova 24.
Casler,
M. D., J. F. Pedersen, and D. J. Undersander.
2003. Forage yield and economic
losses associated with brown-midrib trait in sudangrass. Crop Science 43: 782-789.
Chambliss,
C.G. 2002. Producing millets and
sorghum. Publication SS-AGR-89. Agronomy Department, Cooperative Extension
Service, University of Florida.
Gainesville, FL. http://edis.ifas.ufl.edu/AG157.
Donkin,
S. G., M. A. Eitema, P. L. Williams. 1995. Toxicity of glucosinolates and their
enzymatic decomposition products to Caenorhabditis elegans. Journal of
Nematology 27:258-262.
Duke,
J.A. 1983. Handbook of Energy Crops.
Unpublished. http://www.hort.purdue.edu/newcrop/duke_energy/Sorghum_bicolor.html.
Duke,
J.A., and K.K. Wain. 1981. Medicinal plants of the world. Computer index with more than 85,000
entries. 3 vols.
Feliks,
K.B., M. Andrzej, and K. Monika.
2000. Hordenine as a stimulating
drug in horses. Medycyna Weterynaryjna
56: 214-217.
Fries,
L.L.M., R.S. Pacovsky, G.R. Safir, J.O. Siqueira. 1997. Plant growth and
arbuscular mycorrhizal fungal colonization affected by exogenously applied
phenolic compounds. Journal of Chemical
Ecology 23: 755-1767.
Gallaher,
R.N., R. McSorley, and D.W. Dickson.
1991. Nematode densities
associated with corn and sorghum cropping systems in Florida. Supplement to Journal of Nematology 23:
668-672.
Guenzi,
W.D., and T. McCalla. 1966. Phenolic acids in oats, wheat, sorghum, and
corn residues and their phytotoxicity.
Agronomic Journal 58: 303-304.
Halcomb,
M. 2002. Nursery field production.
Agricultural Extension Service, University of Tennessee. Knoxville, TN. http://www.utextension.utk.edu/hbin/Field
Prod rev w equip.pdf.
Hapke,
H.J., and W. Strathmann. 1995. Pharmacological effects of hordenine. Deutsche Tieraerztliche Wochenschrift 102:
228-232.
Iptas,
S., and A.R. Brohi. 2003. Effect of nitrogen rate and stubble height
on dry matter yield, crude protein content and crude protein yield of a
sorghum-sudangrass hybrid (Sorghum bicolor (L.) Moench x Sorghum
sudanense (Piper) Stapf.) in the three-cutting system. Journal of Agronomy and Crop Science 189:
227-232.
Johnson,
A.W., G.W Burton, and W.C. Wright.
1977. Reactions of
sorghum-sudangrass hybrids and pearl millet to three species of Meloidogyne. Journal of Nematology 9: 352-353.
Koehler,
G.W., ed. 2000-2001. New England Apple Pest Management
Guide. Pest Management Office,
Cooperative Extension, University of Maine.
Orono, ME. http://pmo.umext.maine.edu/apple/PestGuidePDF/2000-2001NEAPMGdirectory.htm.
Magness,
J.R., G.M. Markle, C.C. Compton.
1971. Food and feed crops of the
United States. Interregional Research
Project IR-4, IR Bul. 1. Bulletin 828,
New Jersey Agricultural Experiment Station.
Marks,
C.F., and J.L. Townshend. 1973. Multiplication of the root lesion nematode Pratylenchus
penetrans under orchard cover crops.
Canadian Journal of Plant Science 53: 187-188.
McSorley,
R., and R.N. Gallaher. 1991. Nematode population changes and forage
yields of six corn and sorghum cultivars.
Supplement to Journal of Nematology 23: 673-677.
McSorley,
R., D.W. Dickson, and J.A. deBrito.
1994a. Host status of selected
tropical rotation crops to four populations of root-knot nematodes. Nematropica 24: 45-53.
McSorley,
R., D.W. Dickson, J.A. deBrito, and R. C. Hochmuth. 1994b. Tropical rotation
crops influence nematode densities and vegetable yields. Journal of Nematology 26: 308-314.
Mishanec,
J. 1996. Use of sorghum-sudangrass for improved yield and quality of
vegetables produced on mineral and muck soils in New York: Part II - Sudan
trials on muck soils in Orange County.
Research Report. Cornell
Cooperative Extension. Ithaca, NY.
Mojtahedi,
H., G.S. Santo, and R.E. Ingham.
1993. Suppression of Meloidogyne
chitwoodi with sudangrass cultivars as green manure. Journal of Nematology 25: 303-311.
Monsanto
Company. 2003. Monsanto imagine. http://www.monsanto.com/monsanto/us_ag/layout/seed/default.asp.
Morton,
J.F. 1981. Atlas of medicinal plants of middle America. C. C. Thomas, Springfield, IL.
Nimbal,
C.I., J.F. Pedersen, C.N. Yerkes, L.A. Weston, S.C. Weller. 1996.
Phytotoxicity and distribution of sorgoleone in grain sorghum germplasm. Journal of Agricultural and Food Chemistry
44: 1343-1347.
Orfanedes,
M. 1995. Sudangrass trials - What have we learned to date? Lake Plains Vegetable ProgramCornell
Cooperative Extension Program. Ithaca,
NY.
Overland,
L. 1966. The role of allelopathic substances in the “smother crop”
barley. American Journal of Botany 53:
423-432.
Purseglove,
J.W. 1975. Tropical crops.
Monocotyledons. John Wiley &
Sons, New York, NY.
Rehiayani,
S., and S. Hafez. 1998. Host status and green manure effect of
selected crops on Meloidogyne chitwoodi race 2 and Pratylenchus
neglectus. Nematropica 28: 213-230.
Rhoades,
H.L. 1980. Relative susceptibility of Tagetes patula and Aeschynomene
americana to plant nematodes in Florida.
Nematropica 10: 116-120.
Rice,
E.L. 1984. Allelopathy. Academic
Press, Inc., Orlando, FL. Pp. 41-67.
Rodriguez-Kabana,
R., D.B. Weaver, D.G. Robertson, C.F. Weaver, and E.L. Carden. 1991.
Rotations of soybean with tropical corn and sorghum for the management
of nematodes. Supplement to Journal of
Nematology 23: 662-667.
Sarrantonio,
M. 1994. Northeast cover crop handbook.
Soil Health Series. Rodale
Institute. Kutztown, PA.
Sattell,
R., R. Dick, R. Ingham, R. Karow, and D. McGrath. 1998. Sudangrass and
sorghum-sudangrass hybrids. Oregon
Cover Crops, Extension and Experiment Station, Oregon State University. Corvallis, OR.
Sharma,
S.B., and D. McDonald. 1990. Global status of nematode problems of
groundnut, pigeonpea, chickpea, sorghum and pearl millet, and suggestions for
future work. Crop Protection 9:
453-458.
Sipes,
B.S., and A.S. Arakaki. 1997. Root-knot nematode management in dryland
taro with tropical cover crops.
Supplement to Journal of Nematology 29: 721-724.
Southern
States Cooperative, Inc. 2003. Crop Production Guide 2004. Farmer First, Ag Resource Center. http://www.farmerfirst.com/seedbook2004/north/sorghum_north.shtml.
Steiner,
P.W. Orchard Site Bio-Renovation
Program. 1998. Department of Natural Resource Sciences and
L. A. University of Maryland, College
Park, MD. Presented at the
Maryland/Delaware Peach School, Wye Research and Education Center. Queenstown, MD, February 10, 1998. http://www.caf.wvu.edu/kearneysville/articles/SteinerReplant.html.
Summers,
C.G., L.D. Godfrey, and D. Gonzales.
2003. Small grains
greenbug. UC Pest Management
Guidelines. Publication number
3466. Statewide Integrated Pest
Management Program, University of California.
Davis, CA.
Sustainable
Agriculture Network. 2003. Sorghum-sudangrass hybrids. Sustainable Agriculture Research and
Education Program. Cooperative
Research, Education and Extension Service, United States Department of
Agriculture. http://www.sare.org/handbook/mccp2/sorgsudn.htm.
Thies,
J.A., A.D. Petersen, and D.K. Barnes.
1995. Host suitability of forage
grasses and legumes of root-lesion nematode Pratylenchus penetrans. Crop Science 35: 1647-1651.
US
Grains Council. 2003. http://www.grains.org/grains/production_areas.html.
USDA-NASS. 2003.
Chapter 1: Statistics of Grain and Feed. In USDA-NASS Agricultural Statistics 2003. Census of Agriculture, United States
Department of Agriculture, National Agricultural Statistics Service.
Valenzuela,
H., and J. Smith. 2002. Sorghum-sudangrass hybrids. Publication number SA-GM-10, Sustainable
Agriculture, Green Manure Crops.
Cooperative Extension Service, College of Tropical Agriculture and Human
Resources, University of Hawai’i at Manoa.
Honolulu, HI.
Viaene,
N. M. 1996. Damage threshold and biological control of the northern root-knot
nematode (Meloidogyne hapla Chitwood) infecting lettuce (Lactuca
sativa L.) in organic soil. Ph.D. Thesis, Cornell Universitity, 164 pp.
Viaene,
N. M. and G. S. Abawi. Management of Meloidogyne hapla on lettuce in organic
soil with sudangrass as a cover crop. Plant Disease 82: 945-952.
Widmer,
T.L., and G.S. Abawi. 2002. Relationship between levels of cyanide in
sudangrass hybrids incorporated into soil and suppression of Meloidogyne
hapla. Journal of Nematology 34:
16-22.