Summary of Research
Volume 1, Numbe r 1
Texas Alliance for Water Conservation, Box 42122, Lubbock, Texas 79409-2122
Phone: 806.742.2774 Fax: 806.742.0988 Web address: www.depts.ttu.edu/tawc
The TAWC project was made possible through a grant from the Texas Water Development Board
Forage Sorghum Production in the Southern Plains Region
With the influx of dairies into the southern Plains
region of Kansas, New Mexico, Texas and
Oklahoma, the demand for quality silage has
increased dramatically over the last few years.
Currently, about 465,000 milking cows are located
in this region (Southwest Plains Dairy Directory,
2007) with numbers projected to double within the
next four years. The feed and water required to
meet the needs of this
expanding industry are
now a major influence in
the region. These
changes within the
region coupled with the
emerging bio-energy
sector have strengthened
grain prices, thus,
providing an added
incentive to producers to
consider cropping
alternatives to more
traditional crop patterns
in the region.
requiring less water (Bean & McCollum, 2006).
Information emerging from the producer-led Texas
Alliance for Water Conservation’s (TAWC)
monitoring of 26 sites within Hale and Floyd
Counties is validating this on a landscape scale and
demonstrates that profitability to the producer of
sorghum silage was almost twice that of corn silage
while requiring about one half the irrigation water
reflecting the irrigationuse efficiency for
sorghum that is about 2.5
times that of corn (Figure
1; TAWC, 2007).
Forage sorghums may be
particularly useful in the
southern Plains region
with high concentrations
of beef and dairy. They
fit well into dryland and
limited irrigation
situations because of their
tolerance to drought. It is
in these systems that the
While the dairy industry
grasses may have the
is the major consumer of
greatest potential to
corn silage, the region’s
produce large amounts of
beef-finishing feedyard
nutritious forage during
industry, representing
the
summer months and
Figure 1: 2006 Results for TAWC Site #20
about 25% of the nation’s by Yield, Water Applied, and Net Returns
that their inherent
total, is also a consumer
versatility allows them to
of corn silage. With a large proportion of the diets
fit into many different types of cropping or
of milking cows currently based on corn silage,
livestock operations (Marsalis, 2006). Kochenower
demands for irrigation water are increasing relative
and Hicks (2006) stated that
to more traditional cotton production systems.
In the coming years with natural gas
However, more and more dairies as well as
prices rising and the possibility of water
feedyards, are considering forage sorghum silage as
supplies diminishing, sorghum silage
an alternative to corn silage.
may replace corn silage in the Panhandle
region. Sorghum being more drought
Research in the northern Texas Panhandle has
tolerant than corn requires less water,
demonstrated that selected varieties of sorghums
approach corn in both yield and quality while
therefore less irrigation is required. (p. 1)
1950s, today’s researchers are testing several
varieties of forage sorghum. Trials conducted
from 1999 to 2005 at the Texas Agricultural
Experiment Station at Bushland, TX, with
sorghum and sorghum-sudangrass hybrids,
including brown midrib (BMR) and photoperiodsensitive (PS) hybrids, were compared for their
agronomic, yield, and nutrient composition
characteristics. BMR forage sorghums were
shown to have yield, irrigation water use
efficiency, and energy values equal to that of corn.
Photoperiod-sensitive hybrids without BMR had
the highest yield and irrigation water use
efficiency, but had the lowest percent energy
value (Bean 2007). Today’s varieties have the
potential to grow very tall (6 to 15 feet) and can
produce large amounts of vegetative growth
(Marsalis, 2006).
Recent efforts by seed companies to develop high
quality forage sorghums has increased the
potential of sorghum as a viable silage alternative.
Milking and feeding trials have been conducted
showing that forage sorghum can be equal to corn
in milk and cattle gain and have the potential to
replace corn silage in rations both nutritionally
and economically (Alberts, 1999; Aydin, Grant, &
O’Rear, 1999). In addition, brown midrib (BMR)
forage sorghums have exhibited nutritive values
similar to corn silage while using less water to
produce comparable yields (Marsalis, 2006). With
this potential for increased net returns while
saving precious water resources, it is worth the
time of producers to investigate the potential of
this crop in their individual operations.
KEY POINTS
Area research shows that forage
sorghum silage has the potential to
save water and realize greater net
returns per acre.
The use of forage sorghum for silage appears to
be increasing in the region with the USDA (2005)
reporting that 188,000 acres of sorghum were
grown for silage in the four-state region of
Kansas, New Mexico, Oklahoma, and Texas.
While this is about half of the number of acres
planted for corn silage, the number of forage
sorghum acres are increasing with a nearly equal
number of acres (130,000 corn silage vs. 100,000
for sorghum silage) being grown in Texas
Development of Forage Sorghum
Sorghum can be traced back to 8,000 BC and may
have been introduced into the United States by
Benjamin Franklin in the late 1700s (Smith &
Frederickson, 2000). By the early 1900s, grain
sorghum was recognized as a drought tolerant
crop that would outperform corn in the arid
regions of the southern Great Plains. Scientists
with agricultural experiment stations and USDA
personnel in Texas, Oklahoma, and Kansas took
note of sorghums’ drought tolerance and, along
with farmer-seedsmen, began to select improved
phenotypes (Smith & Frederickson, 2000). By
1957, 15% of the U.S. grain sorghum crop was
from hybrid seed.
While grain sorghums were the focus of early
hybrid research, more recent work has increased
the advances in forage sorghums. Research
conducted in the U.S. during the past century,
including the discovery of the brown midrib
genetic mutation at the University of Minnesota in
the 1920s, have helped to develop hybrids with
improved yields and less stalk lodging (Alberts,
1999). While there were few hybrids until the late
(USDA, 2005).
2
KEY POINTS
BMR forage sorghums were shown to
have yield, irrigation water use
efficiency, and energy values equal to
that of corn.
Photoperiod-sensitive hybrids without
BMR had the highest yield and
irrigation water use efficiency, but had
the lowest percent energy value.
Choosing a Sorghum Hybrid
Quality and yield will vary more between
varieties than what is typically observed in corn.
This makes the choice of hybrid a very important
consideration. There are three types of forage
sorghums that are currently being marketed:
conventional, brown midrib (BMR), and
photoperiod sensitive (PS).
PS varieties will stay in the vegetative stage of
growth until day length is less than 12 hour and 20
minutes (McCollum, 2005). For the Texas High
Plains, this occurs on or about October 12,
depending on your location. From a practical
standpoint, these varieties are very unlikely to
produce a head before the region experiences a
hard freeze. These varieties are capable of
producing high yields and can reach heights of 12
ft or more. These varieties should be used
primarily for grazing or wilted for hay production,
or possibly used as green chop. The problem for
using these as silage is their quality is not up to
par with other sorghum types, and they are
normally too wet at harvest to use as silage.
The conventional forage sorghums have been
grown for years. Some of the newer varieties of
forage sorghum are capable of producing very
high grain yields that are comparable to grain
yields produced by some of the best grain
sorghum varieties on the market (Bean, et al.,
2006). These can truly be considered dual-purpose
in that they can be harvested for either grain or
forage. Typically, these sorghums are taller and
leafier than sorghums sold for grain production.
Quality can be variable, but there are some
conventional varieties with excellent quality
(Table 1).
When choosing forage for quality, three forage
analyses are often examined by nutritionists.
These are neutral detergent fiber (NDF), acid
detergent fiber (ADF), and in vitro true
digestibility (IVTD). NDF measures all the fiber
found in forage. This NDF fiber is partially
digestible and is positively correlated with bulk
density making it useful for predicting feed intake.
ADF measures the least digestible fraction of the
fiber (lignin and cellulose). The lower the NDF
and ADF the higher the digestibility of a
particular forage, and thus the higher the quality
or energy value (Figure 2).
BMRs get their name from their expression of a
brown midrib trait. What is also important about
these varieties is that they have less lignin content
than conventional sorghums (McCollum, et al.,
2005). Lowering the lignin content in the plant
increases the overall digestibility of the fiber
component of the forage, and thus improving
overall quality. One potential negative associated
with less lignin content is increased lodging
potential. This potential problem, however, can be
compensated for with appropriate management
practices (Bean, 2007). There is also a wide range
in lodging potential among BMR varieties, again
making hybrid choice an important consideration.
Although BMRs on average are of higher quality
than conventionals, yield is often reduced. In most
years, research has shown BMRs to yield about
10% less than conventionals (Table 1). However,
3
Table 1. Agronomic and forage quality comparison of forage sorghums.
Sorghum
Type
Conventional
Average
Range
Plant
Moist.
Height,
@
%
ft.
Harvest Lodging
Silage,
Ton/Ac
@ 65%
Moist.
Grain
Yield,
lbs/Ac
Crude
Protein,
%
ADF,
%
NDF,
%
IVTD,
%
7.2
5.2 0.6
64.7
57.0 71.2
14.7
0.0 54.3
24.1
18.1 33.3
5,110
1,155 7,424
7.2
5.5 8.6
28.6
24.5 36.5
47.7
39.8 59.6
75.9
67.7 82.1
7.4
6.6 9.2
67.5
63.1 70.4
10.4
0.7 42.5
20.7
16. 5 24.0
3,527
1,966 5,119
7.8
5.8 8.5
26.9
24.7 33.4
45.4
42.3 56.2
81.0
76.3 84.0
10.0
9.0 10.0
72.8
70.8 74.9
5.2
2.2 8.1
29.0
27.9 29.8
0
6.1
5.9 6.3
38.6
37.8 39.3
63.4
62.4 64.6
69.0
68.2 69.8
BMR
Average
Range
PS
Average
Range
0-0
Data summarized from Bean, B. and T. McCollum (2006). Summary of six years of forage sorghum variety
trials. Texas A&M University Department of Soil and Crop Sciences. SCS-2006-04.
because of the range in yield and quality of both
sorghum types, it is important that the
characteristics of each individual hybrid be
considered, regardless of type. It is often assumed
that a high grain yield is necessary for forage
sorghum to produce high quality forage. While
this tends to be true with conventional forage
sorghums, it is not true with BMRs. (McCollum,
2005)
Planting Guidelines
Planting Dates & Soil Temperature
Forage sorghum planting date should be similar to
the planting date used for grain sorghum.
Sorghum needs warm soils to germinate. Planting
in cooler soils will reduce germination and delay
emergence which leaves the plant subject to attack
by microorganisms. However, planting too late
might not allow the crop to reach the optimum
cutting stage before frost.
In Table 1, conventional varieties on average
yielded over 1,500 pounds more of grain than
BMRs. However, BMRs on average had a higher
% IVTD than the conventionals. Research has
shown that BMRs can have a very low percentage
of grain in the silage, yet be very high in quality.
A report by Bolsen and Kuhl (n.d.) with the
Kansas State University Extension recommends
an early to mid-June planting for Kansas
producers with a soil temperature in the 70 to
75°F range. Preferably, the average 10-day six
inch soil temperature should be 60°F or higher
before forage sorghum is planted. Producers can
risk moving up the planting dates when the 10-day
six inch soil temperature is 55°F but should expect
delayed emergence. Marsalis (2006) stated that a
minimum soil temperature of 60°F (3-5 days) is
required for proper germination, and sorghums are
less tolerant of cool temperatures than corn.
KEY POINTS
The choice of hybrid is a critical factor
in your success with forage sorghum.
Let your production and/or feeding
purposes for the harvested forage
sorghum help drive your hybrid
selection.
Use the latest experiment station
research results to make informed
decisions.
4
90
NonBMR
BMR
PS
IVTD, % DM
85
80
75
70
65
60
10
20
30
40
50
ADF, % DM
Figure 2. Acid detergent fiber (ADF) and in vitro true digestibility (IVTD) relationships
for in pre-ensiled normal (non-BMR), brown midrib (BMR), and photoperiodsensitive (PS)
inch rows. Research conducted in Stephenville,
Texas in 2001 and 2002 (Butler & Muir, 2003)
examined row spacing (12, 18, and 36-in.) and
plant maturity at harvest (boot, early head, early
dough, mid-dough, late dough, and hard seed) of
forage sorghum varieties (Brown midrib and
conventional) to determine the effect on silage
production. Based on the results of this study,
forage sorghum silage should be planted on 12 in.
rows and harvested at the late dough stage to
realize greater production and higher silage
nutritive value.
Planting Depth & Row Spacing
Planting depth of ¾ to 1½ inches is generally
recommended for sorghum but this will vary with
soil type and moisture conditions (Bolsen & Kuhl,
n.d.; Marsalis, 2006).
Seeding Rate
Bolsen and Kuhl (n.d.) stated seeding rates are
relatively high as typically 65-70% of the seeds
actually emerge. Seeding rate will depend on
sorghum type and anticipated irrigation amount.
Marsalis (2006) stated that if irrigation is limited,
seeding rates should be reduced with dryland
seeding rates ranging from one-half to two-thirds
of those for irrigated. Increasing seeding rates
does not always result in higher yields, and
excessive rates escalate the risk of potential
lodging of plants.
There is likely some advantage in planting forage
sorghum in narrow rows. However, this is only
true if seeding rate and placement can be
accurately controlled. Excellent yields can be
obtained when planted in 30-inch and even 40-
Seed size varies greatly between varieties. For this
reason it is important to plant number of
5
seeds/acre rather than pounds/acre. Number of
seed per pound can range from 12,000 to 22,000
with the most common being around 17,000 seed
per pound. Bean et al. (2004) reported excellent
yields in the Texas Panhandle with seeding rates
as low as 30,000 seed/acre on 30-inch rows.
Narrow row spacing (6-20 inches) will require
higher seeding rate than wider rows.
diameter to be less, making the forage easier to
dry down, and possibly more palatable to cattle.
Because the BMR stems are more digestible, stem
diameter is not as much of a concern. Under
limited irrigation, consider reducing the seeding
rate to 90,000 seed/acre or less with conventionals
and less than 75,000 with BMRs if lodging is a
concern.
Because of the increased concern of lodging with
the BMR varieties, it is recommended that the
seeding rate in fields under irrigation be reduced
as compared to conventional varieties. Varieties
may respond differently to seeding rate. For this
reason, seed companies should be consulted
concerning their specific recommendation for any
given hybrid. The seeding rates recommended in
Table 2 are based on studies conducted by Drs.
Bean and McCollum at the Texas Agricultural
Experiment Station, near Bushland, TX over
several years, but only on a limited number of
varieties.
Many growers underestimate the ability of these
forages to compensate for low seeding rates and
poor establishment, and will unnecessarily
increase their production costs by planting at
higher rates (Marsalis, 2006). If lower rates are
used, individual plants will tiller more extensively
and will fill in the spaces within and between
rows.
KEY POINTS
Seeding rate will depend on sorghum
type and anticipated irrigation amount.
Increasing seeding rates does not
always result in higher yields.
Increased production and silage
nutritive value is being found with
narrow rows harvested at late dough
stage.
Table 2 Forage sorghum seeding rate
based on anticipated irrigation
applied in-season.
Forage
Anticipated
Planting
Sorghum
Irrigation,
Rate,
Type
(inches/acre)
Seed/acre
Conventional
0
30,000 –
(nonBMR)
50,000
4–8
50,000 –
90,000
9 - 16
90,000 –
120,000
Brown midrib
(BMR)
0
4-8
9 - 16
Fertilizer Requirements
Nitrogen and phosphorus are two nutrients that
will most likely need to be added to the soil for
forage sorghum silage production (Bolsen &
Kuhl, n.d.; Mortvedt, Westfall, & Croissant,
1996). Mortvedt, Westfall, and Croissant (1996)
reported that zinc and iron may also be limiting
nutrients in some soils. Marsalis (2006) stated that
forage sorghums will remove large amounts of
nutrients from the soil, so it is imperative that
producers test their soils frequently in order to
accurately assess their fertilizer needs.
30,000 –
50,000
50,000 –
75,000
75,000 –
100,000
Based on this research, there is very little
advantage in increasing seeding rate of either
sorghum types over 120,000 seed/acre for fields
under full irrigation. Under most full irrigation
conditions, 90,000 seed/acre will produce
maximum yields. However, increasing the seeding
rate of conventionals will tend to cause the stem
Mortvedt, Westfall, and Croissant (1996) reported
that sorghum roots quickly grow into the soil
between the rows. As such, sidedressing nitrogen
fertilizers early in the growing season will help
avoid root pruning. Dryland nitrogen requirements
will be lower than those necessary for irrigated
6
due to lower plant populations and lower expected
yield. Bolsen and Kuhl (n.d.) stated that a high
nitrate concentration in the sorghum is likely if
excessive nitrogen is applied or if production is
limited by drought. As such, a split application
provides better nutrient distribution and reduces
the potential for nitrate or prussic acid
accumulation. Additional results from six field
trials in New York suggest that BMR sorghum
sudangrass needs to be fertilized as a grass rather
than as a corn crop using split applications
ranging from 100-150 lbs N/acre per cut in fields
(Ketterings, et. al., 2005).
The general recommendation is 8 to 9 lbs of
N/acre is needed for every ton/acre (65%
moisture) of forage produced. The phosphorus
(P2O5) recommendation is 3.25 lbs/acre for every
ton of forage. Marsalis (2006) reported that while
sorghums will grow on infertile, low and high pH
soils, they respond well to increase fertility, and
growth is optimized at pH levels of 6.0-7.0 on
well-drained soils.
Studies have shown forage sorghum responds well
to irrigation. Average yield per inch of water used
by the crop is about 1,500 lb/acre of forage
corrected to 65% moisture (McCuistion, 2006).
This includes soil stored water, in-season rainfall,
and irrigation. A field with 4 inches of stored soil
moisture prior to planting that received 8 inches of
timely rainfall, along with an additional 10 inches
of irrigation, could be expected to yield
approximately 16.5 tons/acre of silage at 65%
moisture. This might be a little lower with a BMR
and a little higher with a PS hybrid.
KEY POINTS
Split applications of nitrogen fertilizer will
produce the best results.
Consideration should also be given to
phosphorus, zinc, and iron applications.
Use soil test results to determine fertility
needs.
KEY POINTS
Sorghum is very water efficient and
may need only ½ of the amount of
water of a corn crop.
Timing of irrigation may be key though
no precise research results are available
on that topic.
Irrigation Water Requirements
It has been documented that forage sorghums
have the potential to produce as much, and in
some cases more, dry matter than corn when
grown with the same amount of water (Anderson
& Guyer, 1986; Teutsch, 2002). Sorghums have a
lower transpiration ratio than corn and require less
water per unit of dry matter produced (Martin,
Leonard, & Stamp, 1976). Forage sorghums have
the ability to maintain high yields under water
stress conditions and resume growth after drought
(Sanderson, Jones, Ward, & Wolfe, 1992).
Harvesting & Storage
Harvesting both too early and too late will reduce
energy of the fed product. Stage of maturity has a
much greater effect on the agronomic
performance and nutritive value characteristics of
forage sorghum cultivars than grain sorghum
hybrids (Bolsen, 2004).
In grain producing forage sorghums, whole plant
moisture content between 64 and 70 % usually
occurs when the grain has reached the soft dough
stage. At this stage, the kernel can be mashed
7
between the fingers. Little if any milk should be
present. The BMRs tend to have slightly higher
whole plant moisture (1 – 2 %) at the soft dough
stage compared to conventionals.
1. Achieve a high packing density (minimum of
15 lbs of DM per cubic ft) in the forage within
the top 3 feet of the silage surface.
2. Shape all surfaces so water drains off the
bunker or pile, and the back, front, and side
slopes should not exceed 30 to 35 degrees.
3. Seal the forage surface immediately after
filling is finished.
4. Two sheets of plastic or a single sheet of
improved oxygen barrier film are preferred to a
single sheet of plastic.
5. Overlap the sheets that cover the forage surface
by a minimum of 4 to 6 feet.
6. The sheets should reach at least 4 to 6 feet off
the forage surface around the entire perimeter
of drive-over piles.
7. Put uniform weight on the sheets over the
entire surface of a bunker or pile, and double
the weight placed on the overlapping sheets.
For many years, full-casing discarded tires
were the norm for anchoring bunker silo
covers. These waste tires are cumbersome to
handle, messy, and standing water in fullcasing tires can help spread the West Nile
virus, which is another reason to avoid using
full-casing tires on dairy farms.
Bias-ply truck sidewall disks, with or without
a lacework of holes, are the most common
alternative to full-casing tires.
Sandbags filled with pea gravel are another
effective means of anchoring the overlapping
sheets, and sandbags provide a heavy,
uniform weight at the interface of the sheets
and bunker walls.
Sidewall disks and sandbags can be stacked,
and if placed on pallets, they can be moved
easily and lifted to the top of a bunker wall
when the silo is being sealed and lifted to the
top of the feedout face when the covering
materials are removed.
A 6- to 12-inch layer of sand or soil or
sandbags are an effective way of anchoring
sheets around the perimeter of drive-over
piles.
8. Prevent damage to the sheets during the entire
storage period.
Mow the area surrounding a bunker or pile
and put up temporary fencing.
Regular inspection and repair is
recommended but extensive spoilage can
develop quickly when air and water penetrate
the silage mass.
Marsalis (2006) reported that if forage sorghum is
harvested when the moisture level is greater than
70%, seepage is likely. Seepage will result in a
loss of nutrients and lowers digestibility. Wet
silage promotes the production of butyric acid
(fishy odor) which results in high fermentation
losses and lower intake. Excessively dry silage
will not pack well and eliminating oxygen will be
difficult, thereby causing high temperatures, heat
damaged protein, and a more indigestible, lower
energy product (Marsalis, 2006).
Photo from John Deere Photo Library, Volume 6
Storage
Berger and Bolsen (2006) stated that bunker silos
and drive-over piles are economically attractive
for storing both moderate and large amounts of
ensiled forage, but by design, they allow large
percentages of the ensiled material to be exposed
to the environment. In addition to the weather
influences, silage in bunkers and piles is affected
by other interacting factors involving crop DM
content, exposed surface area during filling,
permeability of the silo walls, length of storage,
and rate of silage removal during feedout
(McDonald, Henderson, & Heron 1991). These
factors produce a wide range of silage DM and
nutrient losses on dairy farms.
Berger and Bolsen (2006) listed eight steps that
producers and their employees should consider to
minimize surface-spoiled silage in bunkers.
8
Feeding
Silage
Five years of research at the University of
Nebraska Institute of Agriculture and Natural
Resources indicated that brown midrib sorghum is
10 percent more digestible than regular sorghum.
As such, dairy cows fed brown midrib sorghum
silage produce 10 more pounds of milk per day
than cows fed regular sorghum silage and the
same amount as those fed corn silage (Alberts,
1999). Similar results were found by Aydin,
Grant, and O’Rear (1999) who found that dry
matter intake and body condition score were not
significantly different between cows fed BMR and
standard sorghum, but cows fed BMR sorghum
resulted in long-term milk production greater than
cows fed standard sorghum and was similar to
cows fed corn silage.
Berger and Bolsen (2006) reported several reasons
why the starch-salt matrix sealed with wax would
be superior to plastic in reducing surface spoilage.
Through their research, they found that the matrix
forms an air-tight seal, and it does not just lay on
the surface of the forage similar to plastic. It
bonds to the forage particles without creating an
air-layer interface. In addition, the salt diffuses
into the top 10 to 15 inches of silage and acts as a
preservative to prevent the growth of yeast and
mold thus providing an effective protection from
air and water. All the ingredients in the
formulation are GRAS (general recognition of
safety) and feed grade, making it totally safe to
feed to livestock. The ingredients in the matrix
also provide essential nutrients that would be
added to the ration, and the cover will blend with
the other ingredients in a normal feed mixer.
When the edible cover was fed at 2.5% of the
ration (DM basis), there was no reduction in DM
intake (Berger & Bolsen, 2006).
KEY POINTS
Timely harvest is important in
producing quality forage sorghum
silage.
Stage of maturity has a much greater
effect on the agronomic performance
and nutritive value characteristics of
forage sorghum cultivars than grain
sorghum hybrids.
Proper storage techniques can reduce
potential spoilage and dry matter loss.
The discarding of surface-spoiled silage from
bunker silos and drive-over piles is not always a
common practice on dairy farms. However,
Berger and Bolsen (2006) reported that surface
spoilage reduces the nutritive value of corn silagebased rations far more than would be expected.
The economic impact of creating and feeding
surface-spoiled corn silage to growing cattle could
cost the producer as much as 15 to 25 dollars per
ton of crop ensiled.
9
has shown that when the crop is cut and fieldcured, or ensiled, the hydrocyanic acid degrades
(2-3 weeks after ensiling) and the danger is
greatly reduced (Undersander, Smith, Kaminski,
Kelling, & Doll, 1990).
Grazed
Trostle (2004) stated that 1999 and 2000 results
from trials conducted by trials conducted by Dr.
Ted McCollum at the Texas Agricultural
Experiment Station, near Bushland, TX,
determined a 12% increase in average daily gain
for stockers in a replicated rotational grazing
system when grazing BMR sorghum sudangrass
vs. a nonBMR sorghum sudangrass. In addition,
grazing preference for BMR forage vs. other
sorghum/sudans has been observed in the field.
When grazing forage sorghum, there is increased
danger of prussic acid poisoning when frost kills
the top-growth, leaving the base of the plant from
which new shoots may emerge. Cattle will
frequently avoid the tall frosted growth and graze
the young shoots, which may contain toxic levels
of prussic acid. Harvesting the crop for silage may
be the best way to handle frost injured sudangrass
or sorghum-sudangrass hybrids (Undersander et
al., 1990).
According to the Upper Midwest research of
Undersander et al. (1990), sudangrass and
sorghum-sudangrass hybrids are usually ready for
grazing 5 to 6 weeks after planting. Since prussic
acid is highest in the immature plant parts, new
shoots may be dangerous until they reach a height
of at least 18 in. Rotational grazing will provide
maximum production at a nutritious, yet safe stage
of growth. Allow time for 18 in. or more of
regrowth before regrazing. Livestock may
selectively graze and trample the crop if the plants
are too tall (over 40 in.).
KEY POINTS
Dairy cattle fed BMR sorghum silage
realized similar milk production results
as cattle fed corn silage.
Grazing of cattle on forage sorghum is
possible if properly managed.
Toxicity Concerns
Summary
Bolsen and Kuhl (n.d.) reported that sorghums can
accumulate potentially toxic nitrate levels when
stressed by drought, shade, frost, or temperature
extremes. Generally, forages that contain more
than 6,000 ppm nitrate (DM basis) should be
considered potentially toxic. Nitrates normally are
highest in young plant growth; however,
concentrations can remain high in mature
sorghum. Raising the cutting bar 6 to 12 inches to
exclude the basal part of the stalk can reduce
nitrate levels. The fermentation phase in the
ensiling process converts about 50% of the
nitrates to a nontoxic form. Because of this, nitrate
levels are seldom high enough to be a problem
when feeding silage.
Research is indicating that forage sorghum silage
present a viable alternative to corn silage for cattle
producers and has the potential to realize water
savings of up to 50%. A recent report by
McCorkle et al. (2007) concluded:
There is tremendous potential for
forage sorghums in the years
ahead. If the 54,000 acres of
irrigated corn silage in the
Panhandle region were converted
to sorghum silage, the amount of
water saved would be an estimated
400,000 acre inches. This would
lower the cost of irrigation pumping
by $2.8 million annually (at a natural
gas price of $7.00/mcf). With water
being an increasingly important
issue and with the rising demand
for silage from the expanding dairy
industry, sorghum silage should be
an even more attractive alternative
crop. (p. 4)
Bolsen and Kuhl (n.d.) stated that prussic acid, or
hydrogen cyanide (HCN) poisoning, is caused by
cyanide production in sorghums that grow rapidly
following a stress situation. Cyanide is
concentrated in young, actively growing leaves
and is commonly associated with new shoot
growth at the end of a summer drought or after the
first autumn frost. Research in the Upper Midwest
10
http://www.nnyagdev.org/reportarchives/2004%20N%2
0rate%20studies%20WCU%20article.pdf.
Kochenower, R., & Hicks, B. (2006). Oklahoma Panhandle
limited irrigation sorghum silage performance trial,
2006 (PT 2006-13). Stillwater, OK: Oklahoma
Cooperative Extension Service, Oklahoma State
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http://www.pss.okstate.edu/oaesgoodwell/sorghumsilage
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Marsalis, M.A. (2006). Sorghum forage production in New
Mexico (Guide A-332). Las Cruces, NM: New Mexico
State University Cooperative Extension Service.
Retrieved July 5, 2007, from
http://cahe.nmsu.edu/pubs/_a/a-332.pdf
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McCorkle, D. A., Hanselka, D., Bean, B., McCollum, T.,
Amosson, S., Klose, S., & Walle, M. (2007). The
economic benefits of forage sorghum silage as an
alternative crop. Texas Cooperative Extension: Texas
A&M University System.
McCuistion, K.C., (2006). Forage sorghum and sorghum x
sudangrass hybrids in ruminant diets. Ph.D.
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0.540). Fort Collins, CO: Colorado State University
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approach to water conservation for agriculture in the
Texas Southern High Plains: 2nd annual report.
Retrieved July 5, 2007, from
http://www.depts.ttu.edu/tawc/Documents/TAWC%20Y
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Web Links
Kansas State University Research and Extension (Silage)
http://www.oznet.ksu.edu/pr_forage/silg.htm
Texas A&M University System Agricultural Research and
Extension Center (Agronomy)
http://amarillo.tamu.edu/programs/agronomy
University of Wisconsin—Extension Forage Resources
http://www.uwex.edu/ces/crops/uwforage/Silage.htm
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11
.
Texas Alliance for Water Conservation
The Texas Alliance for Water Conservation
(TAWC) is the effort of individuals and
organizations with a mission to conserve water
for future generations by collaborating to
identify those agricultural production practices
and technologies that, when integrated across
farms and landscapes, will reduce the depletion
of ground water while maintaining or
improving agricultural production and
This summary of research was authored by
economic opportunities. Collaborating partners
David Doerfert, Texas Tech University with
include the Producers of Hale and Floyd
major contributions from Vivien Allen, Will
Counties, Texas, Texas Tech University, Texas
Cradduck, and Rick Kellison of Texas Tech
Cooperative Extension, High Plains
University and Brent Bean, Ted McCollum,
Underground Water Conservation District No.
and Calvin Trostle of the Texas Cooperative
1, USDA Natural Resource Conservation
Extension Service and the Texas Agricultural
Service, USDA ARS Cropping Systems
Experiment Station. A special thanks to all who Research Laboratory, FARM Assistance, and
assisted in preparing this research summary
the Texas Agricultural Experiment Station.