DECEMBER 1967
Effect of Management on Yield and 
Quality of
Sudax Sorghum-Sudan Hybrid and Gahi-1 Pearlmillet*
C. S. HOVELAND, Associate Professor of Crops
W. B. ANTHONY, Professor of Animal Science
C. E. SCARSBROOK, Professor of Soils
PEARLMILLET, sudangrass, and brown-
top millet have been grown in Alabama
for many years as temporary summer
pastures, particularly for dairy cattle. In
recent years, however, sorghum-sudan
hybrids have replaced much of the millet
and sudan grown for dairy animals, and
these crops are now widely planted for
beef cattle grazing. More than 200,000
acres of the hybrid annuals were planted
on Alabama farms in 1966.
Management and utilization of sor-
ghum-sudan hybrids presents problems
on many farms. Capacity of the crop to
grow rapidly and produce large amounts
of forage in a short time often results in
wasted forage. Forage quality may be
affected by various management prac-
tices, thus influencing animal perform-
ance on these annual grasses.
This leaflet summarizes results of man-
agement experiments with "Sudax" SX-
11 sorghum-sudan hybrid and Gahi-1
pearlmillet at the Plant Breeding Unit,
Tallassee.
* Partial financial support for these studies
was from a grant by DeKalb Agricultural
Association, Aurora, Illinois.
INDIVIDUAL TEST DETAILS
No. 1. Effect of Seeding Rate on
Forage Quality and Yield of Sudax
Sudax was seeded May 20 in 6-inch
rows with a belt seeder. Seeding rates
were 10, 20, 80, 40, and 50 pounds per
acre. A total of 220 pounds per acre of
nitrogen was applied, split into three
applications. Three harvests were made
by cutting at a 6-inch stubble height
when forage was in the early boot stage.
Stem size was measured 10 inches above
ground. The forage was analyzed for
nitrogen, lignin, and fiber.
Using 30 pounds of seed per acre gave
higher forage yields than the 10- or 20-
pound rates and about the same as 40-
and 50-pound seedings. The higher pro-
duction at the 80-pound rate resulted
from more forage at the first harvest,
May 26. Yields at subsequent harvests
were about the same from all seeding
rates. Severe damage by zonate leafspot
(Gloecercospora sorghi) probably was a
factor in poor recovery and erratic stands
during July. The poor recovery growth
after August 8 did not warrant harvest-
ing.
AGRICULTURAL EXPERIMENT STATION
E. V. mith Dircto AUBURNnf UNIERIT Abur, laam
LEAFLET 76
AUBURN UNIVP .RSITY-
E. V. Smith, Director
Auburn, Alabama
TABLE 1. EFFECT OF SEEDING RATE ON FORAGE YIELD, LEAFINESS., AND
.STEM 
SIZE OF SUDAX,, 
1964
Dry forage per acre Leaves in dry forage
May 26 
Season
May 26 total
May 26 June 24
Stem diameter
May 26 June 24
Lb. Lb. Pet. Pct. In. -In.
2,240 a'
2,128 a
2,100 a
1,378 b
1,068 b
6,348 abc
7,191 a
6,734A
5,,506 c
5,995 bc
68 a
60 a
67 a
70 a
63 a
80 a
66 b
58 b
63 b
58 b
7/32 b
6/32 b
7/32 b
8/32 b
12/32 a
9/32 b
9/32 b
10/32 b
10/32 b
13/32 a
* Least significant range for each column. Any two means not marked with the same
letter are significantly different at .05 level.
TABLE 2. EFFECT OF SEEDING RATE ON CRUDE PROTEIN, LIGNIN, AND FIBER CONTENT
OF DRY SUDAX FORAGE, 1964
Seeding rate Crude protein
per acre, lb. May 26 June 24
Pet. Pet.
50-
40-
30-
20.
10-
13.5 a4
17.3 a
15.6 a
15.8 a
15.6 a
17.8 a
19.7 a
18.6 a
16.3 a
19.5 a
Lignin
May 26 June 24
Pet.
2.7 a
2.9 a
3.0 a
3.0 a
2.9 a
Pet.
3.1 a
3.2 a
3.5 a
3.4 a
3.1 a
Fiber
May 26 June 24
Pet.
27.5 b
2,7.9 A
29.1 a
29.2 a
29.1 a
Pet.
30.2 a
31.7 a
32.5 a
30.9 a
32.1 a
I Least significant range. Any two means not marked with the same letter are sig-
nificantly different at .05 level.
Seeding rate did not affect leafiness
at the first harvest, Table 1. At the sec-
ond cutting, however, leaf percentage
was higher on areas seeded with 50
pounds per acre. No separations were
made at the third harvest.
Stem diameter was unaffected by seed-
ing rate except plants from the 10-pound
rate had larger stems, Table 1. However,
this difference was less at the second
harvest. Thus, increasing the seeding
rate above 30 pounds per acre to get
maximum forage yield would not likely
decrease stem size for faster hay curing.
Crude protein content of forage was
uniformly high at both cutting dates and
was not affected by seeding rate, Table
2. Lignin content was low and similar
at all seeding rates, and, this was not af-
fected by stem size. 'Fiber content was
generally unaffected by seeding rate, ex-
cept for a slight reduction at the 50-
pound seeding.
As shown by these results, seeding rate
had little or no effect on forage quality
under the nitrogen fertilization and clip-
ping management used. From the prac-
tical standpoint, a seeding rate of 30
pounds per acre in 6-inch rows would be
best.
No. 2. Effect of Stage of Maturity and
Nitrogen Rate on Sudax Yield and Quality
To compare the 100- and 200-pound-
per-acre rates of nitrogen, Sudax was
planted in 6-inch rows using 30 pounds
of seed per- acre. Cutting was done at pre-
boot, boot, bloom, and seed dough stages,
beginning May 26 and ending Septem-
ber 16. Nitrogen was applied monthly
at rates of 20 and 40 pounds per acre,
and forage was harvested from May 26
to September 16. Prussic acid (HCN)
content of forage was determined at each
harvest. Other procedures were similar
to those of Experiment 1.
At both levels of nitrogen, forage
yields were generally higher when har-
vesting was delayed to the more mature
[ 2]
Seeding rate
per acre, lb.
50-
40-
30-
20-
10-
TABLE 3. EFFECT OF NITROGEN 
FERTILIZATION AND STAGE OF MATURITY 
ON YIELD AND
QUALITY OF SUDAX, 1964
Nitrogen per
acre and
harvest stage
100 pounds N
Pre-boot
Boot
Bloom -------
Dough .......
200 pounds N
Pre-boot .....
Boot
Bloom -------
Dough .......
Total dry
forage
per acre
Season
average
leaves in
dry forage
Lb. Pct.
4,524 c*
5,075 c
9,205 b
11,117 a
6,024 c
6,624 c
10,827 b
15,773 a
66
47
33
29
60
49
30
30
Total
leaves
per acre
Lb.
3,005
2,382
2,896
3,252
ab
c
b
a
3,583 b
3,289 c
3,178 c
4,595 a
* Least significant range for each nitrogen level.
same letter are significantly different 
at .05 level.
Dry forage content, season 
average
Crude
protein
Pct.
9.3 a
7.1 b
6.1 c
4.8 d
11.1 a
9.2 b
6.5 c
5.4 d
Lignin
Pct.
3.6
4.8
5.5
6.1
3.3
4.1
5.4
6.6
Fiber
Pct.
33.8 c
35.6 b
37.9 a
39.3 a
33.2 e
36.1 b
37.5 b
39.7 a
c
b
ab
a
b
ab
a
Any two means not marked 
with the
stages, Table 3. Pre-boot and 
boot har-
vesting stages gave similar yields. When
yields at all cutting stages were averaged,
the 200-pound-per-acre nitrogen rate 
out-
yielded the 100-pound rate by more 
than
a ton. Response to nitrogen was 
greatest
when forage was cut in the dough stage.
Late summer recovery growth was
poor on most plots, probably because of
unusually high incidence of zonate leaf-
spot. Unusually cloudy and wet weather
in June, July, and August probably 
con-
tributed to development of the disease.
Leafiness is generally considered to be
an indicator of forage quality, and in
this study leaf percentage declined
sharply with advancing maturity. Nitro-
gen level had little effect on leafiness.
When leaf production was calculated for
each treatment at each harvest, it was
found that total leaf production per
acre was as high for more mature plants
as for plants cut in the pre-boot and boot
stages. This suggests that leafy forage
would be available to grazing animals in
about the same quantity regardless of
growth stage when grazing was begun.
No differences in stem diameter was
observed between treatments. The range
in stem diameters was 7/82 to 10/32
inch for all treatments, with only a slight
increase as the season progressed.
Crude protein content of forage, rang-
ing from 4.8 to 11.1 per cent, was 
un-
usually low from all treatments. 
Differ-
ences in protein content between 
the
100- and 200-pound nitrogen rates 
fa-
vored the higher one by 1 to 2 
per cent.
Crude protein content dropped 
sharply
as plants matured.
Content of lignin, an undesirable 
con-
stituent, was relatively low in 
forage
harvested at the pre-boot stage, 
but in-
creased rapidly with maturity. 
Plants
harvested at the dough stage 
contained
nearly twice the lignin of plants cut 
at
pre-boot. When cut at the dough 
stage,
lignin contents were high enough 
to seri-
ously lower animal digestibility. 
Fiber
content increased slightly with maturity,
but showed no effect from nitrogen rate.
Forage from all treatments tested 
low
in prussic acid (HCN) throughout 
the
season.
No. 3. Effect of Maturity 
on
Digestibility of Sudax
For the digestibility trials, Sudax 
was
planted at a rate of 80 pounds of 
seed
per acre in 6-inch rows and fertilized
with a total of 200 pounds of nitrogen 
in
split applications. Forage was 
cut at
the appropriate maturity 
(pre-boot, boot,
and seed dough), dried one 
day in the
field, and then dried in a forced 
air oven
at 120'. The dry forage 
was then
[3]
chopped in a hammermill to pass through
a 1/2-inch screen.
Weaned lambs less than 1 year old
were used as experimental animals in
digestion crates. Lambs were fed during
a 10-day standardization and 7-day col-
lection period. Fecal samples were col-
lected and dry matter digestibility de-
termined.
Stage of maturity had a pronounced
effect on protein content of forage, Table
4. Sudax cut in the pre-boot stage was
almost equal to the alfalfa hay used for
a comparison, but protein content
dropped sharply with maturity.
TABLE 4. CHEMICAL COMPOSITION, CON-
SUMPTION, AND DIGESTIBILITY BY LAMBS OF
SUDAX AT THREE MATURITY STAGES AND
ALFALFA, 1964
Daily 
Dry
Forage and Crude intakeas tter
harvest stage protein body digsti-
weight
Pct. Pct. Pct.
Sudax
Pre-boot -------- 15.5 2.90 80.30
Boot----- - 8.2 2.7 70.0
Dough-- - 7.4 2.7 64.2
Alfalfa------- - 16.4 2.8 63.9
* Each figure is an average of results from
3 lambs.
Dry matter digestibility of Sudax for-
age was high at all maturity stages, go-
ing from above 80 per cent for early cut
to slightly lower for more mature forage.
Even Sudax cut at seed dough stage
was similar to alfalfa hay in dry matter
digestibility. It may be argued that re-
sults of this test are not indicative of
forage quality since it was chopped in a
hammermill. However, forage fed as un-
chopped would most likely have yielded
even higher digestibility values because
of animals rejecting stems. In this digesti-
bility trial the lambs consumed both
stems and leaves, making the results
even more impressive. Daily intake of
Sudax forage was comparable to intake
of alfalfa hay, but all intake values were
low. Lambs fed alone, as these were,
seldom consume more than maintenance
requirements. Low daily feed intake con-
tributes to high digestion coefficients.
Comparing Sudax results with similar
data for Coastal bermudagrass helps
place the information in proper perspec-
tive. In many Auburn trials during the
past few years with lambs and steers,
dry matter digestibility of Coastal has
ranged from 45 per cent for the poorest
hay to not more than 55 per cent for the
best quality. Sudax forage in the trial
reported gave considerably better results.
It is pointed out that these values are
for dried forage. In grazed forage, the
value is masked by high moisture con-
tent.
No. 4. Effect of Nitrogen Fertilization
and Maturity on Yield, Protein, Nitrates,
and Digestibility of Sudox Sorghum-Sudan
Hybrid and Gahi-1 Pearlmillet
Gahi-1 pearlmillet was seeded May 20
using 20 pounds of seed per acre and
Sudax at the 30-pound rate, both in 6-
inch rows. Both grasses were fertilized
at 80, 160, and 320 pounds nitrogen per
acre, split into four applications. The
millet was clipped during summer in the
pre-boot stage and Sudax was cut both
at pre-boot and early bloom. Harvest
procedures were similar to Experiment 1.
Forage samples from each replication
were kept on ice before being oven dried,
and then ground and analyzed for total
nitrogen and nitrate. Larger forage sam-
ples were ground and used for digesti-
bility determinations with steers having
a rumen fistula. Nylon bags containing
the forage were inserted into the rumen
through the fistula and left for 24 to 48
hours. Upon removal, samples were oven
dried and weighed to determine per-
centage digestibility.
Total forage yields of millet and Sudax
were similar when cut at pre-boot stage,
averaging 4 tons per acre, Table 5. Sudax
production was higher than millet in
early and late season. Sudax yield was
doubled by delaying harvest from pre-
boot to early bloom stage. Both millet
and Sudax made higher yields at 320-
pound nitrogen rates than when 160
pounds per acre was applied. However,
[41
TABLE 5. EFFECT OF NITROGEN FERTILIZATION AND STAGE OF MATURITY ON FORAGE YIELD,
LEAVES, CRUDE PROTEIN, AND STAND OF PEARLMILLET AND SUDAX, 1965
Nitrogen per acre
and harvest stage
Millet, pre-boot
80 lb. N- - - - -
160 lb. N- - - - -
320 lb. N-
Sudax, pre-boot
80 lb. N ---------- ---
160 lb. N --------- ----
320 lb. N --------- ----
Sudax, early bloom
80 lb. N ---------- ---
160 lb. N --------- ----
320 lb. N --------- ----
Ttl Season
Total 
average
dryge 
leaves
foragre in dry
per ae forage
Lb. Pct.
7,878 b*
7,721 b
9,161 a
6,594
7)145
8,484
14,018
17,352
19,185
11 Least significant range. Any two means
nificantly different at .05 level.
only with Sudax at bloom stage was
there an increase when nitrogen rate
went from 80 to 160 pounds. Similar
yield responses were obtained in 1966,
but drought lowered overall yields.
When cut at pre-boot stage, millet and
Sudax stands declined with increasing
rates of nitrogen. This probably accounts
for lower yield in late summer, Table 5.
A reverse situation was noted for Sudax
cut at early bloom.
Leaf percentage of millet was slightly
higher than Sudax in early season, but
50
58
54
52
54
54
32
33
25
Total
leaves
per
acre
Season
average
crude
protein
Stand
of live
plants,
Oct. 4
Lb. Pct. Pct.
4,577
3)982
4,517
4,215
5,065
4,746
8.2
11.2
13.8
11.9
13.1
15.6
7.3
7.6
7.8
72
50
40
35
32
21
35
45
60
not marked with the same letter are sig-
Sudax was more leafy in fall. As in Ex-
periment 2, nitrogen fertilization had no
effect on percentage leaves.
Crude protein content of Sudax was
higher than millet when both were cut
at pre-boot stage, Table 5. Crude protein
content of millet increased with nitrogen
fertilization. Similar results were ob-
tained with Sudax cut at pre-boot stage,
but at early bloom protein 'content re-
mained low at all rates of nitrogen.
Nitrates reached potentially toxic levels
only at the high rate of nitrogen ferti-
TABLE 6. EFFECT OF NITROGEN FERTILIZATION AND STAGE OF MATURITY ON 
NITRATE
CONTENT OF PEARLMILLET AND SUDAX, 1965
Nitrogen per acre
and harvest stage
Millet, pre-boot
80 lb. N
160 lb. N
320 lb. N ---------
Sudax, pre-boot
80 lb. N ---------
160 lb. N ---------
320 lb. N ---------
Sudax, early bloom
80 lb. N
160 lb. N ---------
320 lb. N ---------
June
11
Pet.
Nitrate content in dry forage
June June July July July Aug. Aug. Sept. Oct.
17 24 6 19 26 12 25 1 8
Pct. Pct. Pct. Pct. Pct. Pct. Pct. Pct. Pct.
.11
.28
.o5
.06
.39
.81
.02
.07
.04
.04
.02
trace
trace
.01
[ 5]
.06
.06
.o5
Oct.
20
Pct.
.05
.04 .12
.17 .10
.04 .14
.04 .14
.09 .12
.03
.06
A03
lization. This occurred only in early
season on both millet and Sudax cut at
pre-boot, Table 6. (Plants containing
0.2 per cent or more nitrogen as nitrate
are considered potentially toxic for rumi-
nant animals.) No nitrate problem oc-
curred with Sudax cut at early bloom.
Extremely dry weather in early June
probably accounted for the nitrate build-
up in plants at that time.
TABLE 7. EFFECT OF STAGE OF MATURITY
ON DIGESTIBILITY IN RUMEN AT 24 AND 48
HOURS OF PEARLMILLET AND SUDAX,
AVERAGE OF ALL HARVESTS, 1965
Forage and harvest
stage
Millet, pre-boot .....
Sudax, pre-boot- ...
Sudax, early bloom --
Dry matter
digestibility
24 hours 48 hours
Pct. Pct.
61.7 a4
63.1 a
55.2 b
76.3
76.3
65.5
* Least significant range for each column.
Any two means not marked with the same
letter are significantly different at .05 level.
The rate of digestion in the rumen is
given by the data in Table 7. In compar-
ing the 24-hour and 48-hour periods that
samples were in the rumen, less vari-
ability between replications was ob-
tained for the longer period. As might
be expected, digestibility pereentages
were higher when forage samples re-
mained in the rumen for a longer time.
The seasonal decline in digestibility was
greater from the 24-hour than the 48-
hour rumen test period, Table 8. Rapid
digestion is desirable; therefore, the 24-
hour values may be a more critical evalu-
ation of forage nutritive value.
Dry matter digestibility of the forage
tested was exceptionally high and fully
comparable to corn grain. Digestibility
of both millet and Sudax declined over
the season, Table 8. Nitrogen fertiliza-
tion had no effect on digestibility.
The digestibility data suggest that
animals should perform well on both of
these forages. However, grazing studies
with steers on millet in Alabama have
resulted in daily gains of only 1 to 1.25
pounds per animal. The higher water
content of these forages may be one
factor, resulting in a large quantity of
green forage being eaten but a relatively
low intake of dry matter.
Delayed harvesting of Sudax from pre-
boot to early bloom doubled the forage
yield but resulted in a large decline
in dry matter digestibility. Selective graz-
ing by the animal may alter this some-
what. Early bloom forage harvested as
hay could be valuable when used in a
blended ration.
SUMMARY
Several experiments were conducted
at the Plant Breeding Unit, Tallassee, to
determine effects of various management
practices on yield and nutritive values
of "Sudax" SX-11 sorghum-sudan hybrid
and Gahi-1 pearlmillet. Results are sum-
marized as follows:
(1) Sudax seeded at 80 pounds per
acre in 6-inch rows gave maximum for-
TABLE 8. EFFECT OF STAGE OF MATURITY AND SEASON ON DRY MATTER DIGESTIBILITY IN
RUMEN AT 24 AND 48 HouRS OF PEARLMILLET AND SUDAX, 1965
Forage and harvest
stage
Millet, pre-boot
Sudax, pre-boot -------
Sudax, early bloom
Seasonal dry matter digestibility
24 hours 48 hours
June July Aug.-Sept. June July Aug.-Sept.
Pct. Pct. Pct. Pct. Pct. Pct.
S63.4 a*
65.6 a
54.6 b
60.1 a
60.5 a
55.7 b
58.7 a
58.0 a
50.0 b
78.1 a
79.5 a
64.2 b
74.5 a
73.1 a
66.8 b
72.9 a
69.3 a
61.1 b
* Least significant range for each date. Any two means not marked with the same letter
are significantly 
different at .05 
level.
[6]
age yield. Stem diameter was similar at
all seeding rates above 10 pounds per
acre. Leaf percentage, crude protein,
lignin, and fiber contents of the forage
were generally unaffected by seeding
rate.
(2) Forage yields, lignin, and fiber
content of Sudax increased as plants
were harvested at more advanced stages
of maturity, and there was a correspond-
ing decrease in crude protein content
and leaf percentage.
(8) Crude protein content of Sudax
was higher than millet at all rates of
nitrogen fertilization when both forages
were harvested in the pre-boot stage.
(4) Prussic acid content of Sudax was
low regardless of maturity.
(5) Nitrates were at potentially toxic
levels only at the highest rate of nitrogen
and only in early season on both millet
and Sudax when cut at pre-boot.
(6) Sudax and millet harvested at
pre-boot had similar dry matter digesti-
bility as measured by in vivo nylon bag
method.
(7) Dry matter digestibility decreased
with increasing plant maturity.
(8) Nitrogen fertilization did not af-
fect dry matter digestibility or leaf per-
centage of either millet or Sudax.
(9) Digestibility determinations with
lambs showed that Sudax was highly di-
gestible, even at dough stage.
(10) Sudax and millet responded to
as much as 820 pounds of nitrogen per
acre, but lower rates would be more
practical.
[7]