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"-jBulletin 568 September 1955
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
J. R. BECKENBACH, Director
Experiments with Napier Grass
ROY E. BLASER, G. E. RITCHEY, W. G. KIRK and P. T. Dix ARNOLD
TECHNICAL BULLETIN .
Fig. 1.-Well fertilized Napier grass gave satisfactory returns under
rotational grazing. Fenced quadrats, as in the middle foreground, were
used in measuring forage yields.
IN TRODUCTION -. -- ... .... - ------ .. ....... ....- ..- .. ......... ...- .. ..... 3
REVIEW OF LITERATURE ......----... ----------...-. ---. .... --- --.-....... 3
ESTABLISHING NAPIER GRASS ..... --........ ....--...--...--- .-----..... ... .........-------.. 4
Adaptation .--------........--.......--..... ... .. ........------------.. ..... ... 4
Strains .---------- ---------........-------.......... ........ ...... -........... .. 4
Propagating and Planting ...-----.. ... ----------.. ....-...----- .. ..- 5
Fertilization .. ................ ......---- ---.. .. ---- 6
Cultivation ..-...------. -..............------------.........------- ..... .. 6
Grazing Management ...... ..-.......-----..--.. ...------------......... .... 7
AGRONOMIC EXPERIMENTS ....-......-- --.......----------- ...----------- -...... 7
Cutting Management ....................... ...... --.......--- ...-------.............. .--- -. 7
Effect of Fertilization on Yields .....-....... ....---- ..------- ..... .-. 10
Quality of Herbage ..--- --.....--------- --......... ............. .. -..... -- ........ 13
Summary of Agronomic Phases .-.. ..--.--..--....... ...--------...---..- .--- .. 15
GRAZING TRIALS WITH BEEF CATTLE .--..-........----......-- --......... -- 15
Grass with High Nitrogen Fertilization --..-...--... -----......-......... .. .... 15
Chemical Composition of Heavily Fertilized Napier Grass ............ 17
Grazing Lightly Fertilized Napier Grass ...............-........................ 20
Summary of Grazing Napier Grass with Beef Cattle .............. .. 22
NAPIER GRASS FOR DAIRY Cows ..--...- ...........- ..- ......-- ..- ... . .. .. 22
Plan of Work with Dairy Cows ..-....... ---------... ----------................ 22
Method of Calculation ................................. ..... ... ...... . 25
Grazing Results ....---------. --- -----.......... ............ ... ... .. .. 25
Five-Year Results and Discussion ......... ... ....... .. ....... 28
Summary of Trials with Dairy Cows .................. ......... .. 30
ACKNOWLEDGMENTS .. -.... .. .... ........................... ......-... .. 31
REFERENCES CITED .. .. ...................................... ..... ............ 31
Investigations with Napier grass (Pennisetum purpureum
Schum.) were conducted at the Florida Agricultural Experiment
Stations for a number of years. The results were not brought
together promptly at the conclusion because of changes and re-
organization of the staff.
Since that time, new grass introductions and changing fer-
tilizer practices have combined to limit the general usefulness of
Napier grass. However, under tropical and sub-tropical condi-
tions when a perennial grass for year-round forage is desired,
this grass still has a place. It is hoped that the information con-
tained here will be of value under such conditions.
Experiments with Napier Grass
ROY E. BLASER', G. E. RITCHEY2, W. G. KIRK3
and P. T. Dix ARNOLD4
It is generally known that quality, reproduction and produc-
tivity in livestock are associated with the nutrients in feeds they
consume as well as with breeding and management. Some native
herbage in Florida is low in nutritive value, but noted improve-
ments are being made in feed supply by introducing and develop-
ing improved forage plants, along with good cultural and man-
Napier grass was grown in Florida long prior to 1937, but its
value as a grazing crop had not been determined previously.
The practice of continual grazing of Napier grass resulted in low
yields and ultimate destruction of the stand. Consequently, it
was not considered practical for pasture. It has been demon-
strated that a stand of Napier grass can be maintained for sev-
eral years by adequate fertilizer applications and rotational graz-
ing, as shown in Figure 1. Grazing trials were started in 1937
to measure the value of Napier grass pasture for fattening
cattle, and in 1938 to determine its importance as a grazing crop
for dairy cows.
REVIEW OF LITERATURE
Napier grass, Pennisetum purpureum Schum., was first intro-
duced into the United States from Africa in 1913 (14)5. It is
a large tropical cane-like perennial which grows 7 to 15 feet in
height. There are many strain differences.
Napier grass was first distributed to Florida farmers in 1915
(14), but is not grown extensively. Two factors which limited
its use and propagation have been improper management and
a fungus disease, eyespott" (Helminthosporium ocellum Faris).
Eyespot was first reported by Leukel and Camp (8) in 1935.
This disease was of such virulence that it destroyed whole
stands in some localities. Eyespot-resistant improved strains
I Now Professor of Agronomy, Virginia Polytechnic Institute, Blacks-
2 Formerly Agronomist, Division of Forage Crops and Diseases.
B.P.L.S.A.E., USDA, Gainesville; more recently Agronomist in Charge.
Suwannee Valley Agricultural Experiment Station, Live Oak, Florida.
Now Vice-Director in Charge, Range Cattle Experiment Station, Ona,
'Associate Dairy Husbandman, Florida Agricultural Experiment Station.
'Italic figures in parentheses refer to literature cited.
4 Florida Agricultural Experiment Stations
of Napier grass were developed subsequently by Ritchey and
Stokes (12) and by Burton (1).
This grass has been used primarily for soiling (cutting and
feeding green) in tropical locations (3, 4, 11 and 16). In Flor-
ida, tests have been made to study its value for silage (10, 13).
The silage was found to be inferior to that of sorghum, corn or
sugar cane when only two cuttings were made during the grow-
There are few experimental data on the grazing value of
Napier grass. Wilkie and Takahashi (16) report that one
Hawaiian plantation has used Napier grass successfully when
grazing was delayed until the grass reached a height of six feet
and with opportunity for regrowth after the herbage was con-
An endeavor has been made by the Florida Agricultural Ex-
periment Station to use this grass for hay, but it was not pos-
sible to preserve it properly because of difficulty in curing the
From later work, it is evident that combinations of some
legumes with sod-forming grasses properly fertilized and man-
aged may extend the grazing season and also return more total
digestible nutrients per acre than Napier grass provided.
ESTABLISHING NAPIER GRASS
Napier grass is adapted widely and the roots and crowns
tolerate all temperature extremes in Florida. The tops are
killed readily by frosts. New growth from the crowns is not
ready for grazing until late spring. In north central Florida
it generally furnishes herbage for grazing from May to No-
vember. The grass furnishes grazing for a short season, and
a high yield of quality herbage can be obtained only under care-
ful grazing management.
This grass is adapted to reasonably well-drained fertile soil.
It is productive on fertilized sandy soils, but grows profusely on
the Everglades peat soils where it has reached the status of a
weed on vegetable farms. It produces a high yield of herbage
on drouthy sand soils.
There are many strains of Napier grass which differ in dis-
ease resistance, yield, leafiness and other characteristics. This
Experiments with Napier Grass 5
grass produces seed readily in South Florida. Space planting
tests show much variability among seedling plants. Any de-
sirable characteristics or phenotypes which occur in seedling
plants need not be fixed, since this grass usually is propagated
by foot and stem cuttings.
In the breeding program the primary objectives have been
to produce high-yielding leafy strains that are eyespot-resistant.
Several strains which proved to be greatly superior to mass
selected types were tested in an experiment under different
management and fertilizer practices during the period 1942 to
1944. Selected strains of Napier grass varied in height and
leafiness, as shown in Figure 2. The average green yields
of three varieties for all fertilizer treatments show that No. 4
was the most productive strain (Table 1). Because of its leafi-
ness and productivity, this strain is recommended over others
and has been distributed to farmers.
TABLE 1.-RELATIVE GREEN WEIGHT YIELD PER ACRE OF THREE STRAINS OF
Strain Fresh Green Forage per Acre
S 1942 1943 1 1944 1 Average
pounds pounds pounds pounds
4 ...........-..... 14,883 10,729 18,446 14,686
160 ................. 11,979 8,281 13,824 11. f1
167 .................. 11,689 7,694 14,581 11,321
Least Significant Difference:
P- .05 .......... 1,542 1,315 2,099
P- .01 ........... 2,033 1,738 2,773 ....
The percentage of leaves of the three strains did not differ significantly.
PROPAGATION AND PLANTING
Although Napier grass produces seed in South Florida, gen-
erally it is propagated readily by planting rootstalks (rhizomes)
or stem cuttings. Seedling plants are difficult to grow and they
usually produce undesirable plant types.
Stem and root cuttings are planted one to two feet apart in
rows spaced five to eight feet. Root cuttings are covered com-
pletely with two to five inches of soil. Three-joint stem cut-
tings are stuck into the soil at about a 45 angle at a depth to
leave the uppermost node exposed.
6 Florida Agricultural Experiment Stations
The planting date is important. Root pieces may be planted
during February and March, while stem cuttings or rootstalks
may be used during June or July. Stem cuttings have been
used successfully for early spring planting by cutting the stems
in late fall before frost and burying them deeply enough in
damp soil to avoid drying or freezing. Early spring plantings
are preferred, because of less weed competition and higher
yields. Although no tests have been made to study seedbed
preparation, it is known that a thoroughly prepared seedbed
gives best results.
It is necessary to apply fertilizer liberally as few, if any,
soils in Florida possess a sufficiently high reserve of fertility
to support good growth of Napier grass. Complete fertilizers,
5-7-5, 6-6-66 or similar formulas, applied at rates of 400 to 600
pounds per acre in the row before planting, have been found to
stimulate growth and shorten the period of establishment. Best
growth response was obtained from nitrogen fertilizers. Growth
was improved on the more acid soils when lime was applied in
addition to the complete fertilizers.
Napier grass does not shade the ground or spread much dur-
ing the first year. Therefore it is necessary to cultivate at least
twice during the first season to control weeds and to augment
release of nitrogen from decaying plant material. After the
first year the necessity of cultivation will depend on weediness
These numbers indicate amounts of nitrogen, phosphoric acid and
potash, respectively, in the fertilizer formulas.
Fig. 2.-Three strains of Napier grass (Nos. 4, 160 and 167) were selected
to investigate for forage purposes, based on growth and leafiness.
Experiments with Napier Grass 7
of the land and growth of the grass. One disking annually in
early spring with a heavy disk harrow gave excellent results
with pastures grazed by beef and dairy cattle.
Napier grass is a tall, erect plant. When grazed heavily and
continuously, the animals remove the leaves. With rather com-
plete leaf removal, organic nutrient reserves (starches, sugars
and other compounds) in the roots and underground stems
become depleted and new growth is produced slowly or the
plants die. The stand of Napier grass can be maintained well,
provided there is a short grazing period (5 to 10 days) followed
by a long re-growth period (20 to 30 days). To maintain this
grass, it must be grazed rotationally and fertilized.
The following experiment illustrates the relationship between
yield and management. Seven management treatments were
compared, as shown in Table 2. Each yield is given as an
average for 24 plots (three strains with each of eight fertilizers).
The grasses were not cut for yield determination during 1941,
to promote establishment of satisfactory stands and store a good
supply of organic nutrient reserves in rootstalks. The total
herbage yields in green weights are given for 1942 and 1943 for
all management treatments. In 1944 all plots were cut two times
to measure residual effects of the various management treat-
ments on yields.
The total grass yields when stripped to simulate grazing at
three feet and five feet were 9,258 pounds and 8,103 pounds per
acre, as shown by the average yields for 1942 and 1943. When
the grass was cut back to five inches tall whenever a height of
three or five feet was reached the yields were 12,065 and 12,847
pounds, respectively. The average green yield was 16,605 pounds
per acre for the plots that were cut twice per season. These
are shown in Table 2.
Quality of herbage is more important than total yield. Herb-
age quality depends upon leafiness. Leafiness was associated
with management treatment, as shown by an average of 88 to
93 percent of leaves for plants stripped to simulate grazing and
50 to 53 percent of leaves when cut at heights of three to five
TABLE 2.-GREEN WEIGHT YIELDS PER ACRE OF FRESH NAPIER GRASS AS AFFECTED BY SEVEN MANAGEMENT TREATMENTS*
Propor- i Total For-
Management Treatments on Separate Plots ............. YearI tion of Average Yield age Yields
_1942 1943 Leaves Forage Leaves 1944"* "
pounds pounds percent pounds pounds pounds .
Leaves stripped when grass 3 ft. high .................... 10,309 8,206 93 9,258 8,610 19,983
Leaves stripped when grass 5 ft. high ---.........--... 9,365 6,841 88 8,103 7,131 19,704
Cut to 5 inches when 3 ft. high .................-.................. 13,213 10,917 50 12,065 6,032 10,839
Cut to 5 inches when 5 ft. high ...............-----............- 14,883 10,810 53 12,847 6,809 11,755
Cut to 20 inches when 3 ft. high .............................. 11,326 9,676 67 10,501 7,036 17,548
Cut to 20 inches when 5 ft. high ..-....--.. --.... ............ 12,269 10,160 57 11,215 6,393 17,345
Cut two time during year .-----------..-................ 18,580 14,623 43 16,605 7,140 12,182
Least Significant Difference P .05.......... ... ........ 2,323 2,291 ........ ....... 3,146 2
P .01......................... 3,122 3,028 .......... 4,174
*Each yield was computed as the average from 24 plots (8 fertilizers with 3 strains).
"** D'uring 1944 all plots were harvested two times to measure residual effects of the management treatments.
Experiments with Napier Grass 9
feet. An average of only 43 percent of leaves was obtained when
cut twice annually. Cutting this grass at infrequent intervals
resulted in the production of high yields of very coarse, stemmy
herbage. Stripping grass to simulate grazing reduced yields,
but the herbage was very leafy. Total leaf production among
these management treatments was similar.
Fig. 3.-The stand of Napier grass was maintained well throughout six
years of rotational grazing. This picture shows the stand in the seventh
Yields taken during 1944 to measure residual effects from
1942 and 1943 cutting treatments show that grass plots stripped
to simulate grazing or cut to 20 inches from the ground pro-
duced higher yields than grass that was cut back to the ground
twice annually or cut after a height of three to five feet was
reached. This indicates that Napier grass is maintained in a
productive condition when the stems are not cut back completely
or defoliated periodically as in grazing. High yields may be
associated with high carbohydrate reserves and possibly lateral
spreading under grazing management conditions. It has been
10 Florida Agricultural Experiment Stations
observed that new leaves develop rapidly from axial buds at
the nodes along the defoliated stems.
The longevity of Napier grass under rotational grazing has
been demonstrated in grazing experiments conducted with dairy
cows. In these trials five lots of Napier grass were grazed ro-
tationally. Grazing was initiated when the grass was three to
five feet in height. The number of cows was adjusted so that
about 90 percent of the leafage was consumed in five to seven
days, after which the cows were moved to another lot, in suc-
cession. This allowed 20 to 28 days for recovery after each
grazing period. Light grazing was practiced during the late
season to prevent excessive reduction of leaf area, and thus
allow a build-up in root reserves. Under this grazing practice
an excellent stand of grass was maintained and the density
of stands increased. The stand of grass after seven years of
grazing is shown in Figure 3.
EFFECT OF FERTILIZATION ON YIELDS
Tests designed to study fertilizer rates and ratios, time of
application, and source of nitrogen on growth of Napier grass
have been made on an Arredondo fine sand soil, as shown in
Tables 3, 4 and 5. The average yield during 1941-1944 was
1,695 pounds of dry matter without fertilizer, as compared with
3,081 pounds when 32 pounds of nitrogen, 64 pounds of phos-
phoric acid (P205) and 32 pounds of potash (KO0) were applied
annually. Double and four times the nitrogen applications in-
creased the yields to 4,226 and 8,868 pounds of dry matter per
Because Napier grass is known to give significant yield in-
creases from nitrogen fertilization, tests were carried on to
measure growth responses from single annual applications com-
pared with several split applications. A total of 64 pounds of
nitrogen was applied in March in one application in one series
of plots, and split into two applications of 32 pounds each in
March and June in another series of plots (Table 3). In two of
the four years yields were significantly higher from the split
application. The four-year average yield was higher from split
nitrogen applications. An average of 4,226 pounds of herbage
was obtained when 64 pounds of nitrogen per acre were applied
in March, as compared with 6,079 pounds of herbage per acre
when 32 pounds of nitrogen were applied in March and June.
In another series of plots nitrogen was applied in March at the
TABLE 3.-EFFECT OF RATE AND TIME OF NITROGEN APPLICATIONS ON DRY MATTER YIELDS OF NAPIER GRASS GROWN ON
ARREDONDO FINE SAND SOILS.
Total Fertilizer Applied* Time of __Dry Matter per Acre _
Nitrogen Acid_ Potash Application** 1941 1942 1943 1944 Average
pounds pounds pounds [ pounds Ipounds pounds pounds pounds .
0 0 0 None ........ 1,458 1,483 2,145 1,695
32 64 32 March 3,217 2,400 2,938 3,769 3,081
64 64 32 March 4,119 3,496 5,127 4,162 4,226
128 64 32 March 8,422 8,800 10,875 7,375 8,868
64 64 32 32 pounds in
March, June 6,381 6,600 5,241 6,164 6,079
128 64 32 32 pounds in
March, June, 6,199 5,943 6,610 5,814 6,142
July, August** __
Least Significant Difference: ....................... .05 2,630 1,621 2,016 1,073 ..-
P-.01 3,509 2,183 2,715 1,446
Thirty-two pounds of nitrogen is equivalent to 200 pounds of nitrate of soda, which was the form used in the test.
Thirty-two pounds of phosphoric acid (P-Os) is equivalent to 200 pounds of superphosphate.
Thirty-two pounds of potash (K2O) is equivalent to 64 pounds of 50 percent muriate of potash.
**The phosphate and potash were applied in March each year, when the nitrogen was used in split applications as indicated.
12 Florida Agricultural Experiment Stations
rate of 128 pounds per acre and in four applications of 32 pounds
of nitrogen each in March, June, July and August (Table 3).
The yields were consistently higher for the plots which received
all the nitrogen in one application. Average yields for the four-
year period were 8,868 pounds per acre when 128 pounds of
nitrogen were applied in March, as compared with 6,142 pounds
when the nitrogen was applied in four applications of 32 pounds
each. With split nitrogen applications, that applied during July
and August apparently was not utilized efficiently.
Yield tests carried on with nitrogen fertilizers from different
sources (nitrate of soda, sulfate of ammonia, urea and calcium
cyanamid) gave variable responses during the individual years
of testing. The differences in average yields for the four years
were not significant (Table 4). These variable yield responses
are attributed to differences in stand and weather conditions.
TABLE 4.-EFFECT OF NITROGEN FROM DIFFERENT SOURCES ON YIELD OF
NAPIER GRAss GROWN ON AN ARREDONDO FINE SAND SOIL.:
Source of Nitrogen _Dry Matter per Acre
S1941 1942 1943 1944 Average
pounds pounds pounds pounds pounds
Nitrate of soda ............ 3,217 2,400 2,938 6,164 3,680
Sulfate of ammonia .... 3,767 4,254 3.649 5,292 4,241
Uramon ..........-- ............ 4,634 3,849 3,903 6,605 4,748
Calcium cyanamid ...... 5,676 2,738 3,324 5,150 4,219
P- .05 .........-- .. 2,630 1,621 2,016 1,073 ...
P- .01 ................ 3,509 2,183 2,715 1,446
All plots received 64 pounds of phosphoric acid (POs) and 32 pounds of potash
(KO2) annually, except in 1944 when one-half the rate of phosphoric acid was used.
Thirty-two pounds of nitrogen was applied annually in March, except in 1944 when
an additional 32 pounds was applied in June.
In the Napier grass grazing test for dairy cows, a complete
fertilizer supplying 30 pounds of nitrogen per acre was applied
in March and additional nitrogen sidedressings at the rate of
30 pounds per acre were made during the growing season
(Table 5). The sidedressing was applied in one application in
May with two of the grazing lots and in four applications of
7.5 pounds each in May, June, July and August in the remaining
Experiments with Napier Grass 13
Yields of herbage were somewhat higher for the plots which
received all the nitrogen in early season. These data also sug-
gest poor nitrogen utilization from late applications. This
would be expected, since Napier grass reaches its peak in pro-
duction during June to August.
TABLE 5.-DRY MATTER YIELDS PER ACRE OF NAPIER GRASS LEAVES AS
INFLUENCED BY NITROGEN APPLICATIONS. THESE YIELDS WERE OB-
TAINED FROM QUADRATS IN DAIRY PASTURES.
Year Lots 1 and 3 Lot 5* I Lots 2 and 4
pounds !pounds pounds
400 pounds of 5-7-5 complete fertilizer in Spring;
and 7.5 pounds of nitrogen after first four grazings.
1939 .....................-- .....--..... 3,850 2,825 3,367
1940 ...............----- -...--..- .... .... : 2,656 2,193 2,636
500 pounds of 6-6-6 complete fertilizer in Spring:
30 pounds of
7.5 pounds of nitrogen after Nitrogen in
first four grazings. May
1941"* ............ ....-....................... 1,751 1,457 1,952
1942 .....----- -----------.............................. .. 2,124 1,848 2,317
1943 ...............-............. .-- .... 2,021 1,995 2,375
1944 ...--..-........ ....------------ .... --2,315 ........ 2,415
Average 1941-1944 .................. 2,053 ........ 2,265
Lot 5 was not considered in these yield comparisons because of a soil variability.
** Late frost and a dry Spring delayed the initial grazing.
QUALITY OF HERBAGE
Grazing management or cutting stage, through its effect on
stemminess or herbage, definitely affects herbage quality. Plant
height, dry matter content, leafiness and protein content of
stems, leaves and ungrazed residue of samples taken from the
fields used for beef cattle grazing tests during 1938 are shown
in Table 6. The dry matter content of Napier grass leaves,
sampled before grazing, ranged from 13.7 to 22.6 percent. The
proportion of leaves varied from 25 to 45 percent under actual
grazing (Table 6). The stemminess tended to increase slightly
as the season advanced. The crude protein content of the leaf
blades at the time grazing started varied from 9.2 to 14.4 per-
cent, as compared with 3.9 to 6.5 percent in the stems. The un-
TABLE 6.-TIME OF YEAR, HEIGHT, LEAFINESS AND COMPOSITION OF NAPIER GRASS UNDER GRAZING, AND AS HARVESTED
S Napier Grass Before Grazing Ungrazed Residues
Grazing Lots Dates*
Tour Plant Dry Leaves Crude Protein Stem Dry Crude
Height Matter i Leaves Stems Height Matter Protein
Inches percent percent percent percent inches percent percent
1 1, 2 May 10, 16 38 16.9 45 10.4 5.1 16 14.5 5.0 t
3, 4 May 21, 27 38 19.1 33 9.2 5.0 14 17.5 5.3
II 1, 2 June, 13, 24 42 10.2 35 11.8 6.2 19. 10.4 8.5
3, 4 July 1, 9 51 13.2 33 11.7 5.0 20 13.8 7.3
III 1 July 20 52 18.4 30 11.4 4.5 19 16.0 5.3
2 July 26 48 13.7 30 11.7 5.2 17 12.5 5.3
3 August 1 54 14.8 30 10.8 3.9 19 16.0 4.7
4 August 8 47 17.8 34 10.0 4.1 20 16.6 4.7
IV 2, 2 August 15, 22 40 17.2 35 11.6 4.0 19 15.3 4.6
3, 4 Aug. 29, Sept. 3 42 19.9 28 10.6 4.9 23 19.8 5.6
V 1, 2 Sept. 14, 21 37 16.2 33 12.2 5.4 20 19.8 4.2
3, 4 Sept. 27, Oct. 4 36 17.6 25 14.4 6.2 19 18.9 5.8
VI 1, 2 Oct. 15, 18 34 22.6 34 11.6 4.8 22 23.1 5.4
3, 4 Oct. 25, 26 28 22.6 30 13.2 6.5 20 23.2 6.2
Average ...............-................... 41.9 11.5 5.0 19.1 5.6
Napier Grass Cut Twice As For Silage
1, 2 August 7 86 I30.2 23 9.5 2.7 .-
3, 4 August 5 87 26.1 25 8.4 2.4
1, 2 October 25 76 24.6 30 12.3 3.5
3, 4 October 25 74 28.4 30 13.7 3.6 .
Grass samples were taken on the days when the grass had been grazed down, and cattle were rotated to the next lot.
Experiments with Napier Grass 15
grazed residue composed largely of stems, ranged from 4.2 to
7.3 percent of crude protein.
When the grass was cut twice annually, as is conventional for
silage, the forage was very stemmy, with only 23 to 30 percent
of leaves. The crude protein in stems varied from 2.4 to 3.6
percent and in the leaves from 8.0 to 13.7 percent. The man-
agement test discussed earlier showed that frequent cutting
resulted in increased leafiness. However, a higher proportion of
leaves was obtained under grazing conditions than from cutting
SUMMARY OF AGRONOMIC PHASES
Eyespot-resistant strains of Napier grass were developed from
selected seedling plants.
Better stands were established from spring planting than from
When cut twice yearly, high yields of grass were obtained
that were stemmy. Yields of leafy herbage were similar for
seven stripping and cutting treatments. The stripped leaves
were higher in crude protein and lower in fiber than the stem
portion of Napier grass.
Higher rates of nitrogen applications resulted in increased
yields of forage under uniform cutting treatments. Four sources
of nitrogen produced similar amounts of forage. Less Napier
grass was produced after applying 64 pounds of nitrogen in
March than from applications of 32 pounds of nitrogen in March
and again in June.
GRAZING TRIALS WITH BEEF CATTLE
GRASS WITH HIGH NITROGEN FERTILIZATION
A 15-acre area on Leon, Plummer and Arredondo sand was
cleared, plowed, fertilized and planted to Napier grass in March
1937. Rhizomes of mass selected eyespot-resistant strains of
Napier grass were planted in seven-foot rows which received
400 pounds of a 5-7-5 fertilizer at time of planting. Thereafter
complete fertilizer was applied annually and two to five applica-
tions of nitrogen at the rate of 12 to 16 pounds per acre were
made as sidedressings.
In 1937 the area was cultivated twice to control weeds. In
following years the grass was disked with a double disk harrow
while dormant in February or March and cultivated once be-
16 Florida Agricultural Experiment Stations
tween the rows in 1938 and 1939. The growth and stand of
grass was retarded in some fields by variation in soil fertility
and excessive moisture during certain times of the year.
In June 1937 the grass was harvested for silage, after which
the area was fenced into five lots of three acres each to practice
rotational grazing. Grazing was begun when the grass reached
a height of three to four feet. The number of yearling steers
was adjusted so that they would consume most of the blades
in five to eight days. The steers were weighed individually each
time they moved to a different lot. Water and mineral supple-
ments were available at all times.
Four movable cages 10 feet square were placed in each lot.
These prevented the grass from being grazed and made it pos-
sible to obtain samples for yield measurements and chemical
analysis. Grass samples, hand stripped to simulate grazing,
were obtained immediately after the animals were moved to
the next lot.
Best results were obtained in 1938 when steers made an aver-
age daily gain of 1.73 pounds and produced 430 pounds per
acre (see Fig. 4). The lowest were in 1940 when the cattle
gains averaged 290 pounds per acre. The low production in 1940
was caused largely by a smaller total application of nitrate of
soda and lack of cultivation with subsequent weed competition.
Improper drainage caused partial flooding of some fields in 1940,
Fig. 4.-These steers made satisfactory gains in weight and condition
on Napier grass grazed rotationally.
Experiments with Napier Grass 17
and cold injury to rhizomes reduced number of shoots, both of
which reduced the yield of grass.
The average grazing days and gains from five lots totaling 15
acres of heavily fertilized Napier grass grazed rotationally
during the 1938, 1939 and 1940 seasons, are given in Table 7.
An acre of Napier grass provided 235 steer-days of grazing in a
season, and cattle made 369 pounds of gain, which gave an aver-
age daily gain of 1.57 pounds.
TABLE 7.-GRAZING DAYS, GAINS PER ACRE AND AVERAGE DAILY GAIN OF
CATTLE ON HEAVILY AND LIGHTLY FERTILIZED NAPIER GRASS WHEN
Heavily Fertilized Grass* Lightly Fertilized Grass**
Grazing Average Average Grazing Average Average
Year Days Gain Daily Days Gain Daily
per Acre per Acre Gain per Acre per Acre Gain
pounds pounds pounds pounds
1938 ........-.... 248 430 1.73 |
1939 ..-..-...-... 227 386 1.70 170 263 1.55
1940 .............. 229 290 1.27 152 193 1.27
Average .... 235 369 1.57 161 228 1.42
Applied annually in March,-400 pounds of 5-7-5 fertilizer. Additional nitrate of soda
applied,-300 pounds in 1938, 375 pounds in 1939 and 210 pounds in 1940.
** Applied annually in March,-400 pounds 5-7-5 fertilizer.
The stand of grass was not as dense in 1940 as in 1938. The
retardation in stand was affected by differences in palatability,
which resulted in some plants being oversized. Since planting
material was taken from mass selections of eyespot-resistant
Napier grass, there were numerous plant variations in such char-
acteristics as leafiness, pubescence, height and thickness of stems,
and productivity. Observations showed that test animals had
quite definite grazing preferences, resulting in overgrazing and
reduction in root reserves and growth with many plants (Figure
5). This indicates the desirability of using plants of uniform
strains when conducting grazing tests with tall growing plants.
CHEMICAL COMPOSITION OF HEAVILY FERTILIZED
In 1938 and 1939 samples from the heavily fertilized Napier
grass were taken at regular intervals for chemical analysis.
Movable cages 10 feet square protected the Napier grass for
TABLE 8.-AVERAGE CHEMICAL COMPOSITION OF HEAVILY FERTILIZED NAPIER GRASS GRAZED IN 1938 AND 1939 AND THE
UNGRAZED RESIDUE IN 1939.
On a Dry Basis
Year Dry Crude Crude N-Free Crude C I
Matter Protein Fiber Extract Fat Ash Ca. P.
Percent Percent j Percent I Percent j Percent Percent Percent TPercent "
Napier Grass Blades Grazed by Steers
1938 ......... 18.9 12.1 32.4 46.2 2.8 6.5 0.47 0.33
1939 ... 20.6 12.5 32.6 45.4 2.9 6.6 0.48 0.33
Average ...... 19.8 12.3 32.5 45.8 2.9 6.6 0.48 0.33
Ungrazed Residue, Primarily Stems and Sheaths
1939 .............. 13.8 5.5 32.2 48.8 1.6 5.9 0.25 0.29
i ~~~~~ ~. I.2 _.2 _ _ 1 _
Experiments with Napier Grass 19
sampling. Samples of grass were taken at the time the steers
were moved to the next lot, after which each cage was placed
in a different part of the field. In Table 8 the average chemical
composition of Napier grass grazed by the steers in 1938 and
1939 and of the ungrazed residue collected in 1939 are given.
The Napier grass eaten by the steers, primarily leaf blades,
averaged 12.3 percent crude protein on a moisture-free basis,
while the ungrazed residue (mostly stems and sheaths) contained
5.5 percent crude protein. The ungrazed residue was lower in
dry matter, fat and ash and higher in fiber than that consumed
by the steers.
Kidder (6) showed that Napier grass leaves on a moisture-
free basis contained 8.4 percent of digestible protein and 65.4
percent total digestible nutrients. It was estimated that in
1938 steers grazing heavily fertilized Napier grass consumed
about 107 pounds of green forage daily.
Since Napier grass grown in 1938 contained an average of
18.9 percent dry matter (Table 8), the steers consumed about
20.2 pounds dry matter daily which contained 1.7 pounds of
digestible crude protein and 13.2 pounds total digestible nutrients.
The average daily gain per steer in 1938 was 1.73 pounds. Thus
the steers consumed 0..98 pounds digestible protein and 7.6 pounds
total digestible nutrients per pound of gain. Shealy and asso-
ciates (13) showed in three trials that steers fattened in dry
lot on a ration of cottonseed meal, ground snapped corn and
Fig. 5.-Cows grazed the Napier grass plant at the left but had not touched
the tall plant at the right.
*.~iiL>Pc *; 7 I
20 Florida Agricultural Experiment Stations
Napier grass silage consumed an average of 1.1 pounds diges-
tible protein and 6.3 pounds total digestible nutrients per pound
GRAZING LIGHTLY FERTILIZED NAPIER GRASS
In 1938 an additional 71/-acre area largely on Arredondo sand
was planted to Napier grass to measure its grazing value when
fertilized at a light rate. During the planting year complete
fertilizer and nitrate of soda were used to insure a good stand of
strong plants. Because of the favorable season and fertilizer
used, this area was ready for grazing by June 29. The area was
divided into five lots of 11/2 acres each to permit rotational
During 1938 in a 117-day grazing period, two-year-old steers
were fed an average of 2.27 pounds of 41 percent cottonseed
meal daily to study the effect of supplemental feed on gains.
The number of steers ranged from 10 to 15, according to the
amount of forage available. The steers made an average daily
gain of 1.72 pounds and 329 pounds gain per acre. Each acre
of Napier grass plus the cottonseed meal provided feed for 191
steer-days. Average daily gain is similar to that made by steers
on heavily fertilized grass, Table 8, and the total gain per acre
is 101 pounds lower for a 131-day shorter period. Results of
this preliminary trial showed that supplemental feeding in-
creased carrying capacity of the pasture.
In 1939 and 1940 an application of 5-7-5 fertilizer at the rate
of 400 pounds per acre was made annually in the spring without
additional sidedressing of nitrogen during the grazing season.
Yearling steers were used as grazing animals in 1939 and yearling
heifers in 1940.
Two-year results show that yearling cattle made an average
daily gain of 1.42 pounds and that 155 animal-days of grazing
were furnished per acre, resulting in a total of 219 pounds gain
in body weight. There was a gradual decrease in amount of
feed available as the grazing season progressed. During the
first two rotations from 8 to 10 animals were required to con-
sume the grass on 7.5 acres, while in the fifth rotation from
three to five animals were sufficient.
A comparison of the animal gains per acre on the heavily
and lightly fertilized Napier grass shows that the amount of
grass is dependent largely upon the amount of fertilizer applied,
Experiments with Napier Grass 21
as presented in Table 7. Figure 6 shows that the rate of stock-
ing on the heavily fertilized grass was one animal per acre in
May and September, while from June 1 to August 31, the height
of the growing season, two acres supported more than three ani-
In these two trials Napier grass furnished good grazing from
May until mid-October, or 165 to 176 days annually. Individual
weights obtained each time the animals progressed in the rotation
showed average daily gains in excess of 1 pound per animal during
the entire grazing season. The grass was palatable and nutri-
tious to the cattle under the rotational system of grazing.
MAY I JUN.I JULY I AUG. 1 SEP. I OCT.! NOV. I
Fig. 6.-Changes in grazing capacity (steers per acre) of heavily fertilized
Napier grass during the 1938, 1939 and 1940 seasons.
Considerable grazing was available from both heavily and
lightly fertilized Napier grass after the experimental animals
were removed in mid-October, but the forage was stemmy and
coarse. The Napier was left ungrazed until late November
to build up a reserve of nutrients in the roots. The forage which
accumulated from October 15 to late November was grazed later
by the breeding herd. Mature cows maintained their body
weight for several weeks on the accumulated growth of Napier
22 Florida Agricultural Experiment Stations
SUMMARY OF GRAZING NAPIER GRASS WITH BEEF CATTLE
Results of the grazing trials show that application of nitrate
of soda during the grazing season increased grazing capacity
from 161 to 235 cattle-days per acre and the gains from 228
to 369 pounds. The average daily gain was 1.42 pounds on the
lightly fertilized grass, compared to 1.57 pounds on the heavily
fertilized grass. Returns obtained from these two methods
of fertilizing Napier grass will depend upon cost of the fertilizer
and the improvement in grade of the cattle making the highest
NAPIER GRASS FOR DAIRY COWS
An area of 8 acres, divided into 5 lots, was planted to mixed
strains of Napier grass in March 1938 for evaluation of this
crop with dairy cattle. The method of establishment was the
same as for the beef cattle phase. After the first year the
area was disked once each spring. This controlled weeds satis-
factorily and seemed to stimulate early growth.
During 1938 through 1940 an application of 5-7-5 fertilizer at
the rate of 400 pounds per acre was made in March. Four appli-
cations of nitrate of soda were made at the rate of 12 pounds
of nitrogen per acre. Beginning with 1941 the fertilizer prac-
tices were changed so as to compare early-season nitrogen ap-
plication with several split applications. A 6-6-6 complete ferti-
lizer was applied at the rate of 500 pounds in March and an
additional 30 pounds of nitrogen was applied in May on two
lots. The remaining three lots (1, 3 and 5) each received 7.5
pounds of nitrogen applied after each of the first four grazing
tours. Yields for these treatments are given in Table 5.
When grazing was delayed until the grass in lots reached three
to four feet in height, the lots grazed during the last part of a ro-
tation became tall and coarse. To avoid this, grazing was
initiated somewhat early and the cows were moved from lot to
lot, allowing about three or four days in each during the first
Three movable cages were placed in each lot to obtain quadrat
yields of grass and samples for analysis. The grass in the caged
quadrats was stripped by hand twice while each lot was being
grazed. The stripped leaves were to simulate the amounts
PLAN OF WORK WITH DAIRY COWS
The area was divided into five 1.6-acre lots to provide for
rotational grazing-the plan being to graze each lot approxi-
Experiments with Napier Grass 23
mately one week and allow four weeks for the grass to grow
before being grazed again. The time interval for rotation was
estimated by observation of the growth of the plant and by be-
havior under grazing with beef cattle in the preceding year.
Gates were placed from each lot to a lane where water, mineral
supplement and shade were accessible for the cows at all times.
Only one gate was opened at a time into the lot currently being
It has been pointed out in the agronomic phase of this study
that Napier grass has an upright growth habit. Re-growth
following grazing comes from axial buds along the ungrazed
stems or canes. Too close grazing reduces the stems and the
number of buds, so that leaf production is impaired. On the
other hand, insufficient grazing allows the stems to grow tall
(8 to 16 feet) and produce little axial growth or desirable leafy
material within reach of the cows.
Grazing was begun in the spring in the Gainesville area7
when the grass was three to four feet tall, and the number of
grazing animals was adjusted so as to leave the grazed stems
at three to four feet in height when the cows were moved to the
next lot. This practice appeared to allow plenty of buds for re-
growth and yet not let the stems grow too tall (see Fig. 7).
Early in the grazing season when herbage was limited from
8 to 10 cows were used. Later, during the period of more lux-
uriant growth, six to eight more cows were added to utilize
S The top growth of Napier grass is killed to the ground when the
temperature goes lower than freezing.
Fig. 7.-Napier grass before and after a grazing tour by dairy cows.
24 Florida Agricultural Experiment Stations
the forage produced. Still later in the season, the number of
animals was reduced to adjust for the declining growth rate of
the grass in autumn. Late in autumn all cows were removed
in an attempt to permit sufficient regrowth to generate adequate
nutrient root reserves for over-wintering and to stimulate rapid
early spring growth the following year.
Jersey cows from the Experiment Station dairy herd were
used throughout the study. Animals selected for this work
were past the peak of production in the current lactation and
were mature in most instances. Younger cows had to be in-
cluded at times when too few mature animals were available at
the proper stage of lactation. It was necessary to use even dry
cows occasionally in 1943 to utilize fully the growth of herbage.
The cows were weighed on three consecutive days at the be-
ginning and end of each trial and once weekly during the grazing
season. All cows were milked twice daily in the barn and com-
plete milk production records were kept. Individual composite
samples of one day's milk were obtained near the middle of each
month for butterfat determinations. The cows were on pasture
continuously except for about an hour at each milking time.
A concentrate mixture was fed in the barn at milking time at
the rate of about 1 pound of concentrates to 3 pounds of milk
produced-the offering being adjusted at weekly intervals, when
necessary, to the decline in production due to advancing lacta-
tion. Concentrates were fed in even pounds for convenience of
attendants at the barn. The concentrates were a mixture of corn
feed meal, wheat bran, dried brewers grains, dried citrus pulp
and cottonseed meal. It was calculated to contain 17 percent of
total crude protein, 13.5 percent of digestible protein and 75.0
percent of total digestible nutrients based upon average com-
positions as given by Morrison (9). Due to wartime changes in
availability of feed, several substitutions of ingredients were
necessary in the 1942 and 1943 seasons so that the concentrate
mixture was calculated to contain 16 percent of total crude
protein and 70.8 percent of total digestible nutrients during
The investigation began with a preliminary year while the
stand of Napier grass was becoming established. Evalution of
the grazing value in terms of cow-maintenance and milk pro-
duced per acre of crop was continued over the following five-
year period. This duration took into account possibility of
seasonal differences (rainfall and temperature) and age of the
Experiments with Napier Grass 25
plants. Also a larger number of records tended to offset varia-
tions expected between individual cows.
METHOD OF CALCULATION
The inverse calculation method was used to estimate the
amount of total digestible nutrients which the cows obtained
from Napier grass. For this purpose the nutrient requirements
of each cow were computed by applying the Morrison standard
with regard to body weight, milk yield and butterfat percen-
tage. The running average weight of each cow obtained from
the weekly weighing was used to calculate the maintenance
requirements for total digestible nutrients during the week. Re-
quirements for milk production were calculated weekly from
the amount of milk produced, using the butterfat test for the
current month. The difference between the calculated nutrient
requirement and the nutrients supplied by supplementary con-
centrates fed during milking time were presumed to have been
obtained from the pasture.
When it was necessary to use dry cows to help utilize the
forage, the requirements for maintenance, together with the
factors for changes in weights, were calculated according to the
method of Knott, Hodgson and Ellington (7). These are the
methods of computation recommended in the "Preliminary Re-
port on Pasture Investigation Technique" by a joint committee
of American Society of Agronomy, American Dairy Science As-
sociation and American Society of Animal Production (5).
Preliminary Season-1938.-Crowns of Napier grass of mixed
unselected strains were planted in March. By June, sufficient
growth had been attained to begin grazing. Since little was
known about the behavior of Napier grass under grazing, and
since the first-year stand was expected to produce somewhat less
herbage while becoming established, it was felt that this season
should be regarded as preliminary. However, complete records
were kept so as to analyze the plan and to make any adjustments
deemed advisable before starting the planned five-year trial.
Ten cows started the trial and later four more were added. A
total of 1,218 cow-days of grazing was obtained during 107
calendar days on eight acres during the preliminary season.
It was calculated that 1,168 pounds of total digestible nutrients
per acre were obtained and that 53.6 percent of the nutrients
2d Florida Agricultural Experiment Stations
required for maintenance and milk production were provided by
It was estimated that a cow consumed 70 or more pounds of
Napier grass daily per 1,000 pounds live weight. This amount
provided neither sufficient protein nor enough total digestible
nutrients to maintain body weight and optimum milk produc-
tion. Two cows (343 UF and 401 UF) on Napier grass alone dur-
ing the preliminary season dropped in both milk production and
body weight until about 16 to 18 pounds of milk were being pro-
duced daily. Thereafter, body weight no longer declined, al-
though milk production continued to decrease. When these two
cows were returned to the regular herd, where they received
supplemental concentrates, both cows increased sharply in milk
yields, as shown by the curves after point "X" in Figure 8.
Based on these observations, mixed concentrates were offered in
later trials, enabling both milk production and body weights to
be maintained reasonably. Jersey cows yielding a high-solids
milk were used throughout the trials.
28 Daily milk yield on Napier grass
Average yield in 3 previous lactations------
Relurn to herd feeding x-
12 \ ,401
Days in Milk
O 30 60 90 107
Fig. 8.-Relation of milk production of cows 343 UF and 401 UF while
grazing Napier grass without supplemental concentrates, as compared
with conventional concentrate-and-roughage feeding.
The decline in milk production and loss in body weight were
to be expected, since the protein content of Napier grass was
Experiments with Napier Grass 27
insufficient to provide for the cows' needs. Analyses showed the
crude protein of fresh Napier grass leaves for the season to be
2.75 percent. Digestion trials at the Florida station by Kidder
(6) showed later that fresh Napier grass leaves provided 0.8
percent of digestible crude protein and 13.7 to 14.0 percent
of total digestible nutrients. Harrison (2) found 0.8 to 1.2
percent of digestible crude protein and 8.7 to 11.3 percent of
total digestible nutrients in trials conducted in Trinidad, British
West Indies. An investigation in Hawaii (15) showed the dry
matter of Napier grass to contain from 7.9 to 5.6 percent of
total crude protein at the sixth to fourteenth weeks of growth.
1939 Season.-The grazing season during 1939 started April
17 and continued until November 6, 205 calendar days, for a total
of 2,062 cow-days. Six cows were used at the beginning and
the number was increased to 15 at the period of most luxuriant
growth. In August the number was reduced to 10 and in Sep-
tember it was further reduced to six cows until the end of the
season. A milk yield of 64,218 pounds of 4.0 fat-corrected milk
was produced, or an average of 8,027 pounds per acre. It was
computed that grazing supplied 18,523 pounds of total digestible
nutrients, or 2,315 pounds per acre for the season. Slightly
over 54 percent of the requirements for maintenance and milk
production was calculated as coming from the pasture.
1940 Season.-A grazing season of 161 calendar days from
April 29th to October 6 provided 1,647 cow-days of grazing for
16 different cows with a total production of 44,232 pounds of 4.0
of fat-corrected milk. It was calculated that 14,364 pounds of
total digestible nutrients were obtained from the Napier grass
off the eight acres for the 1940 season.
1941 Season.-The 1941 season did not start until May 19,
due to late frosts followed by dry weather in the spring. Six-
teen different cows were used over a 166-calendar-day period
ending October 27 and totaling 1,529 cow-days. During the
season the milk yield was 43,173 pounds of 4.0 percent fat-
corrected milk. A calculated yield of 13,566 pounds of total
digestible nutrients was credited to the eight acres of Napier
grass for the 1941 season.
1942 Season.-The Napier grass was ready for grazing May
1 when seven cows were started. Later six other cows were
added, making a total of 13 cows on the trial during the season
which ended October 26 after 174 calendar days. The Napier
grass provided 1,600 cow-days of grazing for the period. A
28 Florida Agricultural Experiment Stations
milk yield of 36,855 pounds of 4.0 percent fat-corrected milk was
produced. A computation showed that 15,440 pounds of total
digestible nutrients were provided from the pasture for the 1942
1943 Season.-The 1943 season started May 31, the delay being
due to dry weather and a lack of milking cows in a suitable
stage of lactation. Ten milking cows grazed the area for a
total of 855 cow-days and 14 different dry cows were pastured
on the area part of the season to utilize the growth of herbage
for 737 cow-days. In all, 1,592 cow-days of grazing were ob-
tained during 151 calendar days ending October 28. The milk-
ing cows produced 20,729 pounds of 4.0 percent fat-corrected
milk during the period. Total digestible nutrients provided by
the grass for the milking cows amounted to 7,885 pounds, while
the dry cows utilized 6,085 pounds, making a calculated total
digestible nutrient production of 13,970 pounds provided by
grazing during 1943.
FIVE-YEAR RESULTS AND DISCUSSION
A summary of the data for the five-year grazing trial by dairy
cows on fertilized Napier grass is presented in Table 9. The
various grazing seasons started from April 17 to May 31, de-
pending on weather conditions in the spring. Late frosts and
lack of rainfall influenced early-season growth. The close of the
season was determined arbitrarily to allow sufficient time for the
plants to store up nutrient reserves in the roots before frost
so that ample early regrowth would be possible the subsequent
As much as a six-week difference occurred between the times
when Napier grass was at a height for grazing in the spring.
The closing date for each season was arbitrated on appearance
of the grass.
Rates of grazing in cow-days from eight acres of fertilized
Napier are shown season by season in Figure 9. Frost and
weather conditions affected the dates when grazing began or
terminated during each season. Climatic conditions also were
reflected in the period of peak grazing, being later in the third
and fifth trials than during other trials. The Napier grass took
some time to become established, and hence the preliminary year
was not regarded as an integral part of the grazing trials.
Total digestible nutrient yields per acre as computed by in-
verse calculation from live weights of the cows, their milk
TABLE 9.-INTENSITY OF GRAZING, MILK PRODUCTION, SUPPLEMENTAL CONCENTRATES AND NUTRIENTS OBTAINED BY DAIRY
Cows FROM EIGHT ACRES OF NAPIER GRASS GRAZED ROTATIONALLY DURING FIVE SEASONS.
SActual Butter- 4.0% fat- Require- T. D. N. T. D. N.
Grazing Season Cow Milk fat Corrected Grain ments for from from
Season Start Close ] Days j Days Produced Produced Milk*** Fed T. D. N. Grain Grazing
I pounds pounds pounds pounds pounds pounds pounds
1939 Apr. 17 Nov. 6 205 2,062 57,907 2,737 64,218 20,904 34,201.6 15,678.0 18,523.6
1940 Apr. 29 Oct. 6 161 1,647 39,931 1,884 44,232 14,337 25,117.4 10,752.8 14,364.6
1941 May 19 Oct. 27 166 1,529 39,196 1,833 43,173 13,933 24,016.3 10,449.8 13,566.5
1942 May 11 Oct. 26 174 1,600 32,626 1,587 36,855 11,238 23,404.3 7,963.6 15,440.7
1943 May 31 Oct. 28 151 855' 18,899" 878* 20,729 6,943* 12,801.4* 4,915.7:: 7,885.7*
1943 May 31 Oct. 28 151 737*-' --- -- ..-......- 6,085.5** -......-.... 6,085.5* :
Total ......8,430 188,559 8,919 209,207 67,355 125,628.5 49,759.9 75,866.6
Data from cows in milk.
** Data from dry cows, used in part because too few milking cows were available to utilize grass.
*** 4.0%o fat-corrected milk is computed on an equal-energy basis, applying the formula of Gaines: Fat-corrected milk 0.4 X milk, plus
15 X butterfat.
TABLE 10.-YIELD ESTIMATES OF NAPIER GRASS OF THE FIVE LOTS GRAZED BY DAIRY COWS.
Year Grazing Season Calendar Pounds of Dry Matter per Acre
Days Lot 1 Lot 2 Lot 3 Lot 4 Lot 5 Average
1939.-...........-...... April 17 Nov. 6 205 3,847 3,748 3,853 2,986 2,825 3,452
1940................... April 29 Oct. 6 161 2,723 3,069 2,588 2,202 2,193 2,555
1941*': ............. May 19 Oct. 27 166 1,668 1,997 1,834 1,906 1,451 1,771
1942---- .......... --May 1 Oct. 28 174 2,202 2,554 2,046 2,080 1,848 2,146
1943--..........----. May 31 Oct. 28 151 2,292 2,487 1,750 2,263 1,997 2,158
SAverage ....................... 171.4 2,546 2,771 2,414 2,287 2,063 2,416
These are based on averages from yields in three quadrats per lot, stripped by hand to simulate grazing. CO
** Late frost and dry weather delayed Spring grazing.
30 Florida Agricultural Experiment Stations
yields and butter fat percentages varied with the years. It was
computed from the eight-acre totals in Table 9 that the total
digestible nutrients ranged between 1,696 and 2,315 pounds per
acre annually, with an average of 1,897 pounds over the five-year
period. Likewise, the Napier grass samples plucked from caged
quadrats ranged between 1,771 pounds and 3,452 pounds of dry
matter, with an average of 2,416 pounds per acre (Table 10).
It was computed that a pound of dry matter furnished 0.785
pound of total digestible nutrients-a value slightly above the
coefficient of digestibility of Napier grass leaves (66.0 percent)
determined by Kidder (6). This may be explained by the fact
that the cows may have grazed more closely than the forage
samples were plucked for yield estimates. The difference is in
favor of efficiency of the cows in their grazing habits.
10 10 9 9 7 7 6
Fig. 9-Average number of cows per acre per tour during the pre-
liminary and five experimental grazing seasons. Differences were observed
in initial, peak and final grazing periods each season, as well as in level
of cow days of grazing during each tour. Cows were added or withdrawn
as forage increased or decreased.
SUMMARY OF TRIALS WITH DAIRY COWS
A total of 209,208 pounds of 4.0 percent fat-corrected milk
was produced from the eight-acre area for the five-year period.
Experiments with Napier Grass 31
This was in addition to the maintenance requirements of all
cows. The 1943 season's herbage was utilized partly by milk-
ing cows and partly by dry cows. Grazing days for milking
cows for the entire period amounted to 7,673 cow-days. Thus
a production of 27.26 pounds of 4.0 fat-corrected milk was ob-
tained daily per cow when fed concentrates at the rate of 1
pound of feed to approximately 3 pounds of milk produced.
Excluding the 1943 season, 188,478 pounds of 4.0 percent fat-
corrected milk was produced for four seasons on the eight-acre
area, making an annual production per acre of 5,889 pounds of 4.0
percent fat-corrected milk.
Throughout the five-year period it was computed by standard
methods that the Napier grass on the eight-acre area provided
75,866 pounds of total digestible nutrients, or an average of
1,897 pounds per acre per season. This is equivalent to about
two tons of green leafy grass hay per acre. The season aver-
aged 171 calendar days and 1,686 cow-days grazing. Thus the
total digestible nutrient yield averaged 88.5 pounds per calendar
day and 9.0 pounds per cow-day.
Dr. H. Harold Hume, then associate director, made an 8-acre
area available especially for the Napier grass trials. Frazier
Rogers accurately surveyed the area into 5 equal lots. Dr. A. L.
Shealy and the late W. E. Stokes provided facilities and counsel
during the investigation. Dr. G. B. Killinger assisted in agrono-
mic evaluations during the latter part of the grazing trials.
Analyses of feed and grass samples were supervised in the Nu-
trition Laboratory by Drs. W. M. Neal, L. L. Rusoff and George
K. Davis. Dr. R. B. Becker assisted with the project plans and
preparation of the manuscript. The photograph for Fig. 5 was
made by R. W. Kidder. Graphs were drawn by Alf O. Barth.
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3. HENKE, L. A., and G. W. H. Goo. Comparative Value of Napier and
Sudan Grass when Used as Soiling Crops for Dairy Cows. Jour.
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32 Florida Agricultural Experiment Stations
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