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HAWAII AGRICULTURAL EXPERIMENT STATION
Under the joint supervision of the
UNITED STATES DEPARTMENT OF AGRICULTURE
UNIVERSITY OF HAWAII
BULLETIN No. 72
Washington, D.C. July 1934
NAPIER GRASS (PENNISETUM PURPUREUM)
A PASTURE AND GREEN FODDER CROP FOR HAWAII
By C. P. WILSIE, agronomist, and M. TAKAHASHI, assistant in agronomy 1
Introduction--..--- -----------.----------- I Utilization as a soiling or fodder crop--------- 8
Description- _----_ ----------------------- 2 Napier-grass pastures------------------------ 9
Varieties of Pennisetum purpureum .... 3 Rotational grazing -------------------------- 10
Distinguishing features of the Napier and Experiments on the yield of Napier grass -.. 11
Merker varieties --------------------- 3 Persistence of stand --.----------------- 12
Climatic requirements.-- ------------------ 4 Effect of spacing on yield -------------- 13
Boil requirements .------------------------ 5 Yields of Napier and Merker strains ..-- 13
Preparation of the soil_ --------------------- 6 Yields in other regions.. ---------------- 14
Methods of planting----------------------- 6 Chemical composition ------------------ 14
Planting with root clumps ------------- 7 Summary_ ------------------------------ 16
Cultivation and irrigation....------. ------.. 7 Literature cited ---------------------------- 17
Napier grass (Pennisetum purpureum), also known locally as
elephant grass or Napier fodder, was introduced into Hawaii in 1915
by the Hawaii Agricultural Experiment Station. This large canelike
perennial is a native of tropical Africa (1, p. 334),2 where it naturally
attains a height of 6 to 8 feet.
Experiments in different parts of South Africa (6, p. 60; 8, p. 8)
showed Napier grass to be of especial value as a green-fodder crop and
capable of being made into silage of good quality. All kinds of live-
stock and particularly horses were fond of the grass and it produced
enormous yields. Once the valuable features of this tropical grass
became known, its use spread rapidly. Napier grass became common
in the extreme southern part of the United States, various countries in
South America, Australia, and subtropical and tropical regions the
Investigation by the Florida Agricultural Experiment Station on the
agronomic possibilities of the grass, reported by Thompson (11),
indicated it to be of great promise as a forage crop. At the present
1 The authors are indebted to D. W. Edwards of the chemistry division, Hawaii Agricultural Experiment
Station, for the chemical analyses reported in connection with this investigation.
Stalic numbers in parenthesis refer to Literature Cited, p. 17.
is one of its very desirable characteristics. .
Introductions into Hawaii were made, both from the r
Plant Industry, United States Department of Agriculture, a 4.
the Florida Experiment Station. After repeated trials at the
Experiment Station and at the University of Hawaii (7) hai sh
adaptability, its high nutritive value as a forage, and its ex c
yielding ability, the grass was distributed to interested ranchq-u
dairymen throughout the Territory. At first it was grown m'
small areas and used as a soiling crop. Later it was found to
desirable pasture possibilities and larger acreages were plante"
ranch has had as much as 600 acres planted to pure stands of :Nap
grass, all of which was used for pasturing beef cattle and hors Eis:...
At the present time Napier grass finds wide use both as aipA
crop for beef cattle and as a soiling crop for dairy cows. For 0-.i
medium elevations where the climatic conditions are favorablee, *
is probably no forage crop now under cultivation that will prodi.
roughage of good quality as economically as will Napier grass. I i
distinctive features are aggressiveness, long life, drought resistgao
high productivity, and ability to recover after being cut. The aea
of the grass could well be extended on many of the ranches in..i
Napier grass is a leafy, branching, vigorous-growing percent
attaining, under favorable conditions, a height of 10 to 15 ........
maturity. It has a strong, extensive fibrous root system which ena..
the plant to become quickly and permanently established in the:.dtl
The leaf blades are usually 1 to 1% inches wide and 2 to 3 feet }o"
The leaf carries a conspicuous ligule consisting of a fringe of fine :hai
about three-eighths of an inch in length. Tillering in this species
profuse, and often as many as 50 to 100 stalks are produced fiain
single plant. When the plants approach maturity numerous: i
branches appear, growing out from the leaf axils of the main at-si
These branches as well as the main stems bear terminal condanUl
panicles or seed heads which are golden yellow to tawny in color: afd
from 5 to 10 inches in length. The inflorescence is made up of a bag
number of spikelets borne singly or in groups of 2 or 3 on prif
branchlets, the branchlets being arranged spirally on the centralaijJe
Each spikelet consists usually of a single fertile terminal floret aS.
second empty lemma or sterile floret, together with a pair of .oia
glumes of unequal length. The group of spikelets on each branchlieii
subtended by an involucre of bristles which are longer than eAlM
spikelets and arranged in a whorl. This involucre of bristles fal9
with the matured spikelets and evidently aids in the dissemination4
seed by the wind and by animals. ..
It has been observed that when blooming begins the stigmas emTW
from 2 to 4 days before the stamens. This, it seems, would tend :
promote cross-pollination and may account in part for some of: W
partial sterility observed in this species. A botanical description i l
Pennisetum purpureum has been given by Hitchcock (4, p. 679):, i
NAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 3
agronomic description by Piper (10, p. 21), and descriptions of the
genus Pennisetum by Phillips (9, p. 167), and by Bews (1, p. 241).
VARIETIES OF PENNISETUM PURPUREUM
Besides the Napier variety, Bews (1, p. 334) describes a taller-
growing type, known in Africa as elephant grass, which is typical of
the tropical high-grass savannas of central Africa. Pentz (8, p. 8)
mentions a variety called locally "Umfufu", which he says is only
another strain of the same species, having narrower leaves and a taller
growth. Possibly these two just described are one and the same
Two varieties have been introduced into Hawaii-Napier and
Merker. Merker grass was introduced as a distinct species, but is
recognized today as merely a different strain of Pennisetum purpureum.
Both of these grasses are spoken of as elephant grass, although the
term was formerly used principally for the Napier variety.
DISTINGUISHING FEATURES OF THE NAPIER AND MERKER VARIETIES
Napier grass is characterized by its wide, bright green leaves; its
slightly decumbent growth in the early stages; the reddish appearance
of its stems, particularly in very early growth; and its thick, some-
what soft stalks present until the plant approaches maturity. The
growth rate of Napier grass is somewhat slower than that of Merker
grass, and maturity comes considerably later. The Napier-grass
plants tend to tiller more, however, and become more leafy, thus
making up for slower growth. The total amount of dry matter pro-
duced per year is usually equal to or greater than that produced by
Merker grass. Napier grass blooms in the autumn and winter and
seldom at any other time during the year. It seems to set seed but
rarely in Hawaii and has not been known to produce seed in the field
to any extent. Figure 1 shows a typical growth of Napier grass about
60 days old growing at the Hawaii Experiment Station.
Merker grass has somewhat narrower leaves than Napier grass and
appears to have a rather blue-green color. It has a slightly more
upright growth in the early stages, less red pigment appearing in the
stems, and finer and harder stalks as the plant approaches maturity.
It has a very rapid growth rate and a quick recovery after cutting.
Merker grass often begins to bloom 60 days after planting and has
been known to reseed itself readily in the field. Blooming is more
profuse than in Napier grass, particularly during the summer months.
Its more favorable seeding habit is possibly of some agronomic impor-
tance in propagation, although for forage purposes both of these
grasses are propagated almost entirely by vegetative means. A typical
growth of Merker grass, in which blooming has begun at an age of
60 days, is shown in figure 2.
In spite of the characteristic differences possessed by these two
varieties, at times, particularly in old stands of grass, it becomes
difficult to distinguish between them. If they are grown side by side,
however, from seedling stage to maturity, it is usually easy to identify
either. The more pronounced reddish color of the stems, observable
in new plantings, is one of the most characteristic features of Napier
grass. The semiprostrate early growth is also distinctive in this
variety. In the more mature stages the Napier grass is more leafy
in appearance, the leaves are wider, and the stalks are
thicker than those of the Merker variety.
CLIMATIC REQUIREMENTS :
Napier grass is truly a tropical species, but it is very adap 4
nature and can be grown successfully in the subtropics and v
*.. .: ....:...
) 4?. 'I
"... ......., ...
be made per season in the cooler sections where it is grown, while 5
to 7 cuttings are common in the tropical regions. In Hawaii it I:
adapted to the climatic conditions found at elevations of from se :
level up to about 4,000 feet. At the higher limit of these elevationat:
the growth is much slower and the plants are much smaller, ide
conditions being found only below 2,500 feet. According to BewSn'
S .. : : .'
h ame etin ofteTmeaeZn.Teyed fgasi.!:..".,i
NAPIER GRABS, A PASTURE AND FODDER CROP FOR HAWAII 0
(1, p. 384), Napier grass is easily injured by frosts. Observations in
Paraguay (6, p. 60), however, indicate that frost injury does not
materially damage the grass for feeding purposes. It was found that
although frost had injured the tips of the grass badly, the cattle
relished the fodder and suffered no ill effects from eating large quan-
tities of it. Napier grass is exceedingly drought-resistant and although
little growth is made during an extremely dry period, the grass
FIGURE 2.-Merker grass in bloom 60 days after cutting.
recovers promptly whenever moisture conditions are again favorable
Napier grass has been grown successfully on a wide range of soil
types in various parts of the world. Langer (6, p. 60) reports good
results even on very poor sandy soils, in South America. The tonnage
of material harvested during a period of years with such a rank-growing
crop as Napier grass necessarily means the removal of a
quantity of the available plant nutrients from the soil. Soii
fertility, then, are of course desirable, unless liberal qua
fertilizer can be used to supply the lacking constituents in t he.7.
soils. Most Hawaiian soils are suitable for the growing of'
grass with the exception of some of the beach sands whi i
high brackish water table, and some of the extremely hear
clays which are poorly drained. Plats located at the Hawai
ment Station on a heavy clay bottom-land soil showed ai ma
yellowing of plants and a lower forage yield following a pe
which heavy rains had flooded the land and water had stood for
a few hours on the plats. Many of the upland residual silt lobms
clay loams, fairly fertile and well drained, as well as the med~iumtp:
deep ash soil types are quite suitable to the growing of this crop.
Napier grass responds readily to fertilizer treatments on mai
Hawaiian soils. At the university farm, Manoa Valley, on fields tbfl
have been under crop rotation and on which green-manuring crs
have been grown extensively, experiments now in progress are s
a marked response to the addition of nitrogenous and phosphitxo 'i
fertilizers. Data obtained by Chung at the Hawaii Experiment Sta-!i.:
tion (2, p. 30) show definite increases in yield from the applicatiqanA:
of 450 pounds of sodium nitrate per acre. A demonstration cainrried
out through the cooperation of the Agricultural Extension Service ofW
the University of Hawaii with a ranch on the Island of Kauai, reported i
by Krauss (5, p. 38), showed remarkable results from the use of 4Q::00 :'`ii
pounds of superphosphate per acre. The fertilized area was ready
for pasturing in 5 months from the date of planting, while the u fir-:i
tilized areas required at least 8 months or more before the cattle could
be turned into the paddocks. Exact information on the use of f: -
tilizers for Napier grass is very meager, and further investigations ar
needed on which to base specific recommendations for local areas.
PREPARATION OF THE SOIL
Although Napier grass is aggressive and perennial in nature, comrn- :'i
peting very well with most weeds, it becomes well established in perfect i'
stands only if planted in a thoroughly prepared seed bed. On new ;
land or land that has been out of cultivation for some years, several
plowings may be necessary. The soil should be allowed to aerate "
thoroughly after the first plowing, and it should be disked several
times to kill as many weeds as possible. This procedure of plowi :,ng .: .
and disking should be repeated once, twice, or more if necessary,: mi
order to get the soil in a good physical condition as well as to rid it ...
of weeds which will come up after the first plowing. On more improved
lands it may be that one plowing will be all that is essential. Thorough .,.::ia
harrowing, however, is bound to pay, for if the plantings are weedy a. ..
good stand is hard to establish and maintain. Time spent in prepa+::;6:. i
ration of the soil is usually well repaid in the subsequent ease Ofi
management and the greater yields obtained.
METHODS OF PLANTING
Napier grass is propagated largely by vegetative means, either using.
stalk cuttings or root-clump divisions. Stalk cuttings for planting ,ii,
are best secured from a field which has been cut a few months previous-:
SNAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 7
to the time the planting material is needed. Well-developed hard
stalks are best, not less than 3 or 4 months of age and not older than
8 to 12 months. The stalks at this stage are well supplied with buds
located at the nodes or joints just beneath the leaf sheaths. Seed
canes may be planted full length or cut into pieces having from one to
several nodes. Unless planting material is very scarce, it is advisable
S to plant only cuttings having at least 2 or 3 nodes each or, better
still, canes with 4 or 5 nodes. A very successful method is to cut seed
canes into lengths of 3 to 5 feet and lay the pieces end to end in the
bottom of furrows plowed out about 4 feet apart. The furrows are
then filled, covering the canes with 3 or 4 inches of soil, and the
grass soon germinates. With this method of planting, a plant should
appear at intervals of from 12 to 18 inches, or less, and a good stand
should thus be obtained under favorable growing conditions.
.When planting on irrigated land the furrows may be made deeper
than is necessary for good coverage. The seed canes are planted in
the bottom of the furrow, covered with 4 or 5 inches of soil, and the
furrow is not completely filled. The grass can then be irrigated,
using the planting furrows to carry water, and germination is hastened
by applying water a day or two after planting.
Another method of planting, if less seed material is available, is to
use stalk cuttings with 2 nodes each and to space them about 2 feet
apart in the row, planting horizontally in the bottom of furrows. If
single-node cuttings are used, the pieces may be pushed into the soil
at an angle of about 60 with the surface of the ground. This
method is not recommended unless planting material is very difficult
to obtain and good care can be given to the field after germination
PLANTING WITH ROOT CLUMPS
A large plant with 50 or more tillers offers a good source of material
for planting with root-clump divisions. After the top growth has
been removed the root clump may be dug out and divided into a
large number of pieces, each of which may be planted separately.
If this system of planting is used, rows should be spaced about 4 to 6
feet apart and root divisions planted in hills about 2 feet apart in the
row. There is usually very little difference in yields obtained by
either the root- or stem-cutting methods.
CULTIVATION AND IRRIGATION
New plantings of Napier grass should be cultivated at frequent
intervals until the grass has become well established. If the field is
kept free from weeds until the Napier grass gets a good start, little
trouble will be had,4for this crop competes very successfully with the
most persistent types, including Japanese nutgrass (Cyperus rotundus).
I While the Napier grass does not kill the nutgrass it seems to be affected
but little by the latter. Cultivation between the rows at intervals
throughout the year after the grass is cut has been found to be good
practice. The root system tends to become heavy and a more or
less sod-bound condition results. At intervals of 6 months or a year
a good plowing or subsoiling treatment between the rows would
doubtless produce very favorable results. In pastures the cultivation
S treatments are usually limited to the earlier stages in the establish-
i ment of the stand of grass with possibly an occasional subsoiling or
plowing to rejuvenate old stands. More of this sort of,
would no doubt be well worth while.
With a well-distributed rainfall of from 50 to 100 inches pa
excellent yields can be obtained. In many regions whe :e
grass can be grown, however, the rainfall is not nearly so hea~
as well distributed. In these drier sections, having an annual
of from 20 to 40 inches, irrigation is essential for high yidt:
furrow system is quite satisfactory, applying water about Wr i
days during the dry weather. Napier grass will withstand
dry conditions, remaining somewhat dormant and recovering
diately when enough moisture is supplied, but its growth andiI
are greatly reduced unless sufficient moisture is available throw
the season. This can be understood readily when one realises ll
Napier grass cut for green fodder contains from 85 to 90 percent o:
water, and that from 75 to 100 tons of such fodder are often cut ~it
an acre n a single year.
UTILIZATION AS A SOILING OR FODDER CROP
Napier grass grown as a green feed (soiling crop) for dairy co iis i
be fed in the barn or feed lot can be handled in much the same way
as a crop of corn or sorghum. The first cutting may be made when:':i
the grass has reached a height of 4 to 5 feet. Under favorableii
growing conditions this first cutting can be made about 60 to 8iil
days after planting, depending on the temperature, length of d iay,
and available moisture present. It has been observed that a manct
more rapid growth takes place during the warmer months, p aticu: "
larly when the days are longest..
The grass may be cut close to the ground level, for the new gro t.r: il
comes out from the crown of the plant. The grass should not h
allowed to mature, for the stalks begin to lignify rapidly and '::i;:it i
digestible nutrients per ton of fodder are lowered markedly. The- ,.
protein content in particular decreases rapidly and the fiber increases
as the plant approaches maturity. Some dairymen in Hawaii out '
Napier grass when it stands about 3 feet in height. At this stage it
is very palatable and has a higher protein content than most grasses ;3
cut for green fodder. If the grass is cut in a very immature stage..
continuously over a long period the yield may be lowered and th:
root reserves may become so depleted that the stand will be paxr-:i::
The best stage at which to cut and the number of cuttings that:|
should be made per year to obtain the maximum yield and palata- ..
ability are not definitely known. For dairy cows, however, it is
important that the grass be cut while it is still very palatable so. that
the stalks as well as the leaves will be eaten without much wast.:ii
If it is fed with alfalfa or other high-protein roughage, it can be 'fTedi
in a slightly more mature stage than when it is the sole source i::
protein in the roughage. When grown under irrigation in the vi(inity:
of Honolulu, 5 or 6 cuttings can be obtained each year and a good :::!
stand successfully maintained. Such stands should give good ratoo ...ns. .'.
for 5 to 6 years or more, particularly if some attention is given to
fertilization and cultivation during that period.
When the grass is succulent and soft the whole stalks can be fed II
without much waste. If harvested at a more mature stage, the gr~as ".:...
- KJA~bJ.i U. Afc **..
NAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 9
should be cut or chopped before feeding. Taking the waste or uneaten
portions from the mangers of the dairy cows and feeding it to young
cattle, dry stock, or horses might bring about a more efficient use of
the fodder in many instances. Napier grass is probably fed most
successfully with alfalfa, pigeon peas (Cajanus indicus), or ekoa
(Leucaena glauca) in Hawaii.
Because of the heavy tonnage produced and the ease of growing the
crop, Napier grass is one of the most economical roughages that the
dairyman in Hawaii can feed.
Both Napier grass and Merker grass are used quite extensively for
pasture purposes. The use of these large, coarse fodder grasses for
pasturage seems to be a rather recent idea. At least it presents a far
different picture from the usual conception of a pasture in the Tem-
perate Zones. Napier grass, however, does make a very successful
FIGURE 3.-Napier-grass pasture under a system of rotational grazing.
pasture at the lower elevations where there is sufficient rainfall through-
out the year. These pastures have been particularly outstanding in
the Kaneche district on Oahu and in the Hanalei district on Kauai.
Certain locations on Maui, especially in the Kipahula district and the
lower slopes of Haleakala, are well adapted to the growing of Napier
Ranchers in the vicinity of Hilo, as well as in the Kona district of
Hawaii, could no doubt benefit greatly by the establishment of more
Napier pastures. Probably one of the most outstanding examples of
the successful use of Napier grass for this purpose is to be found on
the Princeville Plantation Co.'s ranch on Kauai. Here may be found
more than 600 acres in pure stands of Napier grass, the paddocks
ranging in age from recent plantings to others more than 12 years old.
The horses as well as the cattle on the ranch are fed almost entirely
on Napier grass and they keep in excellent condition. The paddocks
are grazed heavily, the cattle being turned in only after the grass has
reached a height of 6 feet or more. After the pasture has been well
S ... ... ::: :i i
eaten down, the cattle are put into a paddock which has been .
or recovering. Thus fresh paddocks are available for
successive intervals and the stand of grass maintained with
productive capacity. Other ranches in the Territory have had
success and Napier grass has definitely shown its value as :.
grass (fig. 3).
Napier grass, like other grasses in improved pastures, s
be grazed continuously. In order to maintain a good stand'n
level of productivity, a grass must be allowed to rest and recover ..
heavy grazing. The root reserves of a plant can be built up only,.
the plant is allowed to make some top growth and manufacturer i
bohydrates in its leaves. If the leaves are continually being re...
root reserves become depleted and the plant is easily killed. This
... .. .
FIGUR 4.-An excellent Napier-grass pasture which has been properly grazed. .....:
especially important with grasses of the bunch-grass type of growh
and Napier grass belongs in this group.
The ranch should be divided into a number of paddocks and theme: 'i
grazed in rotation. Each paddock may be heavily grazed for .
short period and then rested for a number of weeks so that the grZaSea.~::
will have ample time to recover and accumulate a good supply of f@ C
top growth. ... :.
The present method of pasturing Napier grass is to allow the gr...s
to become fairly mature before the cattle are turned in. Many of i.if.
h con eq en c .... ..
coarser and harder stalks are left uneaten, with consequent consider
ble waste. It is believed that by the proper method of rotational
grazing of paddocks, pasturing heavily when the grass is fairly youz.g]
and succulent, removing the cattle to another paddock before the graq|
has become permanently injured by close grazing and tramping, and.
a more frequent grazing of all paddocks for a shorter period each time .
a paddock is pastured, more efficiency and better quality feed would
be obtained. The carrying capacity of a Napier-grass pasture und,-..
,... .. .
favorable growing conditions is high. One rancher estimates that oat
.c" "EE! :.:. :.- "::...!!... :
*i "" ..E'+
NAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 11
S mature head of beef cattle per acre per year can be fattened on his
Napier-grass pastures. Compared with other pasture plants, it can
readily be seen that Napier grass offers extremely good possibilities
wherever it is well adapted (fig. 4).
EXPERIMENTS ON THE YIELD OF NAPIER GRASS
In May 1932 an experiment was begun at the university farm to
determine the comparative yields of four grasses grown under irri-
gation. Plats of Napier and Merker grasses, Sudan grass (Sorghum
afdgare var. sudanense), and guinea grass (Panicum maximum) were
planted. A crop of piegeonpeas and mixed legumes was plowed
under a few months before planting the grasses, but no manure nor
commercial fertilizer was applied to this field.
Stem cuttings were used for planting in case of Napier and Merker
grasses, root-clump divisions in case of guinea grass, and seed sown
FIouREs 5.-Harvesting Merker-grass plats at the University of Hawaii farm, June 1933.
at the rate of 20 pounds per acre in case of Sudan grass. Two spacings
were used with each grass. With the Napier and Merker grasses,
rows were spaced 4 feet and 6 feet apart with plants 2 feet apart in the
row. The guinea and Sudan grasses are much smaller in growth and
the rows were spaced 2 and 3 feet apart (fig. 5).
Each grass was cut at what was considered to be the proper stage for
feeding as a soiling or green-fodder crop. Sudan grass was cut when
in early bloom, guinea grass when starting to bloom, and Merker and
Napier grasses when the plants were about 5 feet in height. At this
stage the Merker grass was often just starting to bloom and during
the winter months the Napier grass sometimes showed a few flowering
heads. Subsequent cuttings were made at as nearly the same stage
as could be determined by observation. The yields of green forage
harvested, air-dry forage, and percentage of air-dry forage in the green
material harvested for the first year of the experiment are given in
TABLE 1.--Yields of Napier and other grasses (1 years hih 4
rass things weight per
per year acre fo
Number Tons Percent
Napier --------------- ----------------5 8.------ 5 87.75 12.S 7W
Merker--.--.--...------------------------- 7 59.77 t 14.
Guinea----------------------------------------------- 48.20 .4 1
Sudan---------------------------------------- -- -. 8 48.97 21.0 1r
1Standard error in tons for a mean of 6 plats. All yields given are calculated from six j34o~a
each variety, after the border rows were removed.
It will be noted that on the green basis Napier grass produce.:
much higher yield than did the other grasses in the test. As t a
shows, however, the Napier grass had the lowest percentage of 4lpii
dry forage of any of the four, and on the dry basis guinea-grap i :. ..
duced slightly more and Sudan grass only slightly less total.
per acre. The yield of Merker grass was somewhat lower .u
others, but not significantly lower than that of Napier grass. .ii ias
observed that throughout the season the Merker grass grew .loi. *E
rapidly than the Napier grass and as a consequence two more cittf:it
were possible. Each cutting of Napier grass, however, gave a larger
yield than the cuttings of Merker grass, and the total yield during thei
year was slightly higher.
It was observed that dairy cows liked the Sudan and Napier grasses
somewhat better than the Merker and guinea grasses. The Na .lg.
grass had softer stems and was fed with less waste than the Merke
PERSISTENCE OF STAND
At the end of the first year of this experiment the grasses were .sa
in excellent condition except the Sudan grass, which had become some- ,
what thinned out. Because of its shallow root system this species
suffered considerable injury during the cutting process, especially if :
dull sickles were used, many of the plants of Sudan grass being pulled
up or at least partially broken loose from the soil, with the result that
after a few months the stand was considerably weakened. However,
a remarkable total yield was obtained from Sudan grass in t his ..
The guinea grass seemed to be in excellent condition, but the yid3 l
were falling off rapidly before the end of the year. Although iti
total yield of the guinea grass was higher than that of any of the
other grasses, nearly one half of this yield was produced in the plant
crop. This grass might be used more successfully as-a pasture gras ,
for its ratoon growths are too small to cut satisfactorily, requiring
about twice as much time for harvesting as does Napier or Mearker
grass. All plats of Napier and Merker grasses showed excellent
stands at the end of the year and offered promise of maintaining ai
high level of production for future cuttings. A need for fertilizer
was apparent, however, in practically all cases.
The true perennial nature of the Napier and Merker grasses with i:
their strong spreading root systems makes for permanence, and it is
probable that with proper cultivation, plenty of moisture, and the
addition of fertilizers when needed, excellent yields could be main-
tained for 5 to 6 years from a single planting.
NAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 13
EFFECT OF SPACING ON YIELD
Yields of Napier grass and of Merker grass grown in rows spaced
4 and 6 feet apart are shown in table 2.
TABLE 2.-Effect of spacing on yield of Napier and Merker grasses
Spacing Green Air-dry
Grass between weight per weight per
rows acre acre
Feet Tons Tons
Napier. ---------------------------------------------- 4 85.14 10.44
S6 90.36 11.14
M erker------------------------------------------------------------ 4 57.56 8. 25
Merker__-4 57. 56 8. 25
6 62. 31 8. 84
The yield appears to have been affected but little by difference in
spacing. In each case, however, a slightly higher yield was obtained
with rows spaced 6 feet apart. These differences are probably too
small to be of any significance. Within this range of spacing at least,
it appears that the plants tend to fill all of the available space. Close
spacing will prevent profuse tillering, and, although a 4-foot-row
spacing gives 50 percent more plants per acre, the yields, according
to these data, are not higher but actually slightly lower.
YIELDS OF NAPIER AND MERKER STRAINS
Observations on the growth habits of the elephant grasses have
indicated that there are a number of types or strains. In the early
spring of 1932 a plant found growing in a Merker-grass pasture near
Kaneohe, Oahu, was brought to the experiment station for observa-
tion and testing. Cuttings were made and within a few months con-
siderable planting material was available for experimental use. This
particular strain from the one plant had remarkable tillering ability,
a most rapid growth rate, and a darker color than the ordinary
Merker type. Experiments were made to compare the yielding ability
and persistence of this strain with the standard types of Napier and
Merker grasses. A total of four %o-acre plats of each variety were
included in the test, with rows spaced 5 feet apart and plants 2 feet
apart in the row. The yields obtained during the first year of this
experiment are given in table 3.
TABLE 3.-Yields of Napier grass and 2 strains of Merker grass 1
Grass Cuttings Green Air-dry Air-dry
Grass per year weight per forage weight per
Number Tons Percent Tons
Napier .------------------------------------------. 5 80.55 10.8 8.70 2 0. 92
Merker (strain K)----------------- ---------------.. 6 66.84 15.3 10.23= 1.09
Merker (strain P) ----------------- ----------------- 6 71.00 14.8 10. 54 1.12
1 These yields represent means of 4 replicated plats of 4so acre each. The data cover a period of slightly
more than 11 months. The grasses were planted Oct. 27, 1932, and the final harvest reported was made
Oct. 6, 1933.
2 Standard error in tons per acre for a mean of 4 plats. With standard errors of this magnitude, a difference
in yield of approximately 3 tons per acre (air-dry basis) would be necessary to be significant.
The results given in table 3 show again that Napier grass produced
the highest yield in fresh green forage. The percentage of dry matter
was, however, considerably higher in the two strains of Merker grass,
and for that reason the results on the air-dry basis indicate thati
ker slightly outyielded Napier grass. The air-dry weight iti uSA
more accurate basis for the comparison of yields of forage e
the moisture content varies considerably in different varieties
within the same variety at different growth stages. The iffe .
between the yields of the Napier and Merker strains, which r-..
from 1.5 to 1.8 tons per acre per year, are too small to be of as.
practical significance. These data indicate then, as did those-in
1, that Merker and Napier grasses do not differ significantlyr-in t'i
production of dry matter during the first year of their growth. Th e
suggest, however, that Napier grass may be more palatable th..
Merker grass because of its greater succulence and its higher moiit
content. They show little difference in yield of air-dry forage betwoeeL:: .l
the two strains of Merker grass included in the test. "
YIELDS IN OTHER REGIONS :..
Langer (6, p. 63), in reporting on Napier-grass trials in Paraguay,
states that 3 to 6 ratoons will yield from 60,000 to 120,000 kil.ogra :,ms
per hectare, which would be about 26.7 to 53.5 tons per acre. Reports ':::
from the Guam Agricultural Experiment Station (3, p. 9) give an aver-
age of 15,848 pounds per cutting per acre of green forage for Nap ey1
grass and 13,477 pounds for Merker grass. Napier grass has yielded:; .
higher tonnage of green fodder than Merker grass during a period of 6 ::::!
years. On the dry basis, however, there would probably be littl-e
difference between the two varieties.
The chemical composition of a grass determines, to some extent, its.
feeding value. Inherent differences in composition, particularly in
regard to the protein and ash constituents, are of importance. The
greatest single factor in determining the chemical composition of a. i
forage crop is probably the stage at which the plants are cut. Pasture
grasses cut at a very immature stage, when most of the forage con-
sists of leaves and tender stems, are high in protein and total ash..
approaching or surpassing that found in high-protein dried roughages
such as alfalfa. In the choice of a forage crop then, it is important
to know if the crop can be cut at a stage when it contains a high
percentage of protein and a low percentage of fiber. High yields can
be obtained with Napier grass cut at a relatively immature stage,
when it is very palatable and nutritious. Chemical analyses were
made of samples of Napier, Merker, guinea, and Sudan grasses cot-
lected at different times during the year from the university farm
plats and representing the actual condition of the grasses when they
were harvested for dairy cattle feeding. The results are- shown in.
TABLE 4.-Composition of fodder grasses ..
Composition on basis of ovenzy ii'
Grass period Analyses ... .
cuttings Fiber Total ash
Days Number Percent Percent Perest
Napier a p i er- ----------------- 63 13 6.84 33.78 17.44
Merker..------------------------------- 54 13 7.17 34.46 t16.
Sudan ......-------......---------------. 48 7 6.02 33.66 1LB0
Guinea ------....... -------------------- 62 9 4.96 33.10 1 so
NAPIER GRASS, A PASTURE AND FODDER CROP FOR HAWAII 15
The results indicate little difference in protein content between
Napier, Merker, and Sudan grasses. The Napier and Merker grasses
appear to have a higher protein content than does guinea grass. In
crude-fiber content all of the grasses were similar, and in total ash all
were similar except Sudan grass, which was considerably lower in ash
than the others.
Average analyses do not indicate the variation in protein content
due to seasonal growing conditions and to the number of ratoon crops
that have been cut. Although ratoon cuttings were made at approx-
imately the same stage, in any one species, it was noted that the age
of the stand in the field had a marked effect on chemical composition.
The effect of the age of the plats and the number of ratoon crops cut
on the protein content of Napier and Merker grasses is shown in
TABLE 5.-Protein content of plant crop and successive raloons of Napier and
Napier grass Merker grass
Crude Age when Crude Age when
protein cut protein cut
Percent Days Percent Days
Plant crop -- -.----------------------------------- 14.18 77 15.19 70
First ratoon -------------- ----------------------- 9.84 64 8.23 5
Second ratoon ----------------------------------. 5. 42 60 7.15 60
Third ratoon .-------- .----------..-----.---.. 5.39 59 5.00 50
Fourth ratoon..-------------..--------------------- 3.81 76 7.12 65
Fifth ratoon....-- ------------------------.-------. 7.50 65 3.88 63
Sixth ratoon------.----...------------.------ --------- ------------ 4.04 60
SFertilizer was applied 10 days before this harvest, which may account for this higher percentage of
The protein content of the plant crop in both Napier and Merker
grasses was, according to these analyses, much higher than in the sub-
sequent ratoon crops. Although the ratoon crops were harvested at
what seemed to be the same growth stage, produced in even less time
than the plant crop, the protein content after the first ratoon was
rather low. The plant crop was evidently made up of a higher percent-
age of leafy forage with a lower percentage of stalk than appeared in
later cuttings. These data indicate the futility of taking 1 or 2 anal-
yses of a grass and upon those analyses attempting to determine the
amount of protein that will be produced during a yearly period.
Seasonal conditions, the fertility of the soil, and the number of
ratoon crops taken, all seem to be very important factors in determin-
ing the yearly production of protein in a forage grass. It seems likely
that unless a high state of fertility is maintained, these coarse fodder
grasses, particularly in their ratoon crops, will not produce the quality
of forage to be most desired. Further experiments are needed to dem-
onstrate just what can be expected in the way of maintaining a high
protein content through stimulated growth by the application of fer-
tilizers. It is probable that heavy fertilization of a crop, which pro-
duces so abundantly as does Napier grass, would be economical in the
growing of high-quality forage.
Experiments in other regions, cited by Langer (6, p. 64), indicate
that Napier grass is of very desirable chemical composition. Results
of chemical analyses are given in table 6.
16 BULLETIN 72, HAWAII EXPERIMENT STATION: -
TABLE 6.-Composition of Napier grass (dry ba is)
Crude Ether Nitrogen- Crude
Analyses made in- protein extract free extract fiber
.- : :l~l.i
Percent Percent Percent Percent Pawr.i
Florida ----------------------------- -- 14.2 2.7 45.2 20.06 13
New South Wales....-------.-----....-. 10.4 1.5 41.7 38.0 &. :
From the relatively high protein content shown in table 6 it seems :.
probable that the samples were taken from the plant crop when the:
forage was leafy and immature.
Langer states further (6, p. 65) that tests of the digestibility .of
Napier grass have shown its nutritive ratio to be 1:7.7, which com-
pares very favorably with the better-quality grasses. Further trials
on the digestibility of this grass are needed, for it must be remembered
that the nutritive ratio of a grass is much narrower in an immature
grass than in a mature one. For feeding young growing calves and
dairy cows in milk, Napier grass should be cut at a rather immature
stage, with the plants from 3 to 5 feet in height, so as to get the higher
protein content, while for fattening beef cattle it might be fed at a
slightly more advanced stage in growth.
Napier, or elephant grass, a tall vigorous perennial, was introduced
into Hawaii in 1915 and has become important as a pasture and green- i
fodder crop. i
Its outstanding features are its aggressiveness, heavy yields, high
nutritive value, and persistent growth over a period of years.
Propagation is best accomplished by the use of stalk cuttings or
Although drought resistant, Napier grass responds to abundant .
moisture and can be grown very successfully under irrigation.
Yields of from 50 to 90 tons of green fodder per acre per year are
readily obtained under favorable growing conditions. ;:
Napier grass may be successfully pastured if rotational grazing is
practiced, allowing a period for rest and recovery in the various
A carrying capacity of one mature beef animal per acre per year has 3
been obtained with Napier-grass pastures under proper management.
Chemical analyses show that Napier grass has a protein content
similar to that of Sudan grass when cut at the proper stage for feeding
as a green fodder. The percentage of crude fiber is also similar, while
the total ash is considerably higher than that of Sudan grass.
Merker grass, a strain of Pennisetum purpureum and similar to
Napier grass, is considered slightly less palatable, particularly at the
more mature stages of growth. Experiments in Hawaii so far show
very little difference in yields of dry weight per acre, using these two
The greater palatability of the Napier variety, due, probably, to its
more leafy growth and greater succulence, would indicate that it is
usually a more desirable grass than Merker grass for forage purposes.
":. : I ,
NAPIER GRASS A PASTURE AND FODDER CROP FOR HAWAII 17
(1) Bzws, J. W.
1929. THE WORLD'S GRASSES; THEIR DIFFERENTIATION, DISTRIBUTION,
ECONOMICS, AND ECOLOGY. 408 pp., illus. London, New York,
(2) CHUNG, H. L., and LUM, R. K.
1930. REPORT OF THE AGRONOMY DIVISION. Hawaii Agr. Expt. Sta.
Rpt. 1929: 28-32.
(3) GUERRERO, J.
1931. REPORT OF THE ASSISTANT IN AGRONOMY AND HORTICULTURE.
Guam Agr. Expt. Sta. Rpt. 1930: 9-23, illus.
(4) HITCHCOCK, A. S.
1930. THE GRASSES OF CENTRAL AMERICA. U.S. Natl. Mus. Contrib.
U.S. Natl. Herbarium 24 (pt. 9): 557-762, illus.
(5) KRAUss, F. G.
1933. FIFTH ANNUAL REPORT OF THE AGRICULTURAL EXTENSION SERVICE,
UNIVERSITY OF HAWAII, HONOLULU. Hawaii Univ. Agr. Ext.
Serv. Bul. 18, 48 pp., illus.
(6) LANGER, A.
1929. ERFAHRUNGEN MIT TROPISCHEN UND SUBTROPISCHEN FUTTER-
PFLANZEN. Tropenpflanzer 32: -65, 103-129, -169,
(7) Low, J. S.
1928. ELEPHANT OR NAPIER GRASS (PENNISETUM PURPUREUM). Hawaii
Univ. Quart. Bul. 7(1): 34-36. (Hawaii Univ. Agr. Dept. Ann.
Rpt. 10: 34-36.)
(8) PENTZ, J. A.
1932. AGRICULTURAL GRASSES OF SOUTH AFRICA AND MANAGEMENT OF
THEIR PASTURES. Union So. Africa Dept. Agr. Bul. 106, 23 pp.
(9) PHILLIPS, E. P.
1931. AN INTRODUCTION TO THE STUDY OF THE SOUTH AFRICAN GRASSES,
WITH NOTES ON THEIR STRUCTURE, DISTRIBUTION, CULTIVATION,
ETC. 224 pp., illus. Johannesburg.
(10) PIPER, C. V.
1927. IMPORTANT CULTIVATED GRASSES. U.S. Dept. Agr. Farmers' Bul.
1254, 38 pp., illus.
(11) THOMPSON, J. B.
1919. NAPIER AND MERKER GRASSES, TWO NEW FORAGE CROPS FOR
FLORIDA. Fla. Agr. Expt. Sta. Bul. 153, pp. 237-249, illus.
U. S. GOVERNMENT PRINTING OFFICE: 1934
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