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Graminae
Common
names
Mission grass (Fiji), khachornchob (Thailand),
thin Napier grass (India), nigolo (Mali).
Description
An annual or perennial; culms simple or branched,
the branches often flowering. Spikelets 3-5 mm; false
spike 8-10 mm, rarely 6-15 mm wide, excluding the
bristles; longest bristle 15-25 mm long, the others
more than twice as long as the spikelet. When mature,
the spikelets break off at the central axis together
with the bristles (Chippendall & Crook, 1976). It
produces few tillers per plant (Mishra &
Chatterjee, 1968).
Distribution
Throughout the tropics, especially in Thailand and
Fiji where it was introduced.
Season
of growth
Summer.
Altitude
range
Sea-level to 1 500 m.
Rainfall
requirements
It is a high-rainfall grass, but is also grown in
semi-arid regions.
Drought
tolerance
It is drought resistant and suitable for semi-arid
areas in India (Narayanan & Dabadghao, 1972). In
Fiji, growing leaf turns red if subjected to drought.
Soil
requirements
It vegetates the highly phosphate-deficient
nigrescent soil at Sigatoka, Fiji. In Kenya, Thailand
and India it is usually found on sandy soils. In
India it tolerates both acid and alkaline soils.
Ability
to spread naturally
It spreads readily by seed, which survives the
annual burning.
Land
preparation for establishment
It needs a well-prepared seed-bed.
Sowing
methods
Seed is sown broadcast or in drills 15-22 cm apart
in India, or planted out from nurseries as seedlings.
In Fiji it has been planted vegetatively (Partridge,
1979a).
Sowing
depth and cover
It should be surface-sown and rolled.
Sowing
time and rate
At the beginning of the wet season, at 3.4-4.5 kg/ha
in India.
Tolerance
to herbicides
Fisher and Ive (1970) showed the density of P.
polystachyon in an irrigated seed production plot of
Stylosanthes humilis was greatly reduced by the use
of chlorthal or of trifluralin (Treflan) at 1.1 kg AI/ha
applied 14 days before irrigation.
Seedling
vigour
Good, even in poor fertility conditions.
Vigour
of growth and growth rhythm
It grows quickly, flowers in April and seeds in
May/June in Fiji. After this, the flower stems
lignify to a completely inedible straw, which,
because of its bulk and height (2 m), prevents access
to light and restricts the grazing animal to the
lower green leaves (Partridge, 1975). It will remain
green in the dry season in Fiji if grazed to prevent
flowering. In India it is ready to cut three months
from head emergence.
Response
to defoliation
P. polystachyon cannot stand heavy grazing; with
fencing, it can be controlled by heavy stocking (Ellison
& Henderson, 1973). In Fiji under heavy stocking
it becomes invaded by Desmodium heterophyllum and
other species (Partridge, personal communication).
Grazing
management
The grass should be prevented from seeding to
maintain its nutritive value. A six-week cutting
interval gave better material than the 12-week
interval. Complete burning, top-dressing with 450 kg/ha
of single superphosphate and broadcasting siratro or
Stylosanthes guianensis seed at 5 kg/ha each gave a
good pasture mixture at Sigatoka, Fiji (Partridge,
1975; 1979a).
Response
to fire
It tolerates annual fires; it constitutes a
grassland representing a fire disclimax in north-east
Thailand and Fiji. It will burn to ground level
leaving a clean seed-bed suitable for easy legume
establishment by over-sowing (Partridge, 1975).
Dry-matter
and green-matter yields
In India it yields 3 360 kg of green fodder per
hectare per year in three to four cuttings (Narayanan
& Dabadghao, 1972). At Sigatoka, Fiji, Partridge
(1975) obtained 1 500 kg DM/ha in January and March
1972, falling to near zero in July-August. Its yearly
production of 1 390 kg/ha of green matter exceeded
that of five other grasses (Partridge, 1979a).
Suitability
for hay and silage
It makes useful hay if cut before maturity, but is
usually cut and fed green to cattle in India (Narayanan
& Dabadghao, 1972).
Seed
yield
From fertilized pasture, cut mid-January and mid-July
in India, 420 kg/ha (Mishra & Chatterjee, 1968).
Cultivars
There are no registered cultivars.
Diseases
It does not suffer from any major diseases.
Main
attributes
Its ability to invade and dominate wet tropical
areas after fire; producing a great bulk of fodder,
preventing erosion and weed growth.
Main
deficiencies
Its poor quality as it matures, and its
susceptibility to overgrazing.
Optimum
temperature for growth
It makes most growth at 32-35°C in Fiji.
Minimum
temperature for growth
About 12°C in July in Fiji.
Latitudinal
limits
It is common throughout Fiji from latitudes 17-18°S.
Response
to light
It is fairly shade tolerant, persisting under 80
percent shade under Pinus caribaea.
Pests
It has no serious pests.
Palatability
The young grass is fairly palatable, but the
mature material is ignored by stock.
Response
to photoperiod
It is a short-day plant, flowering mainly in May
in Fiji.
Natural
habitat
Grassland on sandy soils, and as a weed.
Tolerance
to flooding
It tolerates flooding well and is good for
waterlogged black clay soils.
Fertilizer
requirements
It is usually not fertilized. With 448 kg/ha of
superphosphate initially, followed by 228 kg/ha per
year, Desmodium heterophyllum volunteers in the
mission grass in Fiji. In India it is sown with
farmyard manure and top-dressed annually with 158 kg
ammonium sulphate.
Compatibility
with other grasses and legumes
Its clumpy growth habit allows legumes such as
Desmodium heterophyllum and Macroptilium
atropurpureum to grow with it. An initial application
of 448 kg superphosphate per hectare, plus 224 kg/ha
each year in Fiji causes Desmodium heterophyllum to
appear spontaneously (Partridge, 1975), but the grass
is not sufficiently productive to warrant fertilizing
it alone. Growing siratro was very effective. In
India it has combined successfully with Atylosia
scarabaeoides, Clitorea ternatea, Calopogonium
mucunoides, Centrosema pubescens and Stylosanthes
guianensis (Singh & Chatterjee, 1968).
Genetics
and reproduction
2n=54 (Fedorov, 1974).
Seed
production and harvesting
Mishra and Chatterjee (1968) in India found
cutting twice yearly and fertilizing with 38.9 kg N/ha
and 22.2 kg P2O5/ha gave the highest "seed"
yield. Caryopses constituted 30 percent of the total
"seed" yield.
Economics
Used as a "cut-and-carry" green fodder
for cattle in Thailand and Fiji. As a fire disclimax,
P. polystachyon grassland invades a good deal of the
mountainous land in both these countries. It is
generally regarded as a weed, but recently Partridge
(1975, 1979a) has shown that it can be fertilized and
combined with the legumes siratro, stylo and hetero
to produce productive pastures.
Dormancy
The seed has no dormancy, and is viviparous in
very wet weather.
Value
for erosion control
It quickly covers the ashes of a fire and forms a
dense tussock grassland, which prevents erosion.
Ability
to suppress weeds
It suppresses weeds well by its vigorous growth
after burning.
Links:.
Links
for the genus:
Further
reading
Mishra & Chatterjee, 1968; Partridge, 1975;
Roberts, 1970b.
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