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Graminae
Synonyms
P. polystachyum R. Br.; P. commersonii Lam.
Common names
Scrobic, scrobic paspalum (Australia), kodo millet.
Description
A loosely tufted, shallow rooting, short-lived perennial or
annual with ascending, somewhat succulent branched stems up to 90 cm high,
tufts up to 60 cm in diameter; culms with four to six nodes. Leaves up
to 30 cm long and 12 mm wide, flat, soft, completely hairless on mature
plants; ligule membranous, no auricles. Inflorescence of three to four
racemes, 49 cm long, borne along a simple unbranched axis. Spikelets one-flowered.
The one glume and sterile lemma are thin and papery at maturity and fall
with the "seed". Seed ellipsoidal, flat on one side and markedly convex
on the other, 2 mm long and 1.5 mm wide (Barnard, 1972).
Distribution
Widespread in Africa. Introduced to Australia from Zimbabwe
in 1931.
Season of growth
Summer, with a decline in autumn (April in Australia).
Altitude range
Sea-level to 3 000 m.
Rainfall requirements
890 mm or more, with reliable opening rains for establishment.
A range of 806-1 638 mm (Russell & Webb, 1976).
Drought tolerance
It is not very drought resistant as it is relatively shallow
rooted.
Soil requirements
It has a wide soil range, from fertile clay loams to sandy
loams.
Ability to spread naturally
It readily spreads by self-sown seedlings.
Land preparation for establishment
It needs a very fine seed-bed prepared, as for wheat, by ploughing,
discing and harrowing.
Sowing methods
It is best sown through a cereal drill in rows 1.3 m apart
on a well-prepared seed-bed (Paltridge, 1955). In mixtures it can be broadcast
or drilled.
Sowing depth and cover
Not deeper than 1.5 cm, lightly covered and rolled.
Sowing time and rate
After good rains in late spring or early summer, at 3.5 kg/ha.
Number of seeds per kg.
660 000.
Seedling vigour
Good.
Vigour of growth and growth
rhythm
It is a vigorous grass.
Response to defoliation
It will not stand heavy grazing.
Grazing management
It requires an intermittent form of grazing to permit sufficient
seeding for regeneration.
Dry-matter and green-matter
yields
At Lawes, south-east Queensland, Paltridge (1955) obtained
2.9 t DM/ha per year; subsequently he harvested 2.3 t/ha unfertilized,
5.4 t/ha when fertilized with sulphate of ammonia, 5.4 t/ha in 1-m rows
unfertilized, and 8.9 t/ha when fertilized. Under partial irrigation during
dry weather, a seven-year stand of the grass grown at 1.3 m spacing yielded,
10 t DM/ha. In southern Africa, a scrobic/lucerne pasture yielded 8.67
t DM/ha under irrigation, which was less than for Chloris gayana/lucerne
and Panicum maximum var. trichoglume/lucerne (Muslera et al., 1975).
Suitability for hay and
silage
It made good silage in Panama when 10 percent molasses was
added (Medling, 1972), and it makes excellent hay (Partridge, 1955).
Value as a standover or
deferred feed
It makes good standover feed as it holds its nutritional value
well into maturity.
Toxicity
No toxicity has been recorded by Everist (1974). Ndyanabo (1974)
recorded 0.23 percent total oxalic acid in the dry matter, but no toxicity.
Seed yield
Paltridge (1955) recorded yields up to 2 500 kg/ha at Lawes,
Queensland. Jones (1973) recorded 47 kg/ha.
Cultivars
The only cultivar recorded at present is cv. Paltridge and
the foregoing characteristics refer to this plant.
Diseases
It can be attacked by the paspalum ergot, Claviceps paspali
(see Paspalum dilatatum) but is more resistant than paspalum.
Main attributes
Very palatable and highly digestible during summer; retains
these characteristics later into maturity than other grasses.
Main deficiencies
Low crude protein and short life span. It is difficult to harvest
its seed as it is shed very readily over a long period.
Optimum temperature for
growth
The mean annual temperature ranges from 19.1-21.9°C (Russell
& Webb, 1976).
Minimum temperature for
growth
The mean minimum temperature of the coldest month ranges from
5.1-11.1°C (Russell & Webb, 1976).
Frost tolerance
Very frost sensitive, but partly frosted material retains a
high degree of succulence until the spring, when new growth is made in
south-east Queensland (Partridge, 1955).
Latitudinal limits
17.3-28.1°S (Russell & Webb, 1976).
Response to light
It will not tolerate much shade.
Ability to compete with
weeds
Paltridge (1955) grew it in spaced rows, intercultivated when
weed growth was eliminated.
Maximum germination and
quality required for sale
40 percent germinable seed, 93 percent purity in Queensland.
Pests
It can be severely affected by felted grass coccid or mealy
bug (Antoninia sp.), which reduces its persistence.
Palatability
Readily eaten and highly digestible up to flowering (Milford,
1960a), but low intake after frosting.
Chemical analysis and
digestibility
Sen and Mabey's (1965) results in Ghana are shown in Table
15.53. On unfertilized P. scrobiculatum pastures grown on black clay soils
at Lawes, Queensland, the crude protein content of the dry matter grazed
by sheep varied from 5.4-5.5 percent during the growing season to 2.6-3.8
percent during late winter and spring. The starch equivalent was 60 during
the growing season (Partridge, 1955). Andrew (1971) recorded 7.3 percent
crude protein with 41 percent digestibility in Sri Lanka with 54 percent
digestibility of the dry matter.
Natural habitat
Semi-swamp forest, damp grassland and swamp.
Tolerance to flooding
It is very tolerant of flooding (Colman & Wilson, 1960).
Fertilizer requirements
It requires nitrogen for its highest potential. Under low nitrogen
and excess phosphorus it declines.
Compatibility with other
grasses and legumes
At Lawes, Queensland, Paltridge (1955) found that there was
too much competition for moisture when scrobic and lucerne were sown together
in deep, black clay soils; it was preferable to sow them in separate areas.
In higher rainfall areas it is compatible with a range of tropical legumes.
Bisset and Marlowe (1974) showed that P. scrobiculatum combined with siratro,
but the mixture was invaded and dominated by Heteropogon contortus and
Cynodon dactylon after a short period.
Genetics and reproduction
It is a tetraploid with somatic chromosome number 2n=40. It
is sexual in reproduction and lack of variation in the field possibly reflects
a high degree of self-fertilization (Pritchard, 1970).
Seed production and harvesting
It flowers freely and sets seed over three to four months,
beginning in January (Queensland). The seeds fall as they mature, which
makes seed harvesting difficult. The seed can be picked up from the ground
by a suction harvester (Partridge & Coaldrake, 1943).
Animal production
It is capable of high levels of animal production. At Beerwah,
south-east Queensland, over a seven-year period, the average annual live-
weight gain per hectare was 297 kg, stocked at 1.6 and 2.5 beasts per hectare.
This performance was better than for Paspalum plicatulum, Digitaria decumbens
and Paspalum dilatatum (Bryan, 1968). At 1.6 beasts per hectare live-weight
gain was 238 kg per hectare, and at 2.5 beasts per hectare the gain was
342 kg per hectare. At Lawes, Queensland, pure scrobic pastures carried
40.25 sheep per hectare over a four-month growing season compared with
28.25 sheep per hectare on Urochloa panicoides, 24.25 sheep on Panicum
maximum and 22.75 sheep on Chloris gayana (Partridge, 1955).
A grazing trial of siratro and scrobic pastures was conducted between
1966-71 in the Burnett district in the Queensland coastal subtropics, under
an annual rainfall regime of 1 000-1 100 mm per year. Bisset and Marlow
(1974) recorded that the scrobic population declined rapidly and the native
Heteropogon contortus and Cynodon dactylon invaded and dominated the grass
component, though siratro persisted. They concluded that the improved pasture
mixtures should be used intensively in autumn-winter-spring, when their
nutritive value is better than the native species.
Further reading
Bryan, 1968; Paltridge, 1955.
Dormancy
There does not appear to be post-harvest dormancy. Seed remains
viable for only one year. Germination will take place at 20-35°C, moistened
with KNO3 solution.
Value for erosion control
Useful in its ecological niche, but there are better grasses
available.
Tolerance to salinity
No record has been found.
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