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Graminae
Synonyms
Andropogon sericeus R. Br.
Common names
Queensland blue grass (Australia), silky blue-stem (United
States).
Description
Erect perennial, often very finely stemmed and not over 30
cm high; nodes bearded, one or two racemes, sessile, the basal, imperfect
spikelets often remaining as an involucre after the rest have fallen; first
glume of the sessile spikelet more or less indurated. There is a good deal
of variation within the species var. mollis is a softly hairy form (Blake,
1944), var. polystachyus has a large head and ten to 30 spikes 3-5 cm long
(Turner, 1891). Queensland blue grass is distinguished by its bluish-green
colour, and soft silky seed-heads.
Season of growth
Spring, summer and autumn.
Altitude range
About 200-300 m in Queensland.
Rainfall requirements
It generally grows in the 500-700 mm rainfall zone. If rainfall
in excess of the higher figure occurs it becomes unpalatable in western
Queensland.
Drought tolerance
It is not as tolerant of drought as the Mitchell (Astrebla
spp.) grasses in western Queensland.
Soil requirements
It grows best on friable black earths on the Darling Downs
and Central Highlands in Queensland where the soils are derived from basalt,
but throughout Australia (except Tasmania) it occurs on a wide variety
of soils. They must, however, be fertile, as the grass is easily pulled
out on poor soils where rooting is poor.
Vigour of growth and growth
rhythm
It grows vigorously when conditions are suitable. It is one
of the earliest grasses to shoot in the spring and flowers February to
May in Queensland.
Response to defoliation
Scateni (1966) showed that cutting in January at Gayndah, Queensland
(lat. 27.5°S, rainfall 745 mm) caused a decrease of 2.9 percent in
the basal cover of Queensland blue grass whereas a February cut gave a
slight increase, as did a May cut. The species flowers in early January.
It stands a good deal of trampling. It disappears under heavy stocking
(Everist, 1935).
Grazing management
It should be moderately stocked or it can be eaten out. It
should be allowed to seed and thicken its stand periodically.
Suitability for hay and
silage
It makes good soft hay.
Cultivars
Strain 64 has been selected by CSIRO (Downes, 1969).
Main attributes
Its palatability and early spring growth.
Main deficiencies
Its frost susceptibility and its extreme palatability tend
to lead to its disappearance. Under heavy rainfall it becomes rank and
unpalatable in central Queensland.
Frost tolerance
Extremely sensitive to frost, but rapidly comes into leaf on
the approach of warm weather.
Latitudinal limits
30°N to below 32°S.>
Maximum germination and
quality required for sale
50 percent germinable seeds and 95 percent purity in Queensland.
Palatability
It is very palatable in the green state, but not attractive
when high rainfall leaches its nutrients.
Chemical analysis and
digestibility
The Queensland Department of Primary Industries recorded 10
percent crude protein, 33.1 percent crude fibre, 1.1 percent ether extract,
0.54 percent CaO and 0.55 percent P2O5 in the dry matter of green material
in seed (Paspalum, 1954).
Natural habitat
Open grassland on heavy black clay soils.
Fertilizer requirements
D. sericeum responded to phosphorus, sulphur and nitrogen on
a red-brown earth soil in north-western New South Wales (Lodge, 1979).
The response was linear up to 90 kg P/ha, 90 percent of maximum yield was
obtained with 10 kg S/ha and response was linear up to 150 kg N/ha. The
grass is not usually fertilized, and it may not respond to fertilizers
when growing on black clay soils.
Genetics and reproduction
2n=20 (Fedorov, 1974).
Seed production and harvesting
It is a heavy seeder. No mechanical harvesting is done in Queensland.
Economics
One of the best natural pastures for sheep and cattle in inland
Australia.
Animal production
In Queensland the carrying capacity of D. sericeum pastures
is rated at about one animal to five hectares in the 600-700 mm rainfall
area of the Darling Downs.
Further reading
White, 1935.
Value for erosion control
Its tussocky nature and not very extensive root system do not
make it effective for erosion control.
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