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Graminae
Synonyms
U. bolbodes (Steud.) Stapf.
Common names
Dubi grass.
Description
Tufted perennial, 30-60 cm high. Leaf blades 6-9 mm wide. Racemes
dense, few to 20, spreading, on a finely-hairy axis; spikelets crowded,
acuminate, 3-4 mm long, glabrous or with fringed margins (Napper, 1965).
It is more densely tufted and robust than U. mosambicensis. It has a stout,
short, creeping rhizome and the culms are sometimes bulbous at the base
(Chippendall, 1955). One extreme form has been found to have a stolon of
reasonable length (Burt, personal communication).
Distribution
Southern, Central and north-east tropical Africa.
Season of growth
Summer, but responds to out-of-season rains (Burt, personal
communication).
Altitude range
1 250-1 800 m.
Rainfall requirements
It grows over a wide range, from 750 to 3 750 mm annually with
various accessions.
Drought tolerance
It is a promising species for the low-rainfall tropics and
has high drought tolerance (Burt, personal communication).
Soil requirements
It seems to prefer lighter soils near Lake Victoria in Kenya,
but appears to tolerate loams; it may be less successful on heavy clays.
Ability to spread naturally
It does not spread as readily as U. mosambicensis cv. Nixon,
but better than Cenchrus ciliaris. It spreads by seed.
Land preparation for establishment
It does not need a fully prepared seed-bed.
Sowing methods
It can be drilled or broadcast.
Sowing depth and cover
It gives satisfactory stands when broadcast, but it is preferable
to roll afterwards.
Sowing time and rate
Just before the wet season, at 1.5-2 kg/ha.
Number of seeds per kg.
900 000 to 1.2 million (Queensland).
Seed treatment before
planting
Seed can be dusted with lindane to deter seed harvesting ants.
Dry-matter and green-matter
yields
In a preliminary trial with U. oligotricha CPI 45608 (in Cape
York Peninsula, on a very poor yellow earth supporting low closed heath,
with an average rainfall of 1 700 mm) Winter (1976) obtained a dry-matter
yield of 5 780 kg/ha grass by the third year, compared with 15 965 kg/ha
from 'Basilisk' signal grass. U. oligotricha cut at 5 cm yielded 57 500
kg/ha of green matter when cut monthly, 67 000 kg/ha with bi-monthly cuts
and 66 800 kg/ha when cut every three months (Semple, 1956).
Yields were poor at an altitude of 1 900 m with rainfall of 1 150 mm
at latitude 1°N in Kenya, but good in Zimbabwe at 19°S, 200 m altitude
and 500 mm rainfall (Whiteman & Gillard, 1971).
Schofield (1944), at South Johnstone, north Queensland, harvested 33
490 kg/ha of green matter per year when cut at two-month intervals and
33 600 kg/ha when cut at three-month intervals. The grass yielded 976.64
kg protein per hectare per year and 114.2 kg CaO and 99.9 kg P2O5 per hectare
in the first 12 months.#
Main attributes
Its good green leaf retention, rapid regrowth and high acceptability
to animals; its wide ecological range and compatibility with legumes. Its
ability to grow on alkaline soils and to spread by seeds.
Main deficiencies
May have seed production problems, and may not suit cracking
clays.
Frost tolerance
Tolerates light frosts at Yarrowmere near Pentland, North Queensland.
Latitudinal limits
In Africa, Swaziland to Kenya; 14-20°S.
Palatability
Very palatable.
Natural habitat
Open woodland, roadsides, and as a weed.
Tolerance to flooding
No record has been found.
Fertilizer requirements
According to soil test results.
Genetics and reproduction
2n=36 (Fedorov, 1974). It is apomictic (Brown & Emery,
1958).
Further reading
Whiteman & Gillard, 1971.
Dormancy
No dormancy problems have appeared in north Queensland.
Tolerance to salinity
It thrives on many alkaline soils in the Caribbean (Burt, personal
communication).
Tolerance to light
It will grow under shade.
Compatibility with legumes
Legumes will invade stands of U. oligotricha.
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