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Graminae
Synonyms
Themeda australis (R. Br.) Stapf.
Common names
Red oat grass (Kenya).
Description
Tufted perennial, 45-180 cm high. Panicle narrow, spatheate,
up to 45 cm long; racemes reduced to a single awned fertile spikelet 5-6
mm long and two pairs of awnless spikelets.
W.D. Clayton of Kew Gardens, London, is unable to separate this species
from T. australis (R. Br.) Stapf. The following varieties are known: var.
burchellii (Hach.) Domin, var. trachyspathea Goossens, var. imberbis (Retz.)
A. Camus and var. hispida (Nees) Stapf.
Distribution
All warm and tropical regions of the old world; abundant in
East Africa where it constitutes 16 percent of the grasslands.
Altitude range
Sea-level to 3 000 m in Africa, dominant at 1 300-3 000 m.
Rainfall requirements
It has a wide range. In places where it grows in areas with
annual rainfall in excess of 760 mm it is not regarded as a good forage
species. Where rainfall is less than 760 mm it is a major African forage
species because of its abundance (Ndawula-Senyimba, 1972). Heady (1966)
selected a 625-900 mm area to study botanical composition. In India it
has a range from 1 000-6 250 mm.
Drought tolerance
It has some tolerance to drought.
Soil requirements
In Kenya and Tanzania, red oat grass forms almost pure stands
on lateritic red earths (latosolic soils) of poor structure, low in lime,
phosphorus and potash. It is also adapted to loose sandy soils, alluvial
silts, and a wide range of other soils.
Sowing time and rate
Summer, at 20-30 kg/ha.
Response to defoliation
Ndawula-Senyimba (1972) showed that T. triandra persists best
when cut at the end of the growing season. Frequent cutting shortens the
life of the stand under semi-arid conditions. Under subhumid conditions,
frequent cutting gives rise to a lawn.
Grazing management
At Rumuruti in Kenya it has been shown that red oat grass should
be rotationally grazed in five blocks, with grazing during the most critical
period of growth confined to only one year in every five. It can thus be
maintained well and kept highly productive at a stocking rate of one head
of cattle to about five hectares (Henderson & Preston, 1959). The best
time to graze T. triandra grassland is when 70 percent of the grass is
green, that is, for a period of four weeks during the short rains (December-March),
and six weeks during the long rains (May-August), both beginning about
the sixth week of the grass's growth (Karue, 1975). Heady (1966) showed
that grazing intensity was the main factor in determining the composition
of T. triandra grassland. In southern Africa, Roberts and Opperman (1966)
showed that an early summer (rather than late summer) rest period gave
maximum production of dry matter, crude protein, roots growth reserves
and flowering culms. Continuous grazing during the winter severely denuded
T. triandra (Coetsee, 1975).
Response to fire
T. triandra is favoured by burning. It readily survives fires
because the corkscrew-like awns, by alternate moistening and drying, drive
the seeds about 2.5 cm into the soil. Some African studies show fires affect
the soil only to a depth of 0.5 cm (Edwards, 1942). Burning followed by
rain greatly increased germination of T. triandra in vacant areas (Ndawula-Senyimba,
1972). It is not found where protection from fire occurs (Göhl, 1975;
Edwards, 1968).
Suitability for hay and
silage
It should be cut for hay at the stage of maximum dry- matter
productionabout eight weeks' growth during the long rains but
Marshall and Bredon (1967) say the hay is unlikely to be a satisfactory
roughage.
Value as a standover or
deferred feed
The crude protein content of the hay is insufficient to meet
the requirements of the grazing animal and would need a supplement to improve
animal performance (Karue, 1975). Hay cut from a four- month-old stand
had 3.4 percent crude protein in the dry matter. It is generally not highly
regarded as a pasture (Harrington & Pratchett, 1972).
Main attributes
Its recovery after fire.
Main deficiencies
Early flowering, variation in palatability within swards, fire
susceptibility.
Palatability
Good when young, unpalatable when mature.
Chemical analysis and
digestibility
A ten-hour intake trial (to simulate a ten-hour grazing day
on the range) with Boran cattle at EAAFRO, Muguga, Kenya, gave a dry-matter
intake of 70.87 + 2.57 g/kg W0.75 (not significantly different from Herefords).
The dry matter of T. triandra hay contained 42.35 percent crude protein
and 6.20 percent gross energy (Karue, 1975).
The chemical composition of the grass in dry and wet seasons is given
by Karue (1974) as percentages of the dry matter in Table 15.76. Botha
(1953) recorded 6.9 percent crude protein in the dry matter of fresh, vegetative
material and only 2.7 percent in mature, fresh material. The digestibility
of the crude protein with sheep was 51.9 percent for fresh, vegetative
material and nil for the mature grass.
Natural habitat
Widespread as grassland and in open woodlands on clay.
Tolerance to flooding
It does not tolerate flooding; its proportion in a pasture
increases with improving drainage (Ndawula-Senyimba, 1972).
Genetics and reproduction
2n=20, 30, 40, 50, 60, 80 (Fedorov, 1974).
Seed production and harvesting
Seed is usually well formed, but harvesting is difficult as
each plant produces a relatively small number of seeds which shed easily
when ripe. The spikelets are awned and each contains a single caryopsis.
When threshed, the caryopses are mixed with a good deal of chaff and are
not easy to separate.
Economics
Themeda triandra is an important grassland constituent of large
areas of productive ranching land in the medium altitude-medium rainfall
(around 1 000-2 000 m and 500-800 mm respectively) zones of eastern tropical
and subtropical Africa.
Animal production
Weight gains of Boran steers were not significantly different
at 1.76, 2.8 and 5.2 ha per head and averaged 0.29 kg per day, over one
year. This varied seasonally from 0.68 kg per day to nil, with short periods
of weight loss. Live-weight gain was less under a three-paddock/one-herd
deferred rotation than it was with continuous grazing at 1.76 and 2.8 ha
per head (McKay, 1971). In Uganda, Harrington (1973) recorded a live-weight
gain of 0.3 kg per head per day for continuous grazing at 0.6 ha per head
and 0.4 kg per head per day for continuous grazing at 2.4 ha per head.
Karue (1975) estimated from dry matter and crude protein contents that
the grass could carry a stocking rate of one 350-kg live-weight animal
to 5 ha during the short rains on the Athi River ranch in Kenya, and, during
the long rains, one 250-kg live-weight animal plus one 100-kg live-weight
calf could be kept on one hectare. A year-long carrying capacity of one
250-kg live-weight animal to 5 ha is usually recommended. If seed were
available in quantity, Bogdan and Pratt (1967) recommend its use in mixtures
to reseed range at altitudes of about 1 800 m.
Further reading
Heady, 1966; Marshall & Bredon, 1967; Ndawula-Senyimba,
1972.
Dormancy
There is some after-ripening dormancy for approximately 12
months before a full germination potential is realized. Dormancy results
from a combination of embryo dormancy and mechanically resistant glumes.
Successful germination of spikelets entails the splitting of the tough
upper glumes by radicles. Glume removal, plus treatment with gibberellic
acid increases germination (Martin, 1975).
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