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Graminae
Common names
Rat's tail grass, white grass (Northern Territory, Australia).
Description
Annual or perennial, culms densely tufted with leaf-blades
up to 30 cm long. Racemes solitary, 7-12 cm long; sessile spikelets pale
green, 8-10 mm long, with a long bristle from the upper glume, and an awn
about 45 mm long from the lemma; pedicelled spikelets purplish (Napper,
1965). Maximum root activity occurs at 60 cm, with maximum depth of roots
at 149 cm.
Distribution
Central East Africa and the Sudan, Southeast Asia, Australia.
The Sehima/Dichanthium association is very important in India (Whyte, 1957).
Altitude range
100-2 750 m.
Rainfall requirements
250-1 375 mm, with the optimum being up to 1 000 mm.
Drought tolerance
It survives the long dry season in northern Australia and dry
seasons in India very well.
Soil requirements
It grows on lava and on black, seasonally waterlogged clays
in Africa, and on lateritic red earths in northern Australia. It grows
well on loamy sands with a pH of 6.5 in India, but grows best on black
soils. There is a progressive increase in yield in India with increasing
soil moisture up to field capacity in black soils (Dabadghao & Shankarnarayan,
1970).
Sowing methods
Seed is broadcast at 11 -13 kg/ha.
Vigour of growth and growth
rhythm
In northern Australia, with the onset of effective rain in
November/December, growth is rapid through the wet season, with flowering
occurring in April/May (a little later than Themeda australis). It then
remains dormant through the dry season from May to November. Virtually
all tillers become reproductive in the season of their initiation (Arndt
& Norman, 1959). In India it is somewhat difficult to establish in
a new locality but, once established, it can stand cutting (Narayanan &
Dabadghao, 1972).z
Response to defoliation
Increasing the cutting interval from ten to 60 days in 1970-72
increased the yield of dry matter from 790 kg/ha to 4 100 kg/ha. Cutting
at 15 cm was better than at 5 or 10 cm.
Dry-matter and green-matter
yields
In India, the dry-matter yield of a Sehima community can be
raised from 4 126 kg/ha unfertilized to 7 561 kg/ha by applying 60 kg N/ha.
Application of 40 kg P2O5/ha increased the yield from 5 824 kg/ha to 6
471 kg/ha. There was no response to potash (Dabadghao & Shankarnarayan,
1970).
Suitability for hay and
silage
It is one of the most important grasses for hay in India.
Palatability
Sehima nervosum was practically neglected by cattle during
the growth period in northern Australia in favour of Sorghum plumosum,
Themeda australis and Chrysopogon latifolius. In India it is regarded as
one of the most palatable grasses and disappears quickly under grazing
(Dabadghao & Shankarnarayan, 1973).
Chemical analysis and
digestibility
Various analyses as a percentage of the dry matter are listed
in Table 15.68. Calculated on a whole-plant basis, Arndt and Norman (1959)
recorded progressive monthly crude protein figures from 10.9 percent in
December to 8.2, January; 5.9, February; 5.2, March; 4.4, April; 1.5, May;
and 1.2 percent in June, which latter figure was maintained until October.
Natural habitat
Rocky hills with grass, or open bush in partial shade.
Fertilizer requirements
It is normally adapted to its natural habitat without fertilizer.
It has given response to nitrogen and phosphorus but not to potash in India
(Dabadghao & Shankarnarayan, 1970) or in northern Australia (Arndt
& Norman, 1959). The nitrogen response in India was in improved crude
protein content but not in yield (Shankarnarayan et al., 1977).s
Genetics and reproduction
2n=20, 34, 40 (Fedorov, 1974).
Economics
In India it is an excellent pasture grass. It is used for grazing,
hay- making and cut forage. In northern Australia it constitutes about
3.2 percent of the tropical tall-grass pasture dominated by Sorghum plumosum,
Themeda australis and Chrysopogon fallax on a lateritic red earth soil
at Katherine, Northern Territory (lat. 14°3'S, altitude 100 m, annual
rainfall 911 mm 93 percent from October to March). It is neglected
by cattle at most times (Arndt & Norman, 1959).
Further reading
Dabadghao & Shankarnarayan, 1970.
Tolerance to fire
It survives annual burning during the dry season in northern
Australia.
Land preparation
In India the land is well ploughed.
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