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Graminae
Common names
Salt-water couch (eastern Australia), sea-shore paspalum (United
States, Western Australia), grama bobo, grama salada (Peru), water couch
grass (Malaysia), grama de mar (Cuba).
Description
A perennial with long creeping rhizomes and stolons; culms
erect, from 15 60 cm. Leaves stiff, narrow, about 15 cm long; racemes usually
two; spikelets elliptical, 3.5-4 mm long. It differs from P. paspaloides
in that the upper glume is glabrous with the mid-nerve sometimes suppressed;
the leaf-blades are usually narrower, up to 4 mm wide, often less, folded
and with inrolled margins; racemes up to 4 cm long, often less, usually
spreading horizontally or deflexed; lower glume absent (Chippendall, 1955).
Distribution
Native to Africa and the Americas; now widely distributed throughout
the tropics.
Season of growth
A summer-growing perennial.
Altitude range
Just above sea-level.
Rainfall requirements
It occupies salt seepage areas in the 400-750 mm rainfall area
of Western Australia. It must have moist areas in summer.
Drought tolerance
It needs good summer rain, but persists during the dry season.
Soil requirements
Adapted to marshy, brackish conditions and saline soils which
are moist in summer.
Ability to spread naturally
Excellent, spreading by rhizomes and stolons.
Land preparation for establishment
Minimum. Holes can be dug or the roots pushed into the moist
soil.
Sowing methods
By pieces of rooted sod, about 6-8 cm square, at 1-m intervals.
Sowing depth and cover
The top of the sod should be planted at ground level.
Sowing time and rate
Sow in spring for a good strike in Western Australia (Burvill
& Marshall, 1951).
Vigour of growth and growth
rhythm
Stolons remain green all year, especially if growing in water.
Response to defoliation
Once it is established it is virtually impossible to graze
it out (Malcolm & Laing, 1976).
Grazing management
It is very productive if no more than half of the current season's
growth (by weight) is grazed off. A 90-day grazing rest improves plant
vigour and produces a forage reserve. Hard-surfaced soils can be cultivated
to assist the runners' rooting. The plants should be well established before
grazing is allowed.
Response to fire
Burning is not recommended as a management practice.
Dry-matter and green-matter
yields
It is more productive than Sporobolus virginicus and common
couch (Millington, Burvill & Marsh, 1951).
Feeding value
An important forage grass. In Suriname, Dirven (1963a, b) says
the nutritional value of the grass is low and cattle grazing it are in
poor condition.
Toxicity
No records of toxicity have been found.
Main attributes
Its adaptability to saline land, thus providing soil stabilization
and beach protection, as well as light grazing.
Main deficiencies
Its low seed production.
Frost tolerance
Leaf-blades turn brown and deteriorate after the first frost,
but stolons survive.
Latitudinal limits
About 30°N and S.
Response to light
It grows as well as Cynodon dactylon and Stenotaphrum secundatum
(buffalo grass) in shade, with better winter survival.
Ability to compete with
weeds
It competes very successfully with weeds.
Palatability
It is quite palatable.
Natural habitat
A littoral species occurring in sands and muds near the seashore,
and in saline soils and swamps (Barnard, 1969).
Tolerance to flooding
It will tolerate waterlogged conditions and periodic flooding
in salt swamps and by tidal waters (Colman & Wilson, 1960).
Fertilizer requirements
In non-salty soils it responds to phosphorus and nitrogenous
fertilizers.
Genetics and reproduction
The somatic chromosome number is 2n=20, (sexual reproduction)
(Bashaw, Hovin & Holt, 1970).
Seed production and harvesting
P. distichum flowers freely in summer but some clones are markedly
self-sterile so that little seed is produced. Some clones are reasonably
self-fertile and cross-pollination between clones may result in satisfactory
seed set (Carpenter, 1958).
Economics
Used by some Angolan farmers for composting the sandy dune
soil of their vegetable farms (Rose-Innes, 1977). It is a very good lawn
grass where only salty water is available, yet also does well with fresh
water. It is good fodder grass, but may become a serious weed in irrigation
channels. It can be a useful coastal sand binder in Australia.
Animal production
No figures are available. It is a useful fodder grass which
stands heavy grazing.
Further reading
Burvill, 1956; Cameron, 1959; Carpenter, 1958; Logan, 1958;
Malcolm & Laing, 1976.
Dormancy
Seed shows some dormancy which seems to require cold to break
(Carpenter, 1958); it germinates best at 20-30°C.
Value for erosion control
It is useful in erosion control on salted lands and areas reclaimed
from tidal influences.
Tolerance to salinity
Excellent. In Western Australia it has grown successfully in
salt seepage patches where the ground water just below the surface contained
3 000 mg of sodium chloride per litre. When the salt content was as high
as 12 000 mg per litre however, it did not grow satisfactorily. It grows
along the sea front in Suriname and is frequently flooded with sea water
(Dirven, 1963a, b). It can stand lawn irrigation with water containing
up to 14 000 mg per litre total soluble salts (Malcolm & Laing, 1976).
Sea water is generally too saline for P. distichum.
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