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Graminae
Common names
Vasey grass, giant paspalum (Australia), regop paspalum, upright
paspalum (southern Africa).
Description
An erect perennial, growing in tufts about 30 cm in diameter
with many erect leaf-blades. The base of the stalks and leaf-sheaths is
hairy and bluish in colour. The flower stalks are 60-200 cm tall, each
flower cluster bearing six to 25 spikes. Flowering culms are produced over
a long period (Wheeler, 1950). It differs from P. dilatatum in having erect
culms, conspicuously hairy leaf-sheaths and ten to 30 or more racemes.
Distribution
A native of Argentina and Uruguay, it has spread to several
tropical areas.
Season of growth
Summer.
Altitude range
Sea-level to 1 000 m.
Rainfall requirements
It is a high-rainfall grass usually growing in regions of 1
000-1 500 mm, with summer dominance.
Drought tolerance
It can withstand severe drought.
Soil requirements
It thrives best on heavy soils, but succeeds well on moist,
sandy land. It has a wide soil range and does well in vleis in Zimbabwe.
Ability to spread naturally
With its heavy seed production it spreads fairly quickly under
favourable moist soil conditions.
Land preparation for establishment
Full land preparation will give best populations.
Sowing methods
Sow with a drill, or broadcast. It is seldom planted, but is
used where it is found in the United States (Bennett, 1973).
Sowing depth and cover
Not deeper than 1 cm; rolled to cover.
Sowing time and rate
Summer, at 22 kg/ha.
Number of seeds per kg.
970 000.
Tolerance to herbicides
To control this grass use 2,2-DPA at 2.3 kg of a 740 g AI/kg
product (e.g. Shirpon, Dowpon, Ellapon) plus paraquat at 85 ml per 200
l of water. Spray to the point of run-off three times, at ten-day intervals.
Alternatively a single application of glyphosate at 6 l/ha of a 360 g AI/l
product (e.g. Round-up) can suffice (Tilley, 1977).
Seedling vigour
Very vigorous.
Response to defoliation
It is killed by heavy grazing. It is not as palatable as other
species, quickly becoming coarse, and is thus avoided by stock.
Grazing management
It should be grazed sufficiently to prevent it flowering.
Response to fire
It will survive fire.
Suitability for hay and
silage
It is cut for hay where it has become abundant in the United
States. The hay is classed as good.
Value as a standover or
deferred feed
It becomes coarse and unpalatable as it matures.
Toxicity
It is generally resistant to paspalum ergot, and no cases of
poisoning have been reported (Everist, 1974).
Diseases
No major diseases occur.
Main attributes
It will thrive on very wet lands, e.g. vleis in Zimbabwe.
Main deficiencies
Its tendency to become a weed, and its low palatability as
it matures.
Optimum temperature for
growth
It flowers at 5.5°C sparingly, and improves up to 22.5°C.
Frost tolerance
It continues to grow in winter, except in very cold weather,
and thus gives a long grazing period (Wheeler, 1950). It does not survive
winter in Washington State, United States.
Latitudinal limits
About 32°N and S.
Response to light
It prefers full sunlight and does not grow well in shade.
Ability to compete with
weeds
Its vigorous, erect growth allows it to compete successfully
with weeds. It can become a weed itself.
Pests
No serious pests attack the plant.
Palatability
It loses its palatability and quality with age.
Response to photoperiod
Below 15.5°C, flowering is limited by light (Bennett, 1959).
Chemical analysis and
digestibility
No figures have been cited.
Tolerance to flooding
It can grow on very wet land.
Fertilizer requirements
It will respond to basic complete fertilizer and top dressings
of nitrogen. There is some nitrogenase activity in association with its
roots (Koch, 1977) in Hawaii.
Compatibility with other
grasses and legumes
It will combine well with most of the tropical legumes.
Genetics and reproduction
2n=40, sexual (Bashaw, Hovin & Holt, 1970). 2n=40, 60 (Fedorov,
1974).
Seed production and harvesting
Seed ripens very unevenly. It is fluffy and smaller than that
of P. dilatatum. It is good practice to use the second crop for seed, the
first crop being cut for hay.
Economics
It is used as a soilage crop in Sri Lanka (Andrew, 1971) and
as a minor forage crop in the United States but it is generally regarded
as a weed in subtropical coastal Australia, and stock do not eat it readily.
Further reading
Bennett, 1959.
Dormancy
There is some post-harvest dormancy and the seed should be
stored to improve germination (Wheeler, 1950).
Value for erosion control
It is rather too tussocky to control erosion.
Tolerance to salinity
No record has been found.
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