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Description
A glabrous perennial, 25-75 cm high, having short rhizomes and slender
to moderately stout arching stolons with short internodes. The grass often
forms a dense mat. Leaf-blades are 5-20 cm long, 2-6 mm wide, flat or
folded with a rounded or obtuse apex. The inflorescence consists of two
to three slender, sessile, erect spikes, the upper pair approximate and
the third a little remote. The spikes are straight and the rachis is 0.5
to 0.75 mm wide. The spikelets, each 2 mm long, are arranged in two neat
rows. The fertile floret almost equals the spikelet in length, and is
white to pale yellow in colour. It differs from A. compressus in having
more slender culms and stolons, narrower leaves and shorter (2 mm) spikelets
which are more obtuse; it has wavy or flexuous peduncles and fertile lemmas
with glabrous apex or only a very reduced tuft of apical hairs (Barnard,
1969) (see Fig. 15.8).
Distribution
A. affinis is believed to have originated either in the southern
United States, the West Indies or Central America. It is now found in the
tropical and subtropical regions of America, Africa, Asia, Australia and
the Pacific islands.
Season of growth
Summer growing, with peak growth in late summer.
Rainfall requirements
Usually in excess of 750 mm per annum.
Drought tolerance
It is more drought-resistant than A. compressus and will invade
hilly, as well as flat, country.
Soil requirements
It prefers a sandy, moist soil and will flourish in sandy and
heath soils too infertile for Paspalum dilatatum. It will respond however
to more fertile conditions.
Ability to spread naturally
Under favourable conditions this grass will rapidly spread
by stolons and rhizomes, and the abundance of light seed enables it to
spread quickly also from seed spread by grazing animals.
Land preparation for establishment
It can be established on a well-prepared seed-bed or broadcast
into ashes after a scrub burn.
Sowing methods
Usually broadcast on the surface and harrowed or rolled in.
Sowing depth and cover
Surface sowing with the minimum of cover.
Sowing time and rate
In the United States it is sown at 6-12 kg/ha from spring to
midsummer.
Number of seeds per kg.
Approximately 2 860 000.
Tolerance to herbicides
Bromacil at 1.8 kg of an 800 g AI/kg product (e.g. Hyvar X)
per 200 litres water plus 250 ml surfactant sprayed at a minimum of 450
litres water per hectare will control it (Tilley, 1977). 2,2-DPA at 4.8
kg/ha sufficiently restrained the growth of carpet grass to allow sod-seeding
of white clover in Alabama, United States (Searcy & Patterson, 1961).
Seedling vigour
It has a very vigorous seedling stage.
Vigour of growth and growth
rhythm
It has a short growing season, extended by early nitrogen application.
Response to defoliation
It stands heavy defoliation. Under high cutting height its
yield is reduced.
Grazing management
It should be kept in the vegetative state by frequent grazing
and periodically renovated and fertilized with nitrogen, especially in
spring to prolong its feeding value.
Response to fire
It recovers quickly from fire.
Dry-matter and green-matter
yields
Yields of fertilized carpet grass ranged from 812-5 197 kg/DM/ha
per year in the south-eastern United States with nitrogen applications
from 56-370 kg N/ha per year (Martin, 1975).
Suitability for hay and
silage
It makes poor-quality hay, since when it is high enough to
harvest it is low in nutritive value.
Value as a standover or
deferred feed
In its mature state it is really only poor-quality roughage.
Toxicity
No toxicity has been reported with this grass.
Cultivars
No cultivars are recorded.
Diseases
No major diseases occur.
Main attributes
It grows on poor soil and covers the ground against erosion,
and it tolerates overgrazing. It is considered a good horse feed, as horses
eat the masses of seed-heads avoided by cattle (McLennan, 1936).
Main deficiencies
It has very low nutritive value, especially after seeding,
low dry-matter yield and response to fertilizer, short growing season,
poor root development and low animal production.
Optimum temperature for
growth
Top growth was maximum at a temperature of 27-32°C with
a day length of 15 hours.
Minimum temperature for
growth
Temperatures below 12.8°C inhibited flowering (Lovvorn,
1945). In Australia it is found further south than A. compressus.
Frost tolerance
It has some degree of tolerance to frost.
Ability to compete with
weeds
It dominates annual weeds in a pasture. It is often a weed
itself.
Maximum germination and
quality required for sale
60 percent germinable seeds, 97 percent purity (Queensland)
germinated at 20-35°C with KNO3 moistening agent.
Pests
No major pests are evident.
Palatability
It is fairly palatable till flowering, after which its palatability
declines.
Response to photoperiod
It flowers in all day lengths from eight to 16 hours, but seed
production is greatest under 12- to 14-hour day lengths (Knight & Bennett,
1953).
Chemical analysis and
digestibility
Its forage is generally of much poorer quality and lower feeding
value than Paspalum dilatatum. Its copper levels are much lower than those
of the latter. After seed set, the crude protein level in mat grass may
fall as low as 4 or 5 percent. Grain or urea-molasses supplements need
to be fed to lactating dairy cattle in this case, and phosphorus should
be available.
Natural habitat
Subhumid and humid woodland and savannah.
Tolerance to flooding
It prefers moist-soil but does not withstand prolonged flooding
or permanently swampy conditions very well, though better than Paspalum
dilatatum.
Fertilizer requirements
It has a low fertility requirement but will respond to fertilizers,
particularly nitrogen, but its efficiency of use of applied nitrogen is
low compared with other pastures. Its shallow root system (96 percent of
roots in the 0- 5 cm layer), lack of root response to fertilizer, and distribution,
suit carpet grass to infertile, moist sandy soils. Apply 224 kg/ha superphosphate
at sowing and annually (McLennan, 1936).
Compatibility with other
grasses and legumes
It is a low-fertility grass; as soil fertility declines it
can successfully invade Paspalum dilatatum pastures, as well as Cynodon
dactylon lawns. Few legumes will grow with it to compete with its dense
sod.
Genetics and reproduction
2n=80, 54 (Fedorov, 1974).
Seed production and harvesting
A. affinis is a prolific seeder and seed is shed easily. If
seed were required it could be beaten off with revolving beaters on to
a tray. It is harvested mechanically in Mississippi and Louisiana, United
States.
Economics
It is a low-quality pasture which indicates declining fertility
throughout the tropical world.
Animal production
Animal live-weight gains from carpet grass are low compared
with other pasture species, and live-weight losses occur in winter. Live-weight
gains from pure pasture alone have been 84-98 kg/ha per year unfertilized;
with white clover and fertilized a peak of 693 kg/ha per year (Martin,
1975). When A. affinis replaces Paspalum dilatatum as a pasture butter
production will drop 33 percent in northern New South Wales (McLennan,
1936).
Further reading
Barnard, 1969; Martin, 1975.
Value for erosion control
In the United States it is widely used to prevent erosion and
stabilise road banks (Bennett, 1962).
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