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Graminae
Common names
Kikuyu grass (after the Kikuyu people of Kenya, east of the Aberdare Mountains, where
the grass thrives).
Description
A prostrate perennial which may form a loose sward up to 46 cm high when ungrazed, but
under grazing or mowing assumes a dense turf. The grass spreads vigorously from rhizomes
and stolons which root readily at the nodes, and are profusely branched. Short, leafy
branches are produced from stolons, with leaf- blades strongly folded in the bud, later
expanding to 44.5114.3 mm long and 6 mm wide, tapering to sub-obtuse tips; leaf surface is
sparsely and softly hairy. The ligule can be recognized by a ring of hairs, and the collar
by its prominent pale yellow colour. The flower is small, consisting of a spike of two to
four subsessile spikelets which are partly enclosed within the uppermost leaf-sheath. The
spikelets are bisexual, or functionally unisexual. The florets are protogynous and the
stamens are rapidly exserted on long filaments, usually in the early morning. The stigma
is branched and feathery. The large seed (2 mm long) is dark brown, flat or ellipsoidal
with a prominent style (Mears, 1970).
Distribution
From Zaire and Kenya the grass has been introduced widely in tropical areas, especially
Costa Rica, Colombia, Hawaii, Australia and southern Africa.
Season of growth
Spring, summer and autumn.
Altitude range
Sea-level to 3 500 m.
Rainfall requirements
In its natural habitat, 1 000-1 600 mm/year either falling in one season or as a
bi-modal rainfall (Mears, 1970). Mean 1 269 + 632 mm (Russell & Webb, 1976).
Drought tolerance
Reasonably good because of its deep root system. It extends to 5.5 m, but only sparsely
below 60 cm, with 90 percent of the total root weight found in the 0-60 cm layer. Added
nitrogen improves the efficiency of water use.
Soil requirements
Its natural occurrence is mainly on deep latosolic soils of good fertility, and it has
quickly adapted to similar soils elsewhere. It also thrives on alluvial soils and on
moist, sandy soils where the fertility has been raised by animal excrete or mineral
fertilizer. It is an excellent colonizer and soil stabilizer in small paddocks around
dairy bails, piggeries and feed-lots, and where non-toxic effluent is discharged from
factories. It does require soils with good drainage.
Ability to spread naturally
Under favourable conditions of moisture and fertility, Kikuyu will spread rapidly from
rhizomes and stolons, and from seeds germinating in dung pats (Wilson & Hennessy,
1977).
Land preparation for establishment
A properly prepared seed-bed is necessary for good establishment from seed. For stem
and root cuttings a rougher seed-bed may suffice, as long as the vegetative material is
adequately planted. Sowing methods. Hand planting of vegetative stem and root cuttings has
been traditional. Sprigs containing two or three nodes, planted on a 1-m grid is a usual
plant spacing, but availability of sprigs and desired rapidity of establishment will
decide procedure. For large areas, broadcasting sprigs (produced by putting plants through
a chaff cutter) and then disc-harrowing them in will give adequate establishment if
accompanied by a fertilizer mixture of nitrogen and phosphorus (Mears, 1970). Now that
seed is available, well prepared seed-beds are essential as seed is costly. Pellet seed
with activated charcoal at 1.3 kg a.c./ha and use atrazine at up to 4.5 a.c./ha. This
reduces weed competition, especially from Eleusine indica and gives satisfactory stands
(Cook & O'Grady, 1978). A drill with attached fluted furrow press wheels gives
excellent results (Wilson, 1978).
Sowing depth and cover
Sow seed at approximately 5 mm depth, and roll to cover. Cultivar Whittet can germinate
from a depth of 5.6 cm (Blair et al., 1974).
Sowing time and rate
Plant in the spring, to compete against weeds at the rate of 2-4 kg/ha. The optimum
temperature for germination is within the range of 19- 29°C with the fastest rate at
29°C (Blair et al., 1974). Sow after the topsoil reaches a temperature of 20°C.
Number of seeds per kg.
About 40 000.
Tolerance to herbicides
Kikuyu itself may become a weed in cultivation. It can be killed by several herbicides
including dalapon, but each successive seedling emergence must be treated. 2.2-DPA at 8
kg/ha will suppress it enough for sod- seeding another species into it. Atrazine at
1.0-1.5 kg/ha will eliminate weeds from a pure Kikuyu pasture.
Seedling vigour
The seedlings should be protected by slashing to reduce weed competition; vigour is
enhanced by high nitrogen and phosphorus in the soil.
Vigour of growth and growth rhythm
On the Atherton Tableland, Queensland, it grows vigorously from December to April (lat.
17°13'S) but may be cut by frost from the first week in April to mid-July and be halted
by dry weather from mid-July to late November (Quinlan & Edgley, 1975). Graphs of
growth rhythm in south-eastern Queensland and northern New South Wales are given in Figure
15.127.L
Response to defoliation
Information has been obtained from cutting experiments. Colman (1966) at Wollongbar,
northern New South Wales, found frequent cutting (every two weeks) reduced dry-matter
yield by 54 to 25 percent, compared with a maximum yield at the 12-week cutting interval;
this depression was greater in the presence of nitrogen fertilizer. Mean yield of nitrogen
in the herbage fertilized with 224 kg N/ha and cut every two weeks was 176 kg/ ha,
compared with 131 kg/ha when cut at 12-week intervals. In Colombia, maximum production of
green herbage and protein was obtained from a Kikuyu/clover sward cut to 5 cm every nine
weeks. In north Queensland, a cycle of three to four weeks' grazing to 13 cm is preferred.
Grazing management
Close grazing or cutting designed to avoid the build-up of a dense mat of stolons is
necessary to maintain temperate legumes with Kikuyu. Renovation of worn-out or degenerate
pastures by mechanical ripping has no long- term effect unless accompanied by
fertilization with inorganic nitrogen or the inclusion of a legume. Where Neonotonia
wightii cv. Clarence was the associated legume, grazing every four weeks reduced the
legume percentage, compared with the eighth- or 12-week grazing interval. The sward should
be maintained with a dressing of at least 150 kg N/ha applied in split dressings in spring
and autumn. If weeds are troublesome the pasture can be slashed. With a Kikuyu/tropical
legume mixture, grazing to a height of 10-15 cm should take place every six to eight
weeks. With strip grazing, 50 beasts per hectare per day can be grazed on a grass/legume
mixture.
Response to fire
Where Kikuyu thrives there should be little fire risk, but in dry times the green top
growth may hide a dry basal layer of dead leaves which can support a creeping fire. The
plants soon recover.
Dry-matter and green-matter yields
In northern New South Wales, a ceiling yield of 30 000 kg/ha of dry matter was obtained
by applying 1 120 kg/ha of fertilizer nitrogen. On the Atherton Tableland, Queensland, a
Kikuyu-dominant pasture produced 12 170 kg DM/ha per year.
Suitability for hay and silage
Although Kikuyu grass silage is palatable to dairy cattle, a considerable loss of dry
matter occurs and digestibility of the silage is about 19.5 units lower than freshly-cut
grass. Milling and pelleting the leaf for sheep resulted in a live-weight increase three
times that of sheep fed the unmilled leaf ration (Hennessy & Williamson, 1976).
Toxicity
It is rarely toxic. Lush grass growing on a heavily-manured, disused cow yard has
caused nitrite poisoning (Everist, 1974; Quinlan & Edgley, 1975), and bloat (Said,
1971). In New Zealand, serious toxicity occurs spasmodically on Kikuyu pastures after
rainfall in excess of 20 mm, grass temperatures above 14°C and invasion of pasture by
army-worms. The toxin is unknown (Martinovich & Smith, 1973).
Seed yield
25 kg/ha from new stands, up to 500 kg/ha from established swards. Increasing the rate
of nitrogen fertilizer from nil to 224 kg N/ha increased leaf production but decreased
seed yield (Wilson & Rumble, 1975).
Cultivars
Edwards (1937) recognized three ecotypes in Kenya.
coarse, with broad leaves and thick stolons which develop rapidly after cutting;
male sterile, anthers never exserted.
a finer plant with narrow leaves and more slender stolons which tend to throw up
shoots from the centre crown after cutting; the stamens are never exserted (Parker, 1941),
and the pollen is sterile.
an intermediate form. The stamens are exserted, and functional pollen is produced.
Barnard (1972) registered two Australian cultivars.
obtained from the Grassland Research Station, Kitale, Kenya, and developed at the
Grafton Experiment Station, New South Wales. A taller, coarser, more broad-leaved and
vigorous plant than the 'Kabete' ecotype above. It survives better than common Kikuyu
under less fertile conditions. Seed is available from Grafton Experiment Station.
also developed at Grafton. It is more densely tillered than 'Whittet', more
prostrate with narrower leaves, thinner stems and shorter internodes. The plants are
female-fertile, but 15-20 percent are male-sterile. Seed is available at Grafton.
Diseases
Kikuyu yellows is common in northern New South Wales, especially in grass fertilized
with nitrogen. To control it, return the area to cultivation of cash crops for a few
years. A leaf-spot caused by Pyricularia pennista produces a spot surrounded by a yellow
halo, and results in some leaf death, but is not of economic importance in a well-managed
and fertilized pasture (Brands & Cook, 1976). A fungus disease caused by Pyricularia
grisea causes high seedling mortality on the Atherton Tableland, Queensland, in wet
seasons.
Main attributes
Kikuyu is a highly digestible, high protein, low fibre, palatable grass which responds
readily to nitrogen, stands heavy grazing, holds soil against erosion and is an excellent
lawn grass.
Main deficiencies
It does not easily lend itself to mixed grass/legume pastures, and may become a weed of
cultivation.
Optimum temperature for growth
16-21°C. It has a poor adaptation to high temperatures. Mean 18.8° + 2.8° (Russell
& Webb, 1976).
Minimum temperature for growth
2-8°C in Kenya (Mears, 1970). Mean 7.7° + 4° (Russell & Webb, 1976).
Frost tolerance
It tolerates an occasional frost but not sustained frosting.
Latitudinal limits
Mean 27°N and S (Russell & Webb, 1976).
Response to light
Kikuyu does not grow well in shade.
Ability to compete with weeds
With adequate moisture and fertility, Kikuyu will suppress weeds.
Maximum germination and quality
required for sale
In Queensland, 60 percent germinable seed of 93 percent purity.
Pests
Larvae of the pasture scarab beetle (Rhopea magnicornis), Tarsonemus mites and soldier
fly (Atlermetapomia rubiceps) have caused temporary damage to Kikuyu in Australia, but the
effects are short-lived (Mears, 1970). In Hawaii, the hunting bull bug (Sphenophorus
vestitis) and grass webworm (Herpetogramma licarsicalis) cause damage (Plucknett, 1970).
Palatability
Very high.
Response to photoperiod
Flowering is not sensitive to changes in day length.
Chemical analysis and digestibility
Quality depends on frequency of defoliation and fertilizer applied. The high protein
content of the leaves (rarely less than 12 percent) gives a high quality margin over the 8
percent crude protein required to obtain positive nitrogen balance, even with grass
regrowth up to 100 days old. Digestibility of the dry matter is in the range of 60-70
percent. Kikuyu grass maintains high levels of digestible crude protein (Milford &
Haydock, 1965) and of digestible organic matter (Holder, 1967). General phosphorus,
potassium, calcium and magnesium levels in the herbage are adequate compared with other
species, but in Hawaii some calcium deficiency in beef cattle has been recorded (Younge
& Otagaki, 1958); in New South Wales, Australia, a mineral supplement of sodium,
calcium and phosphorus increased calf live-weight gain by 27 percent (Kaiser, 1975).g
Natural habitat
Highland grassland on deep red, well-drained latosolic soils at the forest margins, and
in grassy glades at an elevation of between 1 950 and 2 700 m in East and Central Africa
(Ethiopia, Kenya, Tanzania, Uganda and Zaire).
Tolerance to flooding
It tolerates flooding well. It survived ten days flooding at Quirindi, New South Wales
(Dale & Read, 1975).
Fertilizer requirements
Beyond basic nutrient requirements according to soil fertility, Kikuyu responds readily
to nitrogen fertilizer which gives it a competitive advantage against Axonopus spp. and
Paspalum dilatatum in Australia. Colman (quoted by Mears, 1970) in northern New South
Wales obtained an efficiency response of 17-24 kg DM/ha/kg N applied. Responses in
Colombia were recorded up to 150 kg N/ha. An effective association with the legume
Trifolium repens (white clover), where the clover provides 25-60 percent of the pasture,
reduced the need for nitrogen (Mears, 1970). Kikuyu does not give a good response to
phosphorus except on markedly deficient soils, though phosphorus application increases the
legume component. The critical level for phosphorus as a percentage of the dry matter at
the immediate pre- flowering stage is 0.22. Potassium response is not likely unless
intensive removal of the vegetative growth occurs. Symptoms of potassium deficiency appear
as tip- burning and senescence of the lower leaves, and a reduced potassium content of the
herbage (0.64-1 percent). Sulphur may also become deficient under heavy grazing or
cutting. It is usually corrected in one normal superphosphate application (Mears, 1970).
Compatibility with other grasses and
legumes
Under suitable conditions of soil and moisture, Kikuyu will dominate a pasture; most
existing Kikuyu pastures are monospecific. With renovation and application of
phosphorus-containing fertilizers, it can be combined with white and red clovers or
Desmodium uncinatum and D. intortum, but management and fertilizer treatment must be good
to maintain the mixture. Trifolium burchellianum and T. semipilosum occur naturally with
Kikuyu on the East African highlands, and some success has been achieved with the latter
on the Atherton Tableland. Pure Kikuyu pastures, top-dressed with nitrogen, are usually
more productive than grass/legume mixtures.
Genetics and reproduction
The somatic chromosome number of Kikuyu is 2n=36. Bisexual and male-sterile races
exist. The Rongai strain is female-fertile. It has been suggested that apomictic
reproduction occurs (Mears, 1970).
Seed production and harvesting
Seed production for commercial sale is relatively new. Repeated defoliation of the main
shoots is essential to induce flowering from lateral shoots of Kikuyu (Evans, Wardlaw
& Williams, 1964). Seed produced by fertile types is set so close to the ground it is
difficult to harvest; hence, for seed-harvesting the Kikuyu pasture must be flat and even.
Once established, the grass is mown to a height of about 25 mm and the cuttings removed.
This stimulates flowering and seed production. The mower is then raised slightly so that
at the next mowing, leaf growth is removed but the first crop of flowers is untouched.
This promotes a second flush of flowers. Successive seed sets accumulate and the crop is
mown at the end of the season, wind-rowed and threshed with a self-propelled combine
(Quinlan, Shaw & Edgley, 1975).
Economics
Kikuyu grass is essentially a high-quality grass for dairying and cattle finishing in
high-altitude areas of the tropical and subtropical world; a useful lawn grass and soil
stabilizer against erosion.
Animal production
Taylor (1941) recorded that from an area of 0.4 ha of fertilized Kikuyu grass in Natal,
three Jersey cows grazed on a put-and-take system from October to May and fed a supplement
of 0.45 kg maize meal at each milking time, produced a range of 8 260- 15 550 kg milk per
hectare (442-764 kg butterfat/ha) over a seven-year period. At Wollongbar in northern New
South Wales, from a Kikuyu-based pasture fertilized with 336 kg N/ha, stocked at 4.94
cows/ha, 447 kg and 361 kg butterfat/ha were produced over two successive lactations
(Kaiser & Colman, 1969). In Hawaii, beef production from fertilized Desmodium
canum/grass mixtures was 587, 644, 706 and 806 kg/ha per year from native grass, Kikuyu,
Paspalum dilatatum and pangola grass respectively (Younge, Plucknett & Rotar, 1964).
Dormancy
There is some initial hard-seededness, but it is modified by scarification during
harvest or by passage through an animal (Mears, 1970).
Value for erosion control
Kikuyu is excellent for erosion control, being used in a rainfall regime as low as 680
mm on black clays on the eastern Darling Downs, Queensland, although it prefers latosols
in a higher-rainfall area. Its main function in the irrigation areas of New South Wales is
to control erosion of irrigation channel banks, especially near regulators and water
wheels (Read, 1975).
Tolerance to salinity
Kikuyu lawns in western Queensland will tolerate saline soils if adequately watered to
keep soil salts at depth (Everist, 1974). Russell (1976) also found that it had good salt
tolerance.
Links:
Links for the genus:
Further reading
Mears, 1970; Quinlan, Shaw & Edgley, 1975.
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