Kikuyu Grass in New Zealand: History and Agronomy

History

Kikuyu grass was introduced into New Zealand by the Department of Agriculture in the early 1920’s as cuttings from a Rhodesian source, although there may have been earlier informal releases. Kikuyu is the anglicised version of the proper noun Gikuyu, the most populous ethnic group of tribespeople in Kenya.
Kikuyu grass is native to the African countries of Burundi, Democratic Republic of Congo (Zaire), Ethiopia, Kenya, Rwanda, Tanzania and Uganda. It is now naturalised in northern and southern Africa, tropical Asia, Australia, New Zealand, south-west mainland United States, Hawaii, Mexico, Central America, South America, Melanesia and Polynesia.

Department of Agriculture officers conducted trials at Albany (Auckland) and Purewa (Whangarei) and farmers visiting these trials were impressed with the growth of the plant and its adaptation to poorer soils. So cuttings from the trials were readily distributed around the northern North Island.
By 1974 it had spread to about 10% of Northland farmland (some 100,000 ha) and it was considered a dominant pastures species over more than half of Northland farms.

In the 1950’s many of its characteristics as a pasture species were becoming clear and E.H. Arnold, an Assistant Field Superintendent in the Department of Agriculture, Auckland, reported to a Grasslands Conference:

“Kikuyu grass is here to stay and is spreading far and wide. Eradication is possible, but at a prohibitive cost. Most areas are left as an uncontrolled menace, but quite a number of farmers are successfully using this grass to their advantage. Regular controlled grazing management, at times with the use of the electric fence, is essential. Autumn and early winter growth is best eaten off before frosts occur. Most kikuyu areas, instead of being left a liability, can be made into an asset.”

Kikuyu grass responded to improved soil fertility and would allow the presence of complementary species, especially in winter and spring, only if controlled by intensive grazing management or mechanical means. Its feeding value was high when controlled, but uncontrolled it became a vigorous weed of low nutritive value and its eradication was impractical. Its drought tolerance and summer/autumn growth flush was recognised but farmer enthusiasm had waned after the deliberate introduction phase throughout Northland. During the 1960’s and 70’s various research stations began detailed investigations into kikuyu grass productivity. When electric fencing became commonplace and an effective herbicidal control in glyphosate was available, fears of kikuyu grass “taking over the north” diminished. The comments of C. Vallance, a Dargaville farmer, at a Grasslands Conference in Northland in 1967 are interesting.

“Kikuyu is a controversial grass, and where I once used to envy farmers who had none, I no longer do so. Kikuyu, which was once brown and unthrifty, is now thriving, and with a stocking rate of one cow and replacements per acre (2.5/ha), I am having trouble keeping up with its growing capacity.”

Kikuyu Grass Forum
In November, 1985 a Kikuyu Grass Forum was held in Whangarei, organised by the Agricultural Research Division of the Ministry of Agriculture and Forestry (MAF) and the Grasslands Division DSIR, and sponsored by Gallagher Group, of Hamilton. Animal management equipment company Gallaghers was keen to highlight the use of controlled, or strip, grazing behind electric fencing, both permanent and temporary, to keep on top of the vigorous growth of kikuyu grass during summer and autumn months. New Zealand led the way in the development of electric fencing from the 1930s, which became a farm management tool to cost-effectively confine grazing animals onto smaller land areas, to ensure they eat all of the (kikuyu) grass on offer, before moving the mob onto another small area of fresh pasture alongside. MAF researcher Graeme Piggot edited the proceedings of the forum, which were published by Gallagher Group in 1985 under the title Kikuyu Grass Farming for High Production. A second edition with the same name in booklet form was published by Northland Pasture of  Whangarei in 1991 (ISBN 0-473-01427-0) and both editions contain nearly 100 references to published papers on kikuyu grass up until that time.

At the Whangarei forum, long-time Waikato-based farm consultant Vaughan Jones, commissioned by Gallagher, put the NZ experience with kikuyu grass and electric fencing into perspective. “The clear message is that kikuyu grass is a highly productive species which can be grown in balance with other grasses and clovers, provided it is fenced into enough paddocks to allow it to be grazed down in one bite,” Jones said. The widely travelled Jones told of Hawaiian problems with stock underfeeding in the midst of rampant kikuyu grass. Gallagher power fencing was introduced to Hawaii and early adopters increased their productivity and profitability from cattle on kikuyu, while pastures improved as clover re-emerged. Jones concluded with a prototype kikuyu management programme, the first of its kind:
1. Intensive subdivision to allow rotational grazing.
2. High stocking rates.
3. Regular mowing of surpluses.
4. Correct fertilising.
5. Inclusion of the most suitable clovers and winter-growing grasses.
6. Mob stocking in autumn to allow winter growing species through.

Also at the forum, Northland dairy farmer Danny Simms recalled his parlous position with kikuyu-dominant pastures before introducing specialised management. Simms said his kikuyu grass was rampant, the heavy clays were very wet as a consequence and the soil fertility was low. The result was a severe feed shortage in spring, low per cow and per hectare production, low cow fertility and a spread calving pattern. With management improvements Simms doubled his production per hectare in a decade and got 94% of cows calved in the first six weeks. He blitzed the farm with 1.5t/ha of 15% potassic superphosphate, drained the heavy clay flats (to enable the kikuyu grass to be controlled in wet conditions) and resowed after cultivation with Ellett ryegrass, Pitau white clover and Pawera red clover, plus plenty of lime and fertiliser.

“The kikuyu grass regenerated after three years, but the aim was that, with high stocking rates, a two-tier pasture would develop with kikuyu grass providing summer feed and the ryegrass becoming dominant at other times.”

He said the red clover did a good job of preventing the kikuyu grass from becoming summer-dominant. He used beef cows as mulchers in the autumn, at a stocking rate of 6/ha effective, and introduced mechanical topping from the beginning of March.

“The autumn rains should then bring the ryegrass through the kikuyu much earlier,” he said.

Simms provided his own management list:
1. Get the soil fertility high.
2. Drain wet areas.
3. Have a high stocking rate.
4. Establish superior ryegrass and clovers. It is simply not practical to control the whole farm with the mower. The burden must be eased by spraying and re-sowing an area of the farm each year.
5. And, finally, never let it get away; mow, mow and mow again.

Researchers John Rumball (DSIR Kaikohe) and Graeme Piggot and Hugh Morgan (MAF Whangarei) reported on their trial work with sheep and cattle on kikuyu grass pastures. Rumball could find little difference in sheep production parameters between pasture types. The DSIR sheep trials were at about 20 ewes/ha on gumland soil, and the Dargaville beef trials were on podzolised sand soil with bulls at 5/ha and steers at 6/ha, with both soils being naturally poorly drained.

“Inclusion of kikuyu grass was of benefit to sheep production from mid-January to mid-March at the highest stocking rate in some years, but it consistently depressed sheep production in the spring and required extra management in the autumn.” Rumball said the strategies necessary to maximise the value of kikuyu grass included a high stocking rate, uniform utilisation through controlled grazing, delaying of lambing by two to three weeks and doubling the grazing pressure in autumn. Kikuyu would also benefit sheep where white clover growth is poor in the summer, where temperate grasses don’t persist because of low nitrogen fixation and summer drought and insect Inaugural Kikuyu Action Group chairman Murray Jagger addresses the crowd at a KAG field day on his own Whangarei Heads Farm.

Insect damage

At the 1985 Whangarei forum MAF research entomologist Rod Blank reported on the resistance of kikuyu grass to insect attack, namely Australian solider fly, black beetle, black field cricket and cosmopolitan army worm. Solider fly sucks nutrients from the kikuyu roots and had been observed to cause severe damage to small areas of kikuyu grass pasture on volcanic soils around Whangarei. Longer pasture favours the build-up of fly populations and the potential for further outbreaks, although low, must increase with the spread of kikuyu in pastures. Kikuyu grass harbours two to six times higher densities of black beetle larvae than ryegrass based pastures. Either the moister soil conditions or the food source in kikuyu stolons are favourable for black beetle. In most situations, Blank said, kikuyu grass tolerates high larval densities. The stolons are well anchored, which reduced livestock pulling damage. But damage may occur under drought conditions on light soils. Blank concluded that insecticidal control of beetle would be impractical.

Pot trials showed that kikuyu grass was highly favoured by black field crickets with herbage losses three to 10 times that of ryegrasses. In the field the dense mat caused by the stolons provided an excellent shelter for crickets. This enables crickets to build up on sandy and volcanic soils which do not readily crack open and provide shelter in the soil. In dry years, low to moderate cricket populations (10-30/m2) can effectively consume all the dry matter grown over the summer. Under severe cricket attack, kikuyu grass pastures provide virtually no summer feed for livestock. Kikuyu recovers well following autumn rains and the death of crickets, in contrast with ryegrass-based pastures where plants are killed and pasture seed is eaten, preventing pasture recovery.

Army worm infestations of kikuyu grass can occur following periods of heavy rain or floods, where these have been preceded by a dry period. There can be loss of autumn growth and fouling of pastures. Insecticidal sprays can be used but their use is seldom warranted, Blank said. Army worm outbreaks have been linked with outbreaks of kikuyu grass poisoning in livestock. In summary, kikuyu grass provides a favourable attack, and where sheep are subject to animal health challenges such as viral pneumonia and facial eczema.

Piggot and Morgan also reported that weight gains in Angus weaner steers and Friesian bulls in farmlet trials at Dargaville Research Farm (now NARF) from 1979 to 1985 from kikuyu grass pasture were similar to those reported from solely temperate pastures. It was possible, they said, to finish beef cattle to slaughter weights in 17-18 months for Friesian bulls and 24-26 months in Angus steers.
“These results were achieved by running sufficient stock to control kikuyu grass in the autumn and by feeding supplements in late winter or dry periods in the summer if weight loss was likely,” they said.

Agronomy
Kikuyu grass is a C4 plant, which means it grows in hotter and drier environments than C3 plants (like ryegrass). They have different photosynthetic pathways. C3 plants must open their pores during the day to capture and metabolise carbon dioxide.
C4 plants open their pores at night and capture the carbon dioxide when the air temperature is cooler. During the day, with pores closed, they use the sunlight to metabolise the CO2.
C4 photosynthesis is a more energy-consuming physiological process than the C3 metabolism, but is more efficient in terms of water (and nitrogen) use. In hot and dry conditions it allows the C4 plant to capture more CO2 than C3 plants, and so produce more dry matter than C3 grasses, being more vigorous and drought-tolerant. As our climate becomes hotter and drier, C4 grasses have an advantage because of their efficient use of water. However, as carbon dioxide increases they lose their advantage because of the energy cost of their metabolism in comparison with C3 grasses. Modelling suggests that under climate change, increased carbon dioxide will result in stimulated growth in C3 plants, and C4 plants will diminish.

The growth pattern of kikuyu grass is as follows:

Seedling – produces leaves from the crown and then tillers from the leaf axils. New leaves are produced from nodes on the primary and secondary tillers.
Stolon – A tiller which becomes long and prostrate as a result of the internodes becoming elongated.
New tillers and new roots can form at each exposed node, provided the node has been in contact with the soil. Branching of stolons occurs after the node has rooted, the rooted node then effectively becoming a new plant.
Rhizome – An underground stem which forms nodes and extends by elongated internodes.

The tip or the rooted nodes can produce leaf if exposed to light by coming up through the soil surface.
Flowering of kikuyu grass tends to be stimulated in the secondary or lateral tillers by severe defoliation and decapitation of a stolon. In NZ, flowering tends to peak in late spring. Since controlled environment studies and field observations have shown that flowering is not sensitive to temperature and day length, it is likely that the seasonal pattern is a feature of the growth pattern of the plant, i.e. late spring is when the plant produces food source and habitat for these four insects. Solider fly is potentially the most serious pest because it can cause the most serious long term damage, however the risk of outbreaks seems to be confined to volcanic soils. Black beetle and black field cricket are the pests most likely to be encountered in kikuyu grass pastures. Beetle larvae appear to be tolerated, although there may be a risk of damage in drought years. Crickets cause considerable pasture production losses but can be controlled with baits. In general, kikuyu grass tolerates insect pest feeding damage and, with the exception of soldier fly, persists well under severe attack, eliminating the need for pasture renovation if kikuyu pastures are desired.

The way that kikuyu grass grows is clearly illustrated here. It has both surface stolons which can develop new roots at the nodes and underground rhizomes which can grow as much as 3 cm per day therefore penetrate far into bush or forest. But it will tolerate some shading, which enables it to grow up within hedges and bushes, eventually smothering them. Kikuyu tolerates a wide range of rainfall environments although it is poorly adapted to tropical regions and the suspicion is that it doesn’t like high night temperatures or prefers diurnal variation in temperature.

Where soils are suitable, it has become naturalised in areas with rainfall up to 3,000 mm and down to 800 mm/year, and performing well under irrigation the first “crop” on multi-noded stolons in the NZ growth season. Feathery stigmas (female parts) are produced first. If these are fertilised by pollen and a fertilised ovum has formed than filaments (the male stamens) are exserted and pollen is shed. The flower is not seen, only the protruding stigmas or stamens, giving rise to the plant’s Latin name of Pennisetum clandestinum. The early introductions to New Zealand were of male-sterile vegetative material although there have been later introductions of seed. Male-sterility refers to where the flowers only produce female feathery stigmas, not the filamentous male stamens. Because male-sterility was assumed to be genetically recessive, the implication was that male-sterility in the New Zealand pastures of kikuyu would remain a primary factor in its spread. Spread of kikuyu grass would be by vegetative means. But kikuyu grass began appearing at sites where vegetative spread was impossible such as protected offshore islands. Cow dung pats could be packed with seedlings. The issue was resolved in the mid 1980’s discovery from research by Hugh Morgan at Dargaville which showed that male-sterility was genetically dominant. This meant that the male-sterile introductions in the 1920’s were likely to be heterozygous, in other words they carried the recessive gene for male-fertility. Their progeny would contain fully male-fertile plants. A small amount of pollen in the environment from the later introductions of seed would encourage much wider seed set. Today male-fertile strains are common across Northland and the issue of male-sterile strains has become only an intellectual curiosity.

Vigorous Growth
The aggressive kikuyu plant flourishes by establishing itself in thick mats. It prevents new sprouts of other species from growing and can even kill small tree saplings. It is resistant to mowing and grazing due to its strong network of roots, which easily send up new shoots. It springs up in turfs and lawns, and can ruin pathways by forcing itself up between stones and tiles. The plant can be introduced to new areas on ploughing and digging machinery, which may transfer bits of the rhizome in soil clumps. While the grass spreads well via vegetative reproduction from pieces of rhizome, it is also dispersed via seed.
Kikuyu grass doesn’t like deep shade and will not  therefore penetrate far into bush or forest. But it will tolerate some shading, which enables it to grow up within hedges and bushes, eventually smothering them.

Kikuyu tolerates a wide range of rainfall environments although it is poorly adapted to tropical regions and the suspicion is that it doesn’t like high night temperatures or prefers diurnal variation in temperature.
Where soils are suitable, it has become naturalised in areas with rainfall up to 3,000 mm and down to 800 mm/yr, and performing well under irrigation in lower rainfall areas. It is moderately drought tolerant, because of deep root system (to greater than 3 m). Often found along water courses, it can tolerate some water-logging and up to 10 days inundation. Most active growth occurs during periods of high humidity. It is more frost tolerant than many warm season grasses, with only exposed foliage being damaged at about -2°C. Although tops are killed, stands survive temperatures as low as -9°C.

Establishment methods
Kikuyu grass has proven to be a valuable species for re-vegetating bare, areas in Northland; on west coast sand dunes for control of wind erosion, on east coast greywacke soils for re-vegetation of slips, on dry volcanic soils for revegetation of soil slips, gullies and sheetwash and on gumland soils.
Soil conservator Lee Whiley, of the former Northland Catchment Commission, told the Whangarei forum in 1985 that kikuyu’s tolerance of summer drought and low fertility sites made it useful in situations where temperate species struggled to survive. Its stoloniferous habit made it capable of establishing a rapid cover for controlling surface erosion. Farmers used turfs cut from existing pasture and dug into the new site. Large areas of existing turf could be scurfed with a grader blade and then cut into manageable chunks. Pieces of cut stolon could be broadcast over bare areas and then trampled in by stock. Cattle could also be grazed on kikuyu pasture when seeding and then moved to the new area, where seed would germinate within the dung pats. Alternatively, dung which contained germinated seed could be collected from cowsheds or yards and spread in small heaps on eroded areas.
At a Grassland Conference in Tauranga in 1961 J.E. Bell, speaking on Pasture Species and Mixes for the Auckland Province, said:

“Kikuyu grass should be confined to light sandy soils subject to only light frosts. It is an exceptionally good coloniser of raw sand country. Raw sand is extremely liable to dry out in summer, to such an extent that normally only annual clovers will survive. Colonised by kikuyu and especially if top-dressed, white clover grows well on raw sand because the kikuyu grass has increased the moisture content of the top layer of the sand.”

Acknowledgements
Thanks to all the farmers who contributed their time, land, stock and machinery. To Northland Seed and Supplies; D Boyt Machinery; RD1; Ballance Agri-Nutrients; Dexcel, AgResearch, PGG Wrightson Seeds and NuFarm. To Murray Jagger and all the other farmer members and non-farmers of KAG who have given their time and enthusiasm to attend KAG meetings. To the NZ Landcare Trust for project management and continuity. To the funders who made the work possible:
AGMARDT, Sustainable Farming Fund, FITT fund, NRC, Northland Agricultural Field Days Committee and C. Alma Baker.

Especially to Hinerangi Trust without whose initial support back in 1999 this work would not have started.