3037

11: Auxiliary plants

Pueraria phaseoloides (Roxb.) Benth.

Journ. Linn. Soc. 9: 125 (1865).

LEGUMINOSAE - PAPILIONOIDEAE

2n = 22, 24

Dolichos phaseoloides Roxb. (1832).

Tropical kudzu, puero (Australia) (En). Kudzu tropical, puero (Fr). Indonesia: kacang ruji, krandang (Javanese), fuo banga (Ternate). Malaysia: kacang hijau hutan, tampong urat. Philippines: singkamasaso (Tagalog), bahay (Bikol), vaay (Ivatan). Burma (Myanmar): pe ying pin. Laos: pièd, s'üak pièd. Thailand: thua-sianpa (central). Vietnam: d[aa]u ma, d[aa]u dai, d[aa]u r[uf]ng.

Tropical kudzu is indigenous to the lowlands of East and South-East Asia where it occurs on river banks and roadsides, fallow fields and young secondary forest. It has been introduced into other tropical regions and is now cultivated and naturalized throughout the wet tropics.

Tropical kudzu is especially important as a component of grazed and ungrazed cover crop mixtures in rubber, oil-palm and coconut plantations in South-East Asia, Africa and tropical America. In East Africa, it is grown as a cover crop in plantations of sisal (Agave sisalana Perrine). In South-East Asia, tropical America and Australia it is also used as a pasture legume. Its ability to smother weeds makes it a useful pioneer legume often grown in combination with other more permanent species. It is planted on sloping sites to control soil erosion and in rotation with annual crops as a green manure.
The tuberous roots are edible. Strong fibres from the stem are used for rope making. In Malesia, the plant is used in traditional medicine to cure boils and ulcers.

Chemical analysis of a pure tropical kudzu cover crop under oil palm grown on a Selangor-series soil in Malaysia, producing a living biomass of 4.9 t/ha dry matter in 18 months, indicated a nutrient content per 100 g dry matter of: N 2.35 g, P 0.20 g, K 2.14 g, Mg 0.20 g. A similar cover on a Serdang-series soil in Malaysia produced a living biomass of 5.8 t/ha dry matter in 12 months, containing per 100 g: N 3.01 g, P 0.32 g, K 2.02 g, Mg 0.14 g. Litter of tropical kudzu decomposes fairly slowly. In a litterbag experiment in Colombia at an average temperature of 26°C, the half-life of organic matter was about 110 days during the rainy season and 220 days during the dry season. On average, about 75% of K was leached out of the litter after 1 month, while the concentration of N and P in the remaining litter was approximately constant.
Tropical kudzu is very palatable, although its wet-season palatability is reported to be low in tropical America. Nutrient concentrations typically range from 2—4% N, 30—40% crude fibre, 0.15—0.45% P and 0.4—1.6% Ca.
The weight of 1000 seeds is 10—12 g.

Deep-rooting perennial herb with climbing or twining, hairy stems. Roots subtuberous. Main stems about 6 mm in diameter, extending 4.5—10 m, rooting at nodes if in contact with moist soil, lateral stems branching from nodes; young shoots densely covered with brown hairs. Leaves large, trifoliolate; stipules triangular to ovate, 4—11 mm x 2—3 mm, pubescent; petiole 3—11 cm long, hairy; stipels lanceolate to setaceous, 3—7 mm long; petiolule 2—5 mm long; top leaflet symmetrical, triangular or ovate, 2—20 cm x 2—16 cm, thin, base broadly cuneate or subrhomboidal and very shallowly lobed, apex acuminate, lateral leaflets oblique, (4—)6—7(—14) cm x (3—)6—7(—12) cm, thinly hairy on upper surface, greyish-green and densely pubescent on lower surface. Inflorescence an axillary, unbranched raceme, 10—46 cm long, pubescent; peduncle about 13 cm long; bracts 2—5 mm long, pubescent; flowers 10—23 mm long, mauve to deep purple, borne in pairs; bracteoles lanceolate, 1—3 mm long; pedicel 2—6 mm long; calyx campanulate, 6 mm long, hairy, upper teeth broad, lateral ones triangular, the lower lanceolate and all terminating in a bristle; standard orbicular, 1—2.5 cm in diameter, spurred, greenish on outside and white on the inner side with a mauve violet central blotch; stamens 10, diadelphous. Fruit a straight or slightly curved, terete or compressed cylindrical pod, 4—12.5 cm x 3—5 mm, thinly clothed with stiff appressed hairs, black when mature, 10—20-seeded. Seed cylindrical to cubic with rounded corners, about 3 mm x 2 mm, brown to brownish-black.

Seedling growth of tropical kudzu is only moderately vigorous during the first 3—4 months. Seedling vigour is superior to other cover crops such as centro (Centrosema pubescens Benth.) and calopo (Calopogonium mucunoides Desv.). Once established, it is very vigorous and quickly smothers weeds. Unless regularly controlled, it tends to climb the stems of trees and to get entangled in the fronds of young palms. In Malaysia, it reaches 60—70% cover after about 4 months and 90—100% after 8 months. It can form a tangled mat of vegetation 60—75 cm deep. Flowering in Java is from May to October.

Three botanical varieties are distinguished within Pueraria phaseoloides:
— var. javanica (Benth.) Baker (synonym: Pueraria javanica (Benth.) Benth.): leaflets mostly entire, rarely somewhat lobed; flowers 15—23 mm long; bracts and calyx pubescent, lateral calyx lobes obtuse, lower calyx lobe acute; fruit 7—11 cm x 4—5 mm. Worldwide it is the most common variety, also introduced into tropical Africa and America. Its most probable origin is in Java and Peninsular Malaysia.
— var. phaseoloides: leaflets entire, lobed or sinuate; flowers 7—15 mm long; bracts and calyx short-pubescent, lateral calyx lobes acute, lower calyx lobe acuminate-lanceolate; fruit 5—9 cm x 3—4 mm. It occurs mainly in South and South-East Asia. Its most probable origin is in southeastern China.
— var. subspicata (Benth.) van der Maesen (synonym: Pueraria subspicata (Benth.) Benth.): leaflets large, entire to deeply lobed; flowers 15—23 mm long; bracts and calyx densely long-pubescent, lateral calyx lobes acute, lower calyx lobe lanceolate-subulate; fruit 7—12.5 cm x 4—5 mm. It occurs mainly in India, Bangladesh, Burma (Myanmar) and Thailand. Its most probable origin is in north-eastern India.
The ecological requirements of the 3 varieties are the same. Sometimes overlapping morphological characteristics occur. Named cultivars exist in South America and Tanzania, but seed is mostly traded without cultivar name.

Tropical kudzu is best suited to the humid lowland tropics up to 1000 m altitude with an annual rainfall in excess of 1500 mm. In an experiment under controlled conditions, an optimum temperature of 32/24°C (day/night) was found and dry matter yields were reduced by 35% with a change in temperature regime to 26/15°C. Few reports are available on photoperiod responses. In Puerto Rico (latitude 18°N), flowering and seed set occur in the short daylength period from January to March, suggesting that it may be a short-day plant. In Papua New Guinea and Africa, it only sets seed under dry conditions.
In comparison with other legume species tropical kudzu has been ranked highly as a shade-tolerant plant. When grown under 50% shade in coconut plantations in the Solomon Islands it was the most productive legume and it even suppressed the accompanying grasses. This characteristic makes it suitable in integrated livestock/plantation production systems. Under a regime of more than 50% shade, tropical kudzu is still comparatively productive, but in mixtures it gives way to other species like centro (Centrosema pubescens) or desmodium (Desmodium heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi).
Tropical kudzu is tolerant of very wet and waterlogged sites. It prefers heavy soils and is well adapted to acid soils. It is particularly susceptible to Mg and S deficiencies and has moderate to low Ca and P requirements, but it responds to fertilizer application. On poor oxisols and ultisols Pueraria phaseoloides also requires K and Mg fertilizer. It is not tolerant of salinity.

Tropical kudzu is usually established from seed. Having a high proportion of hard seed, germination can be increased by hot water, acid or mechanical scarification. Commercially available seed is often scarified by abrading the seed-coat in a hexagonal drum, lined with sandpaper, rotating at 7.5 rpm for 24 hours.
Tropical kudzu usually nodulates with native cowpea rhizobia but inoculation with an appropriate strain of Bradyrhizobium, such as RRIM 768 in Malaysia, is recommended for new areas. Seed is usually broadcast or drilled in rows 1 m apart. It can also be established by oversowing into an existing pasture if the pasture is disked or burnt beforehand. When seed is scarce, tropical kudzu can be propagated vegetatively, one recommendation being to plant two rooted cuttings, 0.7—1 m long, at each point on a 1—2 m grid. In Africa, a tropical kudzu cover can sometimes be established by selectively weeding the natural regrowth after land clearance. Standard seed mixtures for cover crop contain a 5:4:1 ratio of calopo, centro and tropical kudzu or a 4:1 mixture of centro and tropical kudzu. Seeding rates for these mixtures are 5—10 kg/ha in the inter-row areas between rubber or oil-palm trees.

When planted under palm and other tree crops on former forest land, some initial control of natural regrowth of forest plants is necessary to establish tropical kudzu. Manual weeding gives the best results, but several herbicides have been used successfully (e.g. oxyfluorfen as a post-emergence herbicide at 0.5 kg/ha). During the subsequent two years, tropical kudzu has to be cutlassed or beaten down to a height of 30 cm. Circles around trees are clean-weeded to prevent tropical kudzu from climbing the trees. In sisal plantations in East Africa its vigour is reduced by low rainfall (800 mm) which checks its climbing habit. It competes with oil palm for moisture during dry periods and it has been recommended to check the growth of tropical kudzu at the start of the dry season. The largest effect of tropical kudzu on associated tree crops occurs when it dies off 3—4 years after planting. Marked increases in tree growth and rubber yield are found during that period, not during the first 3 years. Tropical kudzu responds well to added P; linear responses to up to 50 kg/ha of P have been obtained on infertile soil.
Tropical kudzu is very palatable to animals and this can lead to selective grazing and poor persistence. Grazing experiments in Malaysia have shown that under continuous grazing at stocking rates of 2—6 head of local cattle per ha, the proportion of tropical kudzu was significantly reduced with increased stocking even after one year of grazing. Farmers using grass—legume mixtures have also reported excellent growth of tropical kudzu in the first two years, and rapid decline under grazing. The lack of persistence of tropical kudzu is probably also influenced by physical soil characteristics and related to the poor development of rooted stolons on some soils.

Tropical kudzu is remarkably free from diseases, although leaf-eating caterpillars can damage ungrazed swards and pod-borers reduce seed production.

Tropical kudzu is usually directly grazed in mixed pastures but can be cut for hay, silage or for feeding as fresh forage.

Annual dry matter yields of up to 10 t/ha from tropical kudzu swards have been recorded in cutting experiments, with some 65—75% of the yield from the wet season and 25—35% from the dry season. Dry matter yields of up to 23 t/ha have been measured in tropical kudzu—grass swards, 40% of this being tropical kudzu. In tropical America, tropical kudzu—grass pastures have produced live weight gains of 313 kg/ha per year (with Andropogon gayanus Kunth) and 542 kg/ha per year (with Panicum maximum Jacq.)

The largest germplasm collection is maintained by the Centro Internacional de Agricultura Tropical (CIAT), Colombia and a smaller collection is held at the Australian Tropical Forage Genetic Resource Centre (ATFGRC), CSIRO, Australia. There are no known breeding programmes with tropical kudzu in South-East Asia.

Tropical kudzu is, and will probably remain, the most widely grown cover crop throughout the humid tropics, especially in tree plantations. Its main features as a forage legume are its vigorous initial growth on fertile soils and its high palatability. Improvements should primarily be aimed at improving its persistence under grazing.

Chin, S.L., 1977. Leguminous cover crops for rubber smallholdings. Planters' Bulletin 150: 83-97.
Duke, J.A., 1981. Handbook of legumes of world economic importance. Plenum Press, New York, United States. pp. 214-216.
Eng, P.K., Chen, C.P. & 't Mannetje, L., 1978. Effects of phosphorus and stocking rate on pasture and animal production from a guinea grass legume pasture in Johore, Malaysia. 2. Animal live weight change. Tropical Grasslands 12: 198-207.
Han, K.J. & Chew, P.S., 1982. Growth and nutrient contents of leguminous covers in oil palm plantations in Malaysia. In: Pushparadja, E. & Chew, P.S. (Editors): The oil palm in agriculture in the eighties. Vol. 2. Incorporated Society of Planters, Kuala Lumpur, Malaysia. pp. 235-251.
Hardjono, A. & Warsito, T., 1989. Respon tanaman penutup tanah campuran (Calopogonium mucunoides + Centrosema pubescens + Pueraria phaseoloides) terhadap pengapuran. 2. Percobaan lapangan [Response of a mixed cover crop (Calopogonium mucunoides + Centrosema pubescens + Pueraria phaseoloides) to liming. 2. Field experiment]. Menara Perkebunan 57: 19-23.
Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. 2nd Edition. FAO Plant Production and Protection Series No 2. Food and Agriculture Organization of the United Nations, Rome, Italy. pp. 376-388.
Thomas, R.J. & Asakawa, N.M., 1993. Decomposition of leaf litter from tropical forage grasses and legumes. Soil Biology and Biochemistry 25: 1351-1361.
van der Maesen, L.J.G., 1985. Revision of the genus Pueraria DC. with some notes on Teyleria Backer. Agricultural University Wageningen Papers 85-1, Wageningen, the Netherlands. pp. 71-88.
Wong, C.C., 1990. Mineral composition and nutritive value of tropical forage legumes as affected by shade. MARDI (Malaysian Agricultural Research and Development Institute) Journal 18: 125-143.

R.A. Halim

Halim, R.A., 1997. Pueraria phaseoloides (Roxb.) Benth.. In: Faridah Hanum, I & van der Maesen, L.J.G. (Editors): Plant Resources of South-East Asia No 11: Auxiliary plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea