Townsville stylo (Stylosanthes humilis)

Datasheet

Description

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Townsville stylo (Stylosanthes humilis), foliage, Queensland, Australia

Townsville stylo (Stylosanthes humilis), leaf, Queensland, Australia

Common names

Townsville stylo, townsville lucerne [English]; luzerne de townsville, stylo annuel [French]; alfafinha-do-nordeste, alfalfa selvagem, alfalfa de townsville, erva-de-orelha [Portuguese/Brazil]; alfalfa estilosante [Spanish]; magsaysay stylo [Philippines]

Species

Stylosanthes humilis (Kunth) Hester [Fabaceae]

Synonyms

Astyposanthes humilis (Kunth) Herter, Stylosanthes figueroae Mohlenbr., Stylosanthes sundaica Taub.

Related feed(s)

Description

Townsville stylo (Stylosanthes humilis (Kunth) Hester) is a low growing annual (sometimes perennial), prostrate to erect legume. It may reach 50-70 cm in height. Townsville stylo has a taproot and may develop adventitious roots several inches from the taproot when the plant is heavily grazed or under high moisture conditions. The stems are narrow, hairy, many-branched, erect but they may be prostrate under high moisture conditions and then root from the nodes (Cook et al., 2005; Edye et al., 1992). The leaves are trifoliate and the leaflets are narrow and pointed, the terminal one being 15 mm long x 3.5 mm wide. Leaflets are mainly glabrous. Inflorescences are hirsute spikes bearing 5 to 15 bright-yellow flowers that develop into hairy, one-seeded, articulated pods once pollinated (Cook et al., 2005; Edye et al., 1992). Seeds are yellowish to brown, hooked (Cook et al., 2005; Partridge, 2003).

Townsville stylo is useful in heavily grazed areas in the semi-arid to subhumid tropical and lower latitude subtropical regions with a marked dry season (Edye et al., 1992). It has been introduced on natural grasslands with great success and considered an outstanding pasture legume because of its high yield of nutritious fodder, obtainable year after year, by applying only phosphatic fertilizer (Göhl, 1982).

In Australia, Stylosanthes humilis almost doubled the stocking capacity of natural pastures in many instances, mainly because of the drastically reduced weight loss in the dry season (Göhl, 1982). However, in the 1970s, townsville stylo was heavily harmed from a serious outburst of anthracnose disease, caused by the fungus Colletotrichum gloeosporioides. Interest turned to other perennial legumes for the dry tropics (Burt et al., 1979; Edye, 1997). Cultivars of other Stylosanthes species such as Stylosanthes scabra cv. Seca and tetraploid Stylosanthes hamata cv. Verano (also called Verano stylo) have been released and sown in Australia; they amounted to approximately 1 million ha in 2000 (Partridge, 2003; Noble et al., 2000). A similar development happened in Nigeria, where, after its introduction for large-scale range seeding in the 1970, Stylosanthes humilis was replaced by the superior Verano stylo (Agishi et al., 1994). One introduction of Stylosanthes humilis cv. Kohn Kaen, which is anthracnose-resistant, has been released in Thailand but it is not adapted to Australian conditions (Jones, 2001). In Australia, Townsville stylo is no more used as a commercial legume but remains a useful feed for cattle in areas where it is naturalized (Partridge, 2003).

Distribution

Townsville stylo is thought to have originated from northern South America, southern Central America and parts of the Caribbean (Ecocrop, 2011). Its Brazilian origin is now debated: it might have become naturalized in Brazil as it is in Malaysia, Indonesia, Thailand and North Australia (Cook et al., 2005; Edye et al., 1992). It was accidentally introduced into Australia in the early 19th century and its feeding value was discovered near Townsville, hence the name Townsville stylo (Quesenberry et al., 2006). It is now widespread in the tropics and was imported from Australia to Africa (Amodu, 2004). Townsville stylo can be found from 23°N to 28°S, from sea level to an altitude of 1800 m (Cook et al., 2005).

Stylosanthes humilis is a warm-season growing legume. Its optimal growth conditions are annual temperatures ranging from 14°C to 28°C with day temperatures above 30°C and night temperatures above 25°C, and annual rainfall in the range of 635 mm to 1500 mm (Cook et al., 2005; Amodu, 2004; Cruz-Vazquez et al., 2000; Edye et al., 1992). Townsville stylo prefers freely-drained light-textured soils but can also remain on heavier soils that are not necessarily well drained (Cook et al., 2005; Partridge, 2003). Soil pH ranging from 4 to 6.5 is preferred and Townsville stylo is tolerant of Al, Mn and salinity (Ecocrop, 2011). Like many Stylosanthes species, Stylosanthes humilis seems tolerant to low levels of available soil P, which is an advantage over many other legumes for such environments but also makes unfertilised stylo pastures deficient in P (Little et al., 1994).

Townsville stylo can survive drought once well established but has little tolerance of flooding. Winter rain is detrimental to its performance as it may cause secondary fungal infection on over-wintering standing hay (FAO, 2011). Frost and fire kill the plant but seeds survive both, and fire is even favourable to seedling (FAO, 2011; Cook et al., 2005).

Townsville stylo is a full sunlight species: it does not tolerate shade and should not be grown with tall grass or under trees. Its yield is reduced by 47% at 74% daylight and one third of plants die at 38% daylight (Cook et al., 2005; Edye et al., 1992; Sillar, 1967). Regarding photoperiodism, Townsville stylo is a short-day flowering species (FAO, 2011).

Forage management

Pasture

Townsville stylo can be sown in pure stands or mixed with grasses. Dry matter yields of pure stands may be 1-6 t/ha (Ecocrop, 2011). In mixed stands of Pangola grass (Digitaria eriantha)/Townsville stylo, yields were 9.3 t/ha/year compared with 5.2 t/ha from pangola grass alone (FAO, 2011). Used as cattle pasture, townsville stylo could sustain up to 2.5 beasts/ha in mixed stands with sabi grass (Urochloa mosambicensis) (Winter et al., 1977 cited by Lascano, 2001). Stocking rates of 0.5-1 beasts/ha appeared to be more realistic, considerably increasing carrying capacity of unimproved pasture (Cook et al., 2005). Average live-weight gains of 0.3-0.5 kg/hd/day were achievable in Australia and in Africa (Cook et al., 2005; Oyenuga et al., 1966 cited by Lascano, 2001).

Townsville stylo can be mixed with many grasses provided they are not tall and do not shade the legume. It is often sown with grasses such as buffel grass (Cenchrus ciliaris) (low forms), birdwood grass (Cenchrus setiger), marvel grass (Dichanthium annulatum), Pangola grass (Digitaria eriantha), sabi grass (Urochloa mosambicensis), Bothriochloa pertusa, and with legumes such as round leaf cassia (Chamaecrista rotundifolia), lotononis (Lotononis bainesii), Stylosanthes guianensis var. intermedia, Stylosanthes hamata or Stylosanthes scabra (Cook et al., 2005). Townsville also combines naturally with spear grass (Heteropogon contortus) (FAO, 2011).

Before sowing, the land should be heavily grazed or burned to reduce grass competition and allow Townsville stylo to establish. Direct oversowing gives a lower stand density than sowing on disked land. Though a N-fixing legume, Townsville stylo does not necessarily require seed inoculation (Göhl, 1982). An important characteristic of Townsville stylo is that is it less palatable when young than mature, so that animals prefer grass during the first stages of development of the legume, giving it an opportunity to establish satisfactorily. Once established, Townsville stylo can be heavily grazed though it might result in prostrate habit of the plant. If grazing is done until the end of the growing season, seed set may be hampered (Cook et al., 2005).

Cut-and-carry, hay and silage

Though it is mainly grazed by livestock, Townsville stylo can be cut and fed to animals. It can also be made into good quality hay towards the end of the growing season (Edye et al., 1992). Townsville stylo should be mown into windrows, dried and baled within 3-4 days. Hay quality depends on N fertilization; hay yields were about 2.4 t hay/ha/year in Northern Australia (FAO, 2011).

Silage can be made from Townsville stylo if it grows erect among grasses: reports of Pangola grass/Townsville stylo making good quality silage are available (Kretschmer, 1968).

Standover or deferred feed

Townsville stylo acceptability improves with age and the standing dry matter is sought after during winter and spring. The seed content also improves the food on offer (FAO, 2011).

Environmental impact

N-fixing legume

Townsville stylo, as the other Stylosanthes species, is a N-fixing legume. It nodulates readily even if not inoculated with rhizobium. Nodulation is greatly enhanced by P fertilization though Townsville stylo has relatively low P requirements (FAO, 2011).

Bovine tick controller

Several tropical pasture legumes of the genus Stylosanthes can trap and kill larvae of Rhipicephalus microplus (formerly Boophilus microplus). The stems and leaves of these legumes are covered with glandular trichomes, which produce a sticky secretion with a characteristic odour and a volatile toxic agent (Sutherst et al., 1982). This has been observed in Mexico where Townsville stylo has been reported to have significant acaricidal effects (Muro Castrejón et al., 2003; Fernandez-Ruvalcaba et al., 1999).

Weed and soil acidifier

Stylosanthes species have been reported to acidify light textured soils by leaching unused nitrates down the soil profile: it is thus important to combine stylo with grasses that can use legume-fixed nitrogen (Maass et al., 2004; Noble et al., 2000).

Townsville stylo may have too agressive growth and is considered an agricultural weed in some places (Maass et al., 2004). This is the case in Hawaii, though it is not an environmental risk like Stylosanthes guianensis (US Forest Service, 2011).

Nutritional aspects

Nutritional attributes

Townsville stylo has a moderate crude protein content of about 14% DM with values ranging from 7 to 22% at various stages (Feedipedia, 2011; Cruz-Vazquez et al., 2000; Playne et al., 1972; Bhannasiri, 1970; Snook, 1961). Crude fiber values range from 20 to 35% DM (Feedipedia, 2011; Cruz-Vazquez et al., 2000; Bhannasiri, 1970; Snook, 1961). Calcium ranges from 0.73 to 1.70% DM (Feedipedia, 2011; Playne et al., 1972) and phosphorus from 0.07 to 0.33% DM (Feedipedia, 2011). Unfertilised Stylosanthes humilis was found to be a most unusual pasture species, able to supply adequate N for animal nutrition but a very inadequate level of P, due to the tolerance of many stylo species to low levels of available soil P (Little et al., 1994).

Potential constraints

No toxicity has been reported (2011).

Ruminants

Recent literature on the nutritional properties of Stylosanthes humilis is largely non-existant, which is probably due to its almost complete disappearance in Australia due to anthracnose and to the competition of other Stylosanthes species, notably Stylosanthes hamata and Stylosanthes scabra. Literature on Townsville stylo is, therefore, historical, even though this legume is still used as a pasture in the tropics.

Measured in sheep, various stages of maturity provided DM intakes from 43.1 to 58.9 g/kg W^0.75. DM digestibility ranged from 60 to 62% (Playne et al., 1972).

In Australia, beef cattle grazing several stylo species (Stylosanthes humilis, Stylosanthes hamata, Stylosanthes scabra, Stylosanthes viscosa), maintained high levels of dietary nitrogen for most of the year. Cattle grazing the two annual stylos, Stylosanthes humilis and Stylosanthes hamata, recorded higher dietary nitrogen levels than those consuming perennial stylos. Relative preference indices showed that Stylosanthes humilis was the only stylo species eaten in preference to grass over the duration of the experiment (Gardener et al., 1994). Hereford steers (430 kg to 740 kg body weight), in a grazing trial conducted over 7 consecutive years on a pure tropical grass pasture or mixed with Stylosanthes humilis, showed a higher daily weight gain when grazing the mixed pasture: 267 vs. 104 g/d (Shaw et al., 1970). In a comparison between Stylosanthes humilis and Stylosanthes hamata cv Verano, Verano stylo gave significantly greater live-weight gains in drier sites though the differences in gain did not occur when legume yield on both pastures exceeded 600 kg/ha (Gillard et al., 1980).

Pigs

In India, 4-4.5 months old pigs fed a conventional feed and allowed to graze Cynodon dactylon, Stylosanthes humilis, Sehima and Heteropogon contortus for 3 hours per day had higher daily gain, higher body weights and better feed conversion efficiency than pigs fed the conventional feed only. Higher body weights were also observed when the grass was pen-fed rather than grazed (Singh et al., 1998).

Fish

Tilapia (Oreochromis niloticus)

Stylosanthes humilis leaf meal included at 10% in the diet of tilapia fingerlings gave better growth and feed conversion ratio than the control diet (survival was similar) but the results were inferior to those obtained with cassava leaf meal (Nnaji et al., 2010).

Nutritional tables

Tables of chemical composition and nutritional value

Townsville stylo (Stylosanthes humilis), aerial part, fresh

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used