Chamaecytisus palmensis (christ.) Hutch

 

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Leguminoseae

Author: John Frame

Common names

Tagasaste, tree lucerne, false tree lucerne.

Description

Perennial shrub or small tree of the Fabaceae family which grows to a height of 5-6 m and almost to the same diameter. Has long drooping branches with dull, bluish-green trifoliate leaves and minute stipules; leaflets narrowly rhombic with entire margins. On deep sands, roots can penetrate to 10 m and more (Wiley et al., 1994). Inflorescences white, cross-pollinated by bumble bees and also self-pollinated. Seed pods black, flattened, up to 5 cm long, with circa ten oval-shaped black seeds. The plant exhibits wide phenotypic variation in habit and vigour of growth, leaf size and pubescence, and flowering time. In a study of 65 accessions in New Zealand, there was wide genetic variation within and between populations which could be exploited in breeding programmes (Woodfield and Forde, 1987).

Distribution

About 30 species of the genus Chamaecytisus are distributed in Europe as trees or shrubs. Two notable species originated in the Canary Isles, C. palmensis and C. proliferus though the former, sometimes referred to as C. proliferus ssp. Palmensis is regarded as the most important of the two as a source of forage. It is not always clear in publications exactly which tagasaste species is being investigated. This profile mainly deals with C. palmensis but information about C. proliferus is also given.

Tagasaste has become naturalized and/or utilized in several temperate countries, e.g. New Zealand, in regions with Mediterranean-type climates, e.g. Western Australia, and in countries with long hot, dry summers, e.g. Ethiopia. It grows well in a rainfall range of 350-1600 mm (Gutteridge and Shelton, 1998); these authors also suggest that it could be used extensively in dry regions as a windbreak and shelter belt, while its dense wood with a specific gravity of 0.7 could have potential for firewood.

Characteristics

Adapted to a range of environments including temperate, Mediterranean, and tropical highlands. Suited to drought-prone sandy soils. Can develop as a shrub or a tree depending upon the defoliation management imposed (Frame et al., 1998).

Frost tolerance

Can be adversely affected by frost.

Drought tolerance

High.

Tolerance of flooding

Cannot withstand waterlogging.

Rhizobial relationships

Rhizobial isolates from root nodules showed infection features similar to Bradyrhizobium in some instances and to Rhizobium loti in others (Gault et al., 1994).

Sowing methods

Established from seed or rooted seedlings, the latter being favoured. Different permutations of width between rows and spacing of plants within rows are used. Wiley et al. (1994) suggest rows 6-10 m apart and plants every 2m within rows, a method which gives the opportunity of inter-cropping. Plants can be safely grazed or trimmed at 11 months after sowing or when 25 cm high with the aim of encouraging the development of multi-stemmed plants tolerant to grazing.

Sowing time

Normally autumn but some stands have been established in winter in Western Australia.

Number of seeds per kg

Circa 45 000.

Percentage hard seed

Usually very high.

Seed treatment before sowing

Scarification necessary, e.g. using commercial scarifiers as for subterranean clover.

Nutrient requirements

Soil pH of 5.0-7.0 required (Gutteridge and Shelton, 1998). Responsive to phosphate fertilization (Snook, 1982; Dann and Trimmer, 1986).

Nitrogen fixation

An annual N-fixation rate of 100 kg/ha was estimated in Chile from a 5000 plants/ha stand (Ovalle et al., 1996). In a Western Australia comparison of 550 trees/ha row-planted versus 2330 trees/ha in a plantation, 83 kg N/ha and 390 kg N/ha, respectively were fixed annually by C. proliferus (Unkovich et al., 2000); in the second year of the trial 587 kg N/ha was fixed by the undefoliated dense stand, a value close to the maximum reported in the literature for any N-fixing system though grazing and/or cutting would have reduced this value.

Utilization

The original management of tagasaste was by cutting and carrying (zero grazing) to livestock (Francisco-Ortego and Jackson, 1991). However, both continuous and rotational grazing systems for cattle have been developed though rotational grazing is preferred in southern Australia. At times the shrubs have to be trimmed back, firstly to encourage well-branched regrowth and secondly to ensure a vegetation height acccessible to the class of livestock being grazed. In Western Australia the performance of steers grazing C. proliferus was similar for both systems with daily livestock gains of 1.0-1.5 kg/head in winter and spring but dropping to maintenance in late summer and autumn (Edwards et al., 1997); annual liveweight gains were 218-240 kg/ha for one year and 327-335 kg/ha for another. A rotational system with grazing periods limited to 30-45 days is necessary for sheep; under continuous grazing shrub persistency is reduced since they graze young regrowth and eat the bark of the stems is grazed (Oldham, 1993). In extensive farming enterprises in southern Australia 5-10% of the area of a sheep/wheat farm established to tagasaste (C. proliferus) eliminates the need for hand feeding of grain in the dry autumn and maximises economic return (Lefroy et al., 1997). this short-term use once a year requires the shrubs to be cut mechanically to 0.5-0.6 m so that all the edible material can be utilized before removing the sheep.

Dry matter yields

While total annual DM production of 13-18 t/ha may be achievable in New Zealand, the edible DM (EDM) of leaf and fine stem will be 50-60% of this range (Townsend and Radcliffe, 1987; Douglas et al., 1996). Radcliffe (1985) reported leaf DM yields of 4-5 t/ha. In Australia, EDM up to 11 t/ha was obtained under favourable conditions (Snook, 1982). In Ethiopia, annual yields of 4.7 to 10.2 t/ha EDM were obtained with higher yields from increased harvesting interval from 2 to 6 months and age of stand (Assefa, 1998); the leaf proportion decreased from 71.7 to 45.3% and stem increased from 0.4 to 25.8% as harvesting interval was lengthened though most leaf DM was from the longest interval.

Feeding value

Tagasaste usually has lower mineral concentrations than pasture (McGowan et al., 1995). In Ethiopia leaf crude protein content was 18.0-21.2% and leaf organic matter digestibility (DOMD), 65.3-70.5% (Assefa, 1998).

The foliage contains significant concentrations of phenolic compounds which at 70 g/kg DM are associated with good acceptability and a daily voluntary intake of l kg/head by young merino sheep (Borens and Poppi, 1990); in contrast, foliage with total phenolics of over 170 g/kg DM is rejected. Ewe weaners grazing dried-out annual ryegrass/subterranean clover pasture in autumn and supplemented with 200 g/head/day of freshly cut tagasaste foliage gained 60 g liveweight/head/day and grew 11 g wool/head/day compared with a loss in liveweight and growth of 6g wool/head/day for ewes grazed on pasture only (Hemsley et al., 1987).

Forage quality varies with plant part (see Table) but can be maintained through the year (Douglas et al., 1996).

Plant part

Crude protein

(%)

DM digestibility

(%)

Leaf

200-300

70-80

Fine stem

90

50-60

Large stem

60

40-50

Wood

30

-

Bark

130

-

Acceptability

Highly acceptable to livestock.

Diseases

In the Ethiopian highlands plant mortality occurred from Fusarium wilt (Fusarium oxysporum) though it was probably exacerbated by seasonal waterlogging (Berhe and Tothill, 1997). Total mortality of plants occurred within two years on poorly drained soils in north-east Australia due to fungal root rot (Gutteridge, 1990).

Pests

Young plants are susceptible to attack by insect pests and wild animals such as rabbits during early establishment and must therefore be controlled by pesticides, protective fencing, tree guards or repellants as appropriate.

Main attributes

Adaptable to a range of environments. High forage production in regions. Suitable for grazing or ‘cutting and carrying’ to stock (zero grazing). Good feeding value.

Main shortcomings

No selected cultivars as yet. Further investigation needed on its agronomy and utilization.

Links

Main references

Frame et al. (1998); Gutteridge R.C. and Shelton H.M. (1998)