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Sesbania sesban (L.) Merr. |
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Leguminosae (Papillionaceae)
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Author: J.M. Suttie
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Sesban The origins of S. sesban are unclear but it is widely distributed and cultivated throughout tropical Africa and Asia. Until recently, the use of perennial Sesbania species has largely been restricted to south and southeast Asia. In India, these crops have had a long history of agricultural use, primarily as green manures and as sources of forage. Most of the early research on the use of perennial Sesbania for forage production was conducted in India (Patel 1966). Non-forage uses: Onim et al. (1989) reported a yield of 16 t/ha of sun-dried wood from a 4 year old stand at a density of 1,600 plants/ha in Kenya while much higher yields of 63.5 t/ha were reported for S. sesban grown under rainfed conditions in Haryana, India (Singh 1989). Despite the lack of detailed information on yield, von Carlowitz (1989) pointed out that S. sesban is popular for fuelwood because it produces a high woody biomass in a short time which, though soft, is a relatively smokeless, quick, hot burning kindling. Sesbania sesban is used to a lesser extent as a green manure, probably because it is not as fast growing as the annual Sesbanias. The dried leaves of both S. grandiflora and S. sesban are used in some countries as a tea which is considered to have antibiotic, anti-helminthic, anti-tumour and contraceptive properties. Description It is a short-lived shrub or small tree up to 8 m tall. Its leaves are pinnately compound, 2-18 cm long with 6-27 pairs of linear oblong leaflets (26 x 5 mm). The raceme has 2-20 flowers which are yellow with purple or brown streaks on the corolla. Pods are subcylindrical, straight or slightly curved up to 30 cm long and 5 mm wide containing 10-50 seeds. Five varieties of S. sesban are recognised botanically but their differences do not correlate strongly with their agricultural value. S. sesban shows some cool tolerance. It grows well in the subtropics and is significant in extending the nitrogen fixing forage trees into cooler, higher elevation regions of the tropics up to 2,000 m. (Gutteridge and Shelton 1998). It is outstanding in its ability to tolerate waterlogging and is ideally suited to seasonally waterlogged environments. When flooded, it initiates floating adventitious roots and protects its stems, roots and nodules with spongy, aerenchyma tissue. Evans and Macklin (1990) report the rainfall range of S. sesban as 500-2,000 mm. Another outstanding feature is its tolerance of both saline and alkaline soil conditions (Hansen and Munns 1985). However, its tolerance of highly acid, aluminium saturated soils is not known. It is established from seed. Seeds of S. sesban have a hard seed coat and scarification is recommended to ensure uniform seed germination. Domergues et al (1998) recommend inoculation with the appropriate strain of Sinorhizobium teranga when the natural rhizobial population is inadequate. One of the major advantages of perennial Sesbania species over other forage trees and shrubs is their rapid early growth rates. Dutt et al. (1983) reported that S. sesban attained a height of 4-5 m in 6 months in India. More research is required to determine appropriate management systems to maximise yields of edible material. More studies on the effects of direct grazing in extensive feeding systems are also warranted, for S. sesban, to determine the effects of grazing on plant longevity. Seed production Sesbania spp. are pollinated by bees, except for large-flowered species such as S. grandiflora which appear to be pollinated by birds (Brewbaker 1990). Seed collection from most of the perennial sesbanias is easy and large quantities of seed can be rapidly hand harvested and processed. Crop use and grazing management Cutting management has a very important influence on its productivity, S. sesban thrives under repeated cutting and coppices readily with many branches arising from the main stem below cutting height. Cutting frequencies have generally been in the order of three or four cuts yearly but up to eight cuts per year have been taken in some. Yields have ranged from 4 to 12 t dry matter/ha/year depending upon location. Composition Most reports indicate that the crude protein content of both S. sesban and S. grandiflora foliage is generally greater than 20% and often above 25%. Dry matter digestibility of Sesbania species is superior to that of most other tree and shrub legumes. In northeast Thailand, Akkasaeng et al. (1989) found that the in vitro dry matter digestibility of S. sesban and S. sesban var. nubica was 75 and 66% respectively, all higher than that of 15 other tree legumes that were tested. It appears that the most economically efficient and safest use of perennial Sesbania forage for ruminants is as a protein supplement to low quality roughages such as crop residues or dried grasses. This dilutes the effects of anti-nutritive factors and greatly improves the utilisation of the roughages. It appears that the use of the perennial Sesbania species should be restricted to ruminants because of the deleterious effects often observed when they are used as feed sources for monogastrics. However, even with ruminants, there may be adverse effects on animal productivity and health when Sesbania comprises a high proportion of diets for long periods. Research is required to determine whether anti-nutritive factors are present in Sesbania forage and whether they can be controlled or reduced by management practices. Chemical composition S. sesban (% dry matter). Onim et al. (1987) speculated that the perennial Sesbania species could fix up to 600 kg N/ha/year. They felt this was possible because Sesbania roots are readily infected by the less specific cowpea types of Rhizobium giving large numbers of active nodules. Under experimental conditions they reported a total nitrogen yield of 448 kg N/ha from the aerial biomass of S. sesban var. nubica. No work noted. Pests and diseases The crop seems to be relatively pest free.
Akkasaeng, R. et al.(1989); Brewbaker, J.L. (1990); Dommergues, Y. et al.(1999);Dutt, A.K. et al.(1983); Evans, D.O. and Macklin, B. (1990); Gutteridge R. C. and M. Shelton (1998); Hansen, E.H. and Munns, D.N. (1985); Onim, J.F.M. et al(1989) ; Patel, B.M. (1966) ; Singh, N.T. (1989); von Carlowitz, P.G. (1989) |