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Hairy indigo (Indigofera hirsuta)

Datasheet

Description
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Common names 

Hairy indigo, hirsute indigo, rough hairy indigo [English]; indigotier hérissé [French]; falso-anil, indigo, anileira, anileira-do-pasto, anil-roxo [Portuguese]; añil dulce [Spanish]; tom-toman, jukut lulut [Indonesian, Java]; tebawang amjak [Indonesian, Sulawesi]; cermai burong [Malaysian]; tayom [Philippines, Iloko]; tagum [Philippines, Bisaya]; tina-tinaan [Philippines,Tagalog]; tildjil, wiereka [Papua New Guinea]; ครามขน (khram-khon) [Thai]; cây cỏ chàm, cây sục sạc ma, chàm lông [Vietnamese]

Taxonomic information 

Indigofera indica Miller (1768), Indigofera ferruginea Schum. & Thonn. (1829), Indigofera angustifolia Blanco (1837) (Djarwaningsih, 1997). 

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Related feed(s) 
Description 

Hairy indigo (Indigofera hirsuta L.) is a subtropical and tropical legume shrub sometimes used as fodder.

Morphology

Indigofera hirsuta is an annual erect or spreading shrub 0.3 - 1.5 m tall. The name hairy (hirsuta) comes from the presence of very conspicuous brown and rusty hairs on the stems (Djarwaningsih, 1997). The stems are erect, cylindrical and striate, and become woody as the plant matures (Djarwaningsih, 1997). The leaves are compound, imparipinnate, 2.5-10 cm long with 5-9 (-11) opposite leaflets. Leaflet blades are elliptical to obovate in shape, 4 cm long x 2.5 cm broad. The apical leaflet can be up to 6 cm long x 3 cm broad. Leaflets are hairy on both sides (FAO, 2016; Djarwaningsih, 1997). Inflorescences are hairy, many-flowered spike-like racemes, 20 cm-30 cm long. Flowers are papillonaceous, hairy, red to pink in colour, about 4-6 mm long. The fruits are straight, cylindrical dehiscent pods, 1-2 cm long and 1-2.5 mm in diameter. They contain (4-) 6-9 cube-shaped, blotched seeds (FAO, 2016; Djarwaningsih, 1997).

Uses

Hairy indigo has been used as a green manure and cover crop in tropical plantations such as coffee, tea or rubber in Asia and in citrus orchards in Florida. It may help as a cover crop in place where erosion control is required. It is used as an annual fodder in Florida and Brazil and it can be grown in mixtures with grasses. It has valuable potential to grow on low fertile acidic soils of Florida. It would have some resistance to root-knot nematode (see Environmental Impact below). It is reported to have ethnomedicinal effects and could be used as a dye in West Africa (Djarwaningsih, 1997). It is considered a weed in some places, particularly in Florida (see Environmental Impact) (US Forest Service, 2010). 

Distribution 

Hairy indigo originated from Africa and Asia. It is now widespread and naturalized in Southern Asia and in Australia. It was introduced into the USA at the beginning of the 20th century where it proved suitable for cultivation in coastal areas of Florida and Texas. It became naturalized in parts of tropical America. Hairy indigo is mainly found in cultivated areas, in grassland, savannah, dry and deciduous forests and on river banks and beaches (US Forest Service, 2010; Djarwaningsih, 1997).

Hairy indigo can be found in both hemispheres, from 32°N in Georgia (USA) to 30°S in Argentina and from sea-level up to an altitude of 1350-1500 m in Africa (FAO, 2016). It can be grown in places where annual mean temperature ranges from 15°C to 28°C and where annual rainfall is between 900 mm and 2500 mm. A dry season is beneficial to flowering and seed production. Indigofera hirsuta does well on a wide range of soils and is particularly tolerant to low fertile and low pH soils provided they are moderately or well-drained. It has neither waterlogging tolerance nor frost tolerance. It has some shade tolerance and can be grown in tree plantations, but it cannot withstand heavy shade (FAO, 2016; Djarwaningsih, 1997).

Forage management 

Establishment

Hairy indigo is a warm season legume. It should be drilled or broadcasted during early or late spring. A well-prepared and firm seed bed is ideal but it may also establish without soil preparation. Cattle trampling and rain cover the seeds that will need 7-9 days to germinate. Early growth of seedlings is very slow in the early stages (Portillo et al., 2009). Weeding is necessary but not possible before 30 days after sowing as the seedlings are not recognisable among weeds. It is not necessary to remove grazing animals from the stands where Indigofera hirsuta has been sown. A reduction of the grazing pressure is sufficient during establishment. After 50 days, hairy indigo is about 30 cm high. It reaches 60 cm after 65 days and 90 cm after 80 days (Djarwaningsih, 1997).

Harvest

Hairy indigo can be harvested when it is 75-90 cm high but if 2 harvest are expected it can be firstly cut at 20-25 cm (higher cuts are deleterious to axillary buds) and the regrowth is grazed or cut for hay. Rotational grazing should be preferred. Hairy indigo intended for hay or silage should be cut at early stage, before the stems become woody and lose their nutritive value (FAO, 2016; Djarwaningsih, 1997).

Environmental impact 

N-fixing legume and green manure

Hairy indigo is a N-fixing legume that could provide 126 kg N/ha/year to companion grasses and 100 kg N/ha to maize crop when sown as a relay crop (Djarwaningsih, 1997; Kalmbacher et al., 1980). In maize-hairy indigo system, hairy indigo provides also about 4-5 t DM/ha. Research on its utilization as green manure was reported to be abandoned in the 1990s (Djarwaningsih, 1997).

Cover crop and nematode controller

When sown as a relay crop of maize, hairy indigo not only provides N to the crop and organic matter but it also protects the soil from erosion. Its role in erosion control may be important and it is recommended for hilly areas (Djarwaningsih, 1997). Hairy indigo was reported to have reducing effect on nematodes when used as a cover crop or as an intercrop in rotation with legumes such as peanuts or soybeans (Rodriguez-Kabana et al., 1988; Rhoades, 1983).

Invasive species

Hairy indigo is a very versatile species that re-seeds readily after fruiting and may become invasive. In 1918, it was already declared a noxious weed in Australia (Gilruth, 1918) and is now classified as invasive in many places, including Australia (where it is classified as "reject for import"), French Polynesia, Palau, Nauru, the Philippines, Singapore, Diego Garcia Island, and Mayotte Island. It is a known weed in the USA ("High risk" species in Florida), China, Puerto Rico, and Brazil (CABI, 2014; Randall, 2012US Forest Service, 2010).

Nutritional aspects
Nutritional attributes 

Indigo hirsuta forage is particularly rich in protein (14-27% DM), with early cuts being the richest. In Florida, the protein content decreased rapidly with plant age (15% DM at 86 days) and regrowth (12% DM after a regrowth at 90 cm) (Kalmbacher et al., 1980). In another study, protein content decreased from 16 to 6% DM between August and November (Williams et al., 1993). In Uganda, protein decreased from 27% DM at 4 weeks to 15% at 21 weeks. The fibre content increased from NDF 35% DM at 4 weeks to NDF 68% at 21 weeks (Sibii, 1979).

Potential constraints 

Hairy indigo is not toxic to cattle (Sellers et al., 2013). Its tannin content can be high (> 10% DM) and above the levels tolerable to ruminants (Ologhodoo, 1989). These tannins may have therapeutic effects for domestic animals and especially anthelmintic effects (Gaur et al., 2010Suvarnalatha et al., 2013).

Ruminants 

Hairy indigo is a protein-rich forage that can be used for pasture, hay or silage. Information about it is rather scarce

Digestibility

In Florida, in vitro OM digestibility at early cut was quite high (60%) and decreased with plant age (51% at 86 days) and regrowth (43% after a regrowth at 90 cm) (Kalmbacher et al., 1980). In another study, In vitro OM digestibility decreased from 53% in August to 37% in November (Williams et al., 1993).  In Uganda, in vitro DM digestibility decreased from 61% at 4 weeks to 45% at 21 weeks (Sibii, 1979).

Pasture

Indigofera hirsuta has been used for pasture by cattle farmers in Florida since the 1940s but was not found very satisfactory. In the 1970s, it was cultivated to improve grass pastures in grass/legume associations (for instance with Bahia grass Paspalum notatum, pangola Digitaria decumbens or setaria Setaria sphacelata var. anceps, Kretschmer et al., 1973). It made also possible to reduce N fertilizer treatments (Hodges et al., 1977). Cultivars have been released by the University of Florida and have been reported to be valuable for cattle grazing (Quesenberry, 1999).

Silage

Early trials in Florida found that hairy indigo made acceptable silage for dairy cows (Becker et al., 1970; Wing et al., 1963). Other trials, however, found that the silage satisfied only maintenance requirements and was not readily eaten (Catchpoole et al., 1971). 

Rabbits 

Hairy indigo is one of the fresh forages used by Nigerian farmers to feed their rabbits in the Benue state. Samples harvested during the dry season reveal a high content of proteins and of crude fibre: 24.1% and 24.3% DM respectively (Carew et al., 1989).

Used as only feed, hairy indigo forage allows a normal medium growth rate, indicating that this forage could be used safely for feeding rabbits (Posri, 1985).

Nutritional tables
Tables of chemical composition and nutritional value 

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

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 21.9   21.8 22.0 2  
Crude protein % DM 20.1 4.1 14.3 26.6 31  
Crude fibre % DM 23.8 1.1 22.7 25.2 4  
NDF % DM 47.0 7.1 34.7 59.5 17  
ADF % DM 24.2       1  
Lignin % DM 4.1       1  
Ether extract % DM 2.9 1.2 1.7 4.5 4  
Ash % DM 10.1 0.7 9.5 11.0 4  
Gross energy MJ/kg DM 18.4         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 19.0 3.5 15.9 22.7 3  
Phosphorus g/kg DM 2.8 1.1 2.0 4.1 3  
Potassium g/kg DM 20.6   18.2 23.0 2  
Sodium g/kg DM 0.3   0.1 0.5 2  
Magnesium g/kg DM 3.8       1  
               
Amino acids Unit Avg SD Min Max Nb  
Alanine % protein 5.7       1  
Arginine % protein 6.1       1  
Aspartic acid % protein 9.9       1  
Glutamic acid % protein 9.4       1  
Glycine % protein 3.9       1  
Histidine % protein 2.8       1  
Isoleucine % protein 4.5       1  
Leucine % protein 7.5       1  
Lysine % protein 4.1       1  
Methionine % protein 1.8       1  
Phenylalanine % protein 6.6       1  
Proline % protein 4.5       1  
Serine % protein 4.0       1  
Threonine % protein 4.4       1  
Tyrosine % protein 4.6       1  
Valine % protein 5.1       1  
               
In vitro digestibility and solubility Unit Avg SD Min Max Nb  
DM digestibility, pepsin % 52.1 6.7 41.5 61.1 18  
OM digestibility, pepsin % 53.2 6.4 42.6 62.4 10  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 77.7         *
Energy digestibility, ruminants % 74.3         *
DE ruminants MJ/kg DM 13.7         *
ME ruminants MJ/kg DM 10.9         *

The asterisk * indicates that the average value was obtained by an equation.

References

Bartha, 1970; Bhannasiri, 1970; Brown et al., 1991; Bui Huy Nhu Phuc et al., 2001; Carew et al., 1989; Holm, 1971; Kalmbacher et al., 1980; Sabiiti, 1979

Last updated on 19/09/2016 00:42:24

References
References 
Datasheet citation 

Heuzé V., Tran G., Hassoun P., Lebas F., 2016. Hairy indigo (Indigofera hirsuta). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/289 Last updated on September 19, 2016, 0:36