Crotalaria juncea is an annual herbaceaous plant utilized for fiber, forage, and as a green manure cover crop. Reaching heights of 3.5 m, C. juncea bears long, slender, trifoliate leaves and typical, butterfly-shaped blooms similar to other legumes.
C. juncea is most often used for fiber (rope, fishing nets, paper, canvas, carpets, etc), or as a green manure cover crop. Grown in rotation with commodity crops, C. juncea fixes up to 135 kg nitrogen/ha As a forage crop, C. juncea is limited in scope, as most varieties have antinutritional characteristics, especially in their seeds and pods, and the stalks are too fibrous to digest.
- Elevation – up to 1500 m
- Rainfall – 200-4300 mm/year
- Soil Types – well-drained soils with pH 5-8.4
- Temperature Range – 4-40° C
- Day Length Sensitivity – not a significant factor for most varieties
- Light – full sun
In tropical settings, sunn hemp can be planted year-round; however, it is photoperiod sensitive and flowering occurs in response to short days. Long day-lengths favor vegetative growth and reduce seed-set, although day-length neutral varieties exist (Mannetje).
C. juncea seed should be planted 2-3 cm deep—or broadast—at a rate up to 55 kg/ha, depending on use. Germination and establishment success can be dependent on moisture conditions and sun exposure, as C. juncea does not tolerate water saturation or shaded conditions well. Upon establishment, C. juncea requires relatively little management.
Harvesting and Seed Production
If utilizing as forage, C. juncea should be harvested 6-8 weeks after planting. For green manure cover crop use, it is recommended to cut C. juncea 10-12 weeks after planting, before full bloom of the stand and before plants become too fibrous to incorporate. For use as fiber, higher stand densities lead to taller, straighter plants, which increases quality of fiber harvested, which can be done after flowering or seed production.
Pests and Diseases
Few major pests, but is sometimes affected by the same pests and diseases as cowpea (Vigna unguicuilata) and pigeon pea (Cajanus cajan). C. juncea has demonstrated ability to suppress some pestilent nematodes.
Cooking and Nutrition
Due to antinutritive properties, C. juncea is not for human consumption.
Clark, A., editor. 2007. Sunn hemp: Crotalaria juncea. In: Managing cover crops profitably. 3rd ed. Sustainable Agriculture Research and Education, College Park, MD. http://www.sare.org/Learning-Center/Books/Mnaging-Cover-Crops-Profitably-3rd-Edition/Text-Version/Printable-Version. Accessed 20 May 2019.
Ecocrop. 1993-2007. Crotalaria juncea. Food and Agriculture Organization, Rome, Italy. ecocrop.fao.org/ecocrop/srv/en/dataSheet?id=801. Accessed 22 May 2019.
Maroyi, A., 2011. Crotalaria juncea L. Record from PROTA4U. Brink, M. & Achigan-Dako, E.G. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. http://www.prota4u.org/search.asp. Accessed 22 May 2019.
Mannetje, Len 't. "Crotalaria juncea L."Grassland Species Profiles(2012). (FAO) Foodand Agriculture Organization of the United Nations. Web. 18 May 2012
Sheahan, C.M. 2012. Plant guide for sunn hemp (Crotalaria juncea). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center. Cape May, NJ. 08210.