Sunn Hemp  Fibre

 
     
     
  World Sunn Hemp  Production Map  
     
 

Sunn Hemp

Sunn hemp (Crotalaria juncea L.) is one of the earliest and most distinctly named fibers of India. It has great potential as an annually renewable, multi-purpose fiber crop. It is the most important species of the Crotalaria genus, which is comprised of over 350 species located in the tropics and subtropics of both hemispheres.Past research efforts have shown that the soft, lignified fibers produced in the stem of sunn hemp could be utilized in the manufacturing of pulp and paper, and more recent efforts have indicated that other potential products can be developed from these fibers. Additional characteristics that enhance the value potential of sunn hemp as a non wood, fiber crop are low nitrogen fertilization requirements, the ability to fix nitrogen and to grow in marginal soils, drought resistance, and resistance to root-knot nematodes. The bast fibers are utilized for the manufacture of cordage and high quality paper. In addition to the uses as a green manure crop and as a fiber source, research is being conducted in Texas to determine if the shorter core fibers of sunn hemp can be utilized in the manufacture of soil-less potting media for commercial nursery application.

Origin

Crotalaria juncea is generally considered to have originated in India; Most of the present-day sunn hemp production is located in India, Bangladesh, and Brazil, where it has been cultivated since prehistoric times. It is grown as a green manure crop, a fodder crop, or for the bast fibers.

Botanical Description

Sunn hemp is a short-day, erect shrubby annual, generally 1 to 4 m in height. The stems are cylindrical and ribbed. Branching in the upper portion is minimized with dense plantings. The simple, elliptic to oblong shaped leaves, are spirally arranged on the stem. The root system is characterized by a long, strong taproot, well developed lateral roots, and much branched and lobed nodules, up to 2.5 cm in length. Extensive cross-pollination occurs in sunn hemp and self-pollination takes place after the stigmatic surface has been insect or mechanically stimulated. Seeds are small, flattened, kidney-shaped, and contain approximately 35% protein. Due to cultivar and environment, seed weight is highly variable, ranging from 18 to 30 seed per gram.

Cultivation and Management

Good land preparation should be made before planting sunn hemp for fiber production. Although reports on fertilization requirements vary, additions of P are generally recommended for low phosphorous soils. Sunn hemp is fast growing and generally suppresses weed populations due to dense canopy shading. However, early season weed control has been shown to improve yields when sunn hemp is grown for fiber. No herbicides are currently registered for use in sunn hemp production.

Planting dates differ among locations; however, adequate soil moisture and frost-free, warm weather conditions will provide rapid emergence and the highest yields.

Economic Importance

As one of the most widely grown green manure crops throughout the tropics, sunn hemp is often grown in rotation with several different crop species. The stems of sunn hemp are composed of two fibers, the bast and woody core. The bast fibers, which are located in the outer bark, are much longer than the core fibers, but the two fiber widths are very similar. The proportion of bark in the total stalk, by dry weight, generally ranges from 15% to 20%.

It produced high organic matter yields, was able to fix nitrogen, and could reduce the build-up of root-knot nematode populations However, the difficulty in producing seed caused many farmers to abandon the growing of this crop. Interest in growing sunn hemp was renewed during World War II, as C. juncea was added to the list of critical war materials in 1942 because of its potential use as cordage fiber, especially for Marine Oakum. Sunn hemp may be superior to kenaf for some fiber properties, including bast fiber length (3.79 vs. 2.62 mm) and width (24.3 vs. 19.7 m).

Sunn hemp possessed the following properties that made it an excellent candidate for papermaking:

(1) Good yields of bleachable sulfate pulps,

(2) Pulp strength properties that are equal to or greater than those of mixed southern hardwood pulp, and

(3) Bast fiber length to width ratio that is greater than those of wood fibers.

 

 

 

 

 

 

 

     
     
     
     
 

 

 
     
     
     
     
     
     
     

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