Sunn hemp
Botanical Information
- Sunn hemp, scientifically known as Crotalaria juncea, holds significance as a lignocellulosic crop and is India’s oldest native fibre-producing plant.
- This natural fibre belongs to the legume family Fabaceae.
- It is an herbaceous, shrubby annual dicot crop.
- It is a warm season plant with relatively shorter growth cycle as compared to the other plants.
Habitat and fibre production
- Sunn hemp is a tropical or sup-tropical plant grown below 1000 feet.
- It can thrive in a broad range of soil types, but it performs particularly well on poor sandy soils compared to many other plants.
- It flourishes in well-drained soils with a pH range of 5.0 pH to 7.5 pH.
- It is a rapid, vigorous growing plant which can achieve a height of 4ft within 60 days under optimum conditions and grows further as time receeds.
- The height of the plant ranges from 3-9ft .
- If heavy rains occur shortly after planting, it does not grow well.
- With a typical yearly yield averaging 409 kg/ha(2023), India leads as the world’s primary Sunn hemp fibre producer, contributing to 23% of the global production.
- Sunn hemp is primarily grown as a biomass to add nutrition to the soil and harvesting seeds for further propagation in India and is highest producer of sunn hemp, with China and Bangladesh being the next leading cultivators.
Table 1. Physical & mechanical properties and chemical composition of areca nut fibres
Physical and Mechanical properties [1]
Length
38-42 cm
Diameter
20 μm
Moisture content
10.6%
Moisture regain
11.5%
Crystallinity index
91%
Chemical composition [1]
Cellulose
66.3%
Hemicellulose
18.6%
Lignin
14.9%
Pectin
4.6%
Ash
4.2%
Wax
0.9%
Features of fibre
- Sunn hemp possesses robust, coarse, shiny, and rigid fibres that are as sturdy as hemp fibres and more durable than jute fibres.
- The fibres are lighter in colour, ranging from whitish to grey to yellow.
- It doesn’t serve as a habitat for diverse pathogens and pests.
- It effectively fixes nitrogen in the company of Rhizobacteria .
- They are resistant to mildew, microorganisms, and moisture .
- When grown as a summer annual crop, it has the ability to produce a biomass of 2268 kg and 46 kg of nitrogen per acre.
- While in winters, it is mainly used as a cover crop or green manure to improve the properties of the soil.
Uses
- It generates substantial biomass, reaching approximately 2268 kilograms of dry biomass per acre in just 9-12 weeks, contributing to a global production of 130,000 metric tons per year.
- It is a weed suppressor that reduces root-knot nematodes (microscopic roundworms that live in soil and on plant roots).
- It helps increase the soil’s organic matter and prevent soil erosion.
- Ropes are generally made through the superior quality of Sunn hemp fibres, whereas the inferior quality fibres are used in the making of cigarette and cheap cordages.
- It is primarily employed as a source of green manure, animal fodder, and a non-wood fibre crop.
- Fibre applications include fishing nets, sacking fabrics, canvas, tissue papers, rug yarns, etc.
