The neglect treasure of super strength
Sisal (Agave sisalana) yields fiber in its leaves that is bio-degradable with good mechanical strength offers a great promise for sustainable societies. Heading towards a bio-based era, entails swapping of many synthetic raw material to more renewable raw materials of plants and animal origin which offers great perspectives for natural fibers. As the popularity and demands of natural fiber worldwide is increasing in industrial uses there are new opportunities for hard fiber to reach high value end-market.
Natural fibers are extracted/obtained from various vegetative parts of the well-defined fiber crops like cotton, jute, sisal, coir, flax, hemp, abaca, ramie, etc. Other fiber having protein base include wool and silk of refine nature. Sisal fiber, among these fibers occupies the position as one of the strongest leaf fiber ever produced in nature and is found scattered in lands of varying texture in extreme climatic zones all over the Pakistan.
Sisal derives its name from port of Sisal at Yucatan in Mexico. It accounts for a large portion of hard fiber produced worldwide and occupies sixth place in fiber plants, representing 2% of world’s production of plant fiber. Its fiber is used for the manufacture of various utensils such as carpets, ropes, twine, marine cables, bags, geotextiles, paper, filters, mattress, wall coverings etc, and also for natural food source (feed) and alcoholic beverages.
A tropical hardy plant survives in range of warm climates even with slight rainfall. The wild sisal is spread over a wide range of geographical areas including deserts in the Punjab and Sindh to coastal belt in Sindh and Balochistan. The adaptation to wide range of climates and inherent tolerance to biotic and abiotic stress made possible for sisal to grow at sea level to a lofty altitude of 2100 meter at Himalayan foothills. The irrigated plains of Punjab favours growth of distinct varieties of narrow, medium and broad leaf varieties of sisal to produce fiber of choice. Other member of the Agave family are in sporadic use as ornamental look in Pakistan. Sisal has successfully cultivated in Faisalabad, the typical area of the central Punjab, with annual rainfall of about 300 mm that too is highly seasonal.
Sisal plant has a stalk on which the leaves are inserted. Its dimensions are about 1.2 m in height, with a diameter of approximately 20 cm. The lance-shaped leaves, growing out from the stalk in a dense rosette, are fleshy and rigid, with grey to dark green colour. Each is 0.8 to 1.5 m long, 7.6 cm wide at the base, and 10 to 16 cm across at the widest portion, terminating in a sharp spine. The Sisal plant has a shallow root system, maximum 60cm deep. 7-10 year life-span and is usually cut first after 2-3 years and then at 6-12 month intervals. A typical plant will produce 200-250 commercially usable leaves in its life-time (hybrid varieties up to 400-450 leaves) and each leaf contains an average of around 1000 fibers.
Production and Management
Sisal is propagated by using bulbils produced from buds in the flower stalk or by suckers growing around the base of the plant. The flowers do not produce seed as the flowers begin to wither, buds growing in the upper angle between the stem and flower stalk develop into bulbils that fall to the ground and take root. At the beginning of the rainy season the plants are transferred to the field, where they are spaced 1 to 2 m apart.
Sisal preferentially is a plant of tropic and subtropics with an average temperature requirement range of 20-28 and annual rainfall of 600-1500 mm. It can tolerate a prolonged periods of drought and higher temperature. Nutrient requirement of the sisal also made it a potential crop in many areas of Pakistan as 30-50 kg N-P ha-1is sufficient for a whole year. There is not a threat of insect attack on sisal due to its leathery epidermis sharp spines on leaves for protection. Only pest known to occasionally reach pest proportions is the Sisal Weevil (Scyphophorus interstitialis).
Under warmer climate of Pakistan, initial cut of leaves is ready after 24 months. About 50 leaves, each weighing up to 1 kg may be cut per plant per year. The ripest lower leaves are cut first and this continues periodically over the next four years. On average, over the first 4 years, two cuttings are made annually. In following years only one cut is made per year, until the flower stalks begin to develop. A total of about 300 leaves may be harvested during the economic life of each plant, giving a total of 500 – 600 tonnes fiber/ha.
A process of hammering and retting is used to extract the fiber from the leaf tissues. Leaves are crushed and beaten by a rotating wheel, set with blunt knives, so that only fibers remain. All other parts of the leaf are washed away by water. Raw fibers are washed before drying in the sun or by hot air. Proper drying is important as fiber quality depends largely on moisture content. Artificial drying has been found to result in generally better grades of fiber than sun drying. Dry fibers are machine combed and sorted into various grades, largely on the basis of the previous in-field separation of leaves into size groups after which fiber enters in value addition stage.
The dried fiber represents only 4% of the total weight of the leaf. The lustrous strands, usually creamy white, average from 80 to 120 cm in length and 0.2 to 0.4 mm in diameter. Its fiber is classified into longer (minimum 90 cm), medium (71-90 cm) and shorter fiber (60-70 cm). Sisal fiber is fairly coarse and inflexible. It is valued for cordage use because of its strength, durability, ability to stretch, affinity for certain dyestuffs, and resistance to deterioration in saltwater.
Pakistan is situated in subtropical region of the world and has continental type of environment with extreme variation of seasonal and daily temperature. Crop production in various ecological regions of country is often limited by extremes of weather. Vast areas in Pakistan are arid and deserts which holds great promise for sisal cultivation. Furthermore, fallow hillocks and plateau areas can successfully be utilized for this purpose. Sisal has a great advantage as it can grow on marginal, desert lands and even in coastal areas where other arable crops are unable to grow hence would not displace food and other commercial crops. Some more disturbed areas are also potential sites for sisal growth like roadside and dry forests. Establishment phase of sisal (initial 2-3 years) offers opportunities for other cash crops to be intercropped in widely spaced sisal rows, make available income to growers. Sisal adaptation to a variety of habitats with its tolerance to biotic and abiotic stresses and lower input requirements make it a very practical option and great prospect to be grown in some otherwise uncultivable areas.
Labor opportunities is the first hand benefit of sisal production. Though sisal production is not labor intensive but fiber extraction and succeeding industrial processes have great employment opportunities. All components of sisal plant are biodegradable hence principally known as environment friendly plant. Small farmers can grow sisal as cash crop if provided with some initial loans, extension services and technical services. Furthermore, biomass left over after fiber extraction amounting upto 96% has its own economic value: to be used in biogas production. Fertilizers and pesticides being not the pre-requisite of sisal production, economic benefits from otherwise waste resources is of great importance especially in underprivileged areas where agriculture is the mainstay of economy. Local fiber industry has capacity to consume thousands of tonnes of hard fiber however, excess fiber after local consumption can be exported to countries including Saudi Arabia, China, Japan, and EU etc. earning valuable foreign exchanges.
Indigenous sisal germplasm is being maintained and propagated in Ayub Agricultural Research Institute, Faisalabad. Researchers are devising most appropriate principles and practices under local conditions for successful and economic sisal production. There is a lot of scope of land use, technical and labour opportunities and induction of sisal based industries that will help in curtailing an import bill currently being spent on import of hard fiber twine, cordage, ropes. Furthermore, it is also a good alternative to jute fiber for the jute industry that relies 99% on imported jute fiber for its 108,917 tonns raw fiber needs. Information and advices on crop husbandry, fiber quality standard and processing may be pursued from Agronomic Research Institute, Jhang Road, Faisalabad.
By. Dr. Muhammad Shoaib, Mukhtar Ahmad, Dr. M. N. Khan, Dr. M. Saeed Ashraf . (This research team belongs to Agronomic Research Institute, AARI, Faisalabad.)