1. JUTE
Jute has been cultivated in Asia and Africa for centuries. Its origin is unknown however it grows in the wild in both Asia and Africa and likes the tropical and sub‐tropical areas. Jute has been produced as a vegetable in the Middle East and Africa and has become a very popular leafy vegetable in the Northern and Eastern regions of South Africa.
This crop produces a fine fibre that is used mainly for manufacturing sacking and is second in commercial importance to cotton. The plants are annuals with thin straight stems that grow to a height of 3 ‐ 5 metres, with the fibers contained in the stems.
CULTIVATION
Jute has an optimum temperature of between 25 ‐ 32ºC. Temperatures of 16ºC and below can be detrimental to the plant. It requires a rainfall of between 600 – 2 000 mm a year and is sensitive to dry or drought conditions. Jute prefers a deep, rich, well‐drained loamy soil, but can grow on a wide variety of soils. It does not tolerate waterlogged soils and shaded areas but the soil need to be moist. It has a pH range of between 4.5 and 8.2.
The crop is grown from seed which is broadcast or direct seeded onto a fine seedbed at the rate of 5
– 6 kg per hectare. Jute can also be propagated as seedlings and transplanted into the lands. The seed will germinate in 3 ‐ 4 days and once they are about 15 cm tall, are thinned out to 10 – 12 cm apart. On rich alluvial soils no fertilizer is required, but on poorer soils a dressing of blended fertilizer can be applied. A soil fertility test should be conducted on the land before any fertilizer is applied. Jute responds well to a side dressing of Nitrogen.
HARVESTING
The crop is harvested about 4 months after planting when 50% of the plants produce young fruits. Leaving the harvesting any later will reduce the quality of the fibre. The tall stems are cut, the leaves removed and the stems soaked in water for a period of up to 2 weeks to remove any soft non‐ fibrous tissue. This process is called retting. The fibres are then washed and dried in the sun. The crop will yield from 1 500 to 2 500 kg of dry fibre per hectare.
If the plants are allowed to grow and mature, the fruits will produce seeds at 7 ‐ 10 months old. Production of seed will be about 280 kg/ha. Pests and diseases are not normally a problem with this crop.
2. KENAF
Kenaf originated in West Africa and is an annual herbaceous plant that requires a warm season and short day length. Kenaf produces a fine fibre that is often used as a substitute for jute fibrer. The plants are long and straight with prickly stems that grow to a height of 5 ‐ 6 metres with a diameter of about 12 mm under good growing conditions in 6 – 8 months. The best yields of fiber are obtained when the stems reach maximum growth before the plant flowers. The crop is grown throughout the Tropics with India being a major producer.
CULTIVATION
Kenaf is best suited to tropical and subtropical conditions with the optimum temperatures between 15 and 27oC with a mean daily temperature of 20oC being the best for the growing season. Kenaf is sensitive to cool conditions and does not like frost. The crop grows best on rich well drained sandy loams that are not alkaline or acidic and requires a rainfall of at least 600 mm per year.
The planting dates for Kenaf depend on what the crop is used for. For fibre production seeds should be planted during November to December to make use of the longer days and requires 12 1/2 – 12 3/4 hours or more for producing longer stems. For seed production, Kenaf should be planted from April to October to make use of shorter day lengths.
The crop is grown from seed which can be broadcast or sown in rows 200 – 300 mm apart with 50 – 100 mm between seeds with seed rates of 25 kg/ha. The seeds should be planted at a depth of 5 – 32 mm.
Fertilizer should be worked into the seed bed before planting and topdressed when the plants are 18
– 25 days old from planting and topdressed again at 60 – 70 days old. The crop requires 60 – 100 kg/ha of Nitrogen. Fertilization should only be done once the soil has been analysed.
HARVESTING
At 3 ‐ 5 months old the crop is harvested at the beginning of the flower stage. The stems are cut, the leaves removed and the stems soaked in water for up to 2 weeks to remove the soft tissue and free the fibres. The fibres are washed, dried in the sun and packed for transport. Dried fibre makes up 16% of the plant stem with the crop yielding 1 000 to 6 000 kg/ha of fibre.
Kenaf can be used for many things including paper pulp, potting mixtures, mulches and films.
The young growing crop should be kept free from weeds and this is done by hand cultivating. Kenaf is liable to attack by various fungal diseases and can be controlled by using different varieties and the use of fungicide sprays. The main pests are stem borers and nematodes (eelworms) which can be controlled by the use of sound rotations.
3. SISAL
Sisal or hemp produces a strong fibre and differs completely from both jute and kenaf. The sisal plant is a perennial and the fibres are produced in the leaves rather than the stem. The economic part of the plant is the phloem fibres in the leaves. Two types of plants which look very much like sisal are Mauritius hemp and Yucatan sisal, but both produce an inferior form of fibre. Sisal originated in South America and is now grown throughout the tropics, particularly in Tanzania, the West Indies and India.
Sisal will grow on most soils having rainfall of 1 000 mm a year. When grown as a commercial crop it is cultivated in large plantations which have their own machines for processing the crop. On small farms it can be used as a hedge for cattle and sheep and the leaves can be processed by hand to make string. Mature plants are large, about 1.5 metres across and have many thick, tough spikey leaves which are produced at ground level ‐ See the figure below.
Figure 4: A Sisal Leaf and Plant
CULTIVATION
Sisal is propagated vegetatively by means of small, miniature plants which appear at the base of the parent plant. The small plants are called bulbils and a mature plant will produce a number of these bulbils each year.
Figure 5: A young Sisal Plant called a Bulbil
The bulbils are planted in nursery beds with 100 mm between the rows and 100 mm between the plants. After spending 6 months in the seedbed nursery, the plants are transplanted to a secondary bed where they are planted 300 mm x 300 mm. After another 6 months they are planted into the lands at a spacing of 1 – 1.5 m x 4 m. Some superphosphate and lime can be worked into the soil
before transplanting and the land should be free from weeds. Beans or other legumes can be grown in the spaces between the rows.
PESTS AND DISEASES
The sisal plant is very strong and tough and the leaves are hard that very few pests cause any problems. The plant can suffer from Boron deficiency which causes the leaves to crack.
HARVESTING
The leaves begin to mature after 5 years in the lands and the lower leaves which are the ripest are harvested by cutting off from the parent plant. Leaves are cut off every 6 months, and can continue for 4 – 5 years before the plants need to be replaced.
After harvesting, the leaves are beaten by the use of a special revolving drum with beater bars.
String can be made on a small scale simply by beating the leaves on a rock to release the fibres.
Once released from the soft tissue the fibres are spread out in the sun to dry. Commercial growers use a machine to comb the fibres straight and clean and the bundles graded and baled for sale.
YIELD
Yield is about 40 tons of leaves per hectare a year, with a fibre percentage of 2% to 5%. From year 5 the expected fibre yield is as follows:
Year 5: 0.25t/ha
Year 6: 0.50 t/ha
Year 7: 1.00 t/ha
Year 8: 1.50 t/ha
Year 9: 0.75 t/ha
Year 10: 0.75 t/ha
Year 11: 0.25 t/ha
Year 12: low
Sisal fibre is used to make strong, rough string, such as baling string, rope and coarse sacking.
