Kenaf is an important bast fibre crop. It is however grown largely in small backyard gardens in most parts of Nigeria especially in the north. India is the major producer.
It originated from the tropical and subtropical Africa where it is commonly wild plant. It has now been taken to most tropical and subtropical countries.
Kenaf is grown between 45°N and 30°S. It requires warm temperatures (15-25°C) and well distributed rainfall over a period of 4-5 months.
The plant is photoperiod sensitive; flowering when days are short (12 hours or less) and growing more vegetative when days are long.
The crop is grown during long days in order to obtain as much rapid vegetative growth as possible before flowering begins.
It thrives best on well-drained, neutral, sandy loam soils, rich in humus. It does not tolerate waterlogging.
The cultivated forms are erect herbaceous annuals, 2.5-4m tall, with well-developed taproots.
The straight stems can be green, red or purple in color with alternate leaves which vary in shape depending on the cultivar; from cordage, deeply divided, palmate to oblong-lanceolate lobes.
The flowers are borne singly in axils of upper leaves and the fruit is a capsule. Seeds are numerous and usually brown.
Generally, self pollination has been observed.
Seeding rate for fibre production about 10 kg/ha. Seedbed for planting should be level and free of weeds.
Dibble the seeds in rows 20-25cm apart and thinned to 5-10cm between plants within rows.
Sowing should be done as soon as soon as rains are established in April (South) and Junen(North).
Avoid growing kenaf after cowpea as both crops are very susceptible to root-knot nematodes.
Weeds can be controlled by weeding 2-3 times after planting at monthly intervals. Herbicides can also be used; e g metolachlor or alachlor at 1.5khg a.I. applied at the rate of 300kg/ha of NPK (25-10-0) just before or after sowing.
Harvesting and Processing
The crop is harvested 3-5 months after sowing. The longer the vegetative phase the greater will be yield.
The best time to harvest is when about 10 flowers are in bloom, at which time the fibre is at its best quality and more easily separable.
If harvesting is delayed until seed has set, the fibre is coarser and lacks lustre. The stems are cut at ground level and tied into bundles.
The leafy tops are cut off and stems are retted in water. Retting takes 5-14 days. The bark is then stripped and is gently beaten to separate the fibre, which are then washed and dried in the sun.
The average fibre out-turn is about 4% of the weight of green stems or 16% of the weight of dry stalks.
Yields if 1300-1500 kg/ha of fibre or ribbon can be obtained under good management; fibre yield of 6000 kg/ha is obtainable.
1. The fibres are used on a fairly large scale, mixed with jute, in the manufacture of bags, sacks, cordage, netting and fishing nets.
2. Because of their strength and durability, the fibres can be used in the manufacture of tags and abrasives (sand paper).
3. The seeds contain about 20 percent oil, whicyis sometimes extracted and used as lubricant. It is also suitable for the manufacture of soap, linoleum, paints and varnish.
Most serious diseases are anthracnose caused by Colletotrichum hibisci, leaf spot caused by Cercospora hibisci, and stem rot caused by Diplodia hibisci.
These diseases can be controlled with fungicides or use of resistant varieties.
Insects affecting kenaf include black flee beetles, cotton stainer larvae Dysdercus spp), cotton aphids (APHIS gossypii)
root-knot nematode Meloidogyne can also affect yield.