Kenaf is a 4,000 year old NEW crop with roots in ancient Africa. A member of the hibiscus family (Hibiscus cannabinus L), it is related to cotton and okra. It offers a way to make paper without cutting trees. Kenaf grows quickly, rising to heights of 12-14 feet in as little as 4 to 5 months.
While the flowering can last 3 to 4 weeks, or more, per plant, each individual flower blooms for only one day. The stalk of the kenaf plant consists of two distinct fiber types.
The outer fiber is called “bast” and comprises roughly 40% of the stalk’s dry weight. The refined bast fibers measure 2.6mm and are similar to the best softwood fibers used to make paper.
The whiter, inner fiber is called “core”, and comprises 60% of the stalk’s dry weight. These refined fibers measure .6mm and are comparable to hardwood tree fibers, which are used in a widening range of paper products.
The Philippines spends a considerable amount of foreign exchange for fiber imports. From 1984 to 1986, the government spent US $404,282 or about P9 million to buy 1,117,783 kg of kenaf fibers needed in making gunny sacks.
To reduce the country’s expenses, and eventually to stop importing fibers and start earning from it, the Fiber Development Authority (FIDA) is urging farmers to plant kenaf.
Kenaf (Hibiscus cannabinus Linn.) is an annual bast fiber plant believed to come from the subtropical regions of Asia and Africa, and brought to the country by Dr. Nemesio Mendiola in August, 1927 from Buiterzong, Java.
Most kenaf plants have spiny petioles, stems and calyx. These spines cause severe itchiness when they come in contact with the skin.
Kenaf grows from 1.83 to 3.7 m high with a diameter of 12 mm. Its ornamental flowers are clean-colored in the morning and gradually turn to pink in the afternoon.
Kenaf fiber is used for fishing nets, ropes and doormats while woven fabric can be made into carpets, cloth and clothes lining.
The most important use of kenaf is in sack making. While the threat of synthetics replacing natural fiber is present, the latter ads qualities which synthetics cannot match.
For one, natural fiber is twice as durable- and more reusable- as synthetic sacks. The former is also able to store grains longer without damaging their eating and milling quality.
Moreover, synthetic sacks cannot be piled up to 18 feet while natural sacks can be piled twice higher. And this is important since millers want their warehouses fully packed.
Today kenaf is being developed for other uses. Researchers have found that its leaves are used as food in Ghana and as livestock feed in the U.S.A. The Bureau of Plant Industry has discovered that the leaves are a very good medium of mushroom spawns due to their 24 per cent crude protein content.
Its wood, however, shows the most promise as a potential source of pulp and paper. Kenaf may also be used as a blending agent to improve lower quality pulps. Tests show that kenaf pulps perform equally well as most softwood and are superior to most hardwood pulps. Moreover, handsheets and experimental papers from them have good bursting quality, tensile strength, folding endurance, surface finish, printing and writing qualities.
There are many kenaf varieties planted in the Philippines. Traditional varieties used are Viridia Vulgaris, Cuban, Everglades, Guatemala, Manchurian, Giza and Java jute, all of which are spiny. Among them, Cuba 108 and G-2 yield the most fibers.
At present , Kenaf varieties are mostly spineless. Thanks to Dr. Nemesio Mendiola and Francisco Cabato Jr. who, in 1965, produced spineless kenaf varieties A59-80, NSDB-63-1 and NSDB-63- 11.
Kenaf grows well in a variety of soil but it does best in deep, rich loam that is neither acidic nor alkaline.
To ensure a good crop, soil must have sufficient amount of organic matter. It must be well-drained even if the plant can stand short periods of shallow standing water. Marginal kenaf also be planted on if the fertilizer is applied.
Kenaf needs a tropical to subtropical climate. It prefers an elevation below 3,000 feet and a rainfall of 25-35 inches during its growing period. Ideal places are those with even rainfall distribution since continuous rain cause yellowing of the leaves. They should also have no marked dry and wet seasons and be far from the typhoon belt. Typhoons can easily fell the plant due to its height and weak root system.
Kenaf plants are photoperiodic; they are sensitive to sunlight. Based on their needed sunlight, kenaf are classified into: long-day, short-day and day-neutral plants.
Long-day plants require 12 hours of sunlight to reach the following stage. Short-day plants need less than 12 hours while day-neutral are not affected by the length of exposure and, hence, can be planted any time of the year.
Since kenaf is photoperiodic, the time of planting is important. For fiber production, plant kenaf during the months of April to October to expose the plant to long daylight. It requires 12-1/2 to 12-3/4 hours or longer to produce long stems of 15 feet or more. To produce seeds, plant kenaf from November to December when daylight is short.
In planting kenaf, plow the land once or twice depending on the soil type. Make furrows 12 to 24 inches apart for fiber and seed production, respectively.
If the soil is moist, seeds sprout in about 5 days or earlier. When the seedlings are a foot high, thin them until only 2 inches separate each seedling. Thinning can fill up vacant hills.
The most important operation during the plant’s early life are weeding and occasional tillage. Weeding is done 3 to 4 weeks after planting. Once the plants are established and have outgrown the weeds, these operations are no longer needed.
Two hundred to 250 kg of ammonium sulfate with 21 per cent nitrogen give better yields. Apply this on the furrows and cover with soil 2-3 cm thick before sowing. Apply fertilizer again 18-25 days after sowing when the seeds have sprouted. Apply again when the plants are 60-70 days old around the area 4 cm from the plant’s base, then cover with soil.
Kenaf plants are prone to small black fly beetle and tussock moth. Fly beetle attacks the plant’s leaves and stems at its latter stage of growth. Control this pest by harvesting early infested areas or by spraying with contact insecticide. The tussock moth, on the other hand, bore holes on the stem.
Anthracnose, leaf-mosaic, petiole-curls and root nematode are the common disease plaguing the kenaf plant.
A fungal disease, anthracnose infects young leaves, stipules and meristems or growing tips which turn brown, wither and die. When the entire plant afflicted, only the withered stems remains. Control this by spraying copper oxychloride on the leaves every other week. Before planting on previously affected areas, treat them with 50 kg potassium per hectare.
Leaf mosaic causes a chlorotic mottling of leaf lamina resulting in low yield. Spray infected area with kersoap pesticide. To prevent this disease, thoroughly analyze the soil and apply balanced nutrients before planting.
A viral disease that causes extreme curling and twisting of the particles is petiole curls. Soil deficiency causes this hence, soil analysis is necessary. Prevent this from spreading: pick out curled leaves burn them. Kersoap pesticide may also be sprayed.
The worst disease of kenaf is the “bohon” causing root nematode which stunts growth, causes yellow foliage and even death. Nodular galls also appear at the roots. To control it, overflood the area nematodes alternately with kenaf. Applying pesticides like Biocon is another way of controlling this disease.
Harvest kenaf by cutting the stem near the plant’s base with a sharp bolo or any cutting tool. Bundle the stem at a diameter of 20 cm. Leave them in the field until the leaves drop; this can serve as mulch for the soil.
In one harvest, average yield of a hectare is 2,000 kg of dry fiber. For spineless varieties, a hectare may yield 70 -80 tons of green stalks or 3,000-4,000 kg representing four to five per cent fiber recovery.
The best time to harvest kenaf for fiber is during the plant’s flowering stage of about months after planting when fiber quality and quantity are at its highest. This also lessens the plant’s exposure to pest, disease and unfavorable weather condition which results in lower yield and profit.
If fiber is harvested before flowering, fiber yield is lower; and if done after its quality is poor.
Harvesting kenaf for seeds, on the other hand, is done 4 to 5 1/2 months after planting when 80 per cent of the plants have 5 to 6 dried capsules. Generally, yield of seeds from 1 to 2 hectares is sufficient to plant 100 hectares.
There are three ways of extracting fiber from the plant’s stalks: using machines, retting or applying chemicals.
Decorticating machines used for abaca, ramie and sisal hemp can be use to extract kenaf fiber. First, cut the stalk close to the ground, defolaite, bundle and haul them to the stripping sheds and to the machines. Soak fibers in water in several days, wash and dry in the sun.
In retting, bacteria or fungi act on the gummy substances where the fibers are imbedded. The bundles of stalks are immersed in a meter-deep water for 10-16 days, or in a sea water for 12 days until the fibers cling loosely to the stalk’s pith and thus, can be easily separated.
Retting period depends upon the plant’s age, water temperature, its circulation, mineral, bacteria and fungi content. To hasten this process, keep water temperature at 32o- 36oC and add hay or straw to feed the bacteria or fungi especially if the water is clean.
Using chemicals in extracting fibers is performed under controlled conditions. Remove the bark by ribboning and treat with chemical. Here is one of the formulas: for every 400 lb of ribbons, use 400 gallons of water, 40-60 lb of ordinary soap and 7 lb of ammonium sulfate. Maintain temperature of the mixture at 60o-65oC for one hour and stir it constantly.
the standard grades of kenaf depends on its strength, type go cleaning and color. There are four standard grades of kenaf wither retted or decorticated:
KR-1 or kenaf excellent. The fiber is soft, silky, fine and free of gummy scales and ever-retted fibers. The color is dull white and the cleaning is excellent.
KR-2 or kenaf Good. The fiber is medium soft with little, thin gummy scales. The color is dingy white and the cleaning is good.
KR-3 or Kenaf Fair. The fiber contains many scales and some bark due to the bruised stems. The color is dingy light brown and the texture is harsh while cleaning is generally fair.
KR-X or Kenaf Mixed. The fibers has not been thoroughly washed and there are many gummy scales with pith clinging to the fibers which stick together especially towards the butt. The color ranges from dull to dark brown.
Dried Kenaf fiber is prepared to shipping or storage by baling. The standard bales has a net weight of 125 kg measuring 100 by 55 x 60 cm. Bales can be stored for many months in a dry, relatively dark warehouse.
Other Uses of Kenaf
End-use products depend on the fiber portion used. Bast fiber goes to make such products as burlap, carpet padding, and pulp. The short-fibered core is processed into poultry house bedding, packing material, oil-absorbent mats, and other items.
Another market for kenaf is in pulp for the newsprint industry. Kenaf-based newsprint is strong (and thus well adapted to modern newsprint machinery), has good ink retention, and does not yellow with age as readily as wood-pulp-based newsprint. Of course kenaf fiber must compete directly with wood pulp prices, since both are used to produce newsprint.
Kenaf can also be used for bean stakes, animal litter, a fiberglass substitute in molded plastic, a fiber source for improving recycled paper quality, a bulking agent for composting sewage sludge, a cellulose fiber for composition panels and boards, and a potting-mix ingredient.
Kenaf also makes excellent animal forage. The crude protein levels in kenaf leaves range from 15 to 35 percent. Kenaf harvested as livestock feed should be cut 75 to 100 days after planting to gain optimum protein production per acre. Generally, after 80 days of growth, fibers build up in the stem, the leaf-to-stem ratio changes, and the protein level drops.
For more information, contact:
Dept. of Science and Technology
Rm. 303 DOST Bldg., DOST Complex,
Gen. Santos Ave., Bicutan, Taguig City 1631
Telephone Nos: (632) 837-20-71 to 82
Fax: (632) 837-8937
D.A. Compound, Elliptical Rd., Diliman,Quezon City
Tel. Nos. (632) 929-6065 to 67 / 920-3991 / 928-1134
source: region10.dost.gov.ph, visionpaper.com, attra.ncat.org, photo from bfafh.de, doa.go.th