• Topics: Agronomy  | Kenaf  | Miscellaneous Field Crops  | Prine, Gordon M  | Riddle, T Charles 

Kenaf - A Possible New Crop for Central Florida¹

Kenaf (Hibiscus canabinus L.) (Figure 1) is an annual plant, native to central Africa, and related to hibiscus (Hibiscus hibiscum L .) , okra (Hibiscus esculentus) , hollyhock (Althaea rosea) and cotton (Gossypium hirsutum L.) (Scott and Taylor, 1988). Individual plants can grow up to 18 ft or more with few side branches when grown in dense stands. Kenaf is being developed as a nonwood fiber crop. The bark, which contains long soft bast fibers, makes up 30 to 40% of the dry weight of the stem. The central core of the stem contains weakly disbursed pith cells surrounded by a thick cylinder of short woody fibers. The kenaf plant has an ideal blend of long and short fibers for many paper and paperboard products (Grower's, 1989). A number of other kenaf fiber products are now being developed and marketed.

Figure 1. 

Kenaf (Hibiscus canabinus L.)

In 1943, the USDA and the Cooperative Fiber Commission (CFC) started a program in southern Florida to determine the feasibility of growing, harvesting and processing kenaf for cordage fibers for making rope, matting, and bags. The effort resulted in the development of high yielding cultivars with resistance to anthracnose (Colletotrichum hibisci) (Taylor, 1984; Summers, 1958; Wilson and Pate, 1958). In 1956, USDA research on kenaf broadened to developing a new crop for use in paper production. Kenaf was selected from among 506 species for continued development studies (Mayberry, 1988).

Most kenaf cultivars are photoperiod sensitive. For example, the cultivars Everglades 41 and 71 don't flower until day length decreases to 12.5 hours. However, Killinger (1967) reported that some varieties began to flower within 60 days of planting, produced seed and were dead at the end of 100 days. Later-maturing varieties produced higher yields. Leaf shape and stem color vary widely among varieties. Kenaf has two distinct leaf shapes, palmatified and entire. The palmatified-shaped leaf closely resembles marijuana (Cannabis sativa) and can be mistaken for the illegal weed. The entire-leaf type looks much like okra and cotton. Stem color can be various shades of red, green, or purple. The plant has a long effective taproot system and a relatively deep, wide-ranging lateral root system making the plant drought tolerant (Grower's, 1989).

POTENTIAL USES FOR KENAF FIBERS

Early efforts to commercialize kenaf centered on using kenaf fibers to produce newsprint. Demonstration work has shown kenaf newsprint to have many desirable qualities, including potentially lower costs than newsprint made from wood fiber. However, paper companies have been unwilling to make the necessary investments to utilize kenaf fibers in their paper mills. Additional efforts to build mills dedicated to making newsprint and other papers from kenaf or kenaf blended with other fibers have so far failed from a lack of financing (Taylor, 1992a, b). Therefore, at this time, there is no market for this crop in Florida.

Commercialization of kenaf as a cash crop in the U.S. is just beginning. More than 4,000 acres have been reported in Texas, Louisiana, and Mississippi (Drapala, 1993; Taylor, 1991). Kenaf bark (bast) and core fibers each have desirable qualities. To establish greater market potential, equipment and methods have been developed to separate the two kinds of fiber (Chen et al., 1995). As a result, markets have been developed for the two different fibers. Bast fibers are used for speciality papers, tea bags, and grass mats (biodegradable mats impregnated with grass and/or flower seeds). The bast fibers may also be used as a fiberglass substitute, blended with plastic, or blended with cotton for fabrics. Core fibers are currently being marketed for animal bedding, cat litter, poultry litter, as an extrusion aid in plastics, an industrial absorbent (oil spill cleanup), a filter medium for fruit juices, as an additive in drilling mud and in "lite" bread dough, and for manufacture of particleboard (acoustic tiles) (Ramaswamy and Boyd, 1994; Sellers et al., 1993; Taylor, 1992b; Martin, 1996).

A potential export market also exists. For example, Japan has committed to using 10% nonwood pulp in their paper products by the year 2000 and is looking to kenaf as the main source (Kelly, 1996).

In 1996, approximately 3,000 acres of kenaf were planted in Mississippi, mainly in Tallahatchie County, home of the Mississippi Delta Fiber Cooperative. The Cooperative, made up of kenaf farmers, processors and marketers, opened the world's first kenaf mechanical separating plant in 1991. Harvested crops are brought to the plant where the bark is separated from the core in a chemical-free process (Russell, 1996).

Kenaf has also been investigated as a forage crop for cattle feed. When harvested at an immature stage of growth (about 6 ft), leaves contain 18 to 30% crude protein (DM basis). After this stage of growth lower leaves shed rapidly. At this stage of growth, moisture content of the plant was reported to be about 85% resulting in a low dry matter yield of only 1.67 tn/A (Killinger, 1969; 1967; Wing, 1967).

POTENTIAL FOR GROWING KENAF IN CENTRAL FLORIDA

Kenaf is a tropical plant and is well-adapted to the hot humid conditions found in central Florida. Kenaf production fits well with central Florida's weather patterns. Planting and harvest activities will take place in the normally dry winter season while few if any field activities will be needed during the wet summer months. Kenaf needs a soil temperature of around 55° F for germination and growth. In central Florida, kenaf could be planted beginning in early March. However, in one year out of 10 a frost can be expected after March 3rd (Ford et al., 1990). Planting could continue through late April and harvest could begin in late October and extend through the end of February.

Kenaf is adapted to a wide range of soils. In central Florida, the most productive soil for kenaf production is believed to be phosphatic clay, a by-product of phosphate mining. Other central Florida soils, including reclaimed overburden and native sandy soils, will also support kenaf production. Frequent crop rotation, or a combination of soil fumigation and crop rotation, will be needed on sandy soils to reduce crop damage from nematodes. Killinger (1967) reported that from 1957 to 1967 kenaf grown on well-drained Gainesville sandy loam soil was nearly always infected with root-knot nematodes (Meloidogyne incognita). On the other hand, kenaf grown on flat, poorly drained Leon fine sand soil exhibited few if any of these organisms. As a result, flatwoods type soils are believed to be the best candidate for growing kenaf.

YIELD TRIAL RESULTS

Phosphatic clay - Beginning in 1993, small plot research studies were conducted on phosphatic clay soils near Bartow, FL, for 3 years (Table 1). For seedbed preparation, the land was plowed with a moldboard plow; after a few weeks it was rolled with a pulvimulcher (corrugated roller).

Before planting, 2% Roundup^® was sprayed to control existing weeds. Plots were planted with a John Deere Flexi 71 Planter in 36" wide rows. Seeds were placed about 2" apart in the row for about 87,120 seeds/A. Ammonium sulfate was applied pre-plant at a rate of 80 lb of N/A with an additional 80 lb N/A side dressed at lay-by. Plots were irrigated at planting to insure good plant emergence. Individual plots consisted of 5 rows 36" apart and 20 ft long. Yields were determined from a 1/1000 acre area of the center row and reported as oven dry tons/A. The experimental design was a randomized complete block with four replications. Yields in 1993 were low mainly because of late planting and a site that had not been cropped before. Results in 1994 and 1995 were much better and are believed to be more representative of the yield potential for kenaf. Some varietal differences were observed in the 2 year average dry matter stem yields, with Everglades 71 and Tainung 2 the highest and Everglades 41 the lowest. Overall average yield for 2 years was 12.1 dry tons/A.

Sandy Soil - Also in 1993, kenaf plots were planted on Sparr fine sand soil near Gainesville (Table 2). A seedbed was prepared and 10 cultivars or assessions were planted in 36" wide rows. Plots were fertilized with 200 lb/A of 20-5-10 (N-P₂O₅-K₂O) preplant and 500 lb/A of 20-5-10 (N-P₂O₅-K₂O) at lay-by for a total fertilizer application of 140-35-70 (N-P₂O₅-K₂ O).

Individual plots consisted of 5 rows 36" apart and 20 ft long. Yields were determined from a 1/1000 acre area of the center row. The experimental design was a randomized complete block with four replications.

Yields from near Gainesville were less than yields reported from near Bartow. The overall average for 7 accessions or cultivars grown in the 2 years that data was gathered was 6.8 dry tons/A (Table 2) compared with 12.1 dry tons/A at Bartow (Table 1). A complete crop failure was experienced in 1994 near Gainesville because of nematode damage. Killinger (1969) reported oven dry stem yields averaged 8.6 tons/A for Everglades 71 and Everglades 41 for 1967-72 at Gainesville. He also reported that kenaf grown at Gainesville averaged 16 to 22 ft tall in 36" rows. It's interesting to note that the variety Everglades 41 was the lowest yielding variety on phosphatic clay at Bartow and among the highest yielding varieties at Gainesville.

CULTURAL PRACTICES

Tillage and seedbed preparation - A well-prepared seedbed is needed. If there is heavy vegetation, it should be mowed or treated with a herbicide and burned. Light crop residue or light vegetation may be plowed or disked. At planting time the soil surface should be fine-textured and free of weeds and grasses. On flatwoods and other soils subject to flooding for several days during the growing season, kenaf is best planted on beds 4 to 6" high.

Planting depth, seeding rates, and plant population - Planting depth should be in the range of 1.5 to 2". Shallower depths are possible with good soil moisture and a fine-textured seedbed. Efforts should be made to get good seed-soil contact. With good soil conditions, optimal temperature, and moisture, plants will emerge in 3 to 6 days. A row spacing of 36 to 40" appears to be adequate. Double row beds spaced 40" on center is recommended in the lower Rio Grande Valley of Texas (Grower's, 1989). The two rows on each bed are spaced 12" apart. Specific row spacing will likely be dictated by requirements of harvesting equipment.

Seed counts average about 16,000 per pound. Taking into account germination rates and seedling losses, a planting rate in the range of 8 to 12 lb/A is recommended. Beginning plant counts of 100,000 to 150,000/A are desired. Kenaf is self-thinning and will reduce its population during the growing season. A final plant count of 80,000 to 100,000/A is desired. Lower plant populations result in undesirable branching and thicker trunks. A mature kenaf stalk should have a base diameter of 1.5 to 2" (Neill and Kurtz, 1994; Anonymous, 1989).

Fertilization - No fertilization work with kenaf has been reported in Florida. For fertilizer recommendations other than N it is important to do a soil analysis. In many production systems stalks are harvested after the leaves have dropped off the plant. It has been estimated that 1 to 2 tn of dry leaf matter, rich in N, returns 60 to 120 lb of N to the soil (Bhangoo et al., 1986).

Kenaf grown on phosphatic clay soil will need only N. A rate of 120 to 140 lb/A actual N is recommended. The N may be applied preplant or 30 to 40 lb N/A side dressed at planting (2" to the side and 2" below the seed) and the balance applied before the plants become too large for field access.

For sandy soils, the following general fertilization recommendation is made in the absence of research on the subject: A rate of 140 to 160 lb of N/A is recommended with 40 lb of N/A applied preplant and the balance by lay-by. Apply 90 lb of P₂O₅ if the soil test is < 16 ppm Mehlich-1 P and 60 lb if the test is between 16 and 30 ppm. Apply 100 lb of K₂O if Mehlich-1 K is < 35 and 70 lb if the test is between 35 and 60 ppm. The crop is not likely to respond if the soil test is above 30 ppm P or 60 ppm K.

Irrigation - Kenaf has a deep tap root and an extensive lateral root system making the crop relatively drought tolerant. For production on phosphatic clay, an irrigation or rain soon after planting is important for good seed-soil contact. Without good seed-soil contact some seeds will germinate while others may not germinate until it rains, resulting in an uneven stand. Once the crop is up, irrigation will not be necessary on phosphatic clay, although yields will likely be increased with irrigation during long dry periods.

The relationship between irrigation and kenaf yields has not been studied. Based on experience near Gainesville (Killinger, 1967; 1969) it appears that satisfactory yields can be achieved without irrigation on sandy flatwoods soils. Irrigation will surely increase production; however, the economic trade-off can only be estimated.

Weed control - A combination of chemical weed control and mechanical cultivation has been used for weed control in kenaf. At the present time only Treflan^® , a pre-emergent grass killer, is registered for use on kenaf in Florida.

Kenaf is a vigorously growing plant and under optimum growing conditions can form a canopy over the row middles in as little as 5 weeks (Neill and Kurtz, 1994). Once kenaf shades the row middles, low growing weeds and grasses are shaded out and there is no need for additional weed control.

Insect pests - Most insect problems with kenaf are likely to occur at seedling emergence and during young seedling growth. Cut worms, leaf miners, and other chewing/sucking insects are potential problems. Late in the season, the plant will tolerate a relatively high population of leaf-chewing insects (Grower's, 1989). The insecticide Azatin^® is registered for use on kenaf.

Nematodes & diseases - One of the greatest problems affecting kenaf production is plant parasitic nematodes, particularly root-knot nematode (Meloidogyne spp.). Nematodes are multicellular, microscopic, worm-like animals that feed mainly on plant root systems (Lawrence, 1994). Leaves on plants infested with nematodes yellow and fall. The plant will be stunted and if the infestation is heavy the plant may eventually die.

Root-knot nematodes can occur in any Florida soil, but are expected to be a more serious problem on well-drained sandy soils in central Florida and somewhat less on flatwoods type soils or on phosphatic clay soils.

Nematodes may be managed by a combination of crop rotation and chemical control. Telone II^® , a soil fumigant, is registered for use on kenaf, but it may be too expensive to use. A third approach is the development of nematode resistant varieties. At the present time, none of the kenaf varieties are considered resistant to nematodes (Grower's, 1989). SF 459, reported to be nematode tolerant, succumbed to root-knot in the 1994 Gainesville trial.

Kenaf is resistant to most plant diseases. One serious disease of kenaf, anthracnose, was reported in the U.S. in 1950. USDA plant breeders were successful in breeding and selecting kenaf cultivars and accessions for resistance. Both Everglades 71 and 41 are highly resistant, as are Tainung varieties, and lines developed in Cuba and Guatemala (Grower's, 1989).

Harvest methods - A number of harvest methods are possible. The USDA has developed a whole stalk harvesting system that cuts the stalks and lays them in an orderly fashion at right angles to the row. Stalks are allowed to dry for around two weeks and are then gathered by a machine that picks up the stalks and arranges them in large bundles; the bundles are transferred to field trailers. The tractor-drawn field trailers haul the bundles to the field margin where they are stacked for shredding (CSRS, 1988; Grower's, 1989).

Another method is to use forage choppers to harvest the crop. This method can be used in colder areas where the crop is allowed to dry after being killed by frost or by a desiccant. This method has been used in Mississippi. The chopped kenaf is stored and transported in cotton modules with the same equipment used for harvesting cotton. (M. J. Fuller, Mississippi State University, personal communication, Oct. 22, 1996; Baldwin et al., 1996).

The crop may also be chopped and baled with forage equipment and, if covered, can be stored as large round or rectangular bales on field edges (Broadway, 1990).

Researchers at Mississippi State University (Chen et al., 1995) have patented a machine to separate the bast and core fibers of kenaf. This machine moves through the field, cuts the stalks and separates bast and core fibers in one operation. The kenaf stalks are crushed as they enter the machine and then pass through beaters. The short core fibers drop to the bottom of the machine and are blown into a wagon pulled alongside. The long bast fibers pass out the back of the machine and fall on the ground. The bast fibers are left to dry and then baled with a hay baler. The core fibers are transported to a drier and dried (Chen and Pote, 1994).

Use of sugarcane harvesting equipment on kenaf is another harvesting method mentioned in the literature. Storage problems from high moisture content were cited when sugarcane harvesting equipment was used (Grower's, 1989; Wood et al., 1978).

SAMPLE BUDGETS FOR PHOSPHATIC CLAY AND SANDY SOILS

Estimated production costs are presented for kenaf production on phosphatic clay and on sandy soil (Table 3 and Table 4). These budgets are intended as a guide for individual growers to evaluate their own costs. No two agricultural operations will have the same cost structure because of differences in age, size, and makeup of equipment, in addition to many other factors.

In addition, Table 5 and Table 6 present the estimated net return for different yield and price combinations for kenaf production on both phosphatic clay and sandy soil. Harvest costs are not included in the production costs. To get a true picture of potential net returns, harvest costs must be deducted from the figures in Table 5 and Table 6 .

Budgets were estimated with the AGSYS budget generator program developed by faculty in the Food and Resource Economics Dept., University of Florida (Smith et al. , 1994). The budget generator estimates the cost of growing one acre of a specific crop in the context of a commercial enterprise. Equipment costs are calculated using data from each equipment item including: age, cost when new, annual hours of use, useful life, fuel costs, repair and maintenance cost, depreciation, and labor cost for the operator. In addition, costs for materials and supplies such as fertilizer, chemicals, and seed are included. Other cost items include land rent, interest, supervision, and overhead.

GROWER'S ATTITUDES TOWARD GROWING NEW CROPS

A survey of agricultural landowners in Polk County was conducted in the spring of 1996 (Rahmani et al., 1996). The study included an area bounded by I-4 on the north, US 27 on the east, and the county line on the south and west. Growers cited potential net returns from a crop as one of the most important factors in deciding to grow a crop. Landowners indicated a willingness to commit about 3,000 acres to new crops if net return per acre were $40.00, about 7,000 acres at $50.00/A and about 12,000 acres if net return were $60.00/A. The major barriers to growing a new crop were landowners not being familiar with a new crop, followed by the need for specialized equipment. Risk in terms of changing income from year to year was also a factor. At this time, potential returns from kenaf production appear to be in the range to attract a number of landowners.

ACKNOWLEDGMENTS

The work reported here was funded in part by the Florida Institute of Phosphate Research, University of Florida and the Polk County Board of County Commissioners. Work on this publication was funded by a grant from the University of Florida Center for Biomass Programs. The authors are grateful for the support.

REFERENCES

• Baldwin, B., M. Kurtz, C. Hovermale, and W. S. Neill. 1996. Kenaf: A guide for production in Mississippi. Research Report 27(8), Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, 3 pgs.

• Bhangoo, M. S., H. S. Tehnani, and J. Henderson. 1986. Effect of planting date, nitrogen levels, row spacing, and plant population on kenaf performance in the San Joaquin Valley, California. Agron. J. 78:600-604.

• Broadway, R. 1990. Scientists find results of kenaf research encouraging. Research Highlights, Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, 53(11):7.

• Chen, L. H., J. Pote, and M. Fuller. 1995. Decorticating machine with variable speed feed and beater rollers. Patent Number 5,465,464. U.S. Patent Office, Nov. 14, 1995.

• Chen, L. H. and J. Pote. 1994. In-field separation of kenaf. pp. 19-20. In M. J. Fuller, (ed.) A Summary of Kenaf Production and Product Development Research 1989-1993. Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, Bulletin 1011, 33 pgs.

• Cooperative State Research Service (CSRS). 1988. New harvester: a big step toward commercial kenaf production. USDA Photography Division, Washington, DC, Photo Feature #322, 4 pgs.

• Drapala, P. Kenaf research has only just begun. MAFES Research Highlights, July-August 1993. Miss. State Univ., Mississippi State, MS, pg. 5.

• Ford, R. D., J. M. Robbins, Jr., J. T. Werner, D. Cowherd, C. N. Gordon, W. B. Warmack, M. M. Brown, K. W. Monroe, W. G. George, T. Sanders and P. M. Basch. 1990. Soil Survey of Polk County, Florida, U. S. Government Printing Office: 1990-262-945/20032.

• Grower's Handbook for Kenaf Production in the Lower Rio Grande Valley of Texas, USA. 1989. Kenaf International with Rio Farms, Inc., McAllen, TX, 21 pgs.

• Killinger, G. B. 1967. Potential uses of kenaf (Hibiscus canabinus L.). Proc. Soil Crop Sci. Soc. FL 27:4-11.

• Killinger, G. B. 1969. Kenaf (Hibiscus canabinus L.), a multi-use crop. Agron. J. 61:734-736.

• Kurtz, M. E. 1994. Weed control in kenaf. pp. 10-12. In M. J. Fuller, (ed.) A Summary of Kenaf Production and Product Development Research 1989-1993. Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, Bulletin 1011, 33 pgs.

• Lawrence, G. W. 1994. Plant parasitic nematodes - pests of kenaf. pp. 13-14. In M. J. Fuller, (ed.) A Summary of Kenaf Production and Product Development Research 1989-1993. Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, Bulletin 1011, 33 pgs.

• Mayberry, D. H. 1988. A new source of paper fiber. The World and I, July 1988:158-163. Washington Times Corp, Washington, DC.

• Neill, S. W., and M. E. Kurtz. 1994. The effect of plant population on kenaf yield. p. 6. In M. J. Fuller, (ed.) A Summary of Kenaf Production and Product Development Research 1989-1993. Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, Bulletin 1011, 33 pgs.

• Rahmani, M., A. W. Hodges, and J. A. Stricker. 1996. Potential producers and their attitudes toward adoption of biomass crops in central Florida. pp. 671-677. In Proc. BioEnergy '96, Vol. II, The Seventh National Bioenergy Conference, Sept. 15-20, Nashville, TN, 1090 pgs.

• Ramaswamy, G. N. and C. R. Boyd. 1994. Kenaf as a textile fiber: processing, fiber quality, and product development. pp. 31-33. In M. J. Fuller, (ed.) A Summary of Kenaf Production and Product Development Research 1989 - 1993. Miss. Agric. and Forestry Exp. Sta., Mississippi State, MS, Bulletin 1011, 33 pgs.

• Russell, K. 1996. Mississippi hosts Japanese paper and pulp executives on kenaf fact-finding mission. Miss. Business J. 18( 23).

• Scott, A. W., Jr. and C. S. Taylor. 1988. Economics of kenaf production in the lower Rio Grande Valley of Texas. Paper presented at National Symposium on New Crops, Indianapolis, IN, Oct. 23-26, 1988, pgs. 292-297.

• Smith, S. A., T. G. Taylor, and S. A. Ford. 1994. AGSYS: budget generator. Circ. SW-091. FL. Coop. Ext. Serv., IFAS, Univ. of Florida, Gainesville, 42 pgs.

• Sellers, T., Jr., G. D. Miller, and M. J. Fuller. 1993. Kenaf core as a board raw material. Forest Prod. J. 43(7/8):69-71.

• Summers, T. E. 1958. Important diseases affecting kenaf in Florida. Proc. Soil Crop Sci. Soc. FL 18:323-326.

• Taylor, C. S. 1984. A systems approach to the commercialization of kenaf. Ph.D. Thesis, University of Missouri-Columbia, Columbia, MO, 111 pgs.

• Taylor, C. S. 1991. Kenaf: an emerging new crop industry. Paper presented to the Second National Symposium on New Crops Exploration, Research and Commercialization, Indianapolis, IN, Oct. 8, 1991, 7 pgs.

• Taylor, C. S. 1992a. Kenaf - an annual crop generating a growing response from industry. Kenaf International, Ltd., McAllen, TX, KI Pub. #12, 4 pgs.

• Taylor, C. S. 1992b. Kenaf as a new annual fiber source for industrial uses: general economic and environmental aspects. Kenaf International, Ltd., McAllen, TX, KI Pub. #13, 4 pgs.

• Wilson, F. D. and J. B. Pate. 1958. Improvement of kenaf through breeding and selection. Proc. Soil Crop Sci. Soc. FL 18:320-322.

• Wing, J. M. 1967. Ensilability, acceptability and digestibility of kenaf. Feedstuffs 39(29):26.

• Wood, I. M., D. J. Quick, R. A. Stiff, and N. H. Adams. 1978. Harvesting kenaf with sugarcane harvesters. World Crops, Sept./October:200-205.

Tables

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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer, Interim Dean.

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