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Evans, D.W. and A.H. Hang. 1993. Kenaf in irrigated central Washington. p. 409-410. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Kenaf in Irrigated Central Washington

David W. Evans and An H. Hang

  1. MATERIALS AND METHODS
  2. RESULTS
  3. DISCUSSION
  4. REFERENCES
  5. Table 1
  6. Table 2
  7. Fig. 1
  8. Fig. 2
Kenaf (Hibiscus cannabinus L., Malvaceae) is an annual crop with uses for fiber, forage and paper pulp (White et al. 1970; Husingi 1989). In the continental United States, kenaf has been most productive in the southern states, but it may also have potential in northern regions. We are investigating the plant development and yield of irrigated kenaf in central Washington State where an annual pulp crop could further broaden our agricultural diversity and reduce pressure on forest resources.

MATERIALS AND METHODS

Three cultivars of kenaf were tested on a preliminary basis in 1987 and four were tested in 1990 at WSU-Prosser. This site is 46° 15' N, 119° 45' W and 275 m above sea level. It averages 160 frost-free days and 0.19 m annual precipitation, mostly in the winter months. Kenaf was raised both years on a silt loam (coarse-silty, mixed, mesic, Xerollic Camborthids) fertilized and furrow irrigated as for maize (Zea mays L.) grain production. The crop was seeded in rows spaced 0.76 m apart at a target population of 25 thousand/ha. Both plantings were surrounded by maize. Stands were hand weeded.

In 1987, single, 6 m long, unreplicated plot rows of 'Everglades 41' ('EV41'), 'Everglades 71' ('EV71'), and 'Tainung 1' ('T1') were planted on 7 May. In 1990, 'EV41', 'EV71', 'T1', and 'Cuba 2032' ('C2032') were seeded on 11 May, in plots 6 rows wide by 20 m long using a randomized complete block design with 5 replications. Plant height was measured monthly in 1987; both height and leaf and stem weight (10 plant samples) were determined weekly from 23 July to 8 Oct. on 'EV41', 'EV71', and 'C2032' in 1990. Defoliated stem yield was determined on all entries from 3 m of each single row in 1987 and from 4.6 m of an interior row of each plot in 1990.

RESULTS

Monthly degree days (10°C base) as determined from air temperatures recorded 600 m from the plot area were warmer than average in May and June 1987, and in July-September 1990 (Table 1). Kenaf grew taller early in the season and reached a greater final height in 1987 than in 1990 (Fig. 1). Flowering began in mid-September both years which was too late to result in viable seed production.

Leaves made up a constantly decreasing fraction of total top weight over the period July 23-Oct. 8 in 1990 (Fig. 2). The leaf fraction in 1990 was described by the relationship y = 35 - 3.67 + 0.014 x2 (r2 = 0.898), where y = fraction of leaf in total top growth (g leaf/kg total top, dry matter basis) and x = days with July 23 = day 1. Prior to the final yield harvest both years, frost killed the leaves which dried and dropped from the plants, leaving bare stalks.

Yields of 'EV41' and 'T1' exceeded 22 Mg/ha in 1987 (Table 2). 'EV71' did not establish well and consequently yields were very low. In 1990, yields ranged between 11 and 14 Mg/ha with 'T1' yielding most, but differences were only significant at the 10% level. The upper ends of kenaf stems may be discarded when kenaf is harvested for fiber (Hays 1989). This stem tip material has potential as animal feed. At yield harvest in 1990, kenaf tops were separated by hand into the basal 6 m and all material above 6 m, and weighed separately. The basal 6 m ranged from 9.3 to 10.4 Mg/ha with no significant cultivar differences. The stem tips ranged between 2.0 ('C2032') and 2.6 ('T1') Mg/ha which was significant only at the 10% level.

DISCUSSION

A yield of 11 to 23 Mg/ha compares favorably with an average hybrid poplar yield of 23.6 Mg/ha per year over a four year period in Washington (Heilman and Stettler 1985). This kenaf yield, however, was obtained on single unreplicated rows and is likely to represent an upper extreme. Average yields of 11 to 14 Mg/ha, as found in 1990, appear more realistic and still approach those reported from some of the more southern growing areas [e.g. 13 to 21 Mg/ha for 1988 in Oklahoma as reported by Dag et al. (1989); 13.6 to 20.1 Mg/ha for 1986 in California as reported by Robinson (1988)]. Based on the height and yield comparisons of 1987 and 1990, it appears that warm temperatures early in the growing season may have an important influence in establishing early growth and maximum performance. The economic prospect of kenaf as a viable central Washington crop, however, will require a stable production area, consistent high yields and the availability of a processing facility set up to handle the pulping requirements.

REFERENCES

Table 1. Monthly mean degree days (°C; 10°C base) at Prosser, Washington.

Degree days
Month 52-yr. 1987 1990
May 147 216 128
June 247 332 281
July 351 332 414
Aug. 328 352 366
Sept. 203 261 299
Oct. 28 74 33

Table 2. Kenaf stand and dry matter yield at Prosser, Washington.

Year Cultivar No. plant/ha
(000)		 Total top dry yield
(Mg/ha)
1987 Everglades 41 254 23.1
Everglades 71 56 6.3
Tainung 1 185 22.3
1990 Everglades 41 144 11.4
Everglades 71 198 12.4
Tainung 1 205 14.0
Cuba 2032 196 11.4
LSD (5%) 28 ---
CV (%) 11.1 13.8


Fig. 1. Kenaf heights at Prosser, Washington; averages of 'EV41' and 'EV71'.

Leaf fraction of Kenaf at Prosser, Washington in 1990; g dry leaf/kg total dry top.
Last update September 15, 1997 aw