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-- Research Bulletin --

Effect of Soil Salinity and Irrigation Levels on Kenaf Production in the San Joaquin Valley, California
by
Mahendra S. Bhangoo, Charles G. Cook
and Kamai Sakouri
CATI Publication #940102
© Copyright January 1994, all rights reserved

ABSTRACT

      Kenaf (Hibiscus cannabinus L.), was grown on a Nahrub clay saline soil (Vertic Torriorthents) with a shallow water table to determine effect of different irrigation treatments on production potential on a saline soil with shallow aquifer. Four irrigation treatments (0.3, 0.45, 0.6 and 0.8 m, or 12, 18, 24, and 31.5 inches of nonsaline canal water with ECiw of 0.7 dS/m) were the main plots, and five kenaf varieties (KK60, Iran Early Best, KU 3876, Cubano, and an Indian variety) were the subplots with four replications.
      Soil and the shallow aquifer water samples were taken during the growing season for chemical analysis. Average salinity of soil on 10 May 1992 in all the plots ranged between 9.9 and 10.7 dS/m. Average salinity of the shallow aquifer on May 10, 1992, was about 87.0 dS/m, and the water table level was 1.7 m (5.7 ft.). Stem yield of all the varieties was highest (7764 Kg/ha or 6932 lb/ac) in the 0.8 m irrigation treatment and lowest (2495 Kg/ha or 2228 lb/ac) in the 0.3 m irrigation treatment. Stem yield was positively correlated with the irrigation treatments (R2 = 0.994). Within each irrigation treatment there was no difference in stem yield among different varieties. Stem height in different irrigation treatments ranged between 90 and 215 cm (3.0 and 7.17 ft) and was positively correlated with the irrigation treatments (R2 = 0.915). Average bast fiber yield as proportion of total stem yield was lowest (30.3 %) for the 0.8 m irrigation treatment and highest (40.4 %) for the 0.45 m irrigation treatment for all the varieties and was negatively correlated with the irrigation treatments (R2 = -0.908). Bast fiber yield (kg/ha) in the irrigation treatments ranged between 985 and 2334 Kg/ha (879 and 2084 lb/ac) and was positively correlated with irrigation treatments. The Cubano variety resulted in the highest and the Indian and KK60 varieties lowest in bast fiber yield. Studies conducted during 1991-1992 indicate that kenaf yield was negatively correlated with soil salinity. Soil salinity above 4.0 dS/m did not appear to be conducive to economical kenaf production even when irrigated with good quality water.


INTRODUCTION

      The soils of the Westlands Water District located in the Central California San Joaquin Valley (SJV) areas have salinity and shallow water table problems. The water table varies between 0.2 and 1.5 m or 8 and 60 in (14). For these soils to be productive, they must be drained to keep the water table below the root zone and to facilitate leaching to lower soil salinity. If nothing is done to combat this problem, by the year 2000, 400,000 hectares (ha) or one million acres of land will become highly saline and no longer suitable for crop production (8,14). Growing a multipurpose crop, such as kenaf, that is moderately salt tolerant, can take part of its water requirements from the shallow water table, and remove substantial quantities of salt from the soil, appears to be an economically viable method of ameliorating the problem.
      Kenaf (Hibiscus cannabinus L.), an annual crop, is a source of fiber that can be used for making high quality paper and other related products and for cattle feed (3,5,9,13). It can be grown in the SJV as a cash crop (1). It is known to be moderately salt tolerant and can be grown on any soil type including saline soils (1,2,4,5,6,11). Curtis and Lauchli (4) reported a kenaf seedling yield decrease of 20 to 40 and 70 to 80% by 75 and 150 mmoles of NaCl, respectively in the growth medium. They placed kenaf in a moderately salt tolerant category. According to Francois et al. (6), kenaf grown on saline soil irrigated with saline water showed 11.6% yield decrease for each unit increase in soil salinity above 8.1 dS/m. These results place kenaf in a salt tolerant category. Robinson (11) reported that kenaf can be grown in the Imperial Valley, California on saline soils when 1.5 m (60 in) of good quality water is used for irrigation, however, maximum yield was achieved with 2 m (80 in) of good quality irrigation water (12). Use of saline water for irrigation of kenaf resulted in a 80 to 90% reduction in yield (11). Muchow and Wood (10) reported that kenaf grown in a semi-arid tropical environment can use as much as 1.2-1.4 m of water (48-56 in).
      Bhangoo and Fernandez (2) during 1990 and 1991 found total dry matter and stem yield of different kenaf varieties to decrease substantially with soil salinity greater than 4.0 dS/m. These workers found kenaf to be effective in removing substantial amounts of salt, boron, and selenium from the soil provided total biomass is removed from the field. Kenaf grown on a saline soil with a shallow aquifer required only O.6 to 0.8 m irrigation water depending on the soil salinity level. This indicates that kenaf was able to use some water from the shallow aquifer as is the case with cotton and alfalfa (7).
      The objectives of this study were to (i) to determine production potential of kenaf grown on a saline soil irrigated with different levels of nonsaline water and (ii) to evaluate the effect of irrigation treatments on the stem and bast fiber yield of different kenaf varieties.


MATERIALS AND METHODS

      The experimental plots were located at the Northwest corner of Adams and Derrick avenues (36° 47' N, 120° 53' N) in the Westlands Water District near Tranquillity, California. The soil type was a saline Nahrub clay (fine, montmorillonitic, thermic, Vertic Torriorthents) with inclusions of Cuervo clay. The effective root depth of crops grown in the area is limited by a perched water table (shallow aquifer) that generally lies at a depth of 0.9 to 1.7 m.
      Five varieties of kenaf, KK60, Iran Early Best, KU 3876, Cubano, and an Indian variety were planted on 2 May 1992. Four irrigation treatments (0.3, 0.45, 0.6, and 0.8 m of nonsaline water with ECiw = 0.7 dS/m were the main plots and the kenaf varieties w ere the subplots with four replications in a split plot design. Kenaf seed was planted on 0.76 m (30 in) wide rows. Plot size consisted of six rows 30 m ( 1 ft) long. All the plots were sprinkle irrigated for seed germination and later furrow irrigated every two weeks until each irrigation treatment was completed. Seed germination, regardless of the salinity of soil was excellent for each variety. Plant density resulted in about 350,000 plants/ha (140,000 plants/ac). Nitrogen, as urea ammonium nitrate, at the rate of 140 kg N/ha (120 lb/ac) was applied in two split applications. Five observation wells, 2.4 m (8 ft) deep, were installed on 2 May 1992 for measuring water table level and getting water samples for chemical analysis before and after each irrigation. Soil samples were taken from each plot to a depth of 30 cm (1 ft) on 15 July and 14 October 1992 for salinity determination.
      Plants were harvested on 14 October from each subplot from middle two rows 10 m long for stem yield. Bast fiber yield was determined at harvest time from middle one meter portion of ten stems per subplot. Soil and water salinity was determined by means of the Electrical Conductivity method. Soil and water analysis and stem and fiber yield data were subjected to analysis of variance as dictated by the experimental design.


RESULTS AND DISCUSSION

Stem Yield and Height
      Stem yield (Table 1), from plots irrigated with different levels of nonsaline water, ranged between 2495 and 7764 Kg/ha (2228 and 6932 lb/ac) and was positively correlated with irrigation levels (R = 0.994). Since the soil salinity among plots was not significantly different, stem yields of different kenaf varieties within each irrigation level showed no significant differences. Stem yield data (Fig. 1) from 1991-1992 for the Indian and KK60 varieties were negatively correlated with soil salinity (R = 0. 871). As compared to the yield on a nonsaline soil, the Indian variety showed a 23% and 44% decrease in stem yield at 4.2 and 10.2 dS/m soil salinity, respectively. The KK60 variety showed a 34 and 51% yield decrease in stem yield at 5.0 and 10.2 dS/m soil salinity, respectively (Table 7). These findings are in variance from the findings reported by Francois et al. (6) who reported that kenaf showed no decrease in stem yield upto 8.1 dS/m of soil salinity. Kenaf grown, during 1991 and 92, on soils with an ECe of 4.5 and 10.2 dS/m and a shallow water table required 0.6 and 0.8 m irrigation water that is 0.9 and 1.2 m less than reported by Robinson (12) on saline soils without shallow water table.
fig1 fig8 fig3

      Stem height (Table 2) of the different varieties ranged between 106 and 205 cm (3.5 and 6.8 ft) and was positively correlated with irrigation levels (R = 0.915). Stem height of kenaf varieties within each irrigation treatment was not significantly different. Based on the 1990-1992 results, stem height from a saline soil was significantly lower than from a nonsaline soil and was negatively correlated with soil salinity (R = 0.871).

fig2

Bast Fiber yield
      Bast fiber yield (BFY), proportion of dry stem tissue (percentage) of different varieties, was significantly different only for the 0.6 and 0.8 m irrigation treatments. The Cubano variety was the highest and the Indian was the lowest in fiber yield. The percentage bast fiber yield was significantly different among irrigation treatments (Table 3). It ranged between 30.3% and 40.4% and was negatively correlated with irrigation treatments (R = 0.908). The 0.45 m irrigation treatment was the highest in percentage fiber yield. Bast fiber yield (Kg/ha) ranged between 985 and 2334 Kg/ha (895 and 2084 lb/ac) in different irrigation treatments and was positively correlated with the irrigation treatments. However, fiber yield of different varieties showed no diffe rence within irrigation treatments except for the 0.8 m irrigation treatment in which the Cubano was the highest (Table 4).
fig4 fig5

Water Table Level and Salinity of Water and Soil
      The water table level (Table 6) on 2 May 1992 was 1.7 m and showed a fluctuation of about 0.6 -0.8 m in the intervals between irrigations during the active kenaf growing season. On 20 November 1992, after harvest time, the water table level was the same as in May 1992. There was no difference in the water table level in the plots regardless of the amount of irrigation water applied. Average salinity level of the shallow aquifer (Table 6) on 2 May 1992 was 87.0 dS/m. During mid October, in the plots irrigated with 0.3, 0.45, 0.6, and 0.8 m water, it decreased to 30, 25, 15, and 15 dS/m, respectively. This decrease in salinity of shallow aquifer was either due to dilution or the salt removed by kenaf from the shallow aquifer. Average Soil salinity (Table 5) in all the plots in July ranged between 9.4 and 11.1 dS/m and showed little decrease by mid-October. Studies conducted by the authors during 1990 and 1991, data not presented here, showed that kenaf grown on a saline soil with shallow aquifer require d only 0.6 m of good quality irrigation water when the soil salinity was less than 5.0 dS/m. However, during 1992, 0.8 m of water was required when soil salinity was 10.2 dS/m. This indicates that kenaf needs more irrigation water when grown on a soil with salinity level higher than 5.0 dS/m.
fig6 fig7


CONCLUSIONS

      Results of this study indicate that kenaf can be grown, with 0.8 m of good quality irrigation water, on a saline soil with the salinity level 0f 10.2 dS/m. The stem yield, however, will be 50% lower than that grown on a nonsaline soil. The soils with salinity levels greater than 4.5 dS/m do not appear to be conducive for kenaf production even when irrigated with good quality water. All the varieties studied were equally good in stem yield within each irrigation treatment. Production of kenaf on saline soils is feasible when planted to salt tolerant varieties.


REFERENCES

      1. Bhangoo, M. S., H. S. Tehrani, 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.

2. Bhangoo, M. S. and Fernando, G. Fernandez, and Charles G. Cook. 1993. Kenaf production on a saline soil and its effect on the salinity of soil and shallow aquifer. Proc. Calif. Plant and Soil Conference, Sacramento, CA, Jan. 25-26, 1993, p. 21-29

3. Brody, J. E. 1988. Scientists eye ancient African plant as better source of pulp for paper. New York Times. The Environment. Dec. (D. E. Kugler, CSRS, USDA).

4. Curtis, P. S. and A. Lauchli. 1985. Responses of kenaf to salt stress: germination and vegetative growth. Crop Sci. 25: 944-949.

5. Dempsey, J. M. Fiber crops. 1975. University of Florida press. Gainesville, Florida.

6. Francois, L.E., T.J. Donovan,, and E.V. Maas. 1992. Yield, vegetatative growth, and fiber length of kenaf grown on saline soil. Agron. J. 84: 592-598.

7. Grimes, D. W., R.L. Sharma, and D. W. Henderson. 1984. Developing the resource potential of a shallow water table. Univ. of Calif.Water Resources Center Contribution No. 188: 39.

8. Jorgensen, G.S., K.H. Solomon, and V. Cervinka. 1992. Agroforestry systems for on farm drain water management. Proc. Amer. Soc. of Agri. Engineers, Sixth International Drainage Symposium, Nashville, Tennessee, Dec. 13-15, 1992, p. 484-490.

9. Moore, C. A. 1979. Kenaf: A potential pulp crop. National Economic Division. ESCA/USDA.

10. Muchow, R. C. and I. M. Wood. 1980. Yield and growth responses of kenaf in a semi-arid tropical environment to irrigation regimes based on leaf water potential. Irrig. Sci. 1: 209-222.

11. Robinson, F. E. 1988. Kenaf: A new fiber crop for paper production. Calif. Agri. 42: 31-32.

12. Robinson, F. E. 1990. Irrigation of Kenaf. Proc. First International Conference on New Industrial Crops and Products, Riverside, California. p. 141-145.

13. Taylor, C. S., G. L. Laidig, R. W. Puls, and J. G. Udell. 1982. General feasibility study, kenaf newsprint system. Amer. Newspaper Publ. Assoc. p. 91-135.

14. San Joaquin Valley Drainage Program. 1990. A management plan for agricultural subsurface drainage and related problems on the westside San Joaquin Valley, Final Report, 1990. E. Imhoff, Program Manager, Sacramento, CA p. 183.


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