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Nelson, J.M. and D.A. Palzkill. 1993. Irrigation effects on growth, cold tolerance of flower buds, and seed yield of jojoba. p. 360-362. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Irrigation Effects on Growth, Cold Tolerance of Flower Buds, and Seed Yield of Jojoba

J.M. Nelson and D.A. Palzkill

  1. METHODOLOGY
  2. RESULTS
    1. Growth
    2. Flower Bud Survival
    3. Seed Yield
  3. CONCLUSIONS
  4. REFERENCES
  5. Table 1
  6. Table 2
  7. Table 3
  8. Table 4
Jojoba [Simmondsia chinensis (Link) Schneid., Buxaceae] is being grown commercially in the very hot arid areas of the southwestern United States for the production of seed containing a high quality liquid wax. One factor limiting jojoba production has been damage to flower buds caused by freezing temperatures. Most of the regions where jojoba is being grown are subject to episodes of freezing temperatures in the winter. Flower buds are present on the plants during the winter months and can be damaged or killed by temperatures of -2° to -5.5°C.

The possibility of using water stress to increase frost resistance of jojoba, although recognized (Yermanos 1983), has not been properly studied. The objective of this research was to determine the effect of early irrigation termination dates on growth and seed production following a cold winter.

METHODOLOGY

This study was conducted in the 1990-91 seasons in a planting established from cuttings in 1984 at the University of Arizona Maricopa Agricultural Center, Maricopa. The planting contained six pistillate clones in groups of five with a plant spacing of 1.2 by 4.1 m. Each sixth plant in the row was staminate. The planting was flood irrigated until March 1988. At that time three irrigation treatments were established (Table 1).

The wet treatment was irrigated using a drip system to provide water based on estimated seasonal evapotranspiration. Medium and dry treatments were flood irrigated with 115 mm of water per irrigation. Data presented in this paper are from the 1990 growing season and include 1991 seed production. In the 1990-91 winter there were several frost episodes in which the air temperature dropped below -5°C in the planting. The lowest temperature recorded was -8deg.C.

RESULTS

Growth

In the third year after irrigation, treatments were established. In 1990, the wet treatment produced 43 and 75% more growth in height than the medium and dry treatments, respectively (Table 2). Plants in the dry treatment produced only an average of 7 cm of growth which greatly reduced flower bud production. A factor that may have contributed to reduced growth in the drier treatments was differential seed yields. In 1990, plants in the medium and dry treatments produced over 400 g of seed per plant compared to 120 g per plant in the wet treatment.

Flower Bud Survival

Flower bud survival was very low in the wet treatment, in which plants were well-watered going into and during the early winter (Table 3). The medium and dry treatments had significantly greater bud survival than the wet treatment. Plants in the medium and dry treatments were water-stressed before and during frost episodes. Large differences among clones in bud survival were observed.

Seed Yield

The highest seed yield came from plants grown under the medium irrigation treatment (Table 4). Yields in the wet and dry treatments were not different even though bud survival was greater in the dry treatment. The lower than expected seed yield in the dry treatment was apparently caused by a combination of factors--reduced shoot growth in 1990, and heavy pruning in the winter of 1990-91, which limited the number of flower buds for 1991 seed production.

CONCLUSIONS

Jojoba plants maintained in a water-stressed condition going into the winter greatly improved the chances of their flower buds surviving frost. Plants which received their final irrigation in September produced significantly more seed than plants which received water until late November. Plants which received their final irrigation in May produced less growth than well-watered plants.

Clones differed in their response to frost in the irrigation treatments and between years. Several clones averaged over 454 g of seed per plant over a two year period in which winter temperatures were low (-8°C). These results indicate that frost resistant jojoba cultivars can increase seed yield and performance under conditions of low temperatures.

REFERENCES

Yermanos, D.M. 1983. Performance of jojoba under cultivation between 1973-1982: Information developed at the University of California, Riverside, p 197-211. In: A. Elias-Cesnik (ed.) Proc. 5th Int. Conf. Jojoba and Its Uses through 1982. Univ. of Arizona, Tucson.
Table 1. Irrigation treatments applied 1988-1990 at Maricopa, Arizona.

Total irrigation (mm) Total water (mm)
Irrigation
treatment		 Date irrigated 1988 1989 1990 1988 1989 1990
Wet Biweekly Mar.-Nov. 386 548 832 529 647 1064
Medium Mar., May, July, Sept. 460 460 460 621 559 692
Dry Mar., May 230 230 230 391 329 462

Table 2. Irrigation effects on plant height of six jojoba clones, 1990.

Plant height (cm)
Clone
Irrigation
treatmentz		 01 03 04 06 15 21 Avg
Wet 33 31 30 21 27 28 28
Medium 13 19 25 12 14 11 16
Dry 5 11 13 3 5 5 7
zLSD (P = 0.05) for irrigation treatments = 4.

Table 3. Irrigation effects on flower bud survival of six jojoba clones following the winter of 1990-91.

Flower bud survival (%)
Clone
Irrigation
treatmentz		 01 03 04 06 15 21 Avg
Wet 2 0 0 0 0 6 1
Medium 61 59 65 15 29 85 52
Dry 20 29 43 9 15 65 30
Avg 28 29 36 8 15 52
zLSD (P = 0.05) for irrigation treatments = 5; for clones = 10.

Table 4. Irrigation effects on seed yield of six jojoba clones, 1991.

Seed yield (g/plant)
Clone
Irrigation
treatmentz		 01 03 04 06 15 21 Avg
Wet 177 163 10 62 9 407 138
Medium 493 457 400 149 476 727 450
Dry 25 175 164 16 186 224 132
Avg 232 265 191 76 224 453
zLSD (P = 0.05) for irrigation treatments = 164; for clones = 155.

Last update April 18, 1997 aw