There are three high-quality edible parts to a juvenile palm stem (Fig. 1). The heart-of-palm is composed of tender developing leaves enclosed within the spear leaf sheath immediately above the apical meristem. The heart accounts for 99% of world trade in vegetable pejibaye (1990 value: U.S.$40 million) and is produced mostly in Latin America, at present (Mora Urpí et al. 1991). The developing stem tissue, extending 10-20 cm below the apical meristem, is also edible. Little edible stem is currently utilized; only 1% of trade in fresh pejibaye consists of stem, mostly in the form of chunks in marinade. The edible leaf is similar to the heart but is not wrapped within the leaf sheath. Consequently, it is difficult to manage during processing, but is of very high quality. All edible leaf produced in Latin America is currently discarded. Chefs in Hawaii are enthusiastic about all three products.
Agronomic research done in Latin America provided a useful guide for the initial formulation of crop management practices in Hawaii, especially regarding plantation density, fertilization, plant management, harvesting, and post-harvest handling (Mora Urpí et al. 1984). Hawaiian agriculture operates under different constraints, however. The most important difference is the cost of labor, including social security, liability insurance, and other indirect costs. Consequently, the Latin American experience had to be modified to fit the limitations of the Hawaiian agroeconomic environment.
As part of the introduction program, growth and yield of half-sib progenies from the Benjamin Constant population of the Putumayo landrace (Brazil) were evaluated at three locations in Hawaii. The effect of planting density was also evaluated in Benjamin Constant progenies and progenies from the Yurimaguas population of the Pampa Hermosa landrace (Peru), using three densities at one location on the Island of Hawaii. Other project objectives were to describe juvenile palm morphology, design a planting scheme suitable for Hawaiian agriculture, compare conventional and organic weed control practices, characterize genetic relationships within the introduced germplasm, evaluate product quality, develop a cost-of-production model, and create a market for the fresh product.
Good sucker (off-shoot) production is essential for long-term survival of the plantation. Sucker number averaged 6-7 (range 0-18) at first harvest, but was substantially lower at second harvest (mean 2, range 0-10) for Benjamin Constant germplasm (Clement 1995). This may have been due to: (1) differences in sucker management, where intense competition among the full sucker complement up to first harvest may have caused abortion of second cycle sucker buds, or (2) different partitioning of resources between shoots and their offshoots during the second cycle, when shoot growth was much more vigorous.
The first possibility was recognized as a potential limitation before field planting. A shortage of germplasm, because of poor germination, did not permit larger plots. The second possibility is probably important too, since the growth rate of each plant is affected by its unique micro-environment. Also, as harvest progressed, the canopies became more irregular, since some plants were removed each month. The third possibility certainly existed during the experimental period, although the magnitude of its effect on LAI is unknown. The older leaves, which may have senesced prematurely due to micronutrient deficiency, would have a relatively small impact on LAI because they were small. The fourth reason is theoretically possible since Corley (1973) observed that vegetative growth in African oil palm (Elaeis guineensis Jacq.) was not reduced at planting densities higher than the optimum for fruiting, although fruit yield dropped dramatically.
Palms are planted in offset double rows with 1-m spacing between plants. Service rows, planted with a legume or grass groundcover, alternate with double rows of palms and permit easy access. This design allows 5000 or more plants/ha. Rows should run along the contours, so that the service rows act to contain erosion. Because all plants are in border rows, the high within-row density should not reduce growth. This design is already being used commercially on the Island of Hawaii.
Groundcovers can also act to control weeds, and they fit well into pesticide-free organic production methods. Three vegetative groundcovers [two legumes (Arachis pintoi, Desmodium ovalifolium) and a grass (Chloris gayana)] and polypropylene mat were compared for efficacy in weed control. All of the vegetative groundcovers competed significantly with the palms, as evidenced by delayed harvest. Consequently, polypropylene mat or organic mulch in the tree rows is an essential complement to the groundcovers to avoid competition. The palms must also receive more fertilizer to compensate for that consumed by the groundcovers.
The plantation design in use on the Island of Hawaii integrates the polypropylene mat with Arachis pintoi. Two-meter-wide polypropylene mat is used to control weeds in the immediate vicinity of the palms in the double rows. A. pintoi is thereby restricted to the service row, where it does not compete with the palms. After full establishment of A. pintoi, it is an acceptable weed-suppressing groundcover, requiring only occasional mowing of weeds that penetrate above its canopy.
Benjamin Constant progenies differed in partitioning to sucker number and sucker growth also (Clement 1995). Some partitioned early to sucker number, but not significantly to sucker growth. Others partitioned early to both number and growth. Others partitioned little to sucker number, but significantly to sucker growth. The latter partitioning pattern may be preferable in Hawaii because it will reduce labor costs for sucker pruning, while providing more rapid growth to the next harvest. However, the marked reduction in number of suckers produced by plants in the field between the first and second harvests may impose limitations on the optimum sucker number that is possible.
With two stems per plant after first harvest, cumulative 18-month yields of hearts-of-palm were 800, 1400, and 1500 kg/ha. When both edible stem and edible leaf were added, 18-month yields were 2.5, 4.5, and 4.8 mt/ha, respectively. Yurimaguas yields were consistently 10% higher than Benjamin Constant yields at the 4.5 mt/ha site, apparently because of lower fiber content.
Response to selection for RGR, EA or earliness depends upon the amount of variation in the population. This, in turn, depends upon the period over which the trait is measured. Three different intervals were examined: a uniform time period (e.g. 292 to 464 days in the field); a uniform developmental period (seedling to harvest); and a mixed category (seedling to 292 days in the field). RGR over the entire seedling-to-harvest period had the lowest variation, but is probably the correct evaluation period (Table 2), since it minimizes variation due to differing developmental morphologies (Clement 1995).
Conventional breeding methods are unlikely to yield rapid genetic gains with this germplasm, because of low variability. Consequently, vegetative propagation is being pursued through tissue culture to capture the best phenotypes for immediate use by farmers.
Negative sensory characteristics found in some samples were astringency and acridity (Table 3). Acridity was more common, occurring in 5% and 8% of Yurimaguas and Benjamin Constant germplasm, respectively. Human sensitivity to acridity ranges from no reaction to an extremely sensitive, perhaps even allergic reaction. Contrary to the finding of Tabora et al. (1993), most consumers in Hawaii do not like the "bite" (acridity) in fresh heart-of-palm. No biochemical assay is currently available to quantify acridity, which limits our ability to evaluate it or determine the relative importance of genetic and environmental factors. Nonetheless, these negative traits are receiving priority attention because of possible health risks which they may pose for a small minority of the population.
Hearts retain fresh flavor and appearance for two weeks when wrapped in plastic film and refrigerated immediately after harvesting. This shelf-life will allow shipping to and marketing in major U.S. markets. Further research is planned to extend shelf-life.
Requirements of individual chefs ranged from 4 to 18 kg/week of palm (including heart, stem, and leaf), so a farmer will need 0.10-0.50 ha to supply one chef. The local restaurant and resort market is estimated to require 80-160 ha of high density plantings. As more area comes into production and supply increases, prices will drop to a level that should allow the demand for hearts-of-palm to expand beyond its present gourmet niche.
California buyers are interested in expanding the area in cultivation in Hawaii to meet mainland and international export market demands. Preliminary research by the USDA/ARS Fruitfly Ecology Lab, Hilo, HI, indicated no fruitfly infestation problem in pejibaye palm hearts. This information is needed by USDA/APHIS to permit importation of heart-of-palm into the continental U.S. Once pejibaye heart-of-palm is cleared for importation, production area may expand beyond the above projections.
(days to harvest)
|292 to 464 days in field||31.9||55.0||0.78z|
|Seedling to 292 days in field||10.7||24.5||1.44z|
|Seedling to first harvest||1.2||9.8||0.74z|
|Evaluation score (1-5 scale)z|
|Plants or sections||Sweetness||Tenderness||Crispness||Moistness||Astringency||Acridity|
|Establishment and first year of management||7.907||50,370|
|Annualized ownership expense||1.091||6,974|
|Operating costs (5th year)|
|Harvesting, processing, shipping costs||2.357||15,067|
|Gross income (5th year)|
|Total gross income||6.048||38,662|
|Total cost of production||5.018||32,135|
|Economic profit (5th year)w||1.030||6,527|
Fig. 1. The three potential palm shoot products.
Fig. 2. Mean annual heart-of-palm yields for seven Benjamin Constant progenies planted at three densities at the best rainfed site in Hawaii.
Fig. 3. Dendrogram based on Nei's (1978) unbiased genetic identities among progenies of the Benjamin Constant population in Hawaii. Cophenetic correlation = 0.69.
Fig. 4. Hypothetical cash flow for a pejibaye heart-of-palm plantation on the Island of Hawaii, assuming a planting density of 5000 plants/ha and a stem value of $6.00.