## INTRODUCTION

Commercially, botanically, and among local populations the Palm Family is held in high esteem. Its products, especially oils and fats, are greatly valued by both indigenous peoples and the multinational food processors. The major source of commercial palm oil, *Elaeis guineensis*, is cultivated on plantations in Africa, Asia, and South America. There is, however, one great drawback to human consumption of palm oil--like coconut oil, it is a prototypic saturated vegetable fat; its major component, palmitic acid, has no double carbon bonds. Consequently, many scientists link its use to increased serum cholesterol levels in human blood and increased risk of heart disease (Trevisan et al., 1990). Oils that are monounsaturated (olive) and polyunsaturated (corn, safflower, soybean, and canola) are recommended over coconut and palm and palm kernel oils (known collectively as tropical oils) whose properties are similar to such animal fats and oils as beef fat, tallow, and lard.

Among eight palm genera that yield oil, two closely related Amazonian genera, *Jessenia* and *Oenocarpus*, yield high quality monounsaturated oils with potential for adaptation to plantation cultivation. One species in particular, *J. bataua*, shows particular promise. In great demand locally and in nearby South American cities, the oil from this palm has been favorably commented upon by Europeans since its "discovery" in the nineteenth century. Chemically, too, it has received high marks for its purity and monounsaturated quality.

Because it is virtually identical to olive oil, its natural markets are Europe and North America, to be marketed as a specialty or gourmet oil, not unlike Swiss walnut oil which is expensive and highly esteemed. In the case of jessenia oil, there would not be the disadvantage, as there is with some specialty oils, of a strong intrinsic flavor that some consumers might justifiably object to.

As a specialty oil, its extent of cultivation and its commercial potential most likely would be limited. Because of this, it is ideally suited to culture in the Caribbean, an area historically noted for such specialties as St. Vincent arrowroot, Jamaican ginger and allspice, and Grenada nutmeg and mace. The challenge is to determine an area in the
Caribbean that would best match the climatic and soil conditions of jessenia's area of natural distribution to best ensure its successful establishment in the Caribbean.

# LITERATURE REVIEW

## Fats and oils

T.P. Hilditch (1956) points out the paradox that "the fats of the simplest and most primitive organisms are usually made up of a very complex mixture of fatty acids [while], as biological development has proceeded, the chief component acids of the fats of higher organisms have become fewer in number. In the animal kingdom this change in type is remarkably progressive and culminates, in the depot fats of the higher land animals, in fats in which oleic, palmitic, and stearic acids are the major components. In vegetable seed fats, as a rule, similar simplicity is seen in the major component acids. Fruit coat fats ... include palmitic and oleic acids as sole major components, irrespective of the plant family in which they occur; linoleic acid is also frequently present, but usually only in minor quantities." Of these fatty acids, "oleic acid [a monounsaturated fatty acid] is undoubtedly the most widespread of all natural fatty acids. In very many fats it forms more than 30 percent of the total fatty acids and up to the present has been found absent in no natural fat or phosphatide.... Two others appear to be nearly as ubiquitous: [polyunsaturated] linoleic and (monounsaturated) palmitoleic."

Palmitic is a characteristic saturated fatty acid occurring prominently in many oils, to which it may contribute 15 to 50 percent. Only myristic and stearic acids approach palmitic in frequency of distribution of saturated fatty acids (Hilditch, 1956). Table 1 shows the average fatty acids of olive, palm, and jessenia oils. Table 2 shows US imports of olive and tropical oils.
<table><caption>Table 1. Average fatty acid content of olive, palm, and jessenia oils¹.</caption><thead><tr><th rowspan="2">fatty acid</th><th rowspan="2">no. double bonds</th><th rowspan="2">no. carbon atoms</th><th colspan="3">percent of total oil</th></tr><tr><th>palm</th><th>olive</th><th>jessenia</th></tr></thead><tbody><tr><td colspan="6"><strong>Saturated</strong></td></tr><tr><td>lauric</td><td>0</td><td>12</td><td>trace</td><td></td><td></td></tr><tr><td>myristic</td><td>0</td><td>14</td><td><strong>2</strong></td><td>trace</td><td></td></tr><tr><td>palmitic</td><td>0</td><td>16</td><td>43</td><td>11</td><td>13</td></tr><tr><td>stearic</td><td>0</td><td>18</td><td><strong>4</strong></td><td><strong>3</strong></td><td>4</td></tr><tr><td colspan="6"><strong>Unsaturated</strong></td></tr><tr><td>palmitoleic</td><td>1</td><td>16</td><td></td><td>1</td><td>1</td></tr><tr><td>oleic</td><td>1</td><td>18</td><td>42</td><td>77</td><td>78</td></tr><tr><td>linoleic</td><td>2</td><td>18</td><td><strong>9</strong></td><td>8</td><td>3</td></tr><tr><td>linolenic</td><td>3</td><td>18</td><td>trace</td><td>1</td><td>1</td></tr></tbody></table>

1. Sources: Balick and Gershoff, 1988; Ecke, 1954; Hilditch, 1956; Lawson, 1985.

<table><caption>Table 2. U.S. imports of olive, palm, palm kernel and coconut oils. Oct-March 1990-91.¹</caption><thead><tr><th></th><th>MT</th><th>'000 $</th><th>% price<br/>$/MT</th><th>olive oil</th></tr></thead><tbody><tr><td>olive</td><td>48,701</td><td>107,994</td><td>2,217</td><td>--</td></tr><tr><td>palm</td><td>71,538</td><td>21,889</td><td>306</td><td>13.8</td></tr><tr><td>palm kernel</td><td>81,717</td><td>30,327</td><td>371</td><td>16.7</td></tr><tr><td>coconut</td><td>252,759</td><td>76,587</td><td>303</td><td>13.7</td></tr></tbody></table>

1. Source: USDA, 1991.
In the U.S., in terms of economic value, soybean oil, virtually unknown prior to World War II, now constitutes over 75 percent of all vegetable oils consumed (Weiss, 1983; USDA, 1990).

## Palm oil

A product of *Elaeis guineensis*, the commercial African oil palm, palm oil is composed mainly of 35-40 percent palmitic acid, a lauric (saturated) fat similar to coconut oil, and 40 percent or more oleic, the main fatty acid in olive oil (Hilditch, 1956).

One method of refining palm oil is to degum with a phosphoric acid wash followed by alkali refining, water washing, and, finally, bleaching if the natural carotene pigments are to be removed and those fatty acids which hasten rancidity reduced. Subsequent fractionation steps can yield various products, each with its own characteristics and potential uses (Purseglove, 1985; Weiss, 1983).

## Olive oil

Olive fruit is a drupe with a pulpy endosperm which, when ripe, is rich in oils (Bailey, 1949). It is the major cooking oil of most southern European countries and one enjoying increased consumption in the US. The composition of olive oil is predominantly unsaturated acids consisting mainly of oleic acid (70 to 85 percent); saturated acids include palmitic (7 to 15 percent) and stearic acid (1.4-2.4 percent) (Hilditch, 1956).

Olive oil was eclipsed for a time while Americans, especially those with elevated cholesterol, were told that polyunsaturated oils, especially corn, safflower, and canola, would lower their cholesterol which, indeed, they can. The drawback to the polyunsaturated oils is that they lower all forms of cholesterol including the high density lipids (HDLs) known as the "good" cholesterol. Beginning in 1985, however, a series of reports of studies comparing fats, saturated, monounsaturated, and polyunsaturated as well as diets low in fats and high in carbohydrate found that the monounsaturated oleic-acid-rich oils, most frequently olive oil, lowered plasma cholesterol and low density lipids (LDLs), but not HDLs (Baggio et al., 1988; Grundy,
1986; Grundy et al., 1988; Mattson and Grundy, 1985; Mensink and Katan, 1987). Olive oil lowered levels of LDLs at least as well as a low-fat high-carbohydrate diet, it did not raise triglycerides, and did not reduce HDL cholesterol (Baggio et al., 1988; Grundy, 1966; Mensink and Katan, 1987). (The best was yet to come. In a 1989 European study of Mediterranean diets, Renaud and de Lorgeril reported that the moderate consumption of alcohol, especially wine, but not polyunsaturated fats appeared to offer protection from heart disease among the French and Italians.)

To obtain olive oil, the most common process involves milling, that is, crushing and pressing (Eckey, 1954; Purseglove, 1968). Oil from the first pressing, possessing fewer free fatty acids and a more delicate flavor, is designated virgin grade (or, in some instances, the technical impossibility of being extra virgin) (Eckey, 1954; Robbelin et al., 1989). Good grades require no refining other than clarification obtained by settling or, in more mechanized operations, centrifuging and filtration (Weiss, 1983). The usual characteristics of olive oil include that it is fluid and clear at room temperature with color pale yellow through greenish-yellow. The color deepens and the flavor becomes less delicate as the grade departs from virgin (Eckey, 1954).

## Jessenia

The genus *Jessenia* is native to the high rainfall areas of the lowland tropics of South America (Balick, 1988; Hodge, 1975). Its members grow in the Amazon Basin at or above flood level (Anon., 1976; Balick, 1988; Calvalcante, 1977) as well as the Orinoco Basin and Gulf of Paria regions of Venezuela (Eckey, 1954) and even on the slopes and valleys of the Colombian Andes at an elevation of 1800 meters (6000 ft.) although seldom above 1450 m (4800 ft) (DeLeon, 1958), thriving below 600 m (2000 ft) (Balick, 1988; Beckerman, 1977). The key cultural requirements for the genus are high rainfall with well-drained soils. The *Jessenia* are areca-like (smooth trunked, feathery leaved) palms with ringed trunk and a prominent crownshaft below the crown. The petioles have broad clasping bases; the leaves are borne at an upward angle, drooping only at the tips (Bailey, 1948; Balick, 1988; Beckerman, 1977). At maturity the sturdy trees can reach a height of 20 m (65 ft) or more (Balick, 1979), occasionally
even more (Tomlinson, 1961) although Balick (1988) has observed naturally short trees in the wild.

The genus was established to honor Dr. Carl Jessen, professor of botany at Eldena, Prussia (Anon., 1960). From the beginning the taxonomic classification of *Jessenia* and the closely related *Oenocarpus* has been disputed (Anon., n.d.; Balick, 1979; Calvalcante, 1977; Dugand, 1961; Eckey, 1954; Glassman, 1965; Spruce, 1908). The confusion was resolved by Balick (1986) in his thorough revision of what is now known as the *Oenocarpus-Jessenia* complex of the Palmae (Balick, 1986).

*Jessenia bataua* (Martius) Burret, the species with the greatest commercial potential in this complex, has two subspecies, *J.b.* subsp. *bataua* with 40-90 pistilate flowers per panicle and the infelicitously-named *J.subsp. oligocarpa*--few fruited-with 3-54 pistilate flowers (Balick, 1986). The former is found in lowland areas of French Guyana, Brazil, Venezuela, Colombia, Panama, Ecuador, and Peru; the latter in the Valencia area of Trinidad plus Venezuela, Guiana, and Surinam. Over 100 local names are recorded for these palms. They include seje and pataua in South America and jagua, palma de jagua, and yagua in Trinidad. Both subspecies bear bunches of nutmeg-sized violet to purple fruit twice in the season between October and April (Beckerman, 1977; Calvalcante, 1977; Eckey, 1954). The 8 to 25 kg bunches (average 15-17.5 kg) are about 70 percent pericarp. This; pericarp contains 18 to 24 percent oil (Balick, 1979; Beckerman, 1977; Eckey, 1954; Markley, 1957) or an average of 3 to 3.5 kg oil per bunch of uncultivated fruit, extracted locally by boiling, maceration, and squeezing in a basket press (Balick, 1988; Uphof, 1968). This oil is in high demand in local markets (Balick, 1988; Calvalcante, 1977; Eckey, 1954; Schultes, 1974), and chemical analysis has confirmed Richard Spruce's opinion, voiced in a letter in 1854 to Sir William Hooker (Spruce, 1908), that it is the virtual equivalent of olive oil (Balick, 1979, 1988; Calvalcante, 1977; Eckey, 1954; Hardy, 1950; Jeffries, 1950; Uphof, 1968), even to its color-clear yellow with a slight greenish tinge (Anon., 1976; Balick, 1986, 1988; Eckey, 1954). Another curious quality of *J. bataua* fruit is that, unlike all other oil palms, the kernel contains less than 1 percent oil (Balick 1979; Eckey, 1954; Hodge, 1975; Markley, 1957).
In addition to the high-grade unsaturated oil, Beckerman (1977) notes that the fruit contains 8 percent dry weight protein; in 4 kg of fruit there are 72 gm fat and 32 gm protein, or slightly more than the protein in five eggs. The protein is remarkably well balanced. Analysis showed that it was superior in all essential amino acids except tryptophan and lysine (90 and 96 percent, respectively, of the FAO/WHO provisional scoring pattern) (Balick and Gershoff, 1988). According to Beckerman (1977), the fruit makes a substantial meal, especially if mixed with manioc. Dissolved in water, the fruit coating produces a refreshing drink that, if mixed with granulated yuca, can be quite filling (Jeffries, 1950). In addition, the spent pulp has been found to be an excellent poultry and swine feed (Balick and Gershoff, 1988).

**Propagation of Jessenia:** DeLeon (1958) writes that most palm seeds have thin seed coats that do not go into a state of dormancy. Rather, under unfavorable conditions, the embryos shrink and dry up. The length of time a seed will remain viable depends on the area to which the tree is native. Those trees from distinct wet-dry or warm-cool regions, or both, bear seed that remains viable for up to three months. Conversely, those such as *Jessenia* and *Oenocarpus*, from areas of slight change in temperature and rainfall have seed viability of only two to three weeks. In consequence jessenia seed should be gathered, packed in a plastic bag with peat moss or damp newspaper, transported quickly, and sown as soon as possible (DeLeon, 1958). Seed were germinated by Jordan (1970) in two lots with 99 and 80 percent success. Balick (1979) reported that *J. bataua* took an average of 20 to 40 days to germinate. In addition, he said that the seeds, if cleaned of epicarp and mesocarp and kept moist and warm, will remain viable for up to six weeks. Soaking the seed for 30 minutes in 50°C water (or one week in cool water) resulted in 98 percent germination with more precocious leaf appearance at 52 days (Balick, 1988).

In the wild, trees bear 1 to 3 panicles, 2 to 3 being most common (Balick, 1986, 1988). Selections for more panicles should bring the reliable number to 2.5 or more per tree (Balick, 1988). The flowers are insect pollinated with no lack of volunteers (Balick et al., 1988). In the wild, trees reach bearing age at 7-10 years. Balick (1988) believes that, like the African oil palm, domestication can halve this
time. Jessenia has 100 percent production in years 15-42 (7-10 more an oil palm), then drops off sharply (Balick, 1988; Purseglove, 1972). Jessenia, like most palms, has a symbiotic relationship with vesicu-lar-arbuscular mycorrhizae (VAM). Because VAM are found in most native soils, it is only nursery-grown jessenia that may be negatively affected by the absence of VAM in potting mix (St.John, 1988). Consequently, if nursey grown, it is advisable to inoculate the mix with VAM.

Assuming the average fruit panicle bore 10.4 kg of fruit and the mature fruit averaged 8 percent oil, 100 bearing trees would yield approxi-mately 130 kg (285 lb) of oil per tree (Balick, 1988). At 216 trees per hectare (which allows for intercropping), nearly 400 kg (880 lb) of oil could be anticipated. The oil weighs 7.63 lb/gallon (15.26 oz/pint), so 880 lbs would yield over 900 pints, processed, packed, and wholesale marketed for an upscale consumer at, presumably, US$1 or more (Table 3). In August, 1991 average grade olive oil retailed in the US for $5.59 per liter.

<table><caption>Table 3. Average unit value of U.S. olive oil imports ($/MT)¹.</caption><thead><tr><th>Year</th><th>1984</th><th>1986</th><th>1988</th><th>1990</th></tr></thead><tbody><tr><td>Price</td><td>1353</td><td>1537</td><td>1632</td><td>2047</td></tr><tr><td>$/lb.</td><td>0.514</td><td>0.697</td><td>0.740</td><td>0.928</td></tr></tbody></table>

1. Source: US Bureau of the Census, 1991.

Processin. Jessenia processing usually consists of harvesting, piling, and covering with leaves or a plastic sheet overnight to further ripen the fruit. They are then dumped into a large vessel of approximately 50°C water and soaked for 2-3 hours. They are then decanted into a smaller pot while the large one is again filled with water and heated to just below the boiling point and removed from the fire. The fruit are placed in this pot to split the epicarp, then removed and pounded in mortars to separate the flesh from the seed. The whole is sifted in a half-inch screen sieve, the seeds drop through, and the rest is transferred to a basket press. Pressure is applied and the oil is expelled
pigmented water. The light green to yellow clarified oil is then bottled
(Balick, 1988).

Intermediate technology substitutes a simple hydraulic hand press for
the basket. The result is a significantly greater percentage of oil
(Balick, 1988).

For the best oil extraction, a small oil processing mill similar to that
described by Blaak (1980, 1988) used in a West African palm oil mill
is necessary. The fruit is stripped from the panicle (often before
transportation to the mill), then steamed and digested to loosen the
mesocarp. The fruit are sifted to remove the seeds, reheated, and
pressed. Next the oil is clarified to remove emulsified water, then
bottled. (Further details are available in the FAO plant production and
protection paper, number 88, 1988: *Jessenia* and *Oenocarpus*: Neo-
tropical.

Oil Palm Worthy of Domestication, by M.J. Balick.) According to
Blaak (1988) and based on the figures for the seje (jessenia) oil mill
in rural Colombia, the approximate cost (extrapolated from the 1980
figures assuming about 2.5 percent annual inflation) is about $22,000
for the imported press and digester plus engine and an additional
$15,000 for shed, foundation, labor, transport, and locally obtainable
equipment.

While no one is likely to get rich, this would be an excellent way to
supplement the incomes of a community.

Climate and soils

Native: The areas where *Jessenia bataua* is native are characterized
by high temperatures with no appreciable seasonal variation. Growth
coincides with the rainy season. Soils are highly weathered with low
mineral reserves, well drained, usually with low cation exchange
capacity. As is typical of many soils in the humid tropics, bases are
quickly recycled by forest vegetation. In general, there are no more
than 90 cumulative days a year of dry weather (Anon, n.d.; Young,
1976).
**Caribbean:** Among the islands in and countries surrounding the Caribbean, both size and elevation are important for attracting rain. These qualifications rule out an island such as Antigua which, despite good and diverse soils, covers only 280 km² and does not have sufficient elevation, particularly in the east, to attract much rain (Anon., 1960; Hardy, 1950). The same is true for Barbados (Anon., 1960; Poynter, 1986). Among the larger islands of the Caribbean, geologically similar Puerto Rico and Jamaica (Hardy, 1950) have volcanic mountains surrounded by limestone plains (Anon., 1960; Bonnet, 1950; Jeffries, 1950; Meyerhoff, 1950). Both islands. Jamaica especially, have areas of tropical rainforest (Anon., 1960; Meyerhoff, 1950).

In the major French islands, Martinique, while somewhat smaller than Guadeloupe, has higher elevations with more remaining forest (Anon., 1960; Moulin, 1950). Geomorphically, both islands benefited from the 1902 explosion on Martinique of Mt. Pelee and the subsequent volcanic ash and dust deposits that replenished soil nutrients in land under sugarcane cultivation (Anon, 1960; Stehle, 1950). The remaining volcanic Windward and Leeward islands are also relatively small. Dominica (750 km²) and St. Lucia (620 km²) each have notable elevations (1447 m and 950 m, respectively) with fertile soils derived from andesite and basalt (Anon., 1960; Hardy, 1950; Rodrigues, 1950). In general, the dry period in the eastern Caribbean lasts from mid-January to mid-April or early May (90-120 days) (Anon., 1960).

Trinidad, has a wide variety of soils and elevations, the wetter northeast especially. It is a geologic continuation of Venezuela (Anon., 1960; Hardy, 1950) and one of the areas where *J. bataua* subsp. *oligocarpa* is native, thus a good candidate.

## DISCUSSION: ESTABLISHING JESSENIA

The greatest initial problem in the cultivation of *Jessenia bataua* would be the selection of seedlings and progeny for highest panicle number, seed oil content, plant vigor, and, if possible, shorter stature. If the time is brief between collection and sowing of seed, good germination is almost assured. An investment in time and travel would
be necessary to ascertain qualities of soil, soil fertility, drainage, and rainfall to nearly duplicate J. *bataua*'s natural habitat or to compensate for any shortcomings.

In addition to the time from germination to planting out the seedlings, there would be a lag between the time of planting and the first harvest of sufficient quantity to warrant marketing the oil, as well as a need for processing and packing facilities. Because of these inevitable and unavoidable delays, cultivation of jessenia most likely would require cooperation and economic contributions from government or private investors or both. Once supply and processing were assured, the oil would require good marketing, stressing the product's many desirable characteristics and directed to upscale consumers—in other words, "boutiquing" the product. Previous campaigns aimed at similar markets have resulted in demand for such products as yogurt, safflower and canola oils, kiwi fruit, alfalfa and other sprouts, and almost any sort of fish imaginable. Jessenia oil has the same potential to carve out a niche in the lucrative upscale markets of Europe and North America.

## ADDENDUM

Plantings of *Jessenia bataua* have been established at CEPLAC (Una) near Itabuna, Bahia, Brazil and at CEPATU, Belem, Brazil coordinated by CENARGEN/EMBRAPA (the Brazilian National Germplasm Conservation Program) (Balick, 1988). Those interested in more information on current seed sources might also write to Dr. Michael J. Balick, Director and Philecology Curator of Economic Botany, Institute of Economic Botany, New York Botanical Garden, Bronx, NY 10458-5126 USA.

## LITERATURE CITED

* Anon. 1960. What's in a name? Principes 4:143.

* Anon. 1975a. Underexploited tropical plants with promising economic value. National Academy of Sciences, Washington, D.C.
Anon. 1975b. Soils of the humid tropics. National Academy of Sciences, Washington, D.C.

Anon. n.d. (approx. 1985). Baedeker's Caribbean. Prentice-Hall, Englewood Cliffs, N.J.

Baggio, G., A. Pagnan, M. Muraca, S. Martini, et al. 1988. Olive-oil-enriched diet: Effect on serum lipoprotein levels and bilary cholesterol saturation. Am. J. Clin. Nutr. 47:960-964.

Bailey, L.H. 1949. Manual of cultivated plants. Macmillan, New York. p.173.

Balick, M.J 1979. Amazonian oil palms of promise: A survey. Econ. Bot. 33:11-28.

Balick, M.J. 1985. Taxonomy of the *Oenocarpus-Jessenia* (Palmae) complex in Brazil. Acta Amazonica, Suppl., 15:87-113.

Balick, M.J. 1986. Systematics and economic botany of the *Oenocarpus-Jessenia* (Palmae) complex. Advances Econ. Bot. 3:1-140.

Balick, M.J., and S.N. Gershoff. 1988. Nutritional value [of *Jessenia*]. In FAO plant production and protection paper 88: *Jessenia* and *Oenocarpus*: Neotropical oil palms worthy of domestication. M.J. Balick et al. pp.10-18.

Beckerman, S. 1977. The use of palms by the Bari Indians of the Maracaibo Basin. Principes 21:143-154.

Blaak, G. 1988. Mechanical extraction and prospects for development of a rural industry. In FAO plant production and protection paper 88: *Jessenia* and *Oenocarpus*: Neotropical oil palms worthy of domestication. M.J. Balick et al. pp.65-83.

Bonnet, J.A. 1950. Comment on Puerto Rico soils. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp.201-202.
Calvalcante, P.B. 1977. Edible palm fruits of the Brazilian Amazon. *Principes* 21:91-102.

DeLeon, N.J. 1958. Viability of palm seeds. *Principes* 2:96-102.

Dugand. A. 1961. Palms of Colombia. *Principes* 5:135-144.

Eckey, E.W. 1954. Vegetable fats and oils. Rinehold, New York.

FAO. 1988. FAO plant production and protection paper 88: *Jessenia and Oenocarpus*: Neotropical oil palms worthy of domestication. M.J. Balick et al. 191pp.

Glassman, S.F. 1965. Geographic distribution of New World palms. *Principes* 9:132-134.

Grundy, S.M. 1986. Comparison of monounsaturated fatty acids and carbohydrates for lowering plasma cholesterol. N.Engl. J. Med. 314:745-748.

Grundy, S.M., L. Florentin, D. Nix, and M.F. Whelan. 1988. Comparison of monounsaturated fatty acids and carbohydrates for reducing raised levels of plasma cholesterol in man. Am. J. Clin. Nutr. 47:965-969.

Hardy, F. 1950. Soil problems of the Caribbean. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp.184-189.

Hilditch, T.P. 1956. The chemical constitution of natural fats. John Wiley and Sons, New York.

Hodge, W.H 1975. Oil-producing palms of the world--A review. *Principes* 19:119-136.

Jeffries, C.D. 1950. The constituent minerals of soils, their determination and some observations on their occurrence in the soils of Puerto Rico. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. p.203.
Jordan, C.B. 1970. A study of germination and use in twelve palms of northeastern Peru. *Principes* 14:26-32.

Lawson, H.W. 1985. Standards for fats and oils. AVI, Westport, CT.

Markley, K.S. 1957. Fat and oil resources and industry in Brazil. *Econ. Bot.* 11:91-125.

Mattson, F.H., and S.M. Grundy. 1985. Comparison of effects of dietary saturated, monounsaturated, and polyunsaturated fatty acids on plasma lipids and lipoproteins in man. *J. Lipid Res.* 26: 194-202.

McCurrach, J.C. 1960. Palms of the world. Harper, New York. p.108.

Mensink, R.P., and Katan, M.B. 1987. Effect of monounsaturated fatty acids versus complex carbohydrates on high-density lipoproteins in healthy men and women. *Lancet* 1987(1):122-125.

Meyerhoff, H.A. 1950. Some observations on the weathering of rocks in Puerto Rico. Soil Science of the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp.204-206.

Moulin, P. 1950. Report on the action taken by the forest service for the conservation and improvement of the soils of Guadeloupe. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp.211-212.

Poynter, A.G. 1986. Philips' Certificate Atlas of the Caribbean. Philips', London.

Purseglove, J.W. 1968. Tropical Crops: Dicotyledons. Longmans, Harlow, Essex. pp.231, 270.

Purseglove, J.W. 1985. Tropical Crops: Monocotyledons. Longmans, New York. pp.479-510.
Renaud, S., and M. de Lorgeril. 1989. Dietary lipids and their relation to ischaemic heart disease: From epidemiology to prevention. J. Internal Med. 255, suppl. 1:39-46.

Robbelen, G., R.K. Downey, and A. Ashri. 1989. Oil crops of the world: Their breeding and utilization. McGraw-Hill, NY.

Rodrigues, G. 1950. The clay minerals of British West Indian soil. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp. 190-192.

Schultes, R.E. 1974. Palms and religion in the northwest Amazon. Principes 19:119-136.

Spruce, R. 1908. Notes of a Botanist on the Amazon and Andes. A.R. Wallace, ed. Macmillan, London.

St. John, T.V. 1988. Mycorrhizal enhancement in growth rate of *Jessenia bataua* seedlings. In FAO plant production and protection paper 88: *Jessenia* and *Oenocarpus*: Neotropical oil palms worthy of domestication. M.J. Balick et al. pp.140-148.

Stehle, H. 1950. The soils of the French West Indies and especially those of Martinique. Soil Science in the Caribbean. Caribbean Commission, Central Secretariat, Port of Spain, Trinidad. pp.207-210.

Tomlinson, P.B. 1961. Essays on the morphology of palms. V: The habit of palms. Principes 5:83-89.

Trevisan, M., V. Krogh, J.L. Freudenheim, A. Blake, P. Muti, et al. 1990. Diet and coronary heart disease risk factors in a population with varied intake. Prevent. Me. 19:231-241.

Uphof, J.C.Th. 1968. Dictionary of Economic Plants, 2nd ed. Verlan von J. Cramer (Stechert-Hafner Service Agency, Inc.), New York. p.288.

US Bureau of the Census. 1991. USGPO, Wash., DC.
USDA. Feb 1988, May 1988, June 1991. Oil crops: Situation and outlook report. USGPO, Wash., DC.

USDA. 1991. Agricultural statistics, 1991. USGPO, Wash., DC.

Weiss, T.J. 1983. Food oils and their uses. AVI, Westport, Connecticut.

Young, A. 1976. Tropical soils and soil survey. Cambridge University Press, Cambridge.
THE EFFECT OF TYPE OF TRELLIS AND PRUNING
ON PASSION FRUIT YIELDS IN DOMINICA

Gregory Robin

Paper to be presented at the 28th Annual Meeting of the
Caribbean Food Crops Society Santo Domingo, Dominican
Republic

August 9th - 15th, 1992

Caribbean Agricultural Research and Development Institute
P.O. Box 346, Botanic Gardens
Roseau
Dominica

THE EFFECT OF TRELLIS AND PRUNING ON
PASSIONFRUIT YIELDS

ABSTRACT

The effects of selective pruning and non-pruning on "Fence" and "T"
trellis systems, were evaluated over a two year period in the Com-
monwealth of Dominica. The "T" trellis gave higher fresh weight
yields 3,511 and 6,916kg/ha in year 1 and 2, as compared to the
"Fence"-trellis which gave yields of 1,170 and 3,830 kg/ha for years
1 and 2 respectively. The nonpruned treatments gave higher yields
i.e. 2,660 and 5,958 kg/ha when compared with the pruned treatments
1,596 and 4,682 kg/ha for years one and two respectively. Economic
evaluation of the different trellis systems and pruning treatments,
indicated that the "T"-trellis with the non-pruned treatments gave the
highest returns EC$7,235/ha (US$2,680) and EC$8,913/ha
(US$330/ha) when sold to the processor and huckster respectively,
over the two year period. Correlations between fresh weight and pulp
weight were (r=0.945) in year one.

Keywords: Passionfruit (Passiflora edulis f. flavicarpa); Dominica; West Indies; trellis; pruning.
## INTRODUCTION

Passion fruit (*Pasiflora edulis f. flavicarpa*) has been identified as one of the major diversification crops for the Organisation of Eastern Caribbean States (OECS) (Anon., 1988). As a result the sub-region has experienced a substantial increase in its production acreage over the past five years.

In the Caribbean Community (CARICOM), Dominica has the largest acreage (120ha) of passion fruit (Andrews, 1991) and ranks among the top ten world producers (Menzel, et al., 1988). With the increasing capacity for processing and fresh fruit export, the Ministry of Agriculture (MOA) proposed to increase the area for its production to 200 ha over the next two years.

Expansion of the passion fruit acreage has been supported by a number of externally-funded projects: the High Impact Agricultural Marketing Project (HIAMP), the Ministry of Agriculture's Tree Crop Project and, most recently, the Caribbean Agricultural Research and Development Institute's (CARDI) Exportable Fruit Crops Project. The objectives of the projects were to increase production either by expansion of acreages and/or introduction of new technologies. This resulted in the movement away from the more traditional methods of production (i.e. growing on gliricidia trees and other non productive trees) to more commercialized methods of production, the "Fence" and "T"-trellis systems.

The "Fence" and "T" trellis systems were used to establish approximately 90 percent of the passion fruit acreage during the 5 year period, 1985-1990. The "canopy" system was used to establish the remainder. Recommended crop husbandry techniques, viz. pruning, fertilizer application, pest and disease control were obtained from the literature (Rajkumar, 1987, Anon, 1991; Akamine et al., 1974; Gachanja and Gurah, 1980). However, farmers were concerned that the number of potential bearing laterals that were removed due to pruning would reduce yields. This coupled with the unavailability of productivity data for the recommended systems of production in local conditions were also cause for concern in the Ministry of Agriculture. It therefore became necessary to evaluate the "Fence" and "T"-trellis systems and
the effects of selective pruning and no pruning had on yield and yield components. An economic assessment of both systems was also conducted, when fruit was sold to the processor and the huckster.

## MATERIALS AND METHODS

The experiment was conducted at the Portsmouth Agricultural Station on kandoid soils. This location is approximately 60m above sea level. Mean annual temperatures range between 26 and 29°C. Moisture regimes are described as udic and annual rainfall is between 1240 and 2500mm.

Secondary forest was cleared and debris windrowed at the base of the gently sloping 0.25 ha plot. The plot was then lined with stakes spaced at 3.0m x 3.7m along the contour.

The experiment was laid out as a split plot design. The main treatments consisted of the "Fence" and "T"-trellis systems with selectively pruned or unpruned sub-plots. There were four replicates, each replicate had two "Fence" and "T"-trellis systems randomly established on which the selective pruning and unpruned treatments were superimposed.

All trellis posts (local hard woods) were treated with the wood preservative Solignum(R). Twelve gauge steel wire was used for establishing the trellises. The "Fence" system contained a single line of trellis wire, whereas the "T" system contained three lines of wire one on top of the trellis post and the other two on either side of the "crosspiece" which was placed 30 - 45cm from the top of the pole Appendix 1 & 2. The cross piece was 90cm long.

The plot sizes were 1.85m² for the "Fence" trellis and 3.7m² for the "T"-trellis. Trellis posts were placed 3.0m x 3.7m.

The crop was established on November 17, 1988. One seedling 25-30cm long was placed in each hole. Holes, 20cm deep with diameter of 10cm, were dug 45cm away from the trellis post. "Training" stakes leading to the trellis wire were placed about 10 -
15cm away from the plant. Seedlings were fixed loosely to the training stakes with twine.

The two most vigorous shoots (leaders) from all plants were allowed to climb the training stake onto the trellis. Leaders were trained in opposite directions, and allowed to run 3.7m on the trellis wire before the tips were cut. Lateral shoots on all leaders, between the ground and the trellis were removed. The other laterals were allowed to develop along the wire and hang down freely by removing the tendrils. All laterals were cut 15cm above the ground.

Selective pruning involved removal of every other lateral along the trellis, during the first crop cycle. After the first crop cycle, dead vines were removed from the trellis; laterals which had borne fruitwere cut back allowing young ones to progress.

Vines were sprayed on three occasions with Diazinon(R) 4ml/litre to control leaf chewing larvae of the Dione spp. On the first sign of rat damage, rat bait was placed on the periphery of the experimental plot as a preventative measure. This was done on two occasions.

in the early stages of establishment the experiment was sprayed with Gramoxone(R) (25/ha). On all other occasions brush weeding was carried out to control weeds.

Fertilizer (NPK; 16:8:24+2MgO) at the rate of 160kg/ha, was applied in a split application (at planting and 5 months after planting) during the first crop cycle. The fertilizer was applied in a circle about 0.3m from the base of the vine. After the first crop cycle, fertilizer was applied after pruning and before flowering.

Data was collected weekly on fruit set (when fruit were at marble-size stage), number of fruit harvested, fresh weight, pulp weight (taken from a random sample of individual fruit which amounted to 40% of each harvest). Cost of production studies involved costings of all material, labour and yields. The trellis systems were amortized over a 3 year period.
# RESULTS

## Yields

Table 1 shows the effects of trellising and pruning on fruit set, number of fruits harvested and fresh weight over the period 1988-1990. In year 1, plants on the "T"-trellises produced three times (6.6 kg) the fresh weight of fruits as those on the "Fence"-trellises (2.2 kg) ($P<0.01$). Unpruned plants yielded more (5.0 kg) than those selectively pruned (3.0 kg) after the first crop cycle ($P<0.05$). On the "Fence" trellises the pruned plants had half the fruitset (34) ($P<0.05$) compared to those that had been selectively pruned (76) ($P<0.05$), but his was not apparent on the "T"-trellises. There was 50% difference in fruit set and fruit harvested.

In Year 2 these effects were no longer significant except that unpruned plants continued to have a higher fruitset and fresh weight ($P<0.05$). Though "T"- trellis yields were almost twice as high (13.0 kg/plot) as those from the "Fence"-trellis (7.2 kg/plot), this was not statistically significant. There were no significant effects due to interaction. There was a 38% difference between fruit set and fruit harvested.

Table 2 shows the extrapolated yields. Overall, first year yields were very (low 1,170 and 3,511 kg/ha for the "Fence" and "T"-trellis respectively); compared to the second year yields which were 3,830 kg/ha and 6,916 kg/ha for the "Fence" and "T"-trellis respectively.

Overall, the highest yields of 3,724 kg/ha in Year 1 and 7,235 kg/ha in Year 2 were obtained from the unpruned treatments on the "T"-trellis.

## Cost of Production

Cost of production studies and margins of returns are shown in Table 3 using the processor's price and in Table 4 using the huckster's price. Table 3 shows revenue losses for all treatments in Year 1. The least returns of $745 EC and $3,298 EC were obtained with the pruned treatments on both the "Fence" and "T"-trellises respectively. The highest returns of $3,724 EC was incurred on the "T"-trellis without
<table><caption>Table 1. The effect of two different types of trellis and pruning on plot yields of passion fruit grown in Dominica from November 1988 to November 1990.</caption><thead><tr><th rowspan="2">TREATMENTS</th><th colspan="3">YEAR 1 (1988-1989)</th><th colspan="3">YEAR 2 (1989-1990)</th></tr><tr><th>No. of Fruitset</th><th>No. of Fruit harvested</th><th>Fresh Weight (kg)</th><th>No. of Fruitset</th><th>No. of Fruit harvested</th><th>Fresh Weight (kg)</th></tr></thead><tbody><tr><td><strong>Trellis</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>"Fence"</td><td>55</td><td>27</td><td>2.2</td><td>123</td><td>89</td><td>7.2</td></tr><tr><td>"T"</td><td>160</td><td>82</td><td>6.6</td><td>208</td><td>151</td><td>13.0</td></tr><tr><td>Level of significance</td><td>**</td><td>*</td><td>**</td><td>NS</td><td>NS</td><td>NS</td></tr><tr><td>SED (3 d.f.)</td><td>9.56</td><td>11.91</td><td>0.715</td><td>37.73</td><td>29.86*</td><td>1.83</td></tr><tr><td><strong>Pruning</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Pruning</td><td>98</td><td>37</td><td>3.0</td><td>151</td><td>120</td><td>8.8</td></tr><tr><td>No pruning</td><td>118</td><td>61</td><td>5.0</td><td>180</td><td>131</td><td>11.2</td></tr><tr><td>Level of significance</td><td>*</td><td>*</td><td>**</td><td>*</td><td>NS</td><td>*</td></tr><tr><td>SED (50 d.f.)</td><td>8.45</td><td>11.42</td><td>0.453</td><td>12.69</td><td>11.42</td><td>1.06</td></tr><tr><td><strong>Interaction</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>"Fence" &amp; Pruning</td><td>34</td><td>18</td><td>1.4</td><td>110</td><td>80</td><td>6.4</td></tr><tr><td>"Fence" &amp; no pruning</td><td>76</td><td>37</td><td>3.0</td><td>136</td><td>93</td><td>8.8</td></tr><tr><td>Level of significance</td><td>*</td><td>NS</td><td>NS</td><td>NS</td><td>NS</td><td>NS</td></tr><tr><td>SED (50 d.f.)</td><td>11.96</td><td>7.81</td><td>0.64</td><td>17.95</td><td>16.15</td><td>1.50</td></tr><tr><td>"T" and pruning</td><td>159</td><td>77</td><td>6.2</td><td>191</td><td>139</td><td>11.2</td></tr><tr><td>"T" &amp; no pruning</td><td>161</td><td>86</td><td>7.0</td><td>224</td><td>164</td><td>13.6</td></tr><tr><td>Level of significance</td><td>NS</td><td>NS</td><td>NS</td><td>NS</td><td>NS</td><td>NS</td></tr><tr><td>SED (50 d.f.)</td><td>11.96</td><td>7.81</td><td>0.64</td><td>17.95</td><td>16.15</td><td>1.50</td></tr></tbody></table>

* = Significant at the 5% level

** = Significant at the 1% level
<table><caption>Table 2. The effect of two different types of trellis and pruning, yields (ha) of passion fruit grown in Dominica from Nov. 1988 to Nov. 1990.</caption><thead><tr><th rowspan="2">TREATMENTS</th><th colspan="3">YEAR 1 (1988-1989)</th><th colspan="3">YEAR 2 (1989-1990)</th></tr><tr><th>No. of Fruitset</th><th>No. of Fruit harvested</th><th>Fresh Weight (kg/ha)</th><th>No. of Fruitset</th><th>No. of Fruit harvested</th><th>Fresh Weight (kg/ha)</th></tr></thead><tbody><tr><td><strong>Trellis type</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>"Fence"</td><td>29,260</td><td>14,364</td><td>1,170</td><td>65,486</td><td>47,384</td><td>3,830</td></tr><tr><td>"T"</td><td>85,120</td><td>43,624</td><td>3,511</td><td>110,656</td><td>80,332</td><td>6,916</td></tr><tr><td><strong>Pruning</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Pruning</td><td>52,136</td><td>19,684</td><td>1,596</td><td>80,332</td><td>63,840</td><td>4,682</td></tr><tr><td>No pruning</td><td>62,776</td><td>32,452</td><td>2,660</td><td>95,760</td><td>69,692</td><td>5,958</td></tr><tr><td><strong>Interaction</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>"Fence" &amp; Pruning</td><td>18,088</td><td>9,576</td><td>7,458</td><td>58,520</td><td>42,560</td><td>3,405</td></tr><tr><td>"Fence" &amp; np pruning</td><td>40,432</td><td>19,684</td><td>1,596</td><td>72,352</td><td>59,476</td><td>4,682</td></tr><tr><td>"T" and pruning</td><td>82,588</td><td>40,964</td><td>3,298</td><td>101,612</td><td>73,948</td><td>5,958</td></tr><tr><td>"T" &amp; no pruning</td><td>85,652</td><td>45,752</td><td>3,724</td><td>119,168</td><td>87,248</td><td>7,235</td></tr></tbody></table>

pruning In Table 4, all systems except the "T"-trellis $1,303 EC profit without pruning showed losses in the first year.

Table 3 shows that in Year 2 all the treatments were profitable. However, cumulative margin was positive ($1,520, EC) for the "Fence"-trellis with the unpruned plants. In the case of the "T"-trellis, both un-pruned and pruned treatments showed positive cumulative margins. In Table 4 all the systems were also profitable and cumulative margins were negative ($259) only for the "Fence"-system with pruning.
Fresh weight and pulp weight

Correlations (0.9732) were obtained between fresh weight and pulp weight in Year one (P < 0.001). The regression model was as follows:

$$ \text{Pulp wt-} = 5.13 + 0.355 (\text{Fresh wt.}) r^2 = 0.945 $$

The standard error of co-efficient of fresh weight = 0.0062 at 61 degrees of freedom.

<table><caption>Table 3: Comparison of per hectare costs and returns for passion fruit production in Dominica using two different trellis systems and pruning methods using the processor's price of EC$1.00/kg.</caption><thead><tr><th rowspan="3"></th><th colspan="4">FENCE TRELLIS</th><th colspan="4">T-TRELLIS</th></tr><tr><th colspan="2">No Pruning</th><th colspan="2">Pruning</th><th colspan="2">No Pruning</th><th colspan="2">Pruning</th></tr><tr><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th></tr></thead><tbody><tr><td>Capital Cost</td><td>2074</td><td></td><td>2074</td><td></td><td>2775</td><td></td><td>2775</td><td></td></tr><tr><td>Maintenance cost</td><td>1050</td><td>1050</td><td>1950</td><td>1950</td><td>1050</td><td>1050</td><td>1950</td><td>1950</td></tr><tr><td>Harvest cost</td><td>93</td><td>272</td><td>43</td><td>191</td><td>216</td><td>420</td><td>191</td><td>347</td></tr><tr><td>Transport cost</td><td>56</td><td>164</td><td>26</td><td>119</td><td>130</td><td>253</td><td>115</td><td>209</td></tr><tr><td>Total COST</td><td>3272</td><td>1485</td><td>4093</td><td>2267</td><td>4171</td><td>1723</td><td>5032</td><td>2507</td></tr><tr><td>Yield (kilo)</td><td>1596</td><td>4682</td><td>745</td><td>3405</td><td>3724</td><td>7235</td><td>3298</td><td>5985</td></tr><tr><td>REVENUE $</td><td>1596</td><td>4682</td><td>745</td><td>3405</td><td>3724</td><td>7235</td><td>3298</td><td>5985</td></tr><tr><td>ANNUAL MARGIN</td><td>-1676</td><td>3197</td><td>-3348</td><td>1138</td><td>-447</td><td>5512</td><td>-1734</td><td>3478</td></tr><tr><td>CUMULATIVE MARGIN</td><td>-1676</td><td>1520</td><td>-3348</td><td>-2210</td><td>-447</td><td>5065</td><td>-1734</td><td>1745</td></tr></tbody></table>
<table><caption>Table 4: Comparison of per hectare cost and returns for passion fruit production in Dominica using two different trellis systems and pruning methods using the huckster price of EC$1.47/kg</caption><thead><tr><th rowspan="3"></th><th colspan="4">FENCE TRELLIS</th><th colspan="4">T-TRELLIS</th></tr><tr><th colspan="2">No Pruning</th><th colspan="2">Pruning</th><th colspan="2">No Pruning</th><th colspan="2">Pruning</th></tr><tr><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th><th>Year 1</th><th>Year 2</th></tr></thead><tbody><tr><td>Capital Cost</td><td>2074</td><td></td><td>2074</td><td></td><td>2715</td><td></td><td>2775</td><td></td></tr><tr><td>Maintenance cost</td><td>1050</td><td>1050</td><td>1950</td><td>1950</td><td>1050</td><td>1050</td><td>1950</td><td>1950</td></tr><tr><td>Harvest cost</td><td>93</td><td>272</td><td>43</td><td>197</td><td>216</td><td>420</td><td>191</td><td>347</td></tr><tr><td>Transport cost</td><td>56</td><td>164</td><td>26</td><td>119</td><td>130</td><td>253</td><td>115</td><td>209</td></tr><tr><td>TOTAL COST</td><td>3272</td><td>1485</td><td>4093</td><td>2267</td><td>4171</td><td>1723</td><td>5032</td><td>2507</td></tr><tr><td>Yield (kilo)</td><td>1596</td><td>4682</td><td>745</td><td>3405</td><td>3124</td><td>7235</td><td>3298</td><td>5985</td></tr><tr><td>REVENUE $</td><td>2346</td><td>6883</td><td>1095</td><td>5005</td><td>5474</td><td>10635</td><td>4848</td><td>8798</td></tr><tr><td>ANNUAL MARGIN</td><td>-926</td><td>5397</td><td>-2998</td><td>2739</td><td>1303</td><td>8913</td><td>-184</td><td>6291</td></tr><tr><td>CUMULATIVE MARGIN</td><td>-926</td><td>4471</td><td>-2998</td><td>-259</td><td>1303</td><td>10216</td><td>-184</td><td>6108</td></tr></tbody></table>

US$ = EC$2.10

Assumptions

Cents/kilo

Picking cost 35

Heading cost 23

Transport cost 3S

## DISCUSSION

Tables 1 and 2 show that first year yields were lower than those of the second year. Average yields of 5-10,000 kg/ha can be expected (Anon, 1987). However, in this trial maximum yields of 3,724 kg/ha were obtained in Year 1. The low yields recorded in Year 1 resulted from the prolonged dry period which followed the mid-November plantings. (Rainfall data is shown in appendix 3). Moisture stress is known to limit vegetative growth, which in turn reduces node production and flowering (Menzel et al; 1986). In addition flowering and fruiting began in April and June respectively, at a period when vine biomass was not fully developed. In Year 2 flowering and fruit set occurred when vine growth was vigorous. As a result yields were much more satisfactory - maximum yields of 7,235 kg/ha were obtained.
Higher yields were obtained from unpruned treatments than the pruned plots in both the first and second years. Similar results were obtained by Gachanja and Gurah (1980) in the first year of a 3-year experiment. Experimental evidence from South Africa where both purple and yellow passion fruit are grown, has shown that unpruned vines consistently out-yielded those which had been pruned (Akamine et al., 1974). The removal of potential flowering vines by pruning seemed to have reduced yield.

Though the results showed that higher yields were obtained from nonpruned treatments it was noticed that as the vines in these treatments got older the canopy became denser and this restricted efficient pruning and spraying against pests and diseases. It was also observed that denser canopies promoted the development of fruit diseases such as anthracnose (Colletotrichum spp.). In the unpruned treatments the increased weight of the vines on the trellis caused the wires to sag from 2.0m to approximately 1 - 1.5m above ground level. This caused increased tangling of vines.

The difference between fruit set and the number of fruit harvested, can be attributed to predial larceny, a limited amount of rat damage and heavy winds which blew fruit of vines making it difficult on ocassion, associated fruit with the various plots. As a result certain fruits on the ground were not included in the harvest.

A review of the economic data showed that the T-trellis system, though more expensive than the "Fence"-type to establish, gave higher economic returns. The "T"-trellis without pruning gave economic returns twice as high as any other treatment.

Table 4 shows that net earnings to the farmer were higher when passion fruit was sold to the hucksters. This was of major concern to the processor who competed directly with the hucksters. Apart from having reduced production, processors obtained half-ripe fruit which were harvested for the fresh fruit trade. These fruit lowered the "brix" and gave the concentrate a greenish yellow colouration rather than the normal reddish yellow. (R. Laronde, 1992; S. Jno.Baptiste, 1992, personal communications).
Correlations between fresh weight and pulp weight are important for the processors to make accurate production projections. First year correlations were favourable, second year correlations were not and therefore not included.

Passion fruit, being a major diversification crop, competes directly with bananas for land, labour and other vital resources. Net returns for the banana plant crop are EC$4,325.00/ha (Oldham, 1989). Thus compared with the passion fruit plant crop which operates at a loss, except for where the "T"-trellis with non-pruned vines showed a profit of EC$379.00/ha bananas would seem to be more lucrative.

Unfortunately, only two years of data were collected. Problems with the trellis systems, root rot and poor plot maintenance caused the experiment to be abandoned in February 1991, instead of February 1992.

## CONCLUSIONS AND RECOMMENDATIONS

Profitable production of passion fruit seems to require no pruning in the first two years. However, because vegetative growth in this situation is extremely vigorous, light selective pruning should be carried out at the end of the first crop cycle.

Both the "Fence" trellis and "T"-trellis have various advantages and disadvantages. However, the initial establishment cost of the "T"-trellis, coupled with the increased difficulties experienced when managing vines suggests that the "Fence"-type trellis may be a more appropriate system for farmers.

It seems that the farmers priority will be to sell to the hucksters, unless the processors increase their prices. Since the hucksters and processors require fruits of different grades and quality, it may become necessary to recommend management practices which are less costly and labour intensive with a view to producing mainly for the processor.
## ACKNOWLEDGEMENTS

This paper is based on results obtained from the passion fruit activity conducted under the British Development Division for the Caribbean (BDDC)-funded Exportable Fruit Crops Project. The author wishes to thank the foreman and staff of the Portsmouth Agricultural Station and all the CARDI Professional, Technical, Field and Support Staff, who helped in making this work possible. Finally, he wishes to thank Mr. Peter Oldham (BDDC) Farm Management Economist) who assisted with the economic analyses, and Messrs. Don Walmsley, Bruce Lauckner, Lennox Daisley, Puran Bridgemohan, and Lennox Andrews who assisted in editing the paper.

## REFERENCES

* Akamine, E.K.; Aragaki; Beaumonth, J.H.; Bowers, F.A.I.; Hamilton, R.A.; Nishida, T.; Sherman, G.D.; Shoji, K.; Storey, W.B.; Martines, A.; Yeé, W.Y.; Shaw, T.H. (1974). *Passionfruit culture in Hawaii*. Cooperative Extension Services, University of Hawaii, Circular 345.

* Andrews, L (1991). *Passion fruit Production*. Production Guide, CARDI, P.O. Box 971, Castries, St. Lucia, W.I.

* Anon (1987). *Passionfruit Production in Dominica*. Extension/Farmer training booklet No.2. Inter-American Institute for Co-operation on Agriculture, Botanic Gardens, Roseau, Dominica.

* Anon (1988). Agricultural Diversification in the OECS.

* Anon (1991). Dominica Country Paper presented at the Regional Workshop on Tropical Fruit Crops, Avocado, Citrus and Passionfruit, 18-22 Feb. 1991; Roseau, Dominica

* Gachanja, S.P. and Gurnah, A.M. (1980). Pruning and trellising purple passionfruit 1. Yields and seasonal trends. *Journal of Horticultural Science* 55 (4). 345-349.
Menzel, C.M.; Simpson, D.R. and Dowling, A.J. (1986). Water relations in passionfruit: Effect of moisture stress on growth, flowering and nutrient uptake. *Scientia Horticulturae* 29 (1986). 239-249.

Menzel, D.M.; Winks, C.W. and Simpson D.R. (1988). Passionfruit in Queensland. Prospects for commercial expansion. *Queensland Agricultural Journal*. Jan - Feb 1988, 13 - 18.

Oldham, P. (1989). Estimated cost of production of bananas. Ministry of Agriculture, Roseau, Dominica.

Rajkumar, D. (1987). *Growing Passionfruit in the West Indies*. Dept. of Crop Science, The University of the West Indies, Trinidad & Tobago.
EVALUACION PRELIMINAR DE LAS VARIEDADES DE MANGO (Mangifera indica L.) PARVIN Y TOMMY ATKINS SOBRE DIFERENTES PATRONES

Ismael Reyes Soto y Arturo Cedeño Maldonado

UNIVERSIDAD DE PUERTO RICO
Estación Experimental Agrícola
Subestación de Fortuna
HC-02 Box 7115
Juana Díaz, PR 00795

Es sorprendente que el mango una fruta maravillosa del mundo tropical sea agrupada botánicamente dentro de la familia de las Anacardeaceas donde se encuentran también varias plantas venenosas. Con su origen en el sur de Asia; especialmente el este de la India, Burma y las Islas de Adaman, se ha propagado a todo el mundo tropical y subtropical. Su comportamiento es mejor desde el Trópico de Cáncer (25 grados N) hasta el Trópico de Capricornio (25 grados S) y cuando se siembra a nivel del mar o hasta elevaciones de 3,000 pies (915 m). El mango llegó a Puerto Rico durante la colonización y se ha naturalizado. Como fruta comercial ha igualado y podría sobrepasar en un futuro cercano las cítricas.

Es importante llevar a cabo estudios que propendan al mejoramiento de las características de producción y calidad de esta fruta. Estudios previos demuestran que el patrón es un factor determinante en el comportamiento de crecimiento y producción. En el presente estudio se pretende determinar el efecto de varios patrones sobre las variedades Parvin y Tommy Atkins. Se utilizaron los patrones Eldon, Colombo Kidney, Mayagüezano, Cubano, Julie, Malda y Pasote o Piña (Terpentina, Hilo). El estudio se está llevando a cabo en la Subestación de Frutales del Colegio de Ciencias Agrícolas de la Universidad de Puerto Rico.

El suelo donde se lleva a cabo esta investigación es de tipo San Antón Arcilloso (Mollisols) con un pH de 7.3 y con materia orgánica de 2.1%. Hay una elevación de 67.8 pies (20.7 m.) sobre el nivel del
mar con una precipitación pluvial promedio de 32" (768 mm) anuales. El mes más lluvioso es septiembre 5.74 pulgadas (138 mm) y el mes más seco es marzo .55 pulgadas (43 mm). La temperatura máxima promedio es de 84.6 grados F y mínima promedio es de 67.6 grados F. La variedad Parvin fue sembrada en junio de 1987 y la Tommy Atkins un año después. La variedad Parvin no fue evaluada con el patrón Pasote o de Hilo (Terpentina). La variedad Tommy Atkins sale de una semilla (seedling) de padres desconocidos en Fort Lauderdale en la Florida en el 1920 y usada comercialmente en el 1950.

En la tabla 1 aparece el resultado de Parvin sobre diferentes patrones en el año 1990. En la tabla 2 aparecen los resultados de Parvin sobre diferentes patrones en el año 1991.

Resultó mejor patrón el Julie, seguido de Malda, Colombo Kidney, Eldon y el Mayagüezáno con el injerto de Parvin en el 1990. En el 1991 el mejor resultado se obtiene con Julie, luego con Malda, Colombo Kidney, Cubano y Eldon.

En la tabla 3 se encuentra un análisis combinado de los años 1990 y 1991 para Parvin, sobre diferentes patrones. La mejor producción de Parvin se obtiene con los patrones Malda y Julie. La producción más baja se obtiene con el patrón Eldon. El promedio de frutas por árbol fue de 166 para Parvin con todos los patrones y el peso promedio de la fruta 15.52 onzas o 439.84 gramos.

En 1992 se le partieron ramas a dos árboles en el experimento (Parvin 2.7%).

Los resultados de la cosecha de 1992 y los datos combinados de tres cosechas se presentan en las tablas 4 y 5, respectivamente. Durante el 1992 los patrones Malda y Julie resultaron excelentes aunque fueron igualados por el patron de la variedad Cubano. Esta tendencia se refleja también en los datos combinados de tres años que se presentan en la tabla 5. En los datos tomados hasta el presente resultaron inferiores los patrones Eldon y Mayagüezáno, siendo estos dos patrones más utilizados en Puerto Rico.
<table><thead><tr><th>Patrón</th><th>Frutas/árbol</th><th>Libras/árbol</th><th>Peso/fruta</th></tr></thead><tbody><tr><td>Eldon</td><td>58 d*</td><td>63 d</td><td>1.16 a</td></tr><tr><td>Colombo Kidney</td><td>169 bc</td><td>167 bc</td><td>0.98 a</td></tr><tr><td>Mayagüezano</td><td>49 d</td><td>54 d</td><td>1.08 a</td></tr><tr><td>Cubano</td><td>123 c</td><td>131 c</td><td>1.09 a</td></tr><tr><td>Malda</td><td>205 ab</td><td>225 ab</td><td>1.11 a</td></tr><tr><td>Julie</td><td>241 a</td><td>254 a</td><td>1.06 a</td></tr></tbody></table>

Promedios con letras iguales son iguales estadísticamente (P= 0.05), según la prueba L. S. D.

<table><caption>Tabla 2. 1991. Componentes de Producción Parvin</caption><thead><tr><th>Patrón</th><th>Frutas/árbol</th><th>Libras/arbol</th><th>Peso/fruta</th></tr></thead><tbody><tr><td>Eldon</td><td>83 d*</td><td>85 b</td><td>1.01 a</td></tr><tr><td>Colombo Kidney</td><td>247 a</td><td>230 a</td><td>0.95 a</td></tr><tr><td>Mayagüezano</td><td>128 b</td><td>132 b</td><td>0.98 a</td></tr><tr><td>Cubano</td><td>134 b</td><td>148 b</td><td>1.10 a</td></tr><tr><td>Malda</td><td>270 a</td><td>275 a</td><td>1.01 a</td></tr><tr><td>Julie</td><td>285 a</td><td>294 a</td><td>1.02 a</td></tr></tbody></table>

Promedios con letras iguales son iguales estadísticamente (P= 0.05), según la prueba L. S. D.
<table><caption>Tabla 3. 1990 y 1991. Componentes de Producción Parvin</caption><thead><tr><th>Patrón</th><th>Frutas/árbol</th><th>Libras/frutas</th><th>Peso/ fruta</th></tr></thead><tbody><tr><td>Eldon</td><td>71 d*</td><td>77 d</td><td>1.08 a</td></tr><tr><td>Colombo Kidney</td><td>208 b</td><td>198 b</td><td>0.96 a</td></tr><tr><td>Mayagüezano</td><td>88 cd</td><td>93 cd</td><td>1.05 a</td></tr><tr><td>Cubano</td><td>129 c</td><td>140 c</td><td>1.08 a</td></tr><tr><td>Malda</td><td>237 ab</td><td>250 ab</td><td>1.05 a</td></tr><tr><td>Julie</td><td>263a</td><td>274 a</td><td>1.04 a</td></tr></tbody></table>

Promedios con letras iguales son iguales estadísticamente (P= 0.05), según la prueba L. S. D.

<table><caption>Tabla 4. 1992 Promedio de la Producción por árbol. Parcela de 4 árboles.</caption><thead><tr><th>Patrón</th><th>Número frutas</th><th>Peso fruta</th></tr></thead><tbody><tr><td>Eldon</td><td>770 c</td><td>745 b</td></tr><tr><td>Colombo Kidney</td><td>890 bc</td><td>831 b</td></tr><tr><td>Mayagüezano</td><td>983 bc</td><td>970 ab</td></tr><tr><td>Cubano</td><td>1490 a</td><td>1453 a</td></tr><tr><td>Malda</td><td>1098 ab</td><td>1009 ab</td></tr><tr><td>Julie</td><td>1377 ab</td><td>1329 a</td></tr></tbody></table>

Promedios con letras iguales son iguales estadísticamente (P= 0.05), según la prueba L. S. D.
<table><caption>Tabla 5. 1990-91-92. Promedio de la producción por árbol. Parcela de 4 árboles.</caption><thead><tr><td>Patrón</td><td>Número frutas</td><td>Peso fruta</td></tr></thead><tbody><tr><td>Eldon</td><td>1336 c</td><td>1357 d</td></tr><tr><td>Colombo Kidney</td><td>2552 b</td><td>2417 b c</td></tr><tr><td>Mayagüezano</td><td>1692 c</td><td>1713 c d</td></tr><tr><td>Cubano</td><td>2519 b</td><td>2571 b</td></tr><tr><td>Malda</td><td>2957 a b</td><td>3007 a b</td></tr><tr><td>Julie</td><td>3491 a</td><td>3521 a</td></tr></tbody></table>

Promedios con letras iguales son iguales estadísticamente (P=0.05), según la prueba L.S.D.

## LITERATURA CITADA

1. Campbell, C. W., 1973. The Tommy Atkins mango. Proc. Fl. St. Hort. Soc. 86 348-350.

2. Campbell, C. W., 1990. The "Van Dyke" mango. Proc. Fl. State Hort. Soc. 103: 298-299.

3. Cedeño Maldonado, A., 1988. Effect of dwarfing rootstocks on tree size and yield of selected mango varieties. J. Agric. Univ. P. R. 72 (1), 1.

4. Knight, R. J., Jr. and H. F. Winters, 1971. Mango and avocado evaluation in southeastern Florida, Proc. Fl. Hort. Soc. 84: 314-317.

5. Ledin, R. B., 1958. Mango varieties in Florida. Hort. Adv. Vol. 11: 16-26.
6. Malo, S. F., 1970. Mango and avocado cultivars present status and future developments. Proc. Fl. St. Hort. Soc. 83: 357-362.

7. Malo, S. F., 1977. The mango in Florida. Hort. Sci. 12(4): 286-367.

8. Mattern, Frank, William Pennock and Santos del Valle Lamboy, 1972. Supplying the New York market with high-quality Puerto Rican mangoes. J. Ag. Univ. of P. R. 56(1): 1-10.

9. Mitchell, E. F., 1971. Mango production and marketing practices. Florida, 1971. Proc. Fl. St. Hort. Soc. 84: 307-311.

10. Morton, J. F., 1987. Fruits of warm climates.

11. Pérez, A., 1987. Growth, yield of mango trees at three stages of development influenced by rootstock, scion variety. J. Agric. Univ. P. R. 71(4), 341.

12. R. de Hernández, E. and Benero, J. R., 1982. Evaluation of four mango cultivars for nectar, J. Agric. Univ. P. R. 66 (3): 153-58.

13. R. de Hernández, E., Guadalupe-Luna, R., and B. de Caloni, I., 1982. Acceptability and keeping quality of marmalades and canned slices in heavy syrop of Mango Cultivars, J. Agric. Univ. P. R. 66(3): 159-67.

14. Segarra, A. E., 1988. Identify and economic importance of fruit flies attacking mango in Puerto Rico: A two-year survey, J. Agric. Univ. P. R. 72 (2), 325 (RN).

15. Wiltbank, W. J., 1977. Mango and avocado cultivars in Brazil. Proc. Fl. St. Hort. Soc. 90: 234-244.

16. Wolf, H. S., 1962. The mango in Florida, 1987-1962. Proc. Fl. St. Hort. Soc. 75: 387-391.

17. Young, T. W. and Julian W. Souls, 1989. The mango industry in Florida. Bull. 189.
RESPONSE TO DAYLENGTH OF NONCONVERTED
AND CONVERTED SELECTIONS OF FORAGE
SORGHUM MILLO BLANCO (Sorghum bicolor (L.)
Moench) IN PUERTO RICO

A. Quiles-Belén, A. Sotomayor-Ríos and S. Torres-Cardona
USDA-ARS, Tropical Agriculture Research Station
Mayagüez, Puerto Rico

ABSTRACT

Information on the effect of daylength on nonconverted and converted selections of sorghum is very limited. This study was designed to evaluate the effect of daylength on plant height (PHt), days to anthesis (DA), and other agronomic traits of local Millo Blanco nonconverted (MBNC) and three Millo Blanco converted (MBC) selections of forage sorghum (Sorghum bicolor (L.) Moench) and BTx406 (a 4-dwarf photoperiodinsensitive temperate grain sorghum used as the control) during an eight-month period in Puerto Rico. The MBC selections were based on approximately plant height of 50, 120 and 170 cm. Plantings were made on the 21st day of each month from May through December, 1991. After an initial 30-day growth period, plants were evaluated every 15 days until harvest. Days to anthesis of MBNC decreased from 175 (May planting) to 61 (October planting), then increased to 70 and 75 (November and December plantings, respectively). The mean plant height of MBNC followed a similar trend ranging from 278 cm (August planting) to 138 cm (November planting). Although a significant correlation was observed between days to anthesis and plant height in MBNC, the MBC selections and BTx406 (the control) were unaffected by planting date. Mean days to anthesis of the three MBC selections was similar throughout the year (61 days). This study demonstrated the possibility of making selections for height from converted sorghums prior to their formal release having by this way an excellent opportunity for its utilization in a year round breeding program.
# INTRODUCTION

The World Sorghum Collection has been the source of new germplasm of which most lines are of tropical origin (4, 6, 8, 10, 11). These sorghums possess many desirable genes which have contributed to the improvement of temperate-adapted sorghums (7, 11). Since most tropical sorghums are sensitive to daylength, the Sorghum Conversion Program (SCP) was started in 1963; as a cooperative venture of the Tesas Agricultural Experiment Station and the U.S. Department of Agriculture (USDA). The SCP makes available new germplasm sources from the World Collection by converting tall, late flowering, photoperiod-sensitive sorghums from the tropics into short, early flowering, photoperiod-insensitive strains (10, 11). Plants fully converted and selected after four backcrosses are theoretically 1/32 temperate and 31/32 tropical material, although they can contain arrays of height and maturity genes resulting sometimes in unstable germplasm in terms of these traits (5, 7). The SCP makes these sorghums indeterminate over a wide range of daylengths showing little or no photoperiodic response. This study was designed to evaluate the effect of daylength on days to anthesis (DA), plant height (PHt) and a series of agronomic traits of Millo Blanco (MBNC), a local photoperiod-sensitive (nonconverted) sorghum (Sorghum bicolor (L.) Moench), three converted Millo Blanco (MBC) selections of different height from the SCP, and BTx406 (control), during an 8-month period.

# MATERIALS AND METHODS

The experiment was conducted at the Isabela experimental farm of the Tropical Agriculture Research Station (TARS), USDA-ARS at an elevation of 128m and ambient temperatures ranging from 18.8 to 29.4° C. The soil is a Coto clay (Tropeptic Haplorthox, clayey Kaolinitic, isohyperthermic) with an organic matter content of 2.5% and pH of 5.5. The experimental design was a randomized block arranged in split-split plots, replicated four times. The main plots consisted of planting dates (PD) made the 21st day of each month from May through December, 1991; the subplots were MBNC, three MBC selections and BTx406. The selections were obtained from the last cycle of conversion of MB (-14E) at Isabela during June 1990, and
based on 50, 120 and 170 cm plant height; later they were identified
as MB-4Dw, MB-3Dw and MB-2Dw, respectively.

Each subplot consisted of two rows 600 cm long spaced 100cm apart
with plants thinned to a distance of 36.5 cm apart within rows. Before
sowing, and four weeks after planting, all plots received 560 kg/ha
of a 15-5-10 fertilizer. Weeds were controlled with propazine (2-chlo-
ro-4,6,-bis(isopropylamino-s-triazine) at a rate of 2.5 kg ai/ha.
Overhead irrigation was applied to all plots as needed.

Measurements were made of plant height (from the ground to the
midpoint of the upper leaf blade) and total leaf blade area (using the
second leaf blade from the top and multiplying its masimum length x
masimum width x 0.747 x number of leaves/plant x tillers). This
calculation is based on the procedure developed by Sticker et al., (12).
Number of internodes, leaf number/main stem, and days to anthesis
were measured simultaneously. All data were subjected to analysis of
variance, and significant differences were identified with Duncan's
multiple range test.

RESULTS AND DISCUSSION

The analysis of variance showed that F values for planting dates (PD), selections (S), and sampling intervals (I) were significant for most traits (Table 1). Previous studies indicated that individual cultivars of sorghum have different critical photoperiods that inhibit floral development (1-4, 6, 8, 9, 11). Our results indicated that days to anthesis of MBNC decreased from 175 (May planting) to 61 days (October planting), but increased to 70 and 75 days for the November and December plantings, respectively (Fig. 1). Floral initiation of MBNC was delayed by the cool temperatures prevailing at the Isabela farm during November and December. When planted in October, MBNC had the same growth pattern as that of the remaining selections, which indicates that its critical photoperiod is less than 11.21 hours. In Puerto Rico (latitude 18° N), daylength ranges from 11.02 (December 21) to 13.13 hours (June 21), factor which is determinant in the flowering response of short-day plants. Although the MBC selections showed minor visual differences in terms of DA, their means were similar to BTx406 at all planting dates (61 days). The MBC selections
and BTx406 flowered 6 to 8 days earlier when planted in June as compared to the December planting. It appears that the critical photoperiod of the MBC and BTx406 is above 13.13 hours.

The plant height of MBNC (Fig. 2) diminished significantly from 278 cm (August planting) to 138 cm (November planting); then increased to 194 cm (December planting). During November planting the plant height of MBNC was similar to that of the MBC selection MB-2Dw. Previous studies have demonstrated a similar and consistent trend of MBNC across planting dates (13). The stability in terms of height of the MB-4Dw selection was comparable to that of BTx406, but better than in the MB-3Dw and MB-2Dw selections. The last two selections responded very similar to the effect of temperature and daylength, although both flowered at approximately 61 days. In general, the long days and high temperatures had an equal effect on all MBC selections as well as on BTx406.

Mean leaf number (Fig. 3) and total leaf area (Fig. 4) of MBNC showed similar trends to those of days to anthesis and plant height across planting dates. Plants had more leaves (over 13) and more total leaf area (over 132,000 $cm^2$) when planted from May to August, and significantly fewer leaves (10 or less) and less total leaf area (less than 48,000) when planted from September to December. On the other hand, PD did not affect the leaf number and the total leaf area of the MBC selections and BTx406. They all had an average of 9 leaves > plant. Lower number of leaves were obtained in the November and December plantings. The number of internodes/plant (Fig. 5) showed a similar tendency to those of days to anthesis, plant height, leaf number and total leaf area.

Miller, et al. (6) found that plant height and days to anthesis were closely correlated in sorghum. In this study, a significant correlation was observed between days to anthesis and plant height in MBNC but not in its converted selections and BTx406 as shown in the following tabulation:
<table><thead><tr><td>Genotype</td><td>Correlation coefficient</td></tr></thead><tbody><tr><td>MB-1DW (Non converted Tropical)</td><td>.86**</td></tr><tr><td>MB-2DW (Converted selection)</td><td>-.72</td></tr><tr><td>MB-3DW (Converted selection)</td><td>-.36</td></tr><tr><td>MB-4DW (Converted selection)</td><td>.21</td></tr><tr><td>BTx406 (temperate)</td><td>.09</td></tr></tbody></table>

** Significant at 1% level.

Significant correlations were also found between daylength/month and most of the agronomic traits studied in MBNC:

<table><thead><tr><td>Character</td><td>Correlation coefficient</td></tr></thead><tbody><tr><td>Plant height</td><td>.85*</td></tr><tr><td>Internodes/plant</td><td>.62</td></tr><tr><td>Leaves/plant</td><td>.94**</td></tr><tr><td>Days to anthesis</td><td>.71*</td></tr><tr><td>Total leaf area</td><td>.92**</td></tr></tbody></table>

** Significant at 1% level.

* Significant at 5% level.

Excellent selections for height can be easily made from the conversion program prior to their formal release. At the same time, these selections are day-neutral which offer excellent opportunities for their utilization in a year round breeding program.
## LITERATURE CITED

Cockshull, K.E. 1984. Light and the flowering process. The photo-periodic induction of flowering in short-day plants. Academic Press, Little Hampton, England, pp. 33-49.

Francis, C.A. 1972. Natural daylength for photoperiod sensitive plants. CIAT, Cali, Colombia, Technical Bul. No. 2, 3-32.

Garner, W.W. and Allaud, H.A. 1923. Further studies in photoperiodism. The response of the plant to relative length of day and night. J. Agr. Res. 23:871-920.

House, L. R. 1976. A guide to sorghum breeding. Genetics of sorghum. ICRISAT, Patancheru Andhra Pradesh, India. pp. 86-93.

Miller, F. R. 1983. Sorghum Workshop. Sorghum Plant Breeding, April 10-16, Mexico City, Mexico.

Miller, F.R., Barnes, D.K. and Cruzado, H.J. 1968. Effect of tropical photoperiods on the growth of sorghum when grown in 12 monthly plantings. Crop Sci. 8:499-502.

Quiles-Belén, A. and Sotomayor-Ríos, A. 1983. The Sorghum Conversion Program. Proc. Carib. Food Crops Soc., XIX; 273-279.

Quinby, J.R. 1967. The maturity genes of sorghum. In: Advances in Agronomy (A.G. Norman, ed.). Academic Press, New York and London XIX:267-305.

Quinby, J.R. and Schertz, K.F. Sorghum production and utilization. Sorghum genetics, breeding, and hybrid seed production. The Avi Publishing Company Inc., Westport, Connecticut, pp. 73-113.

Rosenow, D.T. 1975. International Sorghum Workshop. Progress in sorghum breeding for future improvement. The University of P.R. Press, Mayagüez, P.R., pp. 461-467.
Schertz, K.F. 1975. International Sorghum Workshop. Use and potential of the Sorghum Conversion Program to Reduce' genetic vulnerability in sorghum. The University of Puerto Rico Press. Mayagüez, P.R., pp. 360-378.

Sticker, F. C., Wearden, S., and Pauli, A.W. (1961). Leaf area determination in grain sorghum. Agron. J. 53:187-188.

Sotomayor-Ríos, A., Torres-Cardona, S. and Quiles-Belén, A. 1985. Response of forage sorghum to twelve planting dates in Puerto Rico. Proc. Carib. Food Crops Soc. XXI, 160-164.
<table><caption>Table 1. Analysis of variance for planting dates and selections for Millo Blanco, three of its converted selections and BTx406 at Isabela, Puerto Rico.</caption><thead><tr><th rowspan="2">SOURCE</th><th colspan="5">CHARACTERS</th></tr><tr><th>PLANT<br>HEIGHT</th><th>NO. OF<br>INTERNODES</th><th>LEAVES/<br>PLANT</th><th>DAYS TO<br>ANTHESES</th><th>TOTAL<br>LEAF AREA</th></tr></thead><tbody><tr><td>PLANTING DATE (PD)</td><td>**</td><td>**</td><td>**</td><td>*</td><td>**</td></tr><tr><td>REPLICATION (R)</td><td>**</td><td>**</td><td>**</td><td>*</td><td>**</td></tr><tr><td>SELECTION (S)</td><td>**</td><td>**</td><td>**</td><td>*</td><td>**</td></tr><tr><td>PD X S</td><td>**</td><td>**</td><td>**</td><td>*</td><td>**</td></tr><tr><td>R X S X PD</td><td>**</td><td>**</td><td>**</td><td>*</td><td>**</td></tr><tr><td>MEAN</td><td>130</td><td>8</td><td>9</td><td>81</td><td>45.292</td></tr></tbody></table>

** - Significant at 1% level.

* - Significant at 5% level.
<figure><img src="image_58.png" /><figcaption>Fig. 1: Effect of eight planting dates on days to anthesis of Sorghum Millo Blanco, three of its converted selections, and BTx406 at Isabela, P.R.</figcaption></figure>
<figure><img src="image_59.png" /><figcaption>Fig. 2: Effect of eight planting dates on plant height of Sorghum Millo Blanco, three of its converted selections, and BTx406 at Isabela, P.R.</figcaption></figure>
<figure><img src="image_60.png" /><figcaption>Fig. 3: Effect of eight planting dates on mean leaf number of Sorghum Millo Blanco, three of its converted selections, and BTx406 at Isabela, P.R.</figcaption></figure>
<figure><img src="image_61.png" /><figcaption>Fig. 4: Effect of eight planting dates on mean total leaf area of Sorghum Millo Blanco, three of its converted selections, and BTx406 at Isabela, P.R.</figcaption></figure>
<figure><img src="image_62.png" /><figcaption>Fig. 5: Effect of eight planting dates on number of internodes of Sorghum Millo Blanco, three of its converted selections, and BTx406 at Isabela, P.R.</figcaption></figure>
# EVALUACION DE SUSTRATOS PARA LA PRODUCCION DE PLANTULAS EN VIVEROS FORESTALES

## Avance de Investigación

Ing. Margarita Betances
Ing. Julio Morrobel

## RESUMEN

En la República Dominicana, los principales problemas de la producción de plántulas forestales a raíz dirigida, están relacionados con la calidad del sustrato empleado, teniéndose, a menudo, que importar peat moss para producir un buen sustrato. El objetivo de este estudio fue encontrar un sustrato elaborado con materias primas nacionales que pueda sustituir el peat moss. El mismo fue realizado en el Instituto Superior de Agricultura, La Herradura, Santiago. El diseño empleado fue de parcelas divididas, con 25 combinaciones factoriales [(8 proporciones de mezclas x 3 materias primas) + 1 testigo] en las parcelas grandes y cinco especies forestales (*Pinus caribaea*, *Leucaena leucocephala*, *Caltalpa longissima*, *Azadirachta indica* y *Acacia mangium*) en las subparcelas. Las proporciones de mezclas fueron 10,20,30,40,60,70,80 y 90 por ciento de suelo turboso; el cual estuvo presente en todas las combinaciones. El porcentaje restante correspondió a una de las tres materias primas (cáscara de arroz, fibras de coco y cachaza de caña). El testigo fue 75% peat moss y 25% suelo turboso. Se midió el incremento en altura y la producción de materia seca de las especies y se observó la consistencia del terrón formado por el sustrato. Se encontró diferencias significativas entre los sustratos para el incremento en alturas, pero no en la producción de materia seca. La interacción sustratos-especies no fue significativa en ninguna de las dos variables. Los sustratos 30% cáscara de arroz + 70% turba, 60% cáscara de arroz + 40% turba, 70% cáscara de arroz + 30% turba, 90% cáscara de arroz y 30% fibras de coco + 70% turba tuvieron comportamiento similar al testigo (mejor), no existiendo diferencias significativas entre ellos.
INTRODUCCION

En los países como la República Dominicana los bosques han sido explotados por generaciones sin llevar a cabo su debida reposición. Es por esto que la reforestación tiene una amplia e importante función para suplir la demanda de madera y realizar la protección debida de las montañas.

Para que ésta se lleve a cabo de manera más eficiente, se deben disminuir los costos de instalación de la plantación. Esta disminución sólo sería factible si se bajan los costos de producción de plántulas, su transporte al sitio definido y su establecimiento. En este sentido se ha hecho énfasis en la producción de plántulas a raíz dirigida. Pero el uso inadecuado de sustratos causa grandes pérdidas ya que muchas especies a producirse no logran desarrollarse en dichos medios o crecen muy débiles, disminuyendo la sobrevivencia en el campo definitivo, lo cual aumenta los costos de producción.

Sin embargo, en la República Dominicana, la búsqueda de un medio que garantice el normal desarrollo de las plántulas en vivero, ha sido limitado y esporádico, trayendo como resultado que el empleo de sustratos, en la mayoría de los casos, se fundamente en el uso de suelos que no presentan una buena estructura para el crecimiento de las plántulas en el vivero.

Tanto los altos costos de reforestación con plántulas producidas en sustratos importados, como las pérdidas que se tienen cuando se produce en un sustrato inadecuado, hacen que se piense en la inves-
tigación de un sustrato que mejore la producción de plántulas en viveros y elimine la importación de sustratos.

Partiendo de esta realidad, urge la necesidad de buscar una alternativa a los problemas existentes en los viveros a través de las combinaciones de diferentes materias primas, como lo son: turba, cachaza de caña, paja de arroz y paja de coco molido, donde las plántulas se desarrollen de forma satisfactoria sin depender de un medio costoso.

Este estudio fue realizado en el Instituto Superior de Agricultura, La Herradura, Santiago, con el objetivo de encontrar un sustrato elabo-
rado con materia prima nativa, que pueda sustituir el sustrado importado el cual constituye el 50% del costo total de las plantas producidas en el vivero.

## MATERIALES Y METODOS

El estudio se desarrolló en el vivero forestal del Instituto Superior de Agricultura, ubicado en La Herradura, Santiago, República Dominicana. Esta región tiene una altitud de 160 msnm, temperatura media anual igual a 26°C y precipitación media anual de 980 mm (2).

### Descripción de las Materias Primas Usadas en los Sustratos.

Para la elaboración de los sustratos utilizados en el ensayo se emplearon cuatro tipos de materias primas:

**Turba:** Es un material orgánico que proviene de árboles no totalmente descompuesto.

**Fibras de Coco:** Es el endocarpio del fruto del coco seco molido.

**Cáscara de Arroz:** Es el exocarpio del arroz o la llamada cáscara de arroz.

**Cachaza de Caña:** Residuo de la filtración del jugo de la caña que se separa de la molienda, sometida a envejecimiento.

Con estas materias se elaboraron 24 sustratos diferentes, en los cuales siempre estuvo presente la turba. Cada uno de los sustratos es una mezcla de dos materias primas; las cuales fueron combinadas en diferentes proporciones (Cuadro 1). Estas mezclas fueron numeradas del 1 al 25 para facilitar el trabajo, por lo que al referirse a un sustrato en particular, se hace por medio del número asignado. El sustrato número 25 correspondió a testigo.
<table><caption>Cuadro 1. Composición de los Sustratos Empleados en el Ensayo.</caption><thead><tr><th colspan="3">Composición del Sustrato</th><th colspan="3">Composición del Sustrato</th><th colspan="3">Composición del Sustrato</th></tr><tr><th>Sustrato No.</th><th>Arroz (%)</th><th>Turba (%)</th><th>Sustrato No.</th><th>Coco (%)</th><th>Turba (%)</th><th>Sustrato No.</th><th>Caña (%)</th><th>Turba (%)</th></tr></thead><tbody><tr><td>1</td><td>10</td><td>90</td><td>5</td><td>10</td><td>90</td><td>9</td><td>20</td><td>80</td></tr><tr><td>2</td><td>20</td><td>80</td><td>6</td><td>20</td><td>80</td><td>10</td><td>30</td><td>70</td></tr><tr><td>3</td><td>70</td><td>30</td><td>7</td><td>30</td><td>70</td><td>11</td><td>40</td><td>60</td></tr><tr><td>4</td><td>30</td><td>70</td><td>8</td><td>40</td><td>60</td><td>12</td><td>60</td><td>40</td></tr><tr><td>16</td><td>60</td><td>40</td><td>20</td><td>60</td><td>40</td><td>13</td><td>70</td><td>30</td></tr><tr><td>17</td><td>40</td><td>60</td><td>21</td><td>70</td><td>30</td><td>14</td><td>80</td><td>20</td></tr><tr><td>18</td><td>80</td><td>20</td><td>22</td><td>80</td><td>20</td><td>15</td><td>90</td><td>10</td></tr><tr><td>19</td><td>90</td><td>10</td><td>23</td><td>90</td><td>10</td><td>24</td><td>10</td><td>90</td></tr></tbody><tfoot><tr><td>25</td><td colspan="8">Testigo = 75% de Peat moss y 25% turba</td></tr></tfoot></table>

## Diseño Experimental.

El experimento fue conducido utilizando el diseño de parcelas divididas, con 25 combinaciones factoriales [(8 proporciones de mezclas x 3 materias primas) + 1 testigo] en las parcelas grandes y 5 especies forestales en las parcelas chicas o subparcelas. Las especies utilizadas fueron: *Pinus caribaea* (pino), *Leucaena leucocephala* (leucaena), *Catalpa longissima* (roble), *Azadirachta indica* (neem) y *Acacia mangium* (acacia).

Las parcelas fueron aleatorizadas de acuerdo con el diseño en bloques completamente al azar con 3 repeticiones, mientras que las subparcelas se asignaron siguiendo el diseño completamente al azar. Cada parcela consistió en una caja con 80 tubetes plásticos y cada subparcela en 16 tubetes dentro de la caja, donde se sembró una especie forestal determinada.
Para la toma de datos se midió el crecimiento en altura de las plántulas. Además, se hicieron observaciones cualitativas a partir del tercer mes, para determinar la consistencia del terrón formado por el sustrato. Con el propósito de expresar el crecimiento en términos de materia seca, al final del experimento se tomó una muestra de 12 plantas por sustrato, a las cuales se le midió la altura y se le determinó su contenido de materia seca.

## Labores Culturales.

Las semillas fueron puestas a germinar en arena, la cual fue desinfectada previamente con agua caliente. En el caso de las semillas de Leucaena, éstas fueron sometidas a un proceso de escarificación, en agua a temperatura de 80°C por espacio de 3 minutos y posteriormente sumergidas en agua a temperatura ambiente durante 24 horas para eliminar la capa cerosa que las cubre y facilitar el proceso de absorción de agua para provocar la germinación. Las demás no fueron tratadas.

El trasplante fue hecho en tubetes. Estos envases son de forma cónica truncada, plásticos y de color negro de 12 cm de largo y boca circular de 4 cm de diámetro. 15 días después del trasplante, se realizó la reposición de las plántulas que murieron.

Durante la permanencia de las plántulas en los germinadores se aplicó Dithane a razón de 5.3 g/litro como forma de prevenir el mal de los semilleros (Damping-off). También se hicieron dos aplicaciones más de Dithane después del trasplante, debido al exceso de humedad ocasionado por las lluvias.

Se fertilizó dos veces por semana, aplicando Microfer 10 a razón de 5 g/gl de agua en una de las aplicaciones y Mono Amoniun Phosphate (MAP) a razón de 1.5 libras/50 gl de agua, durante los tres primeros meses. En el último mes se aplicó la fórmula 20-20-20, a una dosis de 0.5 onza/gl de agua. Todos los fertilizantes fueron aplicados con una regadera.
## Análisis de Datos

Los datos de crecimiento fueron analizados utilizando las medias por especies dentro de las parcelas (las medias de las subparcelas). El análisis de la producción de mateira seca se hizo con base a una muestra de cuatro plantas por especie y sustrato, por repetición; es decir, un total de 12 plantas por sustrato. Se realizó análisis de varianza por medio del procedimiento ANOVA del SAS (un paquete general para análisis estadísticos).

## RESULTADOS Y DISCUSION

### Incremento en Altura.

En el Cuadro 2 se presentan los resultados del incremento en altura obtenidos por las distintas especies en los diferentes sustratos utilizados en el ensayo. Como se puede observar en el mismo cuadro, el roble tuvo el mayor incremento en todos los sustratos, con una máxima de 28.50 cm en el sustrato No. 4, seguido por la leucaena que alcanzó un incremento máximo de 24.07 cm en el sustrato No. 4. El neem fue la especie que menos creció, teniendo su mayor crecimiento en el sustrato No. 3.

Los resultados del análisis de varianza para los datos del incremento en altura que tuvieron las plantitas desde el trasplante hasta la edad de cinco meses, son mostrados en el Cuadro 3. En dicho cuadro puede notarse que hay diferencias estadísticamente significativas en el incremento de las especies, debido al efecto de los sustratos. Del mismo modo, hay diferencias entre las especies, lo cual era de esperarse porque se trabajó con especies de hábitos de crecimiento diferentes.

También se observa en el mismo cuadro que la interacción sustrato-especies resultó ser no significativa, lo cual indica que el comportamiento de los sustratos será el mismo, estadísticamente, independientemente de la especie; es decir, que si un sustrato es bueno con una de las especies usadas, también lo será con las demás y viceversa.

Puesto que en el análisis de varianza se encontró diferencias significativas entre los sustratos, se procedió a realizar separación de medias
para determinar entre cuáles sustratos había diferencias. Esta prueba fue hecha por el método de Rangos Múltiples de Duncan. Los resultados de esta separación son dados en el Cuadro 4. De acuerdo con este análisis, las medias que están agrupadas por la misma letra son estadísticamente iguales.

<table><caption>Cuadro 2. Incremento en Altura Promedio por Especie en los Diferentes Sustratos a la Edad de 5 Meses.</caption><thead><tr><th rowspan="2">Sustrato No.</th><th>Pino</th><th>Leucaena</th><th>Roble</th><th>Neem</th><th>Acacia</th></tr><tr><th>Inc (cm)</th><th>Inc. (cm)</th><th>Inc. (cm)</th><th>Inc. (cm)</th><th>Inc. (cm)</th></tr></thead><tbody><tr><td>1</td><td>10.21</td><td>17.17</td><td>21.33</td><td>6.23</td><td>16.40</td></tr><tr><td>2</td><td>12.03</td><td>17.87</td><td>17.73</td><td>8.83</td><td>16.07</td></tr><tr><td>3</td><td>11.53</td><td>17.57</td><td>26.83</td><td>11.29</td><td>20.24</td></tr><tr><td>4</td><td>10.63</td><td>24.07</td><td>28.50</td><td>8.24</td><td>22.20</td></tr><tr><td>5</td><td>7.93</td><td>14.87</td><td>14.49</td><td>9.01</td><td>15.03</td></tr><tr><td>6</td><td>12.97</td><td>16.33</td><td>16.78</td><td>7.88</td><td>13.95</td></tr><tr><td>7</td><td>12.73</td><td>15.90</td><td>21.00</td><td>7.86</td><td>14.86</td></tr><tr><td>8</td><td>10.16</td><td>11.09</td><td>20.47</td><td>6.28</td><td>13.87</td></tr><tr><td>9</td><td>11.24</td><td>17.47</td><td>23.23</td><td>9.03</td><td>9.00</td></tr><tr><td>10</td><td>10.57</td><td>18.18</td><td>18.97</td><td>9.66</td><td>19.93</td></tr><tr><td>11</td><td>13.03</td><td>14.60</td><td>19.80</td><td>8.88</td><td>16.73</td></tr><tr><td>12</td><td>11.49</td><td>20.27</td><td>21.37</td><td>8.76</td><td>17.03</td></tr><tr><td>13</td><td>14.02</td><td>17.47</td><td>23.73</td><td>7.53</td><td>15.57</td></tr><tr><td>14</td><td>14.63</td><td>15.34</td><td>24.23</td><td>9.91</td><td>16.70</td></tr><tr><td>15</td><td>10.19</td><td>19.93</td><td>24.47</td><td>9.00</td><td>16.50</td></tr><tr><td>16</td><td>12.93</td><td>16.34</td><td>24.87</td><td>8.75</td><td>17.30</td></tr><tr><td>17</td><td>11.84</td><td>17.50</td><td>20.43</td><td>7.04</td><td>14.09</td></tr><tr><td>18</td><td>14.83</td><td>15.11</td><td>22.10</td><td>6.98</td><td>19.37</td></tr><tr><td>19</td><td>11.38</td><td>17.00</td><td>24.30</td><td>6.59</td><td>19.93</td></tr><tr><td>20</td><td>11.60</td><td>15.27</td><td>17.60</td><td>6.79</td><td>12.80</td></tr><tr><td>21</td><td>9.24</td><td>12.16</td><td>16.77</td><td>4.72</td><td>11.53</td></tr><tr><td>22</td><td>7.54</td><td>13.17</td><td>12.73</td><td>5.52</td><td>10.32</td></tr><tr><td>23</td><td>9.31</td><td>13.10</td><td>24.00</td><td>5.68</td><td>9.58</td></tr><tr><td>24</td><td>10.37</td><td>16.37</td><td>23.87</td><td>7.25</td><td>18.13</td></tr><tr><td>25</td><td>12.93</td><td>19.57</td><td>20.16</td><td>12.83</td><td>20.20</td></tr></tbody></table>
<table><caption>Cuadro 3. Análisis de Varianza para los Datos de Incremento en Altura</caption><thead><tr><th>Fuente de Variación</th><th>g.l.</th><th>Suma de Cuadrados</th><th>Cuadrados Medios</th><th>F</th></tr></thead><tbody><tr><td>Bloque 2</td><td>256.00</td><td>128.30</td><td>6.50**</td><td></td></tr><tr><td>Sustratos</td><td>24</td><td>1,521.72</td><td>63.41</td><td>3.21**</td></tr><tr><td>Error (a)</td><td>48</td><td>947.19</td><td>19.73</td><td></td></tr><tr><td>Especies</td><td>4</td><td>7,674.60</td><td>1,918.65</td><td>75.76**</td></tr><tr><td>Sustratos-Especies</td><td>96</td><td>1,436.37</td><td>14.96</td><td>0.59</td></tr><tr><td>Error (b)</td><td>200</td><td>5,065.35</td><td>25.33</td><td></td></tr><tr><td>Total</td><td>374</td><td>16,901.83</td><td></td><td></td></tr></tbody></table>

<table><caption>Cuadro 4. Separación de Medias por Sustratos para El Incremento en Altura.</caption><thead><tr><th>Incremento Medio(cm)</th><th>Sustrato</th></tr></thead><tbody><tr><td>18.726 a</td><td>4</td></tr><tr><td>17.492 ba</td><td>3</td></tr><tr><td>17.139 bac</td><td>25</td></tr><tr><td>16.163 bdac</td><td>14</td></tr><tr><td>16.039 bdac</td><td>16</td></tr><tr><td>16.019 bdac</td><td>15</td></tr><tr><td>15.841 bdac</td><td>19</td></tr><tr><td>15.783 bdac</td><td>12</td></tr><tr><td>15.677 bdac</td><td>18</td></tr><tr><td>15.663 bdac</td><td>13</td></tr><tr><td>15.461 bdac</td><td>10</td></tr><tr><td>15.196 ebdac</td><td>24</td></tr><tr><td>14.609 ebdac</td><td>11</td></tr><tr><td>14.506 ebdac</td><td>2</td></tr><tr><td>14.471 ebdac</td><td>7</td></tr><tr><td>14.268 ebdc</td><td>1</td></tr></tbody></table>
<table><thead><tr><td>Incremento Medio (cm)</td><td>Sustrato</td></tr></thead><tbody><tr><td>14.182 ebdc</td><td>17</td></tr><tr><td>13.994 ebdfc</td><td>9</td></tr><tr><td>13.583 ebdfc</td><td>6</td></tr><tr><td>12.809 edfc</td><td>20</td></tr><tr><td>12.373 edf</td><td>8</td></tr><tr><td>12.334 edf</td><td>23</td></tr><tr><td>12.267 edf</td><td>5</td></tr><tr><td>10.885 ef</td><td>21</td></tr><tr><td>9.856 f</td><td>22</td></tr></tbody></table>

En el Cuadro 4 puede apreciarse que hay un amplio grupo de sustratos que, en términos del incremento ocasionado a las plantas, son estádísticamente iguales al testigo (sustrato número 25), el cual es considerado como un buen sustrato para producir plántulas en viveros forestales, utilizando tubetes como envases de producción.

## Producción de Materia Seca

Como ya se indicó, el análisis de la producción de materia seca se hizo con base a una muestra de cuatro plantas por especie y sustrato, por repetición; es decir, un total de 12 plantas por sustrato. En el Cudro 5 se presentan los valores de la producción promedio de materia seca por sustrato y especie. En este se puede observar que el sustrato 25 (testigo) es el que ocasiona una mayor producción de materia seca, siendo el No. 7 el menor. Todas las especies tienen una producción similar, excepto el pino que es inferior a las demás.

Según el análisis de varianza, Cuadro 6, no se encontró diferencias significativas en la producción de materia seca, debido a los sustratos; pero sí entre especies. Esto último era de esperarse, porque las especies son diferentes. Tampoco fue significativa la interacción sustratos-especies, lo que indica que el comportamiento de los sustratos será el mismo independientemente de las especies.
<table><caption>Cuadro 5. Producción de Materia Seca por Sustrato y Especie</caption><thead><tr><th rowspan="2">Sustrato<br>No.</th><th colspan="6">Producción Promedio de Materia Seca (g)</th></tr><tr><th>Acacia</th><th>Leucaena</th><th>Neem</th><th>Pino</th><th>Roble</th><th>Promed</th></tr></thead><tbody><tr><td>1</td><td>0.715</td><td>0.638</td><td>0.723</td><td>0.665</td><td>0.644</td><td>0.677</td></tr><tr><td>2</td><td>0.705</td><td>0.495</td><td>0.718</td><td>0.474</td><td>0.807</td><td>0.640</td></tr><tr><td>3</td><td>0.724</td><td>0.772</td><td>0.897</td><td>0.568</td><td>1.041</td><td>0.800</td></tr><tr><td>4</td><td>0.747</td><td>0.908</td><td>0.827</td><td>0.429</td><td>1.258</td><td>0.834</td></tr><tr><td>5</td><td>1.015</td><td>0.532</td><td>0.644</td><td>0.503</td><td>1.136</td><td>0.766</td></tr><tr><td>6</td><td>0.825</td><td>0.615</td><td>0.724</td><td>0.370</td><td>1.000</td><td>0.707</td></tr><tr><td>7</td><td>0.476</td><td>0.847</td><td>0.617</td><td>0.323</td><td>0.554</td><td>0.563</td></tr><tr><td>8</td><td>0.404</td><td>0.662</td><td>0.684</td><td>0.650</td><td>0.592</td><td>0.598</td></tr><tr><td>9</td><td>0.497</td><td>0.860</td><td>0.832</td><td>0.709</td><td>0.717</td><td>0.723</td></tr><tr><td>10</td><td>1.048</td><td>0.463</td><td>0.864</td><td>0.500</td><td>0.685</td><td>0.712</td></tr><tr><td>11</td><td>0.853</td><td>1.125</td><td>0.845</td><td>0.736</td><td>0.722</td><td>0.856</td></tr><tr><td>12</td><td>0.688</td><td>0.803</td><td>0.718</td><td>0.681</td><td>0.641</td><td>0.706</td></tr><tr><td>13</td><td>0.480</td><td>0.543</td><td>0.794</td><td>0.520</td><td>0.653</td><td>0.598</td></tr><tr><td>14</td><td>0.680</td><td>0.853</td><td>0.878</td><td>0.662</td><td>0.578</td><td>0.730</td></tr><tr><td>15</td><td>0.660</td><td>0.775</td><td>0.950</td><td>0.590</td><td>1.245</td><td>0.844</td></tr><tr><td>16</td><td>0.546</td><td>0.919</td><td>0.969</td><td>0.684</td><td>0.793</td><td>0.782</td></tr><tr><td>17</td><td>0.522</td><td>0.667</td><td>0.734</td><td>0.413</td><td>0.894</td><td>0.646</td></tr><tr><td>18</td><td>0.794</td><td>0.960</td><td>0.848</td><td>0.801</td><td>0.845</td><td>0.849</td></tr><tr><td>19</td><td>0.803</td><td>0.757</td><td>1.060</td><td>0.464</td><td>0.919</td><td>0.800</td></tr><tr><td>20</td><td>0.714</td><td>0.844</td><td>0.921</td><td>0.735</td><td>1.066</td><td>0.856</td></tr><tr><td>21</td><td>0.829</td><td>0.635</td><td>0.595</td><td>0.661</td><td>0.548</td><td>0.653</td></tr><tr><td>22</td><td>0.859</td><td>0.778</td><td>0.771</td><td>0.357</td><td>0.459</td><td>0.645</td></tr><tr><td>23</td><td>0.661</td><td>0.720</td><td>0.665</td><td>0.529</td><td>0.599</td><td>0.635</td></tr><tr><td>24</td><td>0.871</td><td>0.586</td><td>0.803</td><td>0.663</td><td>0.735</td><td>0.732</td></tr><tr><td>25</td><td>1.683</td><td>0.688</td><td>0.779</td><td>0.778</td><td>0.703</td><td>0.926</td></tr><tr><td>Prom.</td><td>0.752</td><td>0.738</td><td>0.794</td><td>0.579</td><td>0.793</td><td></td></tr></tbody></table>
<table><caption>Cuadro 6. Análisis de Varianza para la Producción de Materia Seca Promedio por Planta</caption><thead><tr><th>Fuente de Variación</th><th>g.l.</th><th>Suma de Cuadrados</th><th>Cuadrados Medios</th><th>F</th></tr></thead><tbody><tr><td>Bloque</td><td>2</td><td>0.81</td><td>0.091</td><td>0.58</td></tr><tr><td>Sustratos</td><td>24</td><td>3.392</td><td>0.141</td><td>0.91</td></tr><tr><td>Error (a)</td><td>48</td><td>7.461</td><td>0.155</td><td></td></tr><tr><td>Especies</td><td>4</td><td>2.372</td><td>0.593</td><td>6.11 **</td></tr><tr><td>Sustratos-Especies</td><td>96</td><td>8.981</td><td>0.094</td><td>0.96</td></tr><tr><td>Error (b)</td><td>200</td><td>19.413</td><td>0.097</td><td></td></tr><tr><td>Total</td><td>374</td><td>41.800</td><td></td><td></td></tr></tbody></table>

Relacionando la producción de materia seca con la altura de las plántulas, se encontró un grado de asociación bajo entre estas dos variables, pues los coeficientes de correlación no son altos, a pesar de que los mismos son significativos (Cuadro 7). Esto podría explicar el por qué no se encontró diferencias significativas entre los sustratos para la variable producción de materia seca, si las hubo para la variable incremento en altura.

<table><caption>Cuadro 7. Coeficientes de Correlación entre la Producción de Materia Seca (PMS) y la Altura por Especie.</caption><thead><tr><th>Especie</th><th>Altura Promedio (cm)</th><th>PMS Promedio (g)</th><th>Coeficiente de Correlación</th></tr></thead><tbody><tr><td>Pino</td><td>21.87</td><td>0.57</td><td>0.45**</td></tr><tr><td>Leucaema</td><td>28.16</td><td>0.74</td><td>0.59**</td></tr><tr><td>Roble</td><td>22.15</td><td>0.79</td><td>0.55**</td></tr><tr><td>Neem</td><td>15.83</td><td>0.79</td><td>0.29**</td></tr><tr><td>Acacia</td><td>21.52</td><td>0.76</td><td>0.59**</td></tr></tbody></table>

## Análisis Químico de los Sustratos

En el Cuadro 8 se presentan los resultados del análisis químico realizado a los sustratos empleados en el estudio. Como puede verse, todos los sustratos tienen un alto contenido de materia orgánica y
potasio asimilable, excepto el No. 23 que es bajo en potasio. Todos ellos tienen pH alrededor de 7, con la excepción del testigo (No. 25) que tiene pH de 5.3. En cuanto al contenido de fósforo; todos los sustratos con arroz son bajos, menos el No. 3 que es alto en este elemento. Los sustratos con base de caña son altos en fósforo asimilable, exceptuando el No. 15. Los que contienen coco son altos y bajos en el contenido de fósforo, sin importar la proporción de ese componente.

Relacionando el incremento en altura con el contenido nutricional de los sustratos, sólo se encontró efectos significativos del fósforo sobre el incremento del Pino. Estos resultados son mostrados en el Cuadro 9. Aunque el efecto de la materia orgánica y el potasio sobre el incremento en altura, no es significativo; es necesario destacar que para todas las especies, el coeficiente de correlación es negativo.

A pesar de que estos resultados no son significativos para la producción en este tipo de envase (tubetes), por el poco volumen de sustrato utilizado por planta, puede ser que para otros envases con mayor capacidad, el contenido nutricional del sustrato sea significativo para el incremento en altura de las plántulas.
<table><caption>Cuadro 8. Resultados de los Análisis de Laboratorio para los Sustratos Investigados.</caption><thead><tr><th>Sustrat. No.</th><th>Composición Sustrat. (%)</th><th>pH</th><th>Materia Orgánica (%)</th><th>P<sub>2</sub>O<sub>5</sub> K<sub>2</sub>O (ppm)</th><th>(ppm)</th></tr></thead><tbody><tr><td>1</td><td>10A-90T</td><td>6.8</td><td>37.9 (A)</td><td>0.0 (B)</td><td>336 (A)</td></tr><tr><td>2</td><td>20A-80T</td><td>7.0</td><td>39.5 (A)</td><td>0.8 (B)</td><td>528 (A)</td></tr><tr><td>3</td><td>70A-30T</td><td>7.0</td><td>28.1 (A)</td><td>23.2 (A)</td><td>948 (A)</td></tr><tr><td>4</td><td>30A-70T</td><td>7.0</td><td>31.3 (A)</td><td>1.6 (B)</td><td>1176 (A)</td></tr><tr><td>5</td><td>10C-90T</td><td>7.1</td><td>37.2 (A)</td><td>0.8 (B)</td><td>888 (A)</td></tr><tr><td>6</td><td>20C-80T</td><td>6.9</td><td>31.0 (A)</td><td>505.0 (A)</td><td>1656 (A)</td></tr><tr><td>7</td><td>30C-70T</td><td>6.8</td><td>29.7 (A)</td><td>112.2 (A)</td><td>1584 (A)</td></tr><tr><td>8</td><td>40C-60T</td><td>7.0</td><td>41.8 (A)</td><td>2.4 (B)</td><td>612 (A)</td></tr><tr><td>9</td><td>20CA-80T</td><td>7.1</td><td>31.7 (A)</td><td>60.1 (A)</td><td>1416 (A)</td></tr><tr><td>10</td><td>30CA-70T</td><td>7.2</td><td>26.1 (A)</td><td>345.0 (A)</td><td>828 (A)</td></tr><tr><td>11</td><td>40CA-60T</td><td>7.2</td><td>23.2 (A)</td><td>417.0 (A)</td><td>444 (A)</td></tr><tr><td>12</td><td>60CA-40T</td><td>7.2</td><td>19.9 (A)</td><td>400.8 (A)</td><td>1824 (A)</td></tr><tr><td>13</td><td>70CA-30T</td><td>7.2</td><td>26.1 (A)</td><td>304.6 (A)</td><td>732 (A)</td></tr><tr><td>14</td><td>80CA-20T</td><td>7.4</td><td>27.1 (A)</td><td>472.9 (A)</td><td>1464 (A)</td></tr><tr><td>15</td><td>90CA-10T</td><td>7.2</td><td>33.6 (A)</td><td>6.4 (B)</td><td>660 (A)</td></tr><tr><td>16</td><td>60A-40T</td><td>7.0</td><td>36.2 (A)</td><td>0.8 (B)</td><td>492 (A)</td></tr><tr><td>17</td><td>40A-60T</td><td>7.2</td><td>30.3 (A)</td><td>0.0 (B)</td><td>468 (A)</td></tr><tr><td>18</td><td>80A-20T</td><td>7.1</td><td>34.9 (A)</td><td>0.0 (B)</td><td>372 (A)</td></tr><tr><td>19</td><td>90A-10T</td><td>7.1</td><td>41.8 (A)</td><td>2.4 (B)</td><td>540 (A)</td></tr><tr><td>20</td><td>60C-40T</td><td>6.9</td><td>43.1 (A)</td><td>6.4 (B)</td><td>1536 (A)</td></tr><tr><td>21</td><td>70C-30T</td><td>6.8</td><td>43.1 (A)</td><td>40.1 (A)</td><td>2340 (A)</td></tr><tr><td>22</td><td>80C-20T</td><td>7.2</td><td>34.3 (A)</td><td>09.0 (B)</td><td>2640 (A)</td></tr><tr><td>23</td><td>90C-10T</td><td>6.6</td><td>40.9 (A)</td><td>48.1 (A)</td><td>88 (B)</td></tr><tr><td>24</td><td>10CA-90T</td><td>7.2</td><td>28.7 (A)</td><td>40.0 (A)</td><td>1296 (A)</td></tr><tr><td>25</td><td>70PM-25T</td><td>5.3</td><td>39.0 (A)</td><td>112.2 (A)</td><td>168 (B)</td></tr></tbody></table>

A = Cáscara de Arroz

C = Fibras de Coco

CA = Cachaza de Caña

(A) = Alto, (B) = Bajo

PM = Peat moss

T = Turba
<table><caption>Cuadro 9: Coeficientes de Correlación entre el Incremento en Altura de las Diferentes Especies y el Contenido de Materia Orgánica, Fósforo y Potasio de los Sustratos.</caption><thead><tr><th rowspan="2">Elemento</th><th colspan="5">Incremento en altura (cm)</th></tr><tr><th>Pino</th><th>Leucaema</th><th>Roble</th><th>Neem</th><th>Acacia</th></tr></thead><tbody><tr><td>MO</td><td>-0.39</td><td>-0.24</td><td>-0.24</td><td>-0.39</td><td>-0.28</td></tr><tr><td>P</td><td>0.46*</td><td>0.07</td><td>-0.07</td><td>0.29</td><td>0.08</td></tr><tr><td>K</td><td>-0.28</td><td>-0.16</td><td>-0.39</td><td>-0.26</td><td>-0.37</td></tr></tbody></table>

## Consistencia de los Sustratos

A pesar de que muchos sustratos han producido un buen incremento en la altura de las plántulas con relación al testigo, no necesariamente éstos pueden ser considerados como buenos sustratos. Pues se considera que un sustrato es bueno si, además de producir buen crecimiento de las plántulas, éste forma un terrón de buena consistencia que permita la extracción de la plántula del tubete y su transporte al campo, sin que el mismo se desintegre; por lo que son importantes tanto las condiciones físicas como las químicas (3).

Como puede verse en el Cuadro 10, el sustrato No. 12, por ejemplo, con una composición de 60% de cachaza de caña y 40% de turba, en el cual se consiguió un incremento promedio en las especies de 15.78 cm, que es bastante bueno, tiene una consistencia mala, o sea, que se suelta completamente al extraer la plántula del tubete. Esto demuestra que para la elección de un sustrato debe tomarse en cuenta tanto el crecimiento de la plántula como la consistencia del terrón que éste forma.

Tomando en cuenta estas observaciones, se considera que los mejores sustratos evaluados fueron el No. 4 (30% cáscara de arroz + 70% turba), No. 3 (70% Cáscara de arroz + 30% turba), No. 16 (60% cáscara de arroz + 40% turba), No. 19 (90% cáscara de arroz + 10 10% turba) y No. 7 (30% fibras de coco + 70% turba); los cuales estadísticamente son iguales en términos de crecimiento de las plántulas y tienen una consistencia de buena a regular. Como puede verse,
los mejores sustratos son los elaborados con cáscara de arroz. En este punto es bueno destacar que González H. (1) encontró que la mezcla arena-estiércol-cáscara de arroz (1-1-1) produjo buenos resultados en la producción de plántulas de bruscón (Cassia emarginata).

<table><caption>Cuadro 10: Incremento Promedio en Altura de las Plántulas y Consistencia del Terrón por Sustrato.</caption><thead><tr><th>Sustrat. No.</th><th>Composición (%)*</th><th>Incremento Promedio (cm)</th><th>Consistencia del Terrón</th></tr></thead><tbody><tr><td>1</td><td>10A+90T</td><td>14.27</td><td>Consistencia mala (suelto)</td></tr><tr><td>2</td><td>20A+80T</td><td>14.51</td><td>Consistencia mala (suelto)</td></tr><tr><td>3</td><td>70A+30T</td><td>17.49</td><td>Consistencia regular</td></tr><tr><td>4</td><td>30A+70T</td><td>18.73</td><td>Consistencia regular</td></tr><tr><td>5</td><td>10C+90T</td><td>12.27</td><td>Consistencia mala</td></tr><tr><td>6</td><td>20C+80T</td><td>13.58</td><td>Consistencia mala</td></tr><tr><td>7</td><td>30C+70T</td><td>14.47</td><td>Consistencia regular</td></tr><tr><td>8</td><td>40C+60T</td><td>12.37</td><td>Consistencia mala</td></tr><tr><td>9</td><td>20CA+80T</td><td>13.99</td><td>" "</td></tr><tr><td>10</td><td>30CA+70T</td><td>15.46</td><td>" "</td></tr><tr><td>11</td><td>40CA+60T</td><td>14.61</td><td>" "</td></tr><tr><td>12</td><td>60CA+40T</td><td>15.78</td><td>" "</td></tr><tr><td>13</td><td>70CA+30T</td><td>15.66</td><td>" "</td></tr><tr><td>14</td><td>80CA+20T</td><td>16.16</td><td>" "</td></tr><tr><td>15</td><td>90CA+10T</td><td>16.02</td><td>" "</td></tr><tr><td>16</td><td>60A+40T</td><td>16.03</td><td>Consistencia buena</td></tr><tr><td>17</td><td>40A+60T</td><td>14.18</td><td>Consistencia mala</td></tr><tr><td>18</td><td>80A+20T</td><td>15.68</td><td>" "</td></tr><tr><td>19</td><td>90A+10T</td><td>15.84</td><td>Consistencia regular</td></tr><tr><td>20</td><td>60C+40T</td><td>12.81</td><td>Consistencia mala</td></tr><tr><td>21</td><td>70C+30T</td><td>10.89</td><td>" "</td></tr><tr><td>22</td><td>80C+20T</td><td>9.86</td><td>Consistencia regular</td></tr><tr><td>23</td><td>90C+10T</td><td>13.33</td><td>Consistencia buena</td></tr><tr><td>24</td><td>10CA+90T</td><td>15.20</td><td>Consistencia regular</td></tr><tr><td>25</td><td>Peat moss</td><td>17.14</td><td>Consistencia Excelente</td></tr></tbody></table>

* A = Cáscara de Arroz

C = Fibra de Coco

CA = Cachaza de Caña

T = Turba
REFERENCIAS

1. GONZALEZ SEBELEN, H. P. 1987. Efecto de cinco mezclas con cuatro medios en el crecimiento vegetativo y radicular, en el vivero, de Candelón (Acacia scleroxyla Tuss) y Bruscón (Cassia emarginata L.). Santiago, Rep. Dom. Universidad Católica Madre y Maestra/Instituto Superior de Agricultura. Tesis Ingeniero Agrónomo. 72 p.

2. LORA SALCEDO, R. et al. 1983. Atlas de diagramas climáti-cos de la República Dominicana. Santo Domingo, República Dominicana. Secretaria de Estado de Agricultura (SEA). 91 p.

3. ORTIZ, O. 1981. Diferentes métodos de provocar la germi-nación: siembra directa y uso de almácigo. Curso de Admin-istración y Manejo de Viveros Forestales. ESCANIFOR, Siguatepeque, Honduras.
ESTUDIOS SOBRE LOS EFECTOS DE PROMALIN,
ACIDO GIBERELICO, BENCILAMINOPURINA,
ANCIMIDOL, CLORMEQUAT, ALAR Y ACIDO
NAFTALENOACETICO EN EL DESARROLLO Y
CRECIMIENTO DE LA FRESA(*Fragaria x ananassa*
Duch) VARIEDADES 'TRISTAR' Y 'TRIBUTE'.

Jose M. Rivera, Salvador Salas PhD, Doris Ramírez PhD
& Feiko Ferwerda.

Departamento de Tecnología Agrícola. Universidad de
Puerto Rico, Colegio Regional La Montaña, Utuado,
Puerto Rico.

RESUMEN

La fresa (Fragaria x ananassa Duch.) tiene potencial económico como fruta fresca en Puerto Rico. Se estudió el efecto de reguladores de crecimiento (GA3, BA, Promalín y NAA) e inhibidores de crecimiento en plantas (CCC, ancimidol y Alar) en las variedades 'Tristar' y 'Tribute'. Los resultados demostraron que ácido giberélico (GA3) y Promalín aumentaron la producción de estolones en serie y el alargamiento del pecíolo; además el número de inflorescencias por corona en la variedad 'Tristar' aumentó cuando los tratamientos se aplicaron a temprana edad. Bencilaminopurina (BA) aumentó el desarrollo de coronas en ambas variedades en aplicaciones a temprana edad. Acido naftalenoacético (NAA) inhibió el desarrollo vegetativo en la variedad 'Tristar', pero no tuvo efectos en la variedad 'Tribute'. Cycocel (CCC), A-Rest (ancimidol) y B-Nine (Alar) no tuvieron efecto en el desarrollo vegetativo y la florecida.
STUDIES OF THE EFFECTS OF PROMALIN,
GIBBERELIC ACID, BENZYLAMINOPURINE,
ANCYMIDOL, CHLORMEQUAT, ALAR AND
NAPHTHALENEACETIC ACID ON GROWTH AND
DEVELOPMENT OF STRAWBERRY (*Fragaria x
ananassa* Duch) VAR. 'Tristar' AND 'Tribute'

Jose M. Rivera, Salvador Salas PhD, Doris Ramírez PhD & Feiko Ferwerda. University of Puerto Rico, La Montaña College, Utuado, Puerto Rico.

ABSTRACT

The strawberry (*Fragaria ananassa* Duch) has a great economic potencial as a fresh fruit in Puerto Rico. Studies have been made with plant growth regulators (GA3, BA, Promalin, NAA) and plant growth inhibitors (CCC, ancymidol, Alar). There were used 'Tristar' and 'Tribute' varieties. The results of these experiments demostrated that gibberelic acid (GA3) and Promalin increased the production of stolons serie and the enlargement of the leaf stalk. Also, the number of inflorescences per crown in 'Tristar' variety increased when the treatments were applied 30 days after planting. Benzylaminopurine (BA) increased the development of crowns in both varieties in applications 30 days after planting. Naphthaleneacetic acid (NAA) inhibits the vegetative development in 'Tristar' variety, but it has no effects in 'Tribute' variety. Cycocel (CCC), A-Rest (ancymidol) and B-Nine (alar) have any effects in the vegetative development and neither in the flowering.
ESTUDIOS SOBRE EL EFECTO DE PROMALIN,
ACIDO GIBERELICO, BENCILAMINOPURINA,
ANCIMIDOL, CLORMEQUAT, ALAR Y ACIDO
NAFTALENOACETICO EN EL CRECIMIENTO Y
DESARROLLO DE LA FRESA (Fragaria x ananassa
Duch) VARIEDADES 'Tristar' Y 'Tribute'

Jose M. Rivera, Salvador Salas PhD, Doris Ramírez PhD,
Feiko Ferwerda, Universidad de Puerto Rico, Colegio Regional
La Montaña, Utuado, Puerto Rico

INTRODUCCION

En Puerto Rico se importa aproximadamente 355,000 libras de fruta fresca (Fragaria x ananassa Duch). Esto indica que se debe promover y desarrollar el cultivo para sustituir estas importaciones ya que se tienen las condiciones ambientales favorables para el cultivo de fresa.

Los únicos estudios en fresa en Puerto Rico se realizaron entre 1960 y 1964 en el pueblo de Adjuntas (Singh et al., 1964). En este estudio se concluyó que se puede cultivar fresas en huertos domésticos y posiblemente a escala comercial en la región central occidental montañosa de este país.

Esta investigación se estableció a principio de agosto de 1991 en el pueblo de Utuado, Puerto Rico, a una altitud aproximada de 2,000 pies con el propósito de estudiar el efecto de reguladores de crecimiento en plantas (RCP) [ácido giberélico (GA3, bencilaminopuriña (BA), Promalín (GA3+4 + BA), y ácido naftalenoacético (NAA)]; e inhibidores de crecimiento en plantas (ICP) [Cycocel (CCC), A-Rest (ancimidol) y Alar ("daminozide")] en el desarrollo vegetativo de la fresa, y como afecta la producción de flores. Estos reguladores de crecimiento e inhibidores de crecimiento en plantas han sido motivo de estudios por años en varios países; sin embargo, los resultados difieren de acuerdo a los factores envueltos dentro de cada experimento como hormonas, localidad, temperatura, variedad, fotoperíodo, época de siembra, y otros (Darrow, 1936; Guttridge y Anderson,
1973 y 1981; Lal y Seth, 1980; Sharma y Singh, 1980; Singh et al., 1964; Williams, 1975).

# MATERIALES Y METODOS

Este estudio se estableció bajo condiciones de invernadero en la zona montañosa en el Colegio Regional LA Montaña, Utuado, Puerto Rico. Las variedades de fresa estudiadas fueron 'Tristar' y 'Tribute'. Ambas son variedades de días-neutros, las cuales no responden a cambios drástico en temperaturas ni fotoperíodo y se sembraron en tiestos con una mezcla que contenía "peat moss", perlita y vermiculita a igual proporción.

## Experimento I

En el experimento I se estudió el efecto de GA3, BA y Promalín sobre el desarrollo y crecimiento de la fresa variedades 'Tristar' y 'Tribute'. El diseño experimental fue completamente aleatorizado con 12 plantas por tratamiento. Las concentraciones para GA3 fueron 0.028, 0.057, 0.143 y 0.287 mM de ingrediente activo (i.a.); para BA fueron 0.044, 0.089, 0.223 y 0.446 mM i.a.; y para Promalín fueron 0.036, 0.073, 0.183 y 0.366 mM i.a. En algunas plantas se aplicó los tratamientos en forma foliar 30 días (1 mes) luego de sembradas (tiempo 1), al resto se aplicó los tratamientos al transcurrir 105 días (3 1/2 meses) luego de sembradas (tiempo 2).

## Experimento II

En este experimento se estudió el efecto de GA3 (0.071, 0.14 y 0.287 mM de i.a.); CCC (0.158, 0.316 y 0.632 de i.a.); ancimidol (0.097, 0.195 y 0.39 mM de i.a.); NAA (0.132, 0.264 y 0.528 mM de i.a.); y Alar (0.175, 0.351 y 0.703 mM de i.a.) sobre el desarrollo vegetativo e inflorescencia de la fresa de ambas variedades. Los tratamientos se aplicaron en forma foliar 1 mes luego de la siembra.

Los parámetros medidos en ambos experimentos fueron: a) número de coronas, b) número de estolones en serie, c) alargamiento del pecíolo, y d) número de inflorescencias por corona.
# RESULTADOS Y DISCUSIÓN

## Experimento I

Los efectos de los reguladores de crecimiento en plantas (RCP) fueron muy variados. En la variedad 'Tribute' los tratamientos con BA desarrollaron un promedio de 0.625 coronas en comparación con los tratamientos con GA3 y Promalín con un promedio de 0.219 y 0.208 coronas, respectivamente. Sin embargo, este aumento en el desarrollo de coronas provocada por BA no es significativa con respecto al control (Figura 1). EL control de la variedad 'Tribute' desarrolló más coronas que los tratamientos con GA3 y Promalín; entendiendo así que estos inhibieron el desarrollo de coronas. Aparentemente las aplicaciones de BA promovieron la división celular en las yemas vegetativas en la variedad 'Tribute' que se consideran fuertes productoras de coronas y pobres productoras de estolones. Posiblemente GA3 y Promalín causaron un estrés en las plantas provocando una inhibición. No hubo diferencias en los tratamientos aplicados a la variedad 'Tristar' (Figura 1); tampoco entre los tiempos de aplicación ni concentraciones del mismo compuesto. No obstante, el desarrollo de coronas provocado por aplicaciones de BA es diferente entre variedades. Braun y Kender (1985) reportaron un aumento de coronas en la variedad 'Fortune', una disminución en la variedad 'Earlidawn', y no hubo efecto en la variedad 'Geneva'. Archbold y Strang (1986) no encontraron diferencia en la variedad 'Redchief'.

En la variedad 'Tribute' los tratamientos con GA3 (2.656 estolones en serie) y Promalín (3.229 estolones en serie) promovieron un desarrollo de estolones en serie por corona significativo en comparación con el control y los tratamientos con BA (1.17 estolones en serie) (Figura 2). La respuesta en el alto desarrollo de estolones en serie por corona provocado por GA3 y Promalín podría deberse al efecto de GA en la diferenciación celular ya que ambas variedades son en su naturaleza grandes productoras de coronas. La variedad 'Tribute' desarrolló más estolones en serie que la variedad 'Tristar' en todos los tratamientos. Estas diferencias ocurrieron cuando los tratamientos se aplicaron 1 mes luego de la siembra (tiempo 1), posiblemente a que estas se encontraban en crecimiento vegetativo y las yemas axilares estaban más propicias a su desarrollo. Estos resultados concuerdan
con lo expuesto por Barrit (1974), Dennis y Bennett (1969), y Moore y Scott (1965). Ellos concluyen que las aplicaciones de GA3 durante el crecimiento de la planta promueven el desarrollo vegetativo. Las plantas tratadas con Promalín tuvieron un efecto mayor en el desarrollo de estolones en serie por corona como en el alargamiento del pecíolo de ambas variedades (Figura 2 y 3). Promalín es un producto comercial que contiene $GA_{3+4} + BA$; tanto en esta investigación como reportado por Braun (1985), Waithaka et al. (1978) y Guttridge (1973), el efecto de $GA3$ es intensificado cuando se combina con BA.

El efecto de $GA3$ y Promalín en el alargamiento del pecíolo es directamente proporcional a su concentración. Las plantas de la variedad 'Tribute' desarrollaron un pecíolo más largo que la variedad 'Tristar' para un mismo tratamiento. Esta diferencia es significativa en los tratamientos con Promalín, con un promedio de 19.83 y 18.42 cm de largo del pecíolo de las variedades 'Tribute' y 'Tristar', respectivamente; y en los tratamientos con $GA3$ con un promedio de 16.04 y 14.71 cm en pecíolo de las variedades 'Tribute' y 'Tristar', respectivamente (Figura 3). Este efecto sugiere que GA es el responsable del alargamiento celular ya que aplicaciones de BA solo no tuvieron efecto en dicho alargamiento en comparación al control.

El número de flores por corona resultó superior en los tratamientos aplicados en el tiempo 1 en una misma variedad (Figura 4). Las plantas de la variedad 'Tristar' tratadas con Promalín (1.023 inflorescencias) y $GA3$ (0.953 inflorescencia) promovieron un desarrollo de flores por corona altamente significativo con respecto a su control. Los tratamientos aplicados en el tiempo 1 a la variedad 'Tribute' desarrollaron más flores por corona que en el tiempo 2, aunque no hubo diferencias dentro de un mismo tiempo de aplicación (Figura 4). Sharma (1980) enfatiza la importancia del tiempo de aplicación. Si al momento de la aplicación las yemas están en diferenciación floral, los tratamientos con GA aceleran el desarrollo de flores; por el contrario aumentan el desarrollo vegetativo. Esto sugiere que GA no promueve la diferenciación celular para el desarrollo de flores, sino aumenta la división celular. Singh (1959) informó un aumento en la florecida de la variedad 'Pusa Dwarf Early' tratadas con $GA3$. De igual forma, Braun (1985) reportó el aumento en la florecida de la variedad 'Geneva' tratadas con $GA3$ y $GA_{3+4} + BA$; sin embargo, los resultados fueron
diferentes en la variedad 'Fortune'. Resultados similares se encontraron en esta investigación en donde los tratamientos con GA3 y Promalín aplicados a la variedad 'Tristar' promovieron un desarrollo de flores mayor que BA y el control; mientras que estos RCP no tuvieron efecto en la florecida de la variedad 'Tribute'. Estos resultados confirman que el efecto de los RCP es muy variable entre variedades.

## Experimento II

Los tratamientos con GA3 promovieron un desarrollo de estolones en serie superior en ambas variedades con un promedio de 1.704 estolones en serie en la variedad 'Tribute' y 1.557 estolones en la variedad 'Tristar'. Estos promedios reflejan 3 veces el promedio de sus respectivos controles (Figura 5). Esta respuesta de la planta a las aplicaciones de GA3 podría deberse a su efecto en la división y/o alargamiento celular de las yemás axilares. Los tratamientos con CCC, ancimidol y Alar no desarrollaron más estolones en serie que el control en ambas variedades. Sin embargo, las plantas tratadas con NAA mostraron una inhibición en el desarrollo de estolones en serie siendo esta significativa en la variedad 'Tristar' (Figura 5). Esta investigación concuerda con lo expuesto por Sach (1972), en donde las aplicaciones de CCC y Alar no tuvieron efecto sobre el desarrollo de estolones en serie; y lo expuesto por Waithaka et al. (1980) en donde concluye que NAA no promueve dicho desarrollo. Esto concluye que CCC, ancimidol y Alar podrían actuar como inhibidores de GA (Moore et al., 1989). No hubo diferencias entre RCP, ICP ni variedades en el desarrollo de coronas.

En ambas variedades tratadas con GA3 el alargamiento del pecíolo fue altamente significativo con respecto al control, posiblemente a su efecto en la división y/o alargamiento celular (Figura 6). Los ICP y NAA no tuvieron efecto sobre el alargamiento del pecíolo.

En la variedad 'Tristar' las plantas tratadas con GA3 30 días luego de la siembra desarrollaron un promedio de 0.875 flores por corona lo cual resulta altamente significativa en comparación con el control con un promedio de 0.604 flores por corona. Esto concuerda con Singh (1979) y Sharma (1980) donde reportan un aumento en la florecida
en plantas tratadas con GA3. Ambos señalan la importancia de la variedad y el tiempo de aplicación. Tanto Alar, NAA y ancimidol inhibieron la producción de flores en la variedad 'Tristar' (Figura 7). La variedad 'Tribute' desarrolló un número de flores por corona altamente significativo con respecto a la variedad 'Tristar' en los tratamientos con CCC, ancimidol y Alar con un promedio de 0.883, 0.751 y 0.845 flores por corona respectivamente en la variedad 'Tribute'; y 0.645, 0.461 y 0.526 flores por corona respectivamente en la variedad 'Tristar'. Sin embargo, la diferencia entre RCP e ICP no fueron significativos al control en la variedad 'Tribute' (Figura 7).

## CONCLUSION

Bencilaminopurina (BA) aumenta el desarrollo de coronas en las variedades 'Tristar' y 'Tribute' al aplicarse al momento de la siembra. Este desarrollo puede aumentar la florecida en la próxima cosecha y, por ende, su rendimiento; aunque este aumento en el desarrollo de coronas no es significativo en comparación al control.

Acido giberélico (GA3) y Promalín (PRO) promovieron un desarrollo de estolones en serie superior a los demás RCP e ICP cuando las plantas se encontraban en una edad fisiológica temprana (#) días luego de3 la siembra). Aparentemente el efecto de PRO es causado por su contenido de GA3 ya que aplicaciones solo de BA no causaron este efecto. Se concluye que GA3 podría promover la división y alargamiento celular en la fresa. GA3 aumentó el número de flores y frutas por corona en la fresa cuando se aplicó durante el tiempo 1; por tal razón, es importante la edad fisiológica y época del año en que se siembren y aplique los tratamientos.

Los ICP no promovieron el desarrollo de estolones ni corona. Cycocel (CCC) y Alar promovieron el desarrollo de flores en la variedad 'Tribute' cuando las aplicaciones se realizaron 30 días luego de la siembra. Ambos ICP afectaron la florecida más que el desarrollo vegetativo, posiblemente inhibiendo la síntesis de GA.

Este estudio demuestra que Puerto Rico tiene las condiciones ambientes necesarias para el cultivo de fresa. Pero es necesario estudiar
<figure><img src="image_63.png" /><figcaption>Figura 1.</figcaption></figure>

Efecto de ácido giberélico (GA3), bencilaminopurina (BA) y Pro-
malín (PRO) en el desarrollo de coronas en la fresa (*Fragaria x
ananassa*) variedades 'tristar' (Ts) y 'Tribute' (Tb).

<figure><img src="image_64.png" /><figcaption>Figura 2.</figcaption></figure>

Efecto de ácido giberélico (GA3), bencilaminopurina (BA) y Pro-
malín (PRO) en el desarrollo de estolones en serie por coronas en
la fresa (*Fragaria x ananassa*) variedades 'tristar' (Ts) y 'Tribute'
(Tb).
<figure><img src="image_65.png" /><figcaption>Figura 3.</figcaption></figure>

Efecto de ácido giberélico (GA3), bencilaminopurina (BA) y Promalín (PRO) en el alargamiento del peciolo en la fresa (*Fragaria x ananassa*) variedades 'tristar' (Ts) y 'Tribute' (Tb).

<figure><img src="image_66.png" /><figcaption>Figura 4.</figcaption></figure>

Efecto en el tiempo (T1 y T2) de aplicación de ácido giberélico (GA3), bencilaminopurina (BA) y Promalín (PRO) en el desarrollo de flores por coronas en la fresa (*Fragaria x ananassa*) variedades 'tristar' (Ts) y 'Tribute' (Tb).
<figure><img src="image_67.png" /><figcaption>Figura 5.</figcaption></figure>

Efecto de la aplicación de ácido giberélico (GA3), ácido naftalenoacético (NAA), Cycocel (CCC), anímidoI y Alar en el desarrollo de estolones en serie por corona en la fresa (*Fragaria x ananassa*) variedades 'tristar' (Ts) y 'Tribute' (Tb).

<figure><img src="image_68.png" /><figcaption>Figura 6.</figcaption></figure>

Efecto de la aplicación de diferentes concentraciones de ácido giberélico (GA3) en el alargamiento del pecio en la fresa (*Fragaria x ananassa*) variedades 'tristar' (Ts) y 'Tribute' (Tb).
<figure><img src="image_69.png" /><figcaption>Figura 7.</figcaption></figure>

Efecto en la florecida de la fresa (Fragaria x ananassa) variedades 'tristar' (Ts) y 'Tribute' (Tb) debido a las aplicaciones de ácido giberélico (GA3), ácido naftalenoacético (NAA), Cycocel (CCC), ancimidol y Alar.

más a fondo los requerimientos que este cultivo exige bajo nuestras
condiciones.

Bibliografía

Archbold, D. D. y Strang, J. G. (1986). Effects of BA on growth and yield of 'Redchief' strawberry. Hortscience 21(6):1377-1379.

Barrit, B. H. (1974). The effect of gibberellic acid, blossom removal and planting date on strawberry runner plant production. Hortscience 9(1).:25-27.
Braun, J. W. y Kender, W. J. 1985). Correlation bud inhibition and grown habit of the strawberry as influenced by application of gibberellic acid, cytokinin, and chilling during short daylength. J. Amer. Soc. Hort. Sci. 110(1).:28-34.

Darrow, G. M. (1936). Interrelation of temperature and photoperiodism in the production of fruit-buds and runners in the strawberry. Proc. Amer. Soc. Hort. Sci. 34:360-363.

Dennis, F. G. y Bennett, H. O. (1969). Effects of gibberellic acid and deflowering upon runner and inflorescence development in an ever-bearing strawberry. J. Amer. Soc. Hort. Sci. 94:534-537.

Guttridge, C. G. y Anderson, H. M. (1973). The relationship between plant size and fruitfulness in strawberry in Scotland. Hort. Res. 13(283):125-135.

Lal, S. D. y Seth, J. N. (1980). Correlation studies in strawberry (*Fragaria x ananassa* Duch.). The Indian Journal of Horticulture. 37(4).:371-375.

Moore, J. N. y Scott, D. H. (1965). Effects of gibberellic acid and blossom removal on runner production of strawberry varieties. Amer. Soc. Hort. Sci. 87:240-243.

Moore, T. C. (1989). Biochemistry and Physiology of Plant Hormone. Capitulos 2, 3 y 4. Sringer-Verlag New York Inc.

Sachs, M. ; Izsak, E. y Geisenberg, C. (1972). Effect of chlormequat and SADH on runner developments and fruiting behavior of summer-planted strawberry. Hortscience 7(4):384-386.

Sharma, V. P. and Singh, R. (1980). Bud-differentiation in 'Pusa Early Dwarf' strawberry. The Indian Journal of Horticulture. 37(1):45-47.

Singh, J. P. y Radhawa, G. S. (1959). Effect of gibberellic acid and para-chlorophenoxiacetic acid on growth and fruitfulness in strawberry. The Indian Journal of Horticulture. 16(1):14-17.
Singh, T. ; Melendez, P. y Torres, A. (1964). Experiments on
strawberry-growing in the central western mountainous region of
Puerto Rico. Journal of Agricultural of University of Puerto Rico.
XLVIII(4).:337-351.

Waithaka, K. ; Struckmeyer, B. E. y Dana, M. N. (1978). Growth substances and growth of strawberry stolons and leaves. J. Amer. Soc. Hort. Sci. 103(40).:480-482.

Waithaka, K. ; Hildebrandt, A. C. y Dana, M. N. (1980). Hormonal control of strawberry axillary bud development in vitro. J. Amer. Soc. Hort. Sci. 105(3).:428-430.

Williams, H. (1975). Genotype-environment interactions in strawberry cultivars. Hort. Res. 14(283).:81-88.
# EFFECTS OF PIGEONPEA HEDGEROWS ON SOIL WATER AND YIELD OF INTERCROPPED PEPPER UNDER DRIP IRRIGATION

M.C. Palada, S.M.A. Crossman and C.D. Collingwood
Agricultural Experiment Station
University of the Virgin Islands
St. Croix, U.S. Virgin Islands

## ABSTRACT

An alley cropping experiment was conducted to determine the effects of pigeonpea [*Cajanus cajan* (L.) *Millsp*.] hedgerows on soil water and yield of intercropped pepper (*Capsicum annuum* L.). Results showed that soil water content in hedgerow intercropping was generally higher than the control (no hedgerows) which was attributed to the combined effects of low evapotranspiration, reduced wind speed and green manure mulch. In spite of high soil water content and low evapotranspiration, total water use in hedgerow intercropping was slightly higher than the control. Low pepper plant population due to intercropping and the combined effects of partial shading by hedgerows and competition for soil water resulted in significant (P < .01) yield reduction of intercropped peppers ranging from 48 to 58%. These results indicate that alley cropping pigeonpea with vegetable crops has some limitations even with irrigation in the semi-arid tropics. However, its positive effect on microclimate and soil may lead to long term benefits for vegetable crop production in the semi-arid tropics.

**Key Words:** agroforestry, alley cropping, drip irrigation, intercropping, *Cajanus cajan*, *Capsicum annuum*.

## INTRODUCTION

Hedgerow intercropping, popularly known as alley cropping was developed as an alternative to the traditional bush-fallow farming system in the humid tropics. Basically, it is a form of agroforestry wherein food crops are grown in alleys formed by hedgerows of trees
and shrubs. The hedgerows are pruned periodically to reduce competition with crops and prunings are applied as mulch and green manures (Kang et al., 1984).

Hedgerow intercropping has been proven to benefit continuous crop production in the humid tropics by reducing soil erosion and improving soil fertility (Young, 1989). In semiarid tropics where water is a major limiting factor in crop production, the application of hedgerow intercropping has some limitations (Kessler and Breman, 1991). Studies conducted in semi-arid regions indicated that hedgerows of trees and shrubs compete for soil moisture with food crops resulting in considerable yield reduction (Singh et al., 1989; Rao et al., 1990; Ong et al., 1991). However, with proper selection of tree species and cultural management, particularly plant and hedgerow spacing, hedgerow intercropping can be beneficial to crop production in drier regions. For example, micro-climate modifications such as shading and reduced wind speed due to hedgerow may increase the efficiency with which the crop is able to convert water or light into dry matter and economic yield (Kessler and Breman, 1991; Ong et al., 1991). In areas where irrigation water is available, competition for soil moisture may also be reduced if water is applied directly to the root zone of the intercrop through drip irrigation.

The use of tree species with extensive root systems is less desirable for hedgerow intercropping in semi-arid regions. Trees with such characteristics are aggressive and capable of depleting soil moisture otherwise available for crops. Therefore, in drier areas where annual rainfall is less than 1000 mm, the use of tree or shrub species which are drought tolerant, less aggressive and less competitive would be ideal for hedgerow intercropping.

A potential leguminous shrub for alley cropping in drier areas is pigeonpea [Cajanus cajan (L.) Millsp.]. The plant is a short-lived perennial with deep tap root and a woody stem which can grow over 3 m in height (Nene et al., 1990). The deep tap root allows the plant to survive the long dry season. In the Caribbean, pigeonpea is grown as a full season crop by small-scale farmers or in mechanized large-scale production systems (Ariyanayagam, 1981). In the former system, tall, indeterminate and long duration genotypes are grown at
low plant population and usually intercropped with maize (*Zea mays*), whereas in the latter system, early grain types are grown at high plant population (Ariyanayagam, 1975). Pigeonpea is also grown in small backyard gardens usually as boundary plants or in mixed cropping with vegetables.

In spite of its popularity and wide use in the Caribbean, little research has been conducted on pigeonpea intercropping and alley cropping. Intercropping studies in India-have indicated that perennial pigeonpea behaves like medium-duration types in the first year and is less competitive than leucaena (*Leucaena leucocephala*) to annual crops in the system (Troedson et al., 1990). Multiple prunings for fodder harvest or as a green manure crop are possible, and studies on different cutting intervals and pruning heights have been conducted (Salih, 1981; Tayo, 1985; Venkataratnam and Sheldrake, 1985). Pruning experiments in Trinidad showed good survival rates and regrowth of pigeonpea (Mohoyodeen et al., 1989). In many African countries, pigeonpea is alley cropped with maize, sorghum (*Sorghum bicolor*), cowpea (*Vigna unguiculata*) and cassava (*Manihot esculenta*) (Rachie, 1983; Ali, 1990; Kang et al., 1991). In Zambia, perennial pigeonpea produced almost 5.0 t.ha⁻¹ of dry matter after 7 months of growth, and farmers are considering pigeonpea a good potential agroforestry component (Boehringer and Caldwell, 1989).

Studies on hedgerow intercropping with pigeonpea and vegetables are few. Alley cropping studies with leucaena and vegetable crops in the humid tropics indicated yield improvement and maintenance without fertilizer application (Chen et al., 1989; Palada et al., 1992). Similar research has not been conducted in the semi-arid tropics where hedgerows might play an important role in efficient use and conservation of soil water for crop production. This investigation was carried out to determine the potential of pigeonpea for alley cropping with vegetable crops and to study the influence of pigeonpea on soil water, evapotranspiration, water use and yield of intercropped pepper under drip irrigation.
## MATERIALS AND METHODS

The experiment was established at the Agricultural Experiment Station, University of the Virgin Islands in St. Croix (lat. 17°42'N and long. 64°48'W). The soil is Fredensborg loamy, fine carbonatic, isohyperthermic, shallow, typic Calciustolls (Lugo-Lopez and Rivera, 1980). The average annual rainfall is 1016 mm, but evapotranspiration exceeds rainfall 10 months of the year resulting in a negative water balance.

The experiment used a split plot in randomized block design with four replications. The mainplots were hedgerow and no hedgerow (control). The subplots were three drip irrigation levels corresponding to irrigation regimes of 20, 40, and 60 kPa. Pigeonpea hedgerows were established using 2 month old seedlings transplanted on August 8, 1991. Hedgerows were spaced 4 m apart with a plant spacing of 25 cm within the hedgerow. Three hedgerows were planted forming two 4-m wide alley mainplots. The hedgerows were allowed to grow for four months before intercropping with peppers.

Hedgerows were pruned to 50-cm stubble height using a brush cutter. Pigeonpea hedgerows were pruned on January 15 and May 17, 1992, approximately 5 and 7 months after planting. The prunings were then applied as green manure mulch in the alleys.

Forty five-day old pepper seedlings of the cultivar "Calwonder" were transplanted on January 24, 1992, at a row spacing of 100 cm and a plant spacing of 61 cm. This spacing resulted in plant population equivalent to 12,500/ha for alley crop and 18,750/ha for monoculture. The area occupied by pigeonpea hedgerows reduced pepper plant population by 33 percent. Peppers were fertilized with 200N-100P-50K kg.ha⁻¹. Nitrogen was applied in two splits, 1/3 at 17 days after transplanting and 2/3 at 52 days after the first application. All of the phosphorus and potassium was applied together with the first nitrogen application.

Drip irrigation was applied at various regimes corresponding to soil water tensions of 20, 40 and 60 kPa. The mainlines and submains consisted of 15-mm polyethelene tubes. The laterals were made of
15-mm bi-wall drip strip tube (Hardie Irrigation, California) with laser drilled orifices of 61 cm apart. One week after transplanting, tensiometers (Irrometer Co. Riverside, CA) were installed in two replications per treatment. Tensiometers were placed 10 cm from the plant and at a depth of 15 cm- Tensiometers were checked and read daily and irrigation water was applied to subplots when soil moisture tension reading exceeded the prescribed tensions of 20, 40 and 60 kPa. Water use by treatments was measured weekly through water meter readings.

Soil samples from 0-15 cm depth were taken each week except when soil was too wet after a heavy rainfall. From these samples, soil water content was determined by gravimetric (oven-drying) method. Separate samples were taken from pepper rows adjacent to hedgerows and from the middle rows of peppers. Evapotranspiration (ET) by pepper plants was estimated using the pan evaporation method integrated with crop coefficient values (Doorenbos and Pruitt, 1977). Crop coefficient values for pepper at different stages of growth were obtained from Doorenbos and Kassam (1979) as cited by Stanley and Maynard (1990). Crop coefficient was adjusted using a formula based on the fraction of the ground covered by the plants as reported by Hoare et al (1974). Ground cover was determined from weekly measurements of plant canopy width and ET was estimated weekly from February 27 to April 10, 1992. To obtain a rough estimate of wind velocity in hedgerow and control plots, wind speed was measured using a hand-held wind speed indicator (Wind Wizard, Davis Inst., Hayward, CA). The indicator was held 50 and 100 cm above ground level and measurements were made only during days when there were strong gusty winds.

For each harvest, pepper yield samples were taken from four middle rows in the hedgerow plot and five middle rows in the control plots. The sample size (9 m²) in the hedgerow plot included an area occupied by the middle pigeonpea hedgerow. Total and marketable pepper yields were determined from ten harvests over a period of eight weeks. Fruits were graded according to marketable and non-marketable size.

Pigeonpea biomass production was determined from dry weights of two prunings. Biomass included woody stem and leaves. Statistical
significance of treatment effects was determined using the analysis of variance (ANOVA) of data collected and differences among treatment means were compared using the least significant difference (LSD). Statistical analysis of data was performed using the MSTAT-C Microcomputer Program (Michigan State University, East Lansing).

# RESULTS AND DISCUSSION

## Pigeonpea Biomass Yield

Pigeonpea hedgerows reached a height of 1.95 m at the first pruning. Total dry matter produced from first pruning was $2.06 \ t.ha^{-1}$. The second pruning produced $1.71 \ t.ha^{-1}$ dry matter giving a total of $3.77 \ t.ha^{-1}$ for the two prunings. This value is one ton less than that reported by Boehringer and Caldwell (1989) in Zambia. Varietal characteristics and frequency of pruning may account for the difference in dry matter production. Fresh biomass produced from the two prunings provided a thin layer of mulch for the alley plots.

## Effect of Hedgerows on Plant Growth

Pigeonpea hedgerows suppressed growth of peppers resulting in shorter and smaller plants relative to the control (Fig. 1). The effect was pronounced in plant rows adjacent to pigeonpea hedgerows due to partial shading. Plants in the middle row were less affected and grew almost as high as the controls. During the early stage of growth, plants adjacent to the hedgerows were shaded in early morning and late afternoon resulting in slower growth rate.

The plants slowly recovered during the latter stage. Irrigation regime did not affect plant height. The data would suggest that hedgerow pruning height lower than 50 cm and more frequent harvest may be needed to minimize the competitive effect of pigeonpea and provide optimum growth for pepper.
## Soil Water Content

Soil water content in hedgerow plots was generally higher than the control (Fig. 2). It was observed that soil water content (data not shown) between pepper row and hedgerow and between pepper rows in the control (no hedgerows) was lower than in the middle rows where drip irrigation was applied. Comparing soil water content in samples taken between pepper row and hedgerow with those taken between pepper rows in control plot, it was found that soil water in hedgerow intercropping was higher than the control. This could be explained by the effect of mulch and shading. Irrigation water regime had no effect on soil water content. Mulch from prunings may have reduced soil water loss in the alleys resulting in higher values for hedgerow plots. This result is consistent with the findings of Lal (1989) who reported a higher soil moisture content in the top 0-15 cm layer in agroforestry system than in the control. Furthermore, hedgerows essentially serve as windbreaks which prevent rapid soil moisture evaporation. In this experiment wind speed (data not shown) in hedgerow plots was lower than the control.

## Evapotranspiration

Hedgerow intercropping significantly reduced evapotranspiration (ET) of pepper plants (Fig. 3). There were no significant differences in ET among irrigation regimes. Since ET is directly associated with the size of plant canopy, the high ET of plants in the control can be explained by larger plant canopy and taller plants as compared to plants in the hedgerow. This resulted in higher leaf area with greater evaporative potential. Low ET in the hedgerow plots may be considered an indirect effect of hedgerow. By reducing plant growth and canopy size due to competition, hedgerow intercropping indirectly decreased the rate of ET. Low ET in hedgerow intercropping may also be the effect of lower wind speed and turbulence as previously mentioned. Thus, the combined effects of reduced wind speed and low ET may have led to higher soil water retention in hedgerow intercropping.

The result presented here supports the report of Houerou (1980) as cited by Kessler and Breman (1992) where potential ET under a tree
canopy is considerably reduced as compared to the unprotected open field. The hedgerows provide shelter for the associated crops, thereby reducing wind speed and sunshine intensity. Connor (1983) also reported that windbreaks increase soil moisture availability due to lower evapotranspiration and improved infiltration.

## Water Use

As expected, irrigation water use varied with irrigation regime (Table 1). Water use was almost similar between hedgerow and control plots from February to April, except for the 60 kPa treatment. Water use by plants during May was the highest for the 20 and 40 kPa treatments. During this period plants were at their active reproductive stage and therefore, had a higher demand for water. Total water use for the 4-month period was highest with treatment under 20 kPa in both hedgerow and control plots. Total water use by hedgerow plots for the 40 and 60 kPa treatments were slightly higher than the control. Low ET in hedgerow intercropping should have reduced water use. It was possible that maintenance of high soil water content would require increased water use in hedgerow intercropping. Also, the roots of pigeonpea may have utilized some of the water applied through the drip system, although water was directly applied to peppers. The low soil water content in rows adjacent to the hedgerows may explain for this difference.

The above results seem to be consistent to the reports by Ong et al (1990) who studied water use by trees and crops in an agroforestry system in semi-arid region of India. In a hedgerow experiment involving pigeonpea and groundnut, they reported that total water use as measured by transpiration in the intercropping system was higher than that in pure stands of either crop. They postulated that hedgerow intercropping uses more water than monoculture which should result in higher biomass production although not necessarily in higher crop yields.
## Total and Marketable Yield of Pepper

Hedgerow intercropping significantly reduced pepper yield. As shown in Table 2, total and marketable yields of pepper in hedgerows were lower than the control. Pepper yield in hedgerow intercropping was only 47% of the control. Irrigation water regime did not influence pepper yield, but the lowest yields were obtained from treatment with the lowest rate of irrigation (60 kPa). The low yield in hedgerow intercropping can be attributed to the combined effects of two major factors: lower plant population density and crop/hedgerow competition. As mentioned earlier, under similar row spacing hedgerows replaced 25% of the plot area which reduced pepper plant population by 33%. Partial shading of plants in adjacent rows and competition for soil water depressed plant growth by reducing photosynthesis. Yields of pepper rows adjacent to hedgerows (data not shown) was only 43% of yield of the middle row and 34% of the control.

Reduced crop yields in hedgerow intercropping in the semi-arid tropics have been reported by several researchers. Rao et al (1990) reported 50 to 80% reduction in sorghum yield when alley cropped with leucaena. They attributed the yield decline to severe competition for soil moisture between hedgerows and intercrops. In hedgerow intercropping involving pigeonpea and groundnut, Ong et al (1991) reported that groundnut yields were 90% lower than in pure stands in the second year. Yield reduction was mainly due to narrow alley width (1.2 m) and low plant population. They suggested that competition for water in agroforestry systems can be reduced by modifying the spatial arrangement of trees.

Yield reduction in the experiment reported here is not primarily due to competition for soil water since irrigation water was directly applied to pepper plants and was not a major limiting factor. Reduced yield is mainly due to shading by pigeonpea resulting in suppressed growth.
## CONCLUSIONS

This study has shown some positive effects of pigeonpea hedgerows on soil water and evapotranspiration, but these effects were not reflected in increased yield of intercropped peppers under drip irrigation. Hedgerow intercropping conserved soil water through the effects of green manure mulch applied on surface soil, reduced wind speed and low evapotranspiration. These beneficial effects, however, were outweighed by the negative effect of hedgerows on yield. The reducing effect on yield was mainly attributed to the low plant population inherent to intercropping and partial shading in hedgerow intercropping.

The results of this experiment suggest that under drip irrigation, competition for soil water is minimized in hedgerow intercropping. Although total water use in hedgerow intercropping was slightly higher than sole cropping, water loss through evapotranspiration was reduced suggesting that in the long term, high soil water retention in hedgerow intercropping may eventually decrease water requirement and benefit the associated crops. The results also show that pigeonpea produced a fair amount of biomass and survived after two prunings. This indicates that it has potential as a leguminous shrub for alley cropping in a dry climate of the Virgin Islands. However, to take advantage of its potential, modification in alley arrangement, such as increasing alley width and plant population will reduce crop competition and increase benefits from this system. Additional research is needed to study the interface between crops and hedgerows in a modified system.

## REFERENCES

* Ali, M. (1990). Pigeonpea cropping systems. pp. 279-301. In: Nene, Y.L., Hall, S.D. and Sheila, V.K. (eds). The Pigeonpea. C.A.B. International, Wallingford, Oxon, U.K.

* Ariyanayagam, R.D. (1975). Status of research on pigeonpea in Trinidad. pp. 131-139 In: International Workshop on Grain Legumes. ICRISAT, Patancheru, India.
Ariyanayagam, R.D. (1981). Pigeonpea breeding in the Caribbean Program. pp. 415-426 In: Proc. of the International Workshop on Pigeonpea. Vol. 2 ICRISAT, Patancheru, India.

Boehringer, A. and Caldwell R. (1989). Cajanus cajan (L.) Millsp. as a potential agroforestry component in the Eastern Province of Zambia. Agroforestry Systems. :9 127--140

Chen, Y.S., Kang, B.T. and Caviness, F.E. (1989). Alley cropping vegetable crops with Leucaena in Southern Nigeria. Hortscience 24 839-840.

Connor, D.J. (1983). Plant stress factors and their influence on production of agroforestry plant associations. pp. 401-426 In: Huxley, P.A. (ed). Plant Research in Agroforestry. ICRAF, Nairobi, Kenya.

Doorenbos, J. and Pruitt, W.D. (1977). Guidelines for predicting crop water requirements. Irrigation and Drainage Paper No. 24 FAO, Rome, Italy.

Doorenbos, J. and Kassam, A.H. (1979). Yield response to water. Irrigation and Drainage Paper No. 33. FAO, Rome, Italy.

Hoare, E.R., Garzoli, K.V. and Blackwell, J. (1974). Plant water requirements related to trickle irrigation. pp. 323-328 In: Proceedings of the Second International Drip Irrigation Congress. San Diego, California.

Houerou, H.N. (ed). (1980). Le role des legneux fourragers dans les zones sahelienne et soudanienne. Colloque international fourragers legneux Afrique. April 2-12, 1980. Addis Ababa, Ethiopia.

Kang, B.T., Wilson, G.F. and Lawson, T.L. (1984). Alley Cropping: A stable alternative to shifting cultivation. IITA, Ibadan, Nigeria.

Kang, B.T., Versteeg, M.N., Osiname, O. and Gichuru, M.P. (1991). Agroforestry in Africa's Humid Tropics: Three success stories. Agroforestry Today 3:4-6.
Kessler, J.J. and Breman, H. (1991). The potential of agroforestry to increase primary production in the Sahelian and Sudanian zones of West Africa. *Agroforestry Systems* 13:41-62.

Lal, R. (1989). Agroforestry systems and soil surface management of a tropical alfisol. I. Soil moisture and crop yields. Agroforestry Systems 8:7-29.

Lugo-Lopez, M.A. and Rivera, L.H. (1980). Updated taxonomic classification of the soil of the U.S. Virgin Islands. J. Agric. Univ. Puerto Rico 64:131-137.

Mohoyodeen, K., Wickham, L.D. and Ferguson, T.U. (1989). The effect of different height of cutting back on the regrowth of pigeonpea (*Cajanus cajan*) cultivar UW10. Paper presented at the 25th Annual Meeting of the Caribbean Food Crops Society, Gosier, Guadeloupe July 2-8, 1989.

Nene, Y.L., Hall, S.D. and Sheila, V.K. (eds). (1990). The Pigeonpea. C.A.B. International, Wallingford, Oxon, U.K. 490 p.

Ong, C.K., Singh, R.P., Khan, A.A.H. and Osman, M. (1990). Agroforestry for the drylands: recent advances in measuring water loss through trees. Agroforestry Today 2:7-9.

Ong, C.K., Odongo, J.C.W., Marshall, F. and Black, C.R. (1991). Water use by trees and crops: five hypotheses. Agroforestry Today 3:7-10.

Palada, M.C., Kang, B.T. and Claassen, S.L. (1992). Effect of alley cropping with *Leucaena leucocephala* and fertilizer application on yield of vegetable crops. Agroforestry Systems (in press).

Rachie, K.O. (1983). Intercropping tree legumes with annual crops. pp. 103-116 In: Huxley, P.A. (ed). Plant Research and Agroforestry. ICRAF, Nairobi, Kenya.
Rao, M.R., Sharma, M.M. and Ong, C.K. (1990). A study of the potential of hedgerow intercropping in semi-arid India using a two-way systematic design. Agroforestry Systems 11:243-258.

Salih, A.F. (1981). Effect of number of cuts and time of cutting on pigeonpea forage yield. Pulse Crops Newsletter 1:34.

Singh, R.P., Ong, C.K. and Saharan, N. (1989). Above and below ground interactions in alley cropping in semiarid India. Agroforestry Systems 9:259-274.

Stanley, C.D. and Maynard, D.N. (1990). Vegetables. pp. 921-950 In: Stewart, B.A. and Nielsen, D.R. (eds). Irrigation of Agricultural Crops. Amer. Soc. of Agron. Monograph Series No. 30. Madison, WI.

Tayo, T.O. (1985). Assessment of the effect of ratooning pigeonpea (*Cajanus cajan*) in the lowland tropics. J. of Agric. Science 104:589-593.

Troedson, R.J., Wallis, E.S. and Singh, L. (1990). Pigeonpea: Adaptation. pp. 159-178 In: Nene, et al (eds). The Pigeonpea. C.A.B. International, Wallingford, Oxon, U.K.

Venkataratnam, N. and Sheldrake, A.R. (1985). Second harvest yields of medium duration pigeonpea (*Cajanus cajan*) in peninsular India. Field Crops Research 10:323-332.

Young, A. (1989). Agroforestry for Soil Conservation. C.A.B. International. Wallingford, Oxon, U.K. 276 p.
<table><caption>Table 1. Total monthly irrigation water use (liters/plant) of peppers in hedgerow intercropping and monoculture plots, 1992.</caption><thead><tr><th>Treatment</th><th>Irrigation regime (kPa)</th><th>Feb</th><th>Mar</th><th>Apr</th><th>May</th><th>Total</th></tr></thead><tbody><tr><td rowspan="4">Hedgerow</td><td>20</td><td>5.99</td><td>6.31</td><td>5.99</td><td>16.72</td><td>35.01</td></tr><tr><td>40</td><td>5.36</td><td>6.31</td><td>5.99</td><td>11.36</td><td>29.02</td></tr><tr><td>60</td><td>5.04</td><td>5.36</td><td>1.89</td><td>4.42</td><td>16.71</td></tr><tr><td>Mean</td><td>5.46</td><td>5.99</td><td>4.62</td><td>10.83</td><td>30.25</td></tr><tr><td rowspan="4">No Hedgerow</td><td>20</td><td>7.57</td><td>5.47</td><td>6.73</td><td>17.03</td><td>36.80</td></tr><tr><td>40</td><td>5.46</td><td>4.84</td><td>5.26</td><td>10.09</td><td>26.46</td></tr><tr><td>60</td><td>4.84</td><td>3.79</td><td>1.26</td><td>4.00</td><td>13.89</td></tr><tr><td>Mean</td><td>5.96</td><td>4.70</td><td>4.42</td><td>10.37</td><td>25.71</td></tr></tbody></table>

<table><caption>Table 2. Total and marketable yield (t.ha⁻¹) of peppers in hedgerow intercropping and monoculture, 1992.</caption><thead><tr><th>Treatment</th><th>Irrigation regime (kPa)</th><th>Total yield</th><th>Marketable yield</th><th>Water Use efficiency*</th></tr></thead><tbody><tr><td rowspan="4">Hedgerow</td><td>20</td><td>12.2</td><td>10.0</td><td>27.9</td></tr><tr><td>40</td><td>12.4</td><td>10.2</td><td>34.2</td></tr><tr><td>60</td><td>9.7</td><td>7.9</td><td>46.4</td></tr><tr><td>Mean</td><td>11.4</td><td>9.4</td><td>36.2</td></tr><tr><td rowspan="4">No Hedgerow</td><td>20</td><td>25.7</td><td>22.5</td><td>37.2</td></tr><tr><td>40</td><td>23.5</td><td>19.8</td><td>47.4</td></tr><tr><td>60</td><td>23.5</td><td>18.7</td><td>90.2</td></tr><tr><td>Mean</td><td>24.2</td><td>20.3</td><td>58.3</td></tr></tbody></table>

<footnote>*Kilograms fruits per cu.m. irrigation water applied based on total yield.</footnote>

<footnote>LSD (P=0.05) for comparing means (total yield) = 4.29</footnote>

<footnote>LSD (P=0.05) for comparing means (marketable yield) = 4.76</footnote>
<figure><img src="image_70.png" /><figcaption>Fig. 1. Height of pepper plants as affected by hedgerow intercropping. Row 1 = adjacent to hedgerow; Row 2 = middle row; Row 3 = control (no hedgerow).</figcaption></figure>

<figure><img src="image_71.png" /><figcaption>Fig. 2. Soil water content as affected by hedgerow intercropping.</figcaption></figure>
<figure><img src="image_72.png" /><figcaption>Fig. 3. Estimated evapotranspiration of pepper plants in hedgerow intercropping and monoculture plots.</figcaption></figure>
YIELD EVALUATION OF SWEET POTATO
CULTIVARS IN THE U.S. VIRGIN ISLANDS

S.M.A. Crossman, M.C. Palada and C.D. Collingwood
Agricultural Experiment Station
University of the Virgin Islands
St. Croix, U.S. Virgin Islands

ABSTRACT

Several sweet potato (Ipomoea batatas (L.) Lam) cultivars were field planted in a series of germplasm evaluation trials in the U.S. Virgin Islands. The objective of these trials was to identify and select suitable cultivars for local production based upon yield, sweet potato weevil (SPW) tolerance, growth-vigor and culinary qualities. Cultivars evaluated were obtained from the USDA-Tropical Agriculture Research Station (TARS) in Mayaguez, Puerto Rico; St. Kitts; South Florida and local farmers in St. Croix. There was a tendency for high-yielding cultivars to have a higher percentage of storage roots infested by SPW. In Experiment 1, Miguela and Toquesita produced the highest total yields, while Toquesita had the highest marketable yield. Seventy nine percent of the storage roots produced by Miguela were damaged by SPW. Colorette, Perla, Agata and Amarista produced the highest total yield in Experiment 2. Colorette also produced the highest (P<0.05) quantity of marketable storage roots. Agata and Amarista suffered high levels of SPW damage. In Experiment 3, Twelve Prime produced the highest total (P<0.05), and marketable yields. Trompo Negro also produced a relatively good marketable yield. Of the cultivars evaluated in Experiment 4, Viola, Tapato and Sunny were the best yielding in terms of total storage roots (19.5, 16.4 and 14.3 ton/ha, respectively) and marketable storage roots (16.2, 14.2 and 13.1 ton/ha, respectively). Picadito produced the largest (P<0.05) storage roots, weighing an average of 438 g. In Experiment 5, Perla, Viola, Tapato and Sunny had the highest yields of sweet potato storage roots, while SKB-4, CS-2 and SKB-2 had the highest foliage yield. Tapato produced the largest sweet potatoes (438

<footnote>Paper presented at the 28th Annual Meeting of the Caribbean Food Crops Society, August 9-15, 1992, Santo Domingo, Dominican Republic.</footnote>
g). Sweet potato weevil damage ranged from 0.4 to 2.0 ton/ha. Trompo Negro and Black Rock had the lowest yields and smallest storage roots. Despite their relatively low sugar content, cultivars from TARS (Viola, Tapato and Sunny) had the best culinary qualities as rated by a consumer panel. The results of these evaluations seem to indicate that cultivars from TARS are superior to local cultivars and are better for sweet potato production in the Virgin Islands.

Sweet potato (*Ipomoea batatas* (L.) Lam) ranks seventh in the world among all food crops (FAO, 1984). Sweet potato is one of the world's highest yielding crops with a total food production and food value per unit area exceeding that of rice, while requiring relatively low fertilizer inputs (Selleck, 1982).

Compared to other root/tuber crops, sweet potato has nutritional advantages. Sweet potato roots have higher dry matter content than potato. Sweet potato ranks high in energy, carbohydrates, vitamin A (especially orange fleshed cultivars), vitamin C, calcium and iron. The storage roots of sweet potato are also a good source of dietary fiber (Hill, et al., 1984).

Sweet potato is adapted to the tropics, can be produced throughout the year and is readily propagated from its abundant foliage. It tolerates infertile soils and other tropical stresses and can yield as well as any root or tuber crop (Martin and Rhodes, 1983). The crop is also grown in temperate zones.

Sweet potato adapts well to both low and high input agricultural systems. Optimum to high yields are produced in areas with high levels of inputs and technology, such as the USA and Japan, as well as in many lesser developed tropical countries that use labor-intensive, low cost technology systems primarily for subsistence farmers (Janson and Raman, 1991; Martin and Jones, 1986). Sweet potato can be grown on large acreages or small holdings. The crop is considered relatively drought-resistant but can be grown with applied irrigation (Hill, 1984).

In terms of acreage and production sweet potato is the second most important crop in the Caribbean after cassava (CIAT, 1986). Sweet
potato is an important and significant crop for farmers in the Virgin Islands where it is the most popular root crop. In the Virgin Islands, sweet potato is grown primarily for human consumption of the edible storage roots.

Many cultivars of sweet potato are available in the Virgin Islands from local farmers, neighboring Caribbean nations, breeding programs in the USA, and the USDA-Tropical Agricultural Research Station (TARS) in Puerto Rico. Yields and consumer preferences are variable. It is therefore important to conduct continued germplasm evaluation studies.

The objectives of these trials were to identify locally adapted, consumer acceptable cultivars which produce high marketable yields, are easy to propagate, have good growth vigor, compete well with weeds and exhibit some degree of sweet potato weevil resistance/tolerance.

## MATERIALS AND METHODS

Several sweet potato germplasm evaluations studies were conducted at the University of the Virgin Islands Agricultural Experiment Station, St. Croix. The soil is a Fredensborg clay loam (pH 7.8 - 8.4). This series consists of well drained soils formed over limestone or marl (Rivera et al., 1970). The trials involved cultivars obtained from USDA-TARS, others included were as follows:- from local farmers (Tano, Black Rock, Twelve Prime, Eda, CS-2 and Mc), St. Kitts (SKB-2 and SKB-4), and South Florida (Picadito).

All plots were established with terminal vine cuttings, 0.3 - 0.4 m long. Plot sizes were 3 m x 3.7 m and consisted of 3 rows spaced 1 m apart. Plants were spaced 0.3 m within rows. Micro-irrigation was applied for crop establishment and to prevent moisture stress, using Drip Strip Plus (Hardie Irrigation, El Cajon, CA.) tubing.

The experimental design was a randomized complete block with four replications. At harvest 10 plants from the center row of each plot were harvested. The foliage was cut at ground level and removed. Storage roots were then dug out of the soil, collected and sorted based upon size and SPW damage. Statistical analysis of data was performed
using SAS General Linear Models procedure (SAS Institute, Cary, NC).

Experiments 1 to 3 each consisted of 10 cultivars and were harvested at 120 days after planting (DAP). At harvest the weight of all storage roots of marketable size was recorded as total yield. Sweet potato weevil infested yield was then determined and recorded as a percentage of the total yield (% SPW damage). Uninfested roots were recorded as marketable yield.

Experiment 4 evaluated seven cultivars and was harvested at 120 DAP. In addition to total and marketable yields data was also collected for mean storage root size and yield per plant. Consumer preference was determined by presenting boiled slices of each cultivar to a panel. The slices were assessed for color, appearance, softness, mouthfeel, sweetness, fiber and flavor.

Experiment 5 evaluated nine cultivars including the highest yielding cultivars from experiment 4. This trial was harvested at 150 DAP. Observations made were ease of propagation, plant vigor and ability to smother weeds. Plant foliage was harvested by cutting the main stem at ground level. Total foliage fresh weight was recorded and sub-samples were oven dried at 70° C to a constant weight, for dry matter determination. All storage roots were weighed and recorded as total yield. Storage roots were then separated into marketable and non-marketable categories. Marketable storage roots were then examined for SPW damage. The damaged storage roots were weighed and recorded. Data were collected for mean storage root size and yield per plant. After harvest, sub-samples of storage roots were peeled, sliced and dried at 70° C to a constant weight, for dry matter determination.

## RESULTS AND DISCUSSION

Overall, high-yielding cultivars tended to have a higher percentage of storage roots infested by SPW. Yields were comparatively low from the cultivars evaluated in Experiment 1. Miguela (9.4 ton/ha) and Toquesita (9.0 ton/ha) produced total yields which were significantly higher ($P < 0.05$) than Tano, Limonette, Tapato Fine and Sabino Red
(Table 1). The marketable yield of 4.8 ton/ha from Toquesita was higher ($P<0.05$) than the yield from Tano, Limonette and Sabino Red, even though Toquesita had 49% SPW damage. Whity Thany and Vida had marketable yields of 3.4 and 3.8 ton/ha, respectively. Miguela with a 79% SPW damage had a marketable yield of only 2.0 ton/ha. The high total yield from Miguela is consistent with traditionally high yields produced by this cultivar in Puerto Rico (Badillo-Feliciano, et al., 1976a).

Total yields from cultivars in Experiment 2 ranged from 5.2 to 21.2 ton/ha, and were much higher than from Experiment 1. Colorette produced a total yield of 21.2 ton/ha which was significantly higher ($P<0.05$) than all other cultivars except Perla, Agata and Amarista (Table 2). Colorette also produced a significantly higher quantity of marketable storage roots (9.9 ton/ha) than the other cultivars. Perla (6.8 ton/ha) and EAS-11 (5.2 ton/ha) had the next highest marketable yields. Agata and Amarista which had high total yields also had high SPW damage (79 and 74%, respectively) resulting in low marketable yields. In this experiment, Colorette was clearly the superior cultivar in terms of yield. Viola, a cultivar which has a good consumer acceptance, produced 5.3 ton/ha total yield and 4.0 ton/ha marketable yield, with a 27% SPW damage.

In Experiment 3, Twelve Prime had a significantly higher ($P<0.05$) total yield than all other cultivars tested (Table 3). Yields of marketable roots from this cultivar and Trompo Negro were the highest ($P<0.05$). Mont Blanc produced a total yield of 7.4 ton/ha which was superior ($P<0.05$) to most of the remaining cultivars. However, Mont Blanc, had only 1.7 ton/ha marketable yield due to 80% SPW damage.

Trompo Negro, despite its relatively good production of storage roots, had only 7% SPW damage resulting in a marketable yield of 5.3 ton/ha. Black Rock, a popular local cultivar for both farmers and consumers, produced low yields and had a relatively high level of SPW damage (51%).

Cultivars in Experiment 4 had negligible SPW damage. This was not necessarily due to weevil resistance/tolerance, but probably escape.
The plot was located in an area where sweet potato had not been established for a number of years. Total and marketable yields were generally good, due to the low incidence of SPW. Viola, Tapato and Sunny were the best yielding cultivars in terms of total (19.5, 16.4 and 14.3 ton/ha, respectively) and marketable (16.2, 14.2 and 13.1 ton/ha, respectively) storage roots produced (Table 4). These yields were higher (P<0.05) than the yields of local cultivars Mc and Three Months. Cultivar Picadito produced the largest (P<0.05) marketable storage roots, weighing an average of 438 g/root. Viola and Eda produced significantly more marketable storage roots per plant than Three Months. A consumer preference panel rated Viola, Tapato and Sunny as having good culinary qualities, despite their relatively low sugar content. These three cultivars were bred to produce in heavy soils in Puerto Rico (Martin, 1987).

In Experiment 5 cultivars SKB-4, CS-2 and SKB-2 each produced large quantities of fresh foliage (34.3, 28.1 and 27.2 ton/ha, respectively). The fresh and dry matter yields of foliage from these cultivars were significantly higher (P<0.05) than from the other cultivars (Table 5). The foliage of Perla had the highest percent dry matter even though this cultivar produced the least foliage. Foliage yield was directly related to plant growth vigor and the ability of the cultivars to smother weeds. Vigorous vine growth significantly reduces the number of field weedings. Sweet potato foliage can be consumed as a leaf vegetable and fed to animals besides being used as planting material.

Cultivars from USDA-TARS (Puerto Rico), had the highest total and marketable yield (Table 6). This pattern is similar to the yield obtained in Experiment 4 (Table 4). Perla (28.6 ton/ha) and Viola (26.8 ton/ha) had a higher (P<0.05) total yield than the remaining cultivars except Tapato and Sunny (Table 6). Perla, Viola and Tapato produced more (P<0.05) marketable roots than all other cultivars except Sunny. Perla, a nonsweet type cultivar was the highest yielding. This cultivar has also produced high yields of 27 - 42.1 ton/ha in trials in Puerto Rico (Badillo-Feliciano, et al., 1976b). Trompo Negro and Black Rock had the lowest total and marketable yields. The highest yielding cultivars each had 2.0 ton/ha damaged by sweet potato weevil, with the exception of Tapato which had only 0.4 ton/ha, SPW
damage. Tapato sweet potatoes with an average weight of 446 g/root, were larger ($P<0.05$) than all other cultivars tested. In Puerto Rico this cultivar produced such large roots that it was considered useful for industrial purposes (Martin, 1987). Black Rock and Trompo Negro produced the smallest sweet potatoes.

Trompo Negro and Black Rock produced less ($P<0.05$) fresh and dry biomass than the other cultivars (Table 7). The biomass produced by SKB-4, SKB-2, Viola and CS-2 was over 40 ton/ha fresh and 11 ton/ha dry, twice the amount produced for each parameter by the lowest-yielding cultivars (Trompo Negro and Black Rock).

Perla, Tapato and Sunny produces thin vines which make propagation, handling and crop establishment a little more tedious than for the other cultivars. These cultivars however, along with Viola, which produced a similar quantity of foliage, gave the highest root yields. An inverse relationship between foliage and storage root production is therefore apparent. Sajjapongse and Roan (1982) reported this relationship whereby excessive top growth may result in low root yield. There was a tendency for low yielding cultivars to have a higher percentage of dry matter in their storage roots, compared to the high yielding cultivars.

These trials suggest that the USDA-TARS cultivars are well adapted for sweet potato production in the Virgin Islands in terms of yield and SPW tolerance.

This indicates the possibility of improving the yield of sweet potatoes in the Virgin Islands by utilizing introduced germplasm. The local cultivars tended to produce low yields compared to the yields from the introduced cultivars. A similar finding was reported by Huett (1976) in Australia, where cultivars from the USA yielded 3 to 4 times as much storage roots as the local commercial cultivar.

## REFERENCES

Badillo-Feliciano, J., Morales-Munoz, A. and Sierra, C. (1976 a). Performance of White-Fleshed Sweetpotato Cultivars at Two Locations in Puerto Rico. J. of Agric. of the Univ. Puerto Rico. 60(1):1-8.
Badillo-Feliciano, J., Morales-Munoz, A. and Sierra, C. (1976 b). Performance of Yellow-Fleshed Sweetpotato Cultivars at Two Locations in Puerto Rico. J. of Agric. Univ. P.R. 60(2).:154-162.

CIAT. (1986). Root Crops Production and Research in the Caribbean: Proceedings of a Regional Workshop held in Guadeloupe, 9-10 July, 1985. Cali, Colombia. 236p.

Hill, W.A. (1984). Sweet Potatoes. Chapter 20. In. Detecting Mineral Nutrient Deficiencies that Affect Production of Crop Plants in Temperate and Tropical Regions. D. L.

Plunkett and H. Sprague (Eds). Westview Press, Boulder, CO.

Hill, W.A., Loretan, P.A. and Bonsi, C.K. (1984). The Sweet Potato for Space Missions - Controlled Environmental Life Support Systems. George Washington Carver Agric. Expt. Sta. Monogram # 1. Tuskegee Univ.

Huett, D.O. (1976). Evaluation of Yield, Variability and Quality of Sweet Potato Cultivars in Sub-Tropical Australia. Expl. Agric. 12:9-16.

Jansson, R.K. and Raman, K.V. (1991). Sweet Potato Pest Management - A global Perspective. Westview Press Inc., Boulder, CO. 458p.

Martin, F.W. (1987). Breeding Sweet Potatoes Resistant to Stress: Techniques and Results. In: Exploration, Maintainance, and Utilization of Sweet Potato Genetics Resources. Report of the First Sweet Potato Planning Conference (CIP).

Martin, F.W. and Rhodes, A.M. (1983). Correlations among Characteristics of Sweet Potato Roots, and Intraspecific Grouping. Euphytica 32:453-463.

Martin, F.W. and Jones, A. (1986). Breeding Sweet Potatoes. Plant Breeding Reviews. Vol. 4:313-345. AVI Publishing Co.
Rivera, L.H., Frederick, W.D., Farris, C., Jensen, E.H., Davis, L., Palmer, C.D., Jackson, L.F. and McKinie, W.E. (1970). Soil Survey of the Virgin Islands of the United States, USDA Soil Conservation Service. 78p.

Sajjapongse, A. and Roan, Y.C. (1982). Physical Factors Affecting Root Yield of Sweet Potato (Ipomoea batatas (L) Lam). In: Sweet Potato. Proc. First Int. Symp. AVRDC, Taiwan.

SAS Institute Inc., (1988). SAS/STAT User's Guide, Release 6.03 Edition. SAS Institute Inc., Cary, NC.

Selleck, G.W. (1982). Symposium Overview. In: Sweet potato. R.L. Villareal and T.D. Griggs (Eds). Proc. First Intl. Symp. AVRDC, Taiwan.
<table><caption>Table 1. Yield and storage root damage by SPW, of 10 sweet potato cultivars (Experiment 1).<sup>Z</sup></caption><thead><tr><th>Cultivar</th><th>Total yield (ton/ha).</th><th>Marketable yield (ton/ha).</th><th>SPW damage (%)</th></tr></thead><tbody><tr><td>Miguela</td><td>9.4 a</td><td>2.0 abc</td><td>79 ab</td></tr><tr><td>Toquesita</td><td>9.0 a</td><td>4.8 a</td><td>49 bc</td></tr><tr><td>Squish</td><td>5.7 ab</td><td>2.6 abc</td><td>51 bc</td></tr><tr><td>Whity Thany</td><td>5.4 ab</td><td>3.4 abc</td><td>38 cd</td></tr><tr><td>Vida</td><td>4.7 ab</td><td>3.8 ab</td><td>23 cd</td></tr><tr><td>EAS-12</td><td>4.2 ab</td><td>2.4 abc</td><td>42 cd</td></tr><tr><td>Tapato Fine</td><td>1.9 b</td><td>1.8 abc</td><td>4 d</td></tr><tr><td>Tano</td><td>1.3 b</td><td>1.1 bc</td><td>10 d</td></tr><tr><td>Limonette</td><td>0.9 b</td><td>0.9 bc</td><td>5 d</td></tr><tr><td>Sabino Red</td><td>0.3 b</td><td>0.04 c</td><td>88 a</td></tr></tbody></table>

<sup>Z</sup> Mean separation within columns by Duncan's multiple range test, P = 0.05.

<table><caption>Table 2. Yield and storage root damage by SPW, of 10 sweet potato cultivars (Experiment 2).<sup>Z</sup></caption><thead><tr><th>Cultivar</th><th>Total yield (ton/ha).</th><th>Marketable yield (ton/ha).</th><th>SPW damage (%)</th></tr></thead><tbody><tr><td>Colorette</td><td>21.2 a</td><td>9.9 a</td><td>47 ab</td></tr><tr><td>Perla</td><td>12.6 ab</td><td>6.8 b</td><td>44 ab</td></tr><tr><td>Agata</td><td>12.2 ab</td><td>3.4 c</td><td>79 a</td></tr><tr><td>Amarista</td><td>11.4 ab</td><td>3.0 c</td><td>74 a</td></tr><tr><td>EAS-II</td><td>8.0 b</td><td>5.2 b c</td><td>36 b</td></tr><tr><td>Suabor 2</td><td>7.1 b</td><td>4.7 b c</td><td>27 b</td></tr><tr><td>Suabor</td><td>6.2 b</td><td>3.6 b c</td><td>43 ab</td></tr><tr><td>Dune</td><td>5.8 b</td><td>4.2 b c</td><td>32 b</td></tr><tr><td>Viola</td><td>5.3 b</td><td>4.0 b c</td><td>27 b</td></tr><tr><td>Bonaro</td><td>5.2 b</td><td>3.0 c</td><td>46 ab</td></tr></tbody></table>

<sup>Z</sup> Mean separation within columns by Duncan's multiple range test, P = 0.05.
<table><caption>Table 3. Yield and storage root damage by SPW, of 9 sweet potato cultivars (Experiment 3).<sup>Z</sup></caption><thead><tr><th>Cultivar</th><th>Total yield (ton/ha).</th><th>Marketable yield (ton/ha).</th><th>SPW damage (%).</th></tr></thead><tbody><tr><td>Twelve Prime</td><td>16.6 a</td><td>7.1 a</td><td>56 ab</td></tr><tr><td>Mont Blanc</td><td>7.4 b</td><td>1.7 b</td><td>80 a</td></tr><tr><td>Trompo Negro</td><td>6.0 bc</td><td>5.3 a</td><td>7 b</td></tr><tr><td>EAS-15</td><td>3.7 cd</td><td>2.2 b</td><td>50 ab</td></tr><tr><td>EAS-13</td><td>3.6 cd</td><td>2.6 b</td><td>38 ab</td></tr><tr><td>EAS-10</td><td>3.5 cd</td><td>1.3 b</td><td>72 a</td></tr><tr><td>Black Rock</td><td>3.2 cd</td><td>1.8 b</td><td>51 ab</td></tr><tr><td>Ninety-Nine</td><td>1.8 d</td><td>0.8 b</td><td>80 a</td></tr><tr><td>St. Georges</td><td>0.6 d</td><td>0.4 b</td><td>11 b</td></tr><tr><td>Margarita</td><td>0.2 d</td><td>0.1 b</td><td>33 ab</td></tr></tbody></table>

<sup>Z</sup> Mean separation within columns by Duncan's multiple range test, P = 0.05.

<table><caption>Table 4. Storage roots yield and size of 7 sweet potato cultivars (Experiment 4).<sup>Z</sup></caption><thead><tr><th>Cultivar</th><th>Total yield (ton/ha).</th><th>Marketable yield (ton/ha).</th><th>Root size</th><th>Roots/plant (g).</th></tr></thead><tbody><tr><td>Viola</td><td>19.5 a</td><td>16.2 a</td><td>266 bc</td><td>1.8 a</td></tr><tr><td>Tapato</td><td>16.4 a</td><td>14.2 a</td><td>275 bc</td><td>1.5 ab</td></tr><tr><td>Sunny</td><td>14.3 a</td><td>13.1 a</td><td>212 bc</td><td>1.6 ab</td></tr><tr><td>Eda</td><td>12.3 ab</td><td>10.5 ab</td><td>286 b</td><td>1.7 a</td></tr><tr><td>Picadito</td><td>12.2 ab</td><td>11.3 ab</td><td>438 a</td><td>1.2 ab</td></tr><tr><td>Mc</td><td>3.8 b</td><td>3.3 b</td><td>188 c</td><td>0.8 ab</td></tr><tr><td>Three Months</td><td>3.1 b</td><td>2.6 b</td><td>205 bc</td><td>0.6 b</td></tr></tbody></table>

<sup>Z</sup> Mean separation within columns by Duncan's multiple range test, P = 0.05.
<table><caption>Table 5. Foliage yield of 9 sweet potato cultivars (Experiment 5). Z</caption><thead><tr><th>Cultivar</th><th>Fresh Matter<br>(ton/ha).</th><th>Dry Matter<br>(%).</th><th>Dry Matter<br>(ton/ha).</th></tr></thead><tbody><tr><td>SKB-4</td><td>34.3 a</td><td>19.0 b</td><td>6.6 a</td></tr><tr><td>CS-2</td><td>28.1 a</td><td>21.1 ab</td><td>6.0 a</td></tr><tr><td>SKB-2</td><td>27.2 a</td><td>19.5 b</td><td>5.3 a</td></tr><tr><td>Sunny</td><td>16.9 b</td><td>19.3 b</td><td>3.2 b</td></tr><tr><td>Viola</td><td>14.8 b</td><td>18.8 b</td><td>2.7 b</td></tr><tr><td>Black Rock</td><td>14.4 b</td><td>20.0 ab</td><td>2.8 b</td></tr><tr><td>Tapato</td><td>13.4 b</td><td>20.0 ab</td><td>2.6 b</td></tr><tr><td>Trompo Negro</td><td>12.2 b</td><td>17.8 b</td><td>2.2 b</td></tr><tr><td>Perla</td><td>9.2 b</td><td>23.2 a</td><td>2.1 b</td></tr></tbody></table>

Z Mean separation within columns by Duncan's multiple range test, P = 0.05.

<table><caption>Table 6. Storage roots yield, size and SPW damage of 9 sweet potato cultivars (Experiment 5). Z</caption><thead><tr><th rowspan="2">Cultivar</th><th rowspan="2">TOTAL<br>Yield<br>(ton/ha).</th><th colspan="3">ROOTS OF MARKETABLE SIZE</th><th rowspan="2">Dry matter<br>(ton/ha).</th></tr><tr><th>SPW<sup>X</sup><br>(ton/ha).</th><th>Yield<br>(ton/ha).</th><th>Size<br>(g).</th></tr></thead><tbody><tr><td>Perla</td><td>28.6 a</td><td>2.0</td><td>24.5 a</td><td>306 b</td><td>7.3 a</td></tr><tr><td>Viola</td><td>26.8 a</td><td>2.0</td><td>21.9 a</td><td>238 bcd</td><td>7.3 a</td></tr><tr><td>Tapato</td><td>22.9 ab</td><td>0.4</td><td>21.4 a</td><td>446 a</td><td>6.0 ab</td></tr><tr><td>Sunny</td><td>22.8 ab</td><td>2.0</td><td>17.3 ab</td><td>260 bc</td><td>5.1 bc</td></tr><tr><td>SKB-2</td><td>18.3 b</td><td>1.6</td><td>12.9 bc</td><td>275 bc</td><td>4.2 bc</td></tr><tr><td>CS-2</td><td>15.3 bc</td><td>0.8</td><td>9.2 cd</td><td>192 cd</td><td>3.4 cd</td></tr><tr><td>SKB-4</td><td>15.0 bc</td><td>1.7</td><td>10.3 cd</td><td>213 bcd</td><td>3.8 cd</td></tr><tr><td>Trompo<br>Negro</td><td>8.1 cd</td><td>1.3</td><td>5.1 de</td><td>167 d</td><td>2.0 de</td></tr><tr><td>Black Rock</td><td>6.5 d</td><td>0.8</td><td>1.7 e</td><td>129 de</td><td>0.7 e</td></tr></tbody></table>

X SPW - Sweet potato weevil damaged storage roots of marketable size.

Z Mean separation within columns by Duncan's multiple range test, P = 0.05.
<table><caption>Table 7. Biomass production of 9 sweet potato cultivars (Experiment 5).²</caption><thead><tr><th>Cultivar</th><th>Fresh Biomass<br>(ton/ha).</th><th>Dry Biomass<br>(ton/ha).</th></tr></thead><tbody><tr><td>SKB-4</td><td>49.3 a</td><td>12.1 a</td></tr><tr><td>SKB-2</td><td>45.5 a</td><td>11.3 a</td></tr><tr><td>Viola</td><td>41.6 a</td><td>11.6 a</td></tr><tr><td>CS-2</td><td>40.9 a</td><td>11.5 a</td></tr><tr><td>Sunny</td><td>39.7 a</td><td>9.9 a</td></tr><tr><td>Perla</td><td>37.8 a</td><td>10.6 a</td></tr><tr><td>Tapato</td><td>36.3 a</td><td>9.1 a</td></tr><tr><td>Black Rock</td><td>20.9 b</td><td>5.3 b</td></tr><tr><td>Trompo Negro</td><td>20.2 b</td><td>5.3 b</td></tr></tbody></table>

² Mean separation within columns by Duncan's multiple range test, P = 0.05.
COMPARACION DE CINCO MARCOS DE SIEMBRA
DE DOS VARIEDADES DE BATATA (Ipomoea batatas
(L.) LAM), SANTIAGO, REPUBLICA DOMINICANA

Ramón Hernández*, ISA-CENDA, República Dominicana y
Alberto Beale**, Asesor de Horticultura, Ohio State
University-ISA.

Este experimento se realizó en los terrenos del Instituto Superior de Agricultura (ISA) en Santiago, desde el 9 de octubre del 1991 hasta el 9 de abril de 1992. Tuvo como objetivos evaluar cinco marcos de siembra (1.0 X 0.2 m), (1.0 X 0.3 m.), (1.0 x 0.4 m), (1.0 X 0.5 m) y (1.0 X 0.6 m) y su efecto en la producción de raíces en las dos variedades más cultivadas en la región del Cibao: Copelá y Manicera. Se utilizó un diseño de bloques al azar con cuatro repeticiones y arreglos en parcelas divididas. Aunque no hubo diferencias significativas entre los marcos de siembra, la mayor producción total se obtuvo a (1.0 X 0.2 m) con 21.2 ton/ha promedio, seguido de (1.0 x 0.3 m) y (1.0 x 0.4 m) con 20.5 ton/ha cada uno. Hubo diferencias significativas para la producción comercial entre las variedades, siendo de 17.9 ton/ha promedio para Copelá y sólo 10.4 ton/ha promedio para Manicera. Sin embargo, en la producción total no hubo diferencias significativas entre éstas, con 19.9 ton/ha y 20.9 ton/ha promedio, respectivamente. No hubo diferencias significativas en la interacción variedad por marco de siembra para la producción total. No obstante, la mayor producción la presentó la variedad Copelá a (1.0 x 0.3 m) con 23.8 ton/ha promedio y la Manicera a (1.0 x 0.2 m) con 23.0 ton/ha promedio. Bajo condiciones similares de suelo y clima de nuestro experimento, se recomienda usar cualquiera de los marcos estudiados y usar la variedad Copelá.

INTRODUCCION

La batata es un cultivo de consumo tradicional que se incluye en la
dieta básica de la mayoría de los dominicanos. Para el 1987 se

<footnote>* Ing. Agrón. Enc. Prog. Raíces y Tubérculos. ISA</footnote>

<footnote>** Asesor en Horticultura. Ohio State University-ISA</footnote>
sembraron en el país 8313 ha (133,000 tareas) con un rendimiento promedio de 6.7 ton/ha (9.2 qq/ta) siendo la producción nacional de 54,442 ton (1,199,900 qq). Estos bajos rendimientos asociados a una constante necesidad alimenticia nacional, requieren de una iniciativa para aumentar la productividad del cultivo.

En el país se cultivan un gran número de variedades de batata. Sin embargo, existen pocos estudios donde se indica la adaptabilidad de estas variedades a una región o a unas condiciones edafoclimáticas específicas. Dos de las variedades importantes en la región del Cibao son la Manicera y la Copelá.

Se utilizan en la República Dominicana varias distancias de siembra para la batata, no existe mucha información publicada sobre los mejores marcos de siembra para variedades específicas.

Se realizó el actual trabajo de investigación con los objetivos de:

1) Comparar la capacidad productiva de dos de las variedades más cultivadas en el Cibao: Copelá y Manicera.

2) Evaluar cinco marcos de siembra sobre la productividad de ambas variedades.

3) Determinar si existe alguna interacción entre las variedades y los diferentes marcos de siembra estudiados.

## Materiales y Métodos

El ensayo se realizó en los terrenos del Instituto Superior de Agricultura (ISA), Santiago, en un suelo Franco Limoso.

En la preparación del terreno se dio un corte con arado, dos rastreos y se surqueó a 1 m.

Se sembró el 9 de octubre de 1991 usándose ábanas de 30 cm de largo tratadas con Ethoprop (mocap 20 Ec) a 800 cc de P. C. por 200 litros de agua.
Las guías se colocaron a 0.2, 0.3, 0.4, 0.5 y 0.6 m entre plantas según el tratamiento.

Para el control de malezas fue necesario efectuar cuatro desyerbos manuales a los 8, 21, 35 y 48 días después de la siembra.

Se aplicaron cuatro riegos por gravedad, a la presiembra y a los 14, 56 y 74 días después de la siembra.

## Datos Climáticos Durante el Desarrollo del Experimento

<table><thead><tr><th></th><th colspan="7">Meses</th></tr><tr><th></th><th>Oct.</th><th>Nov.</th><th>Dic.</th><th>Ene.</th><th>Feb.</th><th>Mar.</th><th>Abr.</th></tr></thead><tbody><tr><th>Temp. (°C.)</th><td>26</td><td>24</td><td>22</td><td>21.6</td><td>23.0</td><td>23.6</td><td>23.7</td></tr><tr><th>Precip. (mm)</th><td>97.1</td><td>57.8</td><td>54.9</td><td>25.8</td><td>10.8</td><td>77.0</td><td>207.6</td></tr></tbody></table>

La labor de aporque se realizó a los 35 días de la siembra. No se fertilizó por encontrarse en el suelo niveles altos de materia orgánica, fósforo y potasio.

Para el control de plagas se hicieron tres aplicaciones de insecticidas, una granular al suelo usando Carbofuran (Furadan 5 g) a razón de 28 gr de PC/4m lineales a los 30 días de la siembra. Dos aplicaciones con dicrotophos (Nuvacrón 60) a razón de 5 cc de P. C. por litro de agua, a los 49 y 110 días después de la siembra, lográndose un control excelente contra las plagas del follaje.

Desde los 15 días de plantado el experimento se colocaron trampas con feromonas para atrapar piogán (Cylas sp.).

Se usó un diseño de bloques al azar con cuatro repeticiones y arreglo en parcelas divididas. Se colocaron en las parcelas grandes las variedades y en las pequeñas los diferentes marcos de siembra.

De la combinación de las variedades con 5 marcos de siembra se obtuvieron 10 tratamientos.
<table><thead><tr><th>Variedades:</th><th>Marcos de Siembra:</th></tr></thead><tbody><tr><td>Copelá</td><td></td></tr><tr><td>Manicera</td><td>1 x 0.2m = 3,145 ptas/tareas = 50,000 ptas/ha<br>1 x 0.3m = 2,097 ptas/tareas = 33,333 ptas/ha<br>1 x 0.4m = 1,573 ptas/tareas = 25,000 ptas/ha<br>1 x 0.5m = 1,258 ptas/tareas = 20,000 ptas/ha<br>1 x 0.6m = 1,048 ptas/tareas = 16,667 ptas/ha</td></tr></tbody></table>

## Resultados y Discusión

### Análisis de Varianza a la Producción Total

<table><thead><tr><th>Fte. de Variación</th><th>Fc</th><th>Fr 5%</th></tr></thead><tbody><tr><td>Total</td><td></td><td></td></tr><tr><td>Variedad</td><td>0.9 ns</td><td>10.13</td></tr><tr><td>Bloque</td><td>17.3*</td><td>9.28</td></tr><tr><td>Error (A)</td><td></td><td></td></tr><tr><td>Marco de Siembra</td><td>0.12 ns</td><td>2.78</td></tr><tr><td>Var. x Marco</td><td>2.63 ns</td><td>2.78</td></tr><tr><td>Error (B)</td><td></td><td></td></tr></tbody></table>

* = Significativo al 5%

ns = No significativo

No se encontraron diferencias significativas en cuanto a la producción total de raíces para ninguno de los factores estudiados. No obstante, la variedad Copelá resultó ser numéricamente mayor con 20.9 ton/ha en contraste con la Manicera que produjo 19.0 ton/ha.

De los marcos de siembra evaluados, los de mayor producción fueron 1 x 0.2 m, 1 x 0.3 m y 1 x 0.4 m con 21.2, 20.5 y 20.5 ton/ha respectivamente. La interacción con mayor producción numérica la obtuvo la Copelá a 1 x 0.3 m con 23.8 ton/ha en promedio. Estos resultados coinciden con los reportados por Montaldo, 1983.
## Análisis de Varianza para la Producción Comercial.

<table><thead><tr><th>Fte. de Variación</th><th>Fc</th><th>Fr 5%</th></tr></thead><tbody><tr><td>Variedad</td><td>18.0*</td><td>10.13</td></tr><tr><td>Error (A)</td><td></td><td></td></tr><tr><td>Marco de Siembra</td><td>0.2 ns</td><td>2.78</td></tr><tr><td>Var. x Marco Siembra</td><td>0.8 ns</td><td>2.78</td></tr><tr><td>Error (B)</td><td></td><td></td></tr></tbody></table>

* = Significativo

ns = No significativo

## Producción Promedio de Raices Comerciales.

<table><thead><tr><th>Variedad</th><th>Rendimiento Comercial (ton/ha)*</th></tr></thead><tbody><tr><td>Copelá</td><td>17.9</td></tr><tr><td>Manicera</td><td>10.4</td></tr></tbody></table>

* Significativo al 5%.

Para la producción comercial hubo diferencias significativas entre las variedades, resultando la variedad Copelá con un rendimiento promedio de 17.9 ton/ha frente a la Manicera con sólo 10.4 ton/ha promedio. Estos resultados coinciden con los obtenidos por Hernández 1989.

Esta diferencia de rendimiento comercial se explica por la mayor susceptibilidad de la variedad Manicera al ataque de Cylas y por la facilidad que tiene esta variedad de presentar agrietamiento de la corteza (Cracking) Folquer, 1978.

No hubo diferencias estadísticas significativas ni para el efecto de los distintos marcos de siembra, ni para la interacción variedad por marco de siembra en la producción comercial.
## Análisis de Varianza para la Producción Comercial.

<table><thead><tr><th>Fte. de Variación</th><th>Fc</th><th>Fr 5%</th></tr></thead><tbody><tr><td>Variedad</td><td>2.4 ns</td><td>10.13</td></tr><tr><td>Error (A)</td><td></td><td></td></tr><tr><td>Marco de Siembra</td><td>4*</td><td>2.78</td></tr><tr><td>Var. x Marco Siembra</td><td>2.8*</td><td>2.78</td></tr><tr><td>Error (B)</td><td></td><td></td></tr></tbody></table>

* = Significativo al 5%

ns = No significativo

## Producción Promedio de Raíces no Comerciales para Marcos de Siembra

<table><thead><tr><th>Marcos (m²)</th><th>Rendimientos ton/ha</th></tr></thead><tbody><tr><td>0.2</td><td>2.3</td></tr><tr><td>0.6</td><td>1.5</td></tr><tr><td>0.4</td><td>1.4</td></tr><tr><td>0.3</td><td>1.2</td></tr><tr><td>0.5</td><td>1.2</td></tr></tbody></table>

## Producción Promedio de Raíces no Comerciales para Variedad x Marco de Siembra

<table><thead><tr><th>Variedad</th><th>Marco (m²)</th><th>Rendimiento ton/ha</th></tr></thead><tbody><tr><td rowspan="5">Manicera</td><td>0.2</td><td>2.3</td></tr><tr><td>0.3</td><td>1.4</td></tr><tr><td>0.6</td><td>1.4</td></tr><tr><td>0.5</td><td>0.8</td></tr><tr><td>0.4</td><td>0.7</td></tr><tr><td rowspan="3">Copelá</td><td>0.2</td><td>2.2</td></tr><tr><td>0.4</td><td>2.1</td></tr><tr><td>0.5</td><td>1.5</td></tr></tbody></table>
El análisis de varianza presentó diferencias significativas entre los diferentes marcos de siembra, siendo 0.2 m² el que registró la mayor producción con 2.3 ton/ha promedio de todos los demás. Esto se explica por la mayor competencia entre las plantas que están más cerca entre sí.

La interacción también resultó significativa para la variedad Manicera. El marco que presentó mayor producción fue 0.2 m² con 2.3 ton/ha. Para la variedad Copelá el marco que más raíces no comerciales produjo fue también 0.2 m² con 2.2 ton/ha.

## Análisis de Varianza al Peso de Raíces Dañadas por Piogán (Cylas sp).

<table><thead><tr><th>Fte. de Variación</th><th>Fc</th><th>Fr 5%</th></tr></thead><tbody><tr><td>Variedad</td><td>71.1**</td><td>10.13</td></tr><tr><td>Error (A)</td><td></td><td></td></tr><tr><td>Marco de Siembra</td><td>0.3 ns</td><td>2.78</td></tr><tr><td>Var. x Marco Siembra</td><td>0.9 ns</td><td>2.78</td></tr><tr><td>Error (B)</td><td></td><td></td></tr></tbody></table>

* = Altamente Significativo

ns = No significativo

## Producción Promedio de Raíces Dañadas

<table><thead><tr><th>Variedad</th><th>Dañadas por Piogán<br>ton/ha</th></tr></thead><tbody><tr><td>Manicera</td><td>8.0</td></tr><tr><td>Copelá</td><td>1.3</td></tr></tbody></table>

CV = 53.8%

El ataque por *Cylas* resultó ser altamente significativo entre las variedades, siendo la variedad Copelá (1.3 ton/ha Prom.) menos afectadas que la Manicera (8.0 ton/ha Prom.). Esto indica que el *Cylas* tiene preferencia por la variedad Manicera cuando ambas se siembran juntas. Esto podría ser debido a que la variedad Manicera
es de pulpa más suave, de hábito de crecimiento más superficial y que posee menos látex. Estos resultados concuerdan con los reportados por Hernández 1989. No se encontró diferencia significativa en cuanto al daño realizado por el Piogán a los marcos de siembra ni a la interacción variedad por marco de siembra.

## CONCLUSIONES

Los marcos de siembra estudiados no influyeron en el rendimiento de raíces totales, comerciales ni en el daño por *Cylas*.

El potencial de producción de raíces comerciales de la variedad Copelá es superior al de la Manicera donde existen problemas con *Cylas*.

La interacción var. x marco de siembra no influyó en el rendimiento de raíces totales comerciales ni en el daño por *Cylas*.

## Literatura Citada

Folguer, F. 1978. La Batata o Camote, Estudio de la Planta y su Producción Comercial. IICA, Costa Rica.

Hernández, R. 1989. Determinación del Momento Optimo de Cosecha de Tres Variedades de Batata, CENDA, Santiago, Rep. Dom.

Montaldo, A. 1983. Cultivo de Raíces y Tubérculos Tropicales. IICA, Costa Rica. pp. 144-197.

Secretaria de Estado de Agricultura 1988. Plan Operativo 1989, Departamento de Planificación, Subsecretaría Técnica de Planificación Agropecuaria, Rep. Dom. pp. 41.
# PARASITIC PLANTS

Julius L. Heinis

Florida A&M University, Tallahassee, Florida

## ABSTRACT

Mistletoes, dodder and broomrapes are the best known parasitic higher plants. They are mainly found in Europe and northern North America. In tropical areas, quite a number of additional species are found, and the author reports on what he observed in Costa Rica, North America and Europe, and discusses species found in Australia, New Caledonia and South America.

## OBSERVATIONS

This talk is based on a 6-week stay in Costa Rica this Spring, observations in North America and Europe, as well as a literature search.

Essentially most parasitic higher plants (which excludes fungi, bacteria and viruses) predominate in the tropics. The best known parasites are mistletoe, dodder and broomrape. As we shall see, there are quite a few lesser known genera and species. They belong to several families, and are dicotyledonous angiosperm except one conifer.

The table lists the major parasites. Prominent are the mistletoes. In Europe we find *Viscum album*. This grows on several species of trees including a few fruit trees like apple and pear. It has white berries which are disseminated by birds. Experimentally seeds were germinated without the bird passage. Having green leaves, mistletoes can photosynthesize and are therefore hemiparasites.

In Costa Rica, I have seen the mistletoe (muérdago) *Phoradendron*. It grows on many different trees. Among fruit trees guavas may carry them. Other species of *Phoradendron* grow in North America. They are similar to *Viscum album* except their flowers are much larger. In Florida and Georgia, *Phoradendron* are frequently seen on pecan
trees, as well as other dicotyledonous trees. A few members of this
genus grow on conifers.

*Gaiadendron* is another Loranthaceae that grows in Costa Rica. It has pretty, large yellow flowes and grow in rainforests. Hummingbirds and insects pollinate these flowers.

*Psittacanthus* is a relative, and I have only seen specimen in a herbarium at the University of Costa Rica in San José.

Other "mistletoes" include the dwarf mistletoe (Arceuthobium) that parasitizes several coniferous timber trees in western North America. In the literature, I found that in Australia different "mistletoes" grow on *Casuarina* which we call "Australian Pines" in Florida.

Balanophoracea contains *Corynaea crassa* that is found in Costa Rica where it can parasitize palms, bamboo etc. It is not easily found.

*Rafflesia* has huge flowers and is native to Borneo and Sumatra. One or two relatives are rare in Costa Rica.

Several members of Orobanchaceae (broomrape) are parasitic on several farm crops especially of clover.

*Striga* is called witchweed and grows on sorghum and other grasses. It has been introduced to the Eastern U.S.A. from Asia.

*Cuscuta* or dodder (Kleeseide in German, Lovevine in the Bahamas) has long yellow threads and gets its nourishment from numerous shrubby and herbaceous hosts. It spreads in farm crops with impure seeds.

Strangler fig (*Ficus*) may not be considered a parasite by purists, but it certainly is detrimental to many species of tropical trees by competing for nutrient and light. Very large specimen are common in the rainforests of Costa Rica and other places.
Kudzu (*Pueraria lobata*) also is detrimental to many plants by just over-growing them. It has been introduced into the southeastern U.S.A. from Asia.

Other interesting parasites are *Myzodendron* which only grows in southern South America and called muérdagos plumosos or feathery mistletoes. Olaceae are root parasites that are found in Australia.

Most interesting is that one conifer, *Podocarpos ustus* (syn. *Parasitaxus*) has been reported as a parasite in New Caledonia.

In addition to the genera mentioned here, Kuijit, describes quite a few more in "The Biology of Parasitic Flowering Plants". I'd like to conclude in saying that just a little bit more attention should be paid to parasitic higher plants in plant pathology textbooks.

## REFERENCES

Gomez, L.D. 1991. Plantas Parasíticas (Parásitas verdaderas). In: Janzen, D. H. Historia Natural de Costa Rica. Universidad de Costa Rica, San José. 295-301.

Kujit, J. 1969. The Biology of Parasitic Flowering Plants. University of California Press. Berkeley. 246 pp.

Watkinson, A. R. and C. C. Gibson. 1988. Plant Parasitism: The Population Dynamics of Parasitic Plants and Their effects upon Plant Community Structure. In: Davy, A. J., M. J. Hutchings, A. R. Watkinson: Plant Ecology. Blackwell, Oxford. 393-411.