Crop Production Guidelines
By: Hector Valenzuela and Dwight Sato
University of Hawaii, Assistant Extension Vegetable Specialist and Extension Agent, respectively.
Now that many commercial growers and homegardeners are starting to make plans to re-establish and fix up their gardens and taro patches, it may be a good time to go over some of the recommended cultural practices for taro production developed by researchers at the University of Hawaii. Taro is a very hardy and resilient vegetable which when unwanted in vegetable fields may turn into a bothersome weed. In fact cocoyam, which is a close relative of taro, and consumed by the Latin and Caribbean population, was about the only vegetable that survived the devastating freeze that hit South Florida on the early morning of December 26, 1989. Losses for 1990 in Dade County accountable to the vegetable freeze was in the hundreds of millions of dollars. The undamaged cocoyam corms (the underground storage organ, which is actually stem tissue is called a corm) lying below the soil level, however, re-sprouted once the temperatures rose and plants which were ready for harvest were dug a few months later. Similarly in the Pacific Islands, taro, and other relatives of the aroid family are often the first crops grown in islands and atolls which have been hit by hurricanes or flooding tidal waves. The fast recovery of aroids in areas affected by hurricanes or high tides is a sign of their adaptability to flooding, and also to salty irrigation water. This resiliency despite the recurrence of natural disasters, may explain in part the spiritual symbolic value that taro represents to the Hawaiian heritage.
Taro can be cultivated under both wetland (paddy-taro) and dryland (upland) conditions. Some varieties do well under both types of culture. Important local varieties include Bun Long or table taro mostly grown in the Big Island for fresh market and making chips; Lehua Maoli for poi taro with most of the state's production concentrated in Kauai; Niue or Samoan Taro; and dasheen or araimo for Japanese taro. Dasheen varieties include Tsurunoko, Miyako, and Akado. The wetland or lo'i system, which takes advantage of taro's flood tolerance, was apparently developed early on by Hawaiians to eliminate weed competition and to lower the growing temperature of the corms (the underground storage organ which is actually an underground stem tissue).
For propagation, taro cuttings or hulis are used. The hulis are a part of the stem about 12-18 inches long attached to a 2-3 inch section of the corm. The cuttings are planted vertically with soil covering about one-third to half of the standing huli. Since hulis are difficult to obtain, commercial growers or avid gardeners need to establish their own nurseries with their favorite variety. Initial hulis can be obtained from fellow growers, and also from the Cooperative Extension Service. Several community organizations throughout the state, such as the Ho'okahe Wai, Ho'oulu 'Aina, a charitable organization in Honolulu, are also making efforts to collect old taro varieties to maintain them in cultural gardens throughout the state. Make sure that you start with disease-free propagating material by closely inspecting each cutting, washing with potable water, soaking hulis in a 10% bleach solution for 30 seconds, and by storing the hulis in a dry, cool, and well-ventilated area for 3 to 5 days before planting to allow for old wounds to heal.
In the dryland system of production hulis can be planted by hand or with a modified vegetable transplanter. Plants are spaced 18 inches apart, and rows are spaced 3-4 feet apart. Research in Hilo indicates that liming to a soil pH above 6, may result in lower incidence of corm rots, and improved plant vigor. Lime preferably after field plowing and for best results, at least a month before planting. The early liming treatment will allow for the proper soil reaction and rise in pH by the time the taro is ready to be planted. Commercial taro fields in Hawaii, are heavily fertilized compared to traditional practices in other Pacific Islands or in Africa. In high rainfall areas apply a total of 2000 lbs of 23-0-36 fertilizer per acre divided in six equal doses beginning at planting, and the rest at five monthly intervals. In addition, at pre-plant apply 2500 pounds per acre of a 0-45-0 fertilizer. Costly soil amendments such as dolomite, and hydrated lime are normally not recommended considering the economics of commercial taro production in Hawaii. Gardeners may broadcast before planting 3 pounds of a 10-20-20 fertilizer, and then sidedress 1 pound of a 16-16-16 fertilizer at two, four, and again at 6 months after planting on a 100 square foot area.
HARVEST AND POST HARVEST PRACTICES
Most taros will mature in 6 to 10 months. Corms in the garden can be dug with a shovel. Modified potato harvesters are available to dig taro under commercial conditions. Such a machine has been employed for demonstration purposes by the Cooperative Extension Service in Molokai. In commercial packing sheds of South Florida the corms are conveyed to a machine with circular brushes which removes the soil, washes the corms, selects by size and the corms are then packed with the help of hand labor. A typically-sized machine packs eighty 50-pound boxes per hour with the help of seven laborers. At this point the product may be shipped to a buyer for placement in a cold room. The recommended temperature for prolonged storage is 45-50 F with a relative humidity of 85. Luau leaves can be harvested at any time during the growth of taro. Only young taro leaves are used for luau. Corms yields will be reduced if more than 3 leaves are picked per plant.
PESTS AND DISEASES
Despite its hardiness, taro is susceptible to attack by some important pests and diseases. Slugs may damage corms creating wounds which provide entry of secondary disease organisms. Weed-free fields and hilling may help reduce slug infestations. The golden mystery snail has become a threat to taro production in Hawaii. Yield reductions caused by the golden mystery snail can reach in excess of 60% from feeding in both the foliage and the corm. Hand-picking, irrigation with saline water, and copper based pesticides are among the practices currently being tested for control of this pest Cultural practices to avoid incidence of diseases in taro include the use of disease-free propagating material, avoiding contaminated fields, eliminating diseased plants growing in the field, and increased spacing at planting to improve ventilation. Weeds may also reduce taro yields by competing for space and nutrients. To prevent yield losses from weed competition maintain taro free of weeds during the first three months after planting.
VALUE OF TARO
The value of taro production in Hawaii has increased over the past few years from a farm-gate value of $1.7 million in 1987 to $3 million in 1991. Hawaii taro farmers have an opportunity to capitalize on this trend of increased popularity of taro products by closely working with their present customers, and by establishing new markets with currently unknown buyers. Commercial growers should make careful marketing plans, and identify potential buyers even before the first huli is planted. Costs of production for taro in 1989 were estimated at $6,175 per acre with labor accounting for 49% of total costs, and machinery and equipment for about 23% of the total. Homegardeners, growing taro for family reunions, and for self-consumption can plant taro any time of the year. For homegardeners and part-time farmers taro is a low-maintenance crop that will maintain a ground cover in the field to reduce soil erosion, and will provide a bountiful harvest at 8 to 10 months after planting. Nutritionally the root crop is rich in fibre, calcium, potassium, iron, vitamin A, vitamin B1, vitamin B2, and vitamin C. The quality of the diet of indigenous people living in the Pacific Islands has generally decreased when the consumption of taro has been replaced by other sources of carbohydrates such as white bread. In Hawaii and in other regions taro also has a rich cultural and spiritual value. Traditionally it was prohibited to argue when a bowl of poi was placed on the dinner table, and the kupunas would uncover the poi bowl to end family disputes. Today, that cultural heritage is kept alive by teaching the younger generations about the old spiritual ways, and keeping a taro patch in the field or in the garden is still an easy way to stay in touch with nature.
Notice: Reference to a firm or trade does not imply endorsement over firms or products not mentioned.