Growing Taro
Patricia Chay-Prove and Roger Goebel, Department of Primary Industries and
Fisheries.
Taro (Colocasia esculenta L) is a fast growing crop that takes between 6-12 months to mature. In the Wet Tropical Coast of north Queensland maturity time is typically between 8-12 months. Although a resilient crop species, radiation, temperature and water availability will affect the total yield and the time taken to reach maturity. The information on Taro production in this note is based on field observations, local growers' experience and literature from elsewhere as little research has been conducted in Queensland.
Propagation and land preparation
Field planting can be done at any time in the Wet Tropics. The climatic conditions here do not seem to play a major role so long as irrigation is provided. Planting and therefore harvesting can occur throughout the year in response to consumer demand. However, with a defined alternation of dry and wet seasons, planting is generally done at or shortly before the beginning of the rainy season.
Fig 1. Taro grown in rows as an upland
crop
Taro is generally grown as an upland crop in north Queensland. Land preparation is similar to other crops and consists of weed removal and cultivation to get a friable soil texture. Deep ripping to improve root penetration is recommended if the soil is compacted. Mounding is recommended on the wet tropical coast of north Queensland and in areas where waterlogging or ponding may occur.
As flowering and seed production rarely occurs, taro is propagated by setts (A), which consist of the lower 30-40 cm of the leaf stalk together with the top 1-3 cm of the corm, from sucker corms (B) and full corms (C).
Fig 2. Choice of planting material. A.
Sett. B. Sucker corm. C. Full corm.
Planting holes should be larger than the size of the corm, usually 10 cm - 20 cm depending upon the size of the sett, or alternatively ridges or furrows are prepared. Flat planting is also practised. Shallow planting will result in corms developing above the ground surface and these exposed corms are more likely to be damaged by insect pests and rodents. Water soon after planting to remove air pockets.
Select healthy and vigorous medium to larger setts from the mother plant as these generally yield higher than small setts. Also, the larger setts appear to grow faster and hence give better weed control. Select setts that are clean and not discoloured or blackened and free from mould and soft spots.
Little is known about planting density or distance in north Queensland. Growers generally plant between 1-3 plants per m2, giving a planting density of around 10 000 to 45 000 plants/ha. Taro may be planted in rows or in plots. Higher planting density will produce more but corms will be smaller (anywhere from about 1 500 g down to 400 g) and average yield per plant or per hill is reduced. Spacing of approximately 90 cm x 60 cm is common, and a slightly wider spacing may be used where cloud covers are frequent and growing conditions not optimum. Very wide spacings are not recommended, as weed control may become a serious and time-consuming activity.
Irrigation
Taro is one of a few crop species that can adapt to a range of moisture regimes. Overwatering as a result of excessive rainfall is not deleterious to its growth. Supplementary irrigation, however, is essential for optimum yields since growth will be restricted and suckering and/or reduction in quality may occur if the plants are stressed during the dry season. Water can be applied by sprinkler, furrow or drip irrigation. The amounts however are not known for taro cultivation in north Queensland.
Much of the upland taro grown in Hawaii is not irrigated. The crop depends on the evenly distributed rainfall which occurs in Hawaii. It has been reported that taro will yield reasonably well as long as the annual average rainfall is around 1 500 mm and evenly distributed throughout the growing season.
Weed control
Weed control is essential in any sort of culture, and taro is no exception. Newly planted taro must be kept free from weeds, as the canopy has not fully closed. Weeds are not a problem once the leaf canopy has closed but towards the end of the lifecycle as the crop matures, weeds once again must be controlled. This is a critical period for starch accumulation. Care should be taken when spraying around taro plants. There have been instances of chemical damage to taro plants as a result of spray drift from adjoining properties.
Mulching may also be considered. Plastic mulching however can provide a barrier to growing shoots and corms.
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Fig. 3. Weed control is essential until crop has attained full canopy cover. |
Fig. 4. Mulching used to conserve moisture and for weed control. |
Fertilising
Although there is little information available on the fertiliser requirements for taro culture, fertilised taro has been observed to perform and yield better than unfertilised plots. Nitrogen seems to be the main requirement. Experiments in Hawaii have shown that taro respond to regular applications of N, P and K fertilisers. Improvements in corm size and number of corms are obtained with fertiliser applications.
Like all tuberous crops, taro has a high requirement for potassium, which is essential for starch formation. Liming may be necessary in acid soils. It has been reported elsewhere that applications of fertiliser, especially nitrogen made after full canopy can affect eating quality and palatability of the tuber.
Mulching is beneficial provided the soil is not too high in organic matter already. As mulch breaks down, it improves growth rates by providing nutrients and improving soil structure and soil moisture.
Insect pests and diseases
There are numerous insect pests and diseases of taro recorded in the Pacific region but few have been identified in north Queensland, as this is still a relatively "infant" crop. The rich starchy corm provides a much desired food source for the many chewing insect grubs.
Cluster caterpillars can present a major insect problem in a taro crop as they can strip the upper surface of the taro blade. The eggs are laid in clusters and covered with fine hair-like scales. The mature caterpillar is about 45 mm long, grey in colour above and green below. It has a pale stripe and a series of dark spots along the sides. The young caterpillars of the hawk moth can also cause significant damage by defoliating the leaves. These caterpillars make holes in the leaves. Although various beetles feed on taro, none have been specifically identified as taro beetles.
Erwinia soft rot is caused by Erwinia atroseptica. The corm becomes mushy and smelly and the affected plants eventually wilt and die. The condition appears to be exacerbated by high organic matter particularly in areas previously under pasture. The presence of chewing insects, for example the white cane grubs in north Queensland cane lands, also contributes to the problem.
Shot hole leaf disease is a common fungal disease in the wet tropical coast of north Queensland. The leaves become unmarketable and the reduction in photosynthetic area can cause substantial reduction in corm yield. Initially small round dark spots appear on the leaves. As these spots increase in size, the centre of most spots fall out giving this disease its name and the key characteristic. The disease is worse during wet weather and in closely spaced plants.
Harvesting and postharvest storage
Taro can be harvested when the corm reaches the desired size. At maturity, the leaves begin to turn yellow and the petioles are shorter. The main corms begin to push out of the soil surface. This is usually an indication that the crop should be harvested soon. Crop duration for the different varieties grown in north Queensland varies from 8-12 months and this will also depend on the management of the crop. It has been observed that under high rainfall conditions, the time for upland taro to reach maturity can be longer than twelve months.
Harvesting is laborious, with growers pulling out the matured corms by hand. When picked the skin is still resistant to mechanical damage during handling. The main corms and secondary suckers are broken and loosened from the soil manually. The corms are then pulled out by hand. These are then washed to remove roots and soil and placed in bins for grading and packing.
Corms are graded according to size or weight depending on the market. Corm weight of between 1-1.5 kg is preferred. The preferred weight can vary depending on the variety. Pack only quality sound corms with no rot or other blemishes. Buyers look for firm corms. The cut flesh should also look and smell fresh and juicy.
Storage conditions and their effects on the root are not well known for taro but under ambient temperature, taro does not store very well and should be consumed within 2 weeks. Refrigeration appears to extend storage life.
Yields are variable, in the region of 4-20 t/ha. Yields up to 70 t/ha have been recorded in Hawaii with heavy fertilisation. A low yield of 2 440 kg/ha is quite easily achievable.
Further information
- DPI&F Note - Taro: the plant.
- DPI&F Business Information Centre - phone 13 25 23 (from within Queensland).
- DPI&F, Centre for Wet Tropics Agriculture, South Johnstone - phone 07 4064 3911.
- Taro cultivation in the South Pacific (1982). Lambert, M. (ed.). South Pacific Commission, Noumea, New Caledonia.
- Tropical crops. Monocotyledons 1. (1972). Purseglove, J.W. Longman Group Limited.
- Current national information on agricultural chemicals registered for use on taro is available on the Infopest CD-ROM. Write to DPI&F, GPO Box 46, Brisbane, Qld. 4001, email infopest@dpi.qld.gov.au or phone (07) 3239 3967.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 10 November 2006
