Growing okra
Department of Primary Industries and Fisheries, Queensland.
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Introduction
Okra (Abelmoschus esculentus) is related to cotton and hibiscus. It is cultivated for the pods, which are harvested in the immature stage and used in salads and soups. It is a prime ingredient of the 'gumbos' or stews of Louisiana, USA.
The plant is widely cultivated throughout the year in the tropics and can be grown during the summer in south-east Queensland. It cannot tolerate frost. Commercial production in Queensland is small, because of the limited market demand.
Climate and soils
A warm-weather plant, with a preferred temperature range of between 22°C and 35°C, okra is susceptible to frost and temperatures below 12°C.
Okra can be grown on a wide range of soils, provided the internal soil drainage is good. Soils high in organic matter are preferred. The addition of lime or dolomite may be necessary during soil preparation to bring the pH to about 6.0 to 6.5.
Culture
Varieties
Clemson's Spineless is the most widely grown variety, but other varieties such as Gumbo and Red Finger should be trialed to determine their suitability to the area and their popularity on the market.
Land preparation
Thorough soil preparation commencing two to three months before planting is recommended, to allow organic matter in the soil time to break down. Ripping followed by a deep ploughing and several cultivations should bring the soil to a good planting condition.
Field layout
Plants are spaced in single rows 30 to 45 cm apart. Row spacings may vary from 1 m to 1.5 m dependant on machinery available. Normally eight to ten rows form a bed or bay. Each bed is separated by a roadway about 3.5 m wide which allows access for tractor-mounted boom equipment and other vehicles.
Bedding up, laying plastic mulch and drip irrigation
Practically all okra is grown using plastic mulch and drip (trickle) irrigation. Bed forming, fertilising, drip tape laying and laying of plastic mulch can all be carried out in the one operation. The beds are usually constructed to finish about 10 to 15 cm higher than the surrounding soil. Plastic is laid to give a surface width covering of about 40 to 50 cm.
Planting out
Okra plants may be established either by direct seeding in the field, by growing seedlings in a nursery seedbed, or by raising containerised seedlings in plastic trays. The use of containerised seedlings is by far the most popular method and produces the best plants with few losses. Seedlings are ready for transplanting when they reach 10 to 15 cm in height and are planted in single rows either by hand or by machine through the plastic.
Fertilising
Basal fertiliser is applied to the plant row just before laying the drip tape and plastic mulch. It may be applied in a band approximately 10 cm below and 10 cm to the side of the plant in soils which tie up phosphorous. In other soils spread in a 30 to 40 cm strip on the top of the soil along the plant row and incorporate it to a depth of 12 to 15 cm using a rotary hoe. High (e.g. 12:14:10 at 2 kg/20 m of row) or low analysis (e.g. 5:6:5 at 5 kg/20 m of row) fertilisers may be applied.
A side-dressing of nitram at 300 g or urea at 225 g per 20 metres of row can be applied 10 days after transplanting. Under drip irrigated crops, potassium nitrate can be alternated every two weeks with calcium nitrate both at 20 to 30 kg/ha. After every second or third application of these fertilisers, magnesium sulphate should be applied at 20 kg/ha to prevent magnesium deficiency occurring.
Irrigation
Okra is relatively susceptible to saline conditions, so water conductivity tests should be done before planting the crop. For overhead irrigated crops avoid water exceeding 1.6 dS/m. In furrow and drip irrigated crops water with a reading of up to 2.4 dS/m can be used with caution.
Okra is a heavily foliaged crop so its water requirement is high. No accurate figures on the amount and regularity of water required can be given as this will vary depending on locality, time of year, soil type and type of irrigation required. As a general guideline, the crop could be expected to use 7 ML/ha under sprinkler irrigation, 4 to 6 ML/ha using drip irrigation and up to 8 to 10 ML/ha using furrow irrigation. Drip is the best method of irrigation as it is well suited to the use of plastic mulch and permits the application of fertigation.
Pruning
Okra can be a very robust plant but does not develop any branching until the plant reaches a height of about 30 to 40 cm. Normally 8 to 14 fruit-bearing shoots develop with minimal further branching. If further offshoots develop, the plant may become too dense and some branch thinning will be necessary. Opportunities also exist for ratooning by cutting the bushes back as they become too old and unproductive and allowing them to re-shoot.
Pests and diseases
Weeds
Okra is harvested over a long period and weed control remains important throughout the season. Plastic mulch can suppress weed populations while warming the soil and encouraging plant growth. Shallow inter-row cultivation and hand chipping can be used to keep weeds within rows to a minimum.
Insects
There are many insect pests which may attack okra, but among those most likely to be troublesome are silverleaf whitefly, heliothis, rough bollworm, looper caterpillars and green vegetable bugs. Aphids and mites may also occur on okra crops.
Okra appears to be one of silverleaf whitefly's favoured hosts. Although there are chemicals which will assist with management of this pest, they should only be used under strictly supervised conditions or the insect will quickly develop resistance to them.
Insect management in okra is very difficult as only a small number of insecticides are registered. Some of these have only limited effectiveness against some pests for which they are registered. Monitoring the crop regularly for pests is essential.
Diseases
Verticillium wilt is the most common disease affecting okra. The most conspicuous symptom is a yellowing of the older leaves, which often develop a burnt appearance, particularly around the margins, followed by wilting of the plant. The only control measures recommended are crop rotation and the destruction of diseased plants.
Powdery mildew can become a major leaf problem in drier tropical regions. It may result in heavy leaf shed. No chemicals are registered for powdery mildew on okra.
Ascochyta leaf spot and Cercospora leaf spot have been recorded on okra. No definite control measures have been suggested, but spraying with a registered fungicide may be helpful if either of the leaf spots becomes destructive.
Root-knot nematodes (Meloidogyne species) cause severe galling on okra roots. Infested soil should be treated with a registered nematicide before planting. Crop rotations are an important management tool in preventing a build-up of nematodes or other soil-borne organisms.
Harvesting
The success of okra growing depends on careful handling and packing of the product and rapid cooling of the pods as soon as possible after harvest. The pods should be ready for harvesting within 10 weeks of planting, and regular picking every 2 to 3 days is essential for maximum yields. Mature pods left on the plant will reduce flowering and fruit set. The market demand is for young tender pods about 7 to 10 cm long. Older, tough or stringy pods are unsaleable. Discard pods showing spine growth on the fruit.
Yields of 0.3 to 0.5 kg/plant can be expected. Cut the tender pods from the stalks and handle them carefully, otherwise they may bruise and discolour. It is best to pick fruit into a waist bag to reduce skin damage to the fruit and avoid excessive bending over. It is advisable to wear rubber gloves when harvesting and handling okra pods as the sap will irritate most skins.
The pods are graded into various sizes and then packaged in a 9 litre fibreboard container. Okra should be cooled and sent to the market as soon as possible after harvest. During transport the pods should be held between 7°C and 10°C and 90 to 95% humidity, to prevent wilting. Okra pods are susceptible to chilling injury at lower temperatures. Label the containers with the word 'okra' and the name and address of the grower.
After harvest, the crop can be ratooned by cutting the plants back to about 15 to 20 cm high and re-fertilising.
Uses
The main use of okra is as a flavouring for cooking with meats, and because of the high mucilaginous content, the pods are ideal for both thickening and flavouring stews and soups. The pods can also be boiled or fried and eaten as a vegetable.
DPI&F information and services
- To access DPI&F's information and services, Queensland residents can contact the DPI&F Business Information Centre on 13 25 23 for the cost of a local call, from 8 am to 6 pm Monday to Friday (excluding public holidays). E-mail callweb@dpi.qld.gov.au. Non-Queensland residents phone (07) 3404 6999.
- Current national information on agricultural chemicals registered for use on all crops is available on the Infopest CD-ROM. Write to DPI&F, GPO Box 46, Brisbane, Qld 4001, E-mail infopest@dpi.qld.gov.au, visit the Infopest web page, or phone (07) 3239 3967 for further information.
Industry links
- Industry links is a page of links to various sites of interest to horticultural growers.
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 reviewed 19 September 2007
