Note number: AG0633
Published: June 2000
Updated: March 2011
There is a wide variety of Asian vegetables available in Australia and they have added ingredients to many Australian recipes. The demands for Asian vegetables are increasing mainly due to increasing Asian population, health-consciousness and desire for variety of food. However due to the communication barriers, the cultivation techniques will remain lesser known to main stream growers and home gardeners.
Vegetables that have originated in the East and Southeast Asian countries such as China, Japan, Korea, Indonesia, Philippines, Thailand, Vietnam are called 'Asian Vegetables' or 'Oriental crops'.
The following main varieties and many more have added to the diversity of Asian vegetables; Chinese cabbages, Chinese mustards, Japanese pumpkins, Ceylon spinach, Water spinach, Loofahs, Chinese radish, Japanese bunching onion, Gourds, Chinese beet, Chinese chard, Oriental mushrooms, Oriental pickling melons.
There is limited data available as to the size of the industry or the total production in Victoria. However several states, including Victoria, have conducted programs promoting these new vegetables, as there have been potential export markets identified in Asia.
Asian vegetables can be grown in a range of soil types with different soil physical characteristics similar to the traditional vegetables. The range of soil types could vary from sandy soils to heavy textured clay loams, but friable well-drained soils high in organic matter are preferred. The ideal pH range is 5.5-7.0. If required lime can be applied to acid soils with pH is below 5.5. However management of soil pH has to be approached carefully if soil born diseases such as clubroot are present.
A satisfactory drainage in the soil is important as Asian vegetables require plenty of water supply including irrigation for satisfactory growth. Poorly drained soils cause many Asian vegetables susceptible to root diseases. As these vegetables have shallow root systems irrigation is essential, sometimes daily for establishing crops and especially when the weather is hot. Proper irrigation will increase yields and help prevent nutritional and physiological disorders. Too much watering can cause root death resulting in poor quality produce. Close rotations with other similar crops in the same family grouping should be avoided to prevent pests and diseases.
Excessive wind and heavy frosts can severely affect yield and quality but most areas in South Eastern Australia are suitable for the production of the majority of Asian vegetables. Many commercial growers use polyhouses to extend the growing season and to grow more of the tropical Asian vegetables that require higher temperatures.
The amount and type of nutrient requirements will depend on the soil type, rotations and previous fertiliser history. A soil test is recommended before preparing the soil to develop an accurate fertiliser program. The most important nutrients for Asian vegetable production include nitrogen, phosphorous and potassium. Fertilisers should be applied before planting and as side dressing during growth.
As a general fertiliser guide for leafy Asian vegetables, the following range of rates should be used as a base dressing. On sandy soils rates will need to be higher to take into account nitrogen loss through leaching. A base fertiliser at an N:P:K analysis of 6:6:6 or equivalent should be applied at 800 to 1,500 kg/ha, depending on soil type and previous cropping. This should be banded at transplanting or seeding; if broadcasting, rates should be doubled.
If fowl manure (deep litter) is applied at a rate of 22 m3/ha, the fertiliser rates can be reduced by one third. Fowl manure should be applied around two weeks before sowing.
A side dressing should be applied to leafy Asian vegetables once or twice to transplanted crops and three applications may be required for direct seeded crops. A side dressing can be applied at two weekly intervals to direct seeded crops. A total of 150-280 kg/ha of urea or 250-500 kg/ha of calcium ammonium nitrate should be applied depending on soil type.
Transplanted crops require one or two side dressings around 4-6 weeks after transplanting and if necessary at around 8 weeks after transplanting. Total side dressing applications could include urea from 100-200 kg/ha or calcium ammonium nitrate at 150-300 kg/ha or similar fertiliser such as calcium nitrate.
Magnesium is an important plant nutrient. Deficiency, which is characterised by interveinal yellowing on old leaves, can occur on acid soils. Magnesium can be applied at rates of 50-200 kg/ha magnesium sulphate (epsom salts) which contains 10% magnesium.
Boron is an important trace element for vegetable crops and a range of brassica species. Deficiency causes tissue to become brittle and crack easily and mid ribs of leaves to develop transverse cracks or corkiness. A foliar spray of boron can be used as a preventative measure if this is likely to be a problem.
Farmers who use chemical fertilizers should be aware of the potential dangers of using phosphatic fertilisers with high levels of cadmium. Research has shown that the use of phosphatic fertilisers which contain the heavy metal cadmium as a contaminant can increase cadmium levels in both soil and the produce. There are legal maximum levels of cadmium allowable for vegetables sold in Australia. Fertilisers containing cadmium in excess of 1 mg/kg are required to state the following warning:
"WARNING––this product contains cadmium. Continued use of this product in agricultural situations may lead to residue levels in plant and animal products in excess of the maximum level specified by the Australia New Zealand Food Standards Code and the accumulation of cadmium in soils."
It is in the interest of growers and consumers to minimise the addition of cadmium to soils and agricultural produce. Growers should consult fertiliser suppliers or manufacturers for advice on cadmium levels of fertilisers they are considering using. There are a number of low cadmium horticultural fertilisers marketed today. These have lower levels of cadmium than some superphosphates and other fertilisers.
Pest and diseases
There are number of pests and diseases affecting Asian Vegetables. Despite of the number of chemicals registered for the industry is limited, especially in Victoria due to the small market size farmers can look for chemicals registered for the main stream vegetables from the same family. Growers should also consider adopting Integrated Pest and Disease Management practice to reduce the dependence on chemical control.
Some of the major pest problems are likely to be:
Diamond back moth
Cabbage moth or diamond back moth (Plutella xylostella) can be a potential major problem as it has developed resistance to a number of pesticide groups. If it is likely to be a problem a control strategy should be implemented. Kai lan and Choy Sum are preferred hosts while Buk Choy, Pak Choy, watercress and Chinese radish are also attacked. The pest can also survive on alternative weed hosts such as wild radish, wild turnip and turnip weed.
Good farm hygiene is also important in pest control. Rapid removal of old crop residues is important as otherwise these will act as a reservoir for pests and allow pest populations to build up making control more difficult.
Aphids are small sap sucking insects found on the underside of leaves or concentrated around the growing point. They have grey or green globular bodies and spindly legs and may be winged or wingless. Some aphid species transmit viruses.
Cabbage white butterfly
The caterpillars of cabbage white butterfly (Pieris rapae) are larger than those of cabbage moth and are dull green up to 25 mm long. They feed on the leaves of the cabbage. The adults are white with black markings and are very common around crucifer crops.
Snails and slugs
Snails and slugs can be a significant problem and can damage the plants at all stages of growth. They generally hatch from the soil when conditions become damp and cool in autumn.
Other pests known to be a problem for Chinese broccoli, Chinese chard and Chinese flowering cabbage can include Leaf miner, Looper and Native budworm.
Downy mildew is a disease that is more prevalent under cool and wet weather conditions. The disease is caused by the fungus Peronospora parasitica and is a common disease of cruciferous crops.
Chinese broccoli appears to be more susceptible than most other Asian vegetable crops. The disease is most serious in seedlings, and infected young plants can die. Symptoms of downy mildew are yellow to brown spots on the top surface of leaves that correspond to a white fungal growth on the underside.
Bacterial soft rot
Bacterial soft rot is common to all vegetables and can cause significant crop loss. Chinese cabbage is particularly susceptible and some signs of the disease can generally be found in most wong bok crops. It is caused by the bacteria Erwinia carotova. Soft mushy areas develop on old leaf bases near the ground and move into the head, which can disintegrate into a brown slime.
Clubroot is one of the major diseases of cruciferous crops and is caused by a soil borne fungus Plasmodiophora brassicae. The roots of infected plants swell and become distorted and the first signs are stunting and or wilting during the day. Plants wilt and collapse as the disease advances.
Clubroot remains active in the soil for many years although liming to raise the soil pH may help, as acid soils are more conducive to clubroot development. Many varieties of Chinese cabbage are very susceptible to clubroot, but unlike other crucifers there are also resistant varieties.
White leaf spot
This disease is characterised by the development of light brown to white spots about 10 mm across. The disease is caused by the fungus Pseudocercosporella capsellae and is first observed on older leaves. The disease is most common in wet autumn and early winter conditions.
The fungus survives on seed and plant debris of cruciferous plants. Control methods should include the removal of cruciferous weeds near crops, ploughing crop residue back into the soil and hot water treatment of seeds before planting.
The crops such as Chinese broccoli also infected with diseases such as Fusarium yellows, black leg, Target spot and damping off, and Chinese is attacked by Sclerotinia spot while Chinese flowering cabbage is attacked by Ring spot, Target spot and Brown canker.
Some virus diseases can also affect Asian vegetables and these include turnip mosaic virus and cauliflower mosaic virus. Aphids that are most active in autumn transmit both viruses. The use of tolerant cultivars and good crop hygiene will help reduce disease outbreaks.
If crops are to be direct seeded, a weed free seedbed is essential for crop establishment and growth. Weed control is also important to allow crops sown as seedlings to become established and also for pest and disease control.
However there are currently no herbicides registered for use on most Asian vegetables.
There are also a number of growth disorders that can reduce marketability, as follows:
Tipburn is a field disorder in cruciferous crops that can be caused by a range of factors. Tipburn can affect the outer leaves rendering the head unsightly.
Tipburn is caused by lack of calcium supply to rapidly growing tissue. The margins of the leaves burn in response to the calcium shortage. However the lack of calcium supply may be due to other factors such as vigorous growth, uneven irrigation or inadequate irrigation, salty irrigation water too salty, an unbalanced fertiliser program. High rates of nitrogen can also contribute to tip burn.
Calcium sprays or the use of a calcium fertiliser as a side dressing may reduce tipburn but will be of marginal benefit if the other factors are not addressed. There are also varietal differences in tolerance to tipburn.
The major domestic markets for Asian vegetables are the supermarkets, Asian grocery shops and restaurants. Domestically the demand for Asian vegetables is declining with an oversupply of average quality vegetables. Opportunities exist to supply quality vegetables to supermarkets and for exports.
Potential to export Asian vegetables into Asia has been identified, as the demand for quality vegetable increases and arable land decreases. However, exporting into Asia requires a good understanding of the markets and business requirements. Market opportunities should also be established before production or it may be difficult to sell the produce.
Generally the industry is small scale with many independent producers. The result is increased price competition with pressure to cut costs and to reduce quality. Secondly, whilst supermarkets are looking for more products, they usually want large quantities on a consistent basis. This is often difficult to supply, especially for the smaller independent producers.
In summary, the marketing of Asian vegetables can be very volatile and, in the current industry climate, new growers need to be very aware of all the influences that affect the various potential markets. Growers should always try to secure a market and estimate potential returns before they even start growing vegetables.
Only some costs of production analysis and likely profits from these vegetable crops have been completed and they are beyond this report, as the full details of the analysis is required to be of any use. A gross margin analysis should be carried out prior to growing any Asian vegetable so that there are estimates on the total growing costs and estimates on potential returns.
Prices received for Asian vegetables vary depending on supply and demand at different times of year. Prices received during winter are generally higher because it is generally much harder and slower to grow Asian vegetables than during summer.
- Chew, A. and Morgan, W. (1997) Melbourne Retail Asian Vegetable Survey Part 2. DEPI.
- Chew, A., Moore, S. and Morgan, W. (1997). Melbourne Wholesale Asian Vegetable Survey.DNRE
- Dimsey, R and Barton, N. (2010) Growing Chinese cabbage. Agriculture Note AG0614, DEPI Victoria.
- Murdoch, C., Slobodan, V and Dimsey, R. (2010) Tipburn in Lettuce, Agriculture Note AG1120, DEPI Victoria.
- Hyde, K.W. (1998) The New Rural Industries – A handbook for farmers and investors, RIRDC Publication.
- Larkcome, J. (1991). 'Oriental Vegetables', The Complete Guide for Garden and Kitchen.
- Lee, B. (1996). Australian Asian Vegetables: An Assessment of Market Demand in Australia, RIRDC Publication.
- Vinning, E. (1995) Market Compendium of Asian Vegetables. RIRDC Publication.
Correct diagnosis is essential for effective pest and disease control. A commercial diagnostic service is available at the AgriBio Bundoora.
For further information, phone Crop Health Services on (03) 9032 7515.
For further information on registered chemicals, contact us.
This Agriculture Note was written in June 2000.
It was reviewed by Neville Fernando, Farm Services in March 2011.