Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Chinese cabbage

Introduction

As the name suggests, Chinese cabbage (Brassica rapa var. Chinensis) appears to have originated in China. The earliest known records are from the fifth century, which suggests that it arose from a cross between Pak choi (Brassica rapa var. Chinensis) and turnip (Brassica rapa var. rapifera).

The term `Chinese cabbage' is used to describe a wide range of brassica crops, both loose leaf (with or without flowers) and those which form a dense head. It is the heading types, Brassica pekinensis or B. rapa var. Pekinensis, which will be considered here. Depending on cultivar it can vary substantially in appearance, from the short, squat wong bok types to the long, slender rocket or michihili types.

Chinese cabbage is the most frequently eaten vegetable in Asia. Around 40 million t are consumed in China and 1 million t in Japan each year. It is commonly eaten as a freshly cooked vegetable, for example in stir fry dishes, and is often further processed as a brined product or used in pickles such as kim-chi.

Chinese cabbage has been grown successfully in all Australian states by experienced brassica vegetable growers, using the same sort of cultural practices as for their existing crops. Major pest and disease problems are similar to those which affect other brassica crops. Most can be minimised by growing the proper cultivars at the correct time of the year and by using appropriate cultural and pest management. Perhaps the biggest challenge to producers for optimising niche marketing opportunities is to extend production into the colder months and so supply Asian markets during August to October. Export quality Chinese cabbage is scarce at this time.

There appear to be substantial opportunities to increase sales of Chinese cabbage on both domestic and export markets as a fresh and minimally processed product and in a brined or pickled form.

Markets and marketing issues

Australia's increasing Asian population and the `Asianisation' of Australian diets has rapidly increased the demand for Asian vegetables. Major supermarkets report that this is the fastest growth area in the fresh produce department and demand is out-stripping supply.

Exporters of Chinese cabbage are having problems in sourcing long lines of supply and have been unable to meet some orders. Although the domestic market for Chinese cabbage appears to be increasing, most new growers are looking to export markets.

Exports of Chinese cabbage from Australia have increased from $2.5 million in 1987-88 to $6.5 million in 1995/96. A large proportion is exported to Hong Kong (48%), Singapore (32%) and Taiwan (12.5%). Of the $6.5 million in exports, 59% was exported from Western Australia, 35% from Queensland and 4% from Victoria.

Australia's best time for selling brassica vegetables in Asia is from April to October. However this can vary substantially between countries and between years. Most markets for Chinese cabbage are still considered niche markets which are subject to factors such as local weather, particularly typhoons which can cause severe shortages at times.

Growers interested in the export of Chinese cabbage need to consult with exporters well in advance to identify market opportunities and to ensure their product meets the export market's specifications. Singapore prefers 1 to 1.5 kg heads while Hong Kong will take heads of up to 2 kg.

At this stage substantial market research is required and some is under way to find new market opportunities for Australian Chinese cabbage. These include Malaysia, Indonesia, South Korea, Europe and Taiwan.

There is also potential for value-added products both on local and export markets through minimal processing, brining and pickling.

Production requirements

Temperate or cold-tolerant Chinese cabbage cultivars prefer temperatures between 13 and 20^oC. However cultivars prone to bolting, particularly michihili types, may require warmer temperatures. Where temperatures frequently exceed 35^oC, tropical or `cold-sensitive' cultivars need to be grown. Under these conditions temperate cultivars are unlikely to form heads and are susceptible to disease. In general, Chinese cabbage can be grown in temperate and tropical climates, given adequate rainfall or irrigation. It is a shallow-rooted crop and does not tolerate drought.

Chinese cabbage require deep, well-drained soil because it is susceptible to root rots. It has been grown successfully on a range of soil types from light, sandy loams to quite heavy loams. A soil pH of 5.5 to 7 is ideal and lime should be applied if the pH is below 5.5, as calcium and other nutrients may be unavailable to the plants at low pH. Liming may also reduce the effect of clubroot if that disease is present. A fine, well-prepared, raised bed can help to prevent soil compaction, improve drainage and improve air circulation around the base of the plants, which will reduce the incidence and severity of diseases.

Proper irrigation of Chinese cabbage will increase yields and help to prevent nutritional and physiological disorders. Direct-drilled crops require watering every day until the seedlings emerge. Frequent watering may be necessary during growth and development. Measurements of soil moisture with potentiometers or other devices should be made regularly to determine the need for irrigation. Proper watering is particularly important during head formation. Inadequate watering will substantially reduce yield and may contribute to disorders such as tipburn while too much water during head formation can cause root death and poor quality heads.

Varieties/cultivars

Cultivar evaluation trials have been conducted in Western Australia, South Australia, Tasmania and most recently in Victoria. Most work was based on marketable yield and tolerance to disorders although Victorian studies also determined the relative storage potential of all cultivars tested. The performance of individual cultivars varied considerably between States and planting times. Overall, bolting was a major problem where attempts were made to extend the growing season into cooler months and the michihili types were far more susceptible to bolting than the wong bok types.

In Western Australia the cultivars most tolerant to gomasho and bolting were the wong bok types `WR Green 60', `RS1446' and `China Pride'. Trials in Tasmania showed the wong bok cultivars `RS1446', `China Pride' and `WR 60' were most tolerant to internal rots and gomasho and provided the highest marketable yields. The wong bok cultivar `Hong Kong' is recommended for winter and spring plantings in South Australia and showed resistance to bolting and tip burn. In Victoria a range of varieties were planted between early autumn and early winter. All late plantings bolted except for the cultivars `Cream' and `Manoko' which produced a 60% marketable yield. For early to late autumn plantings `Yuki', `Treasure Island' and `WR Green 60' (all wong bok types) were the best performed varieties and these also did well in storage trials except that WR Green 60 showed evidence of chilling injury after seven weeks of storage at 0^oC.

Key statistics

Cultural practices

Chinese cabbage can be either sown directly from seed or transplanted into a fine, well- prepared, raised seed bed. When sown from seed it is common practice to sow two to three seeds per station 12-15 mm deep in the soil and thin by hand after germination. It is recommended to sow seed at a rate of 500-750g/ha which will give a plant spacing of approximately 35 cm. Common plant spacings are 30 cm between plants and rows, 37.5 cm between plants in the same row and 30 cm between rows to produce heads around one kg and a row spacing of 40 cm with a plant spacing of 35 cm for wong bok and 30 cm for michihili types to produce heads between 1 and 1.8 kg.

Transplants are generally raised in a greenhouse or polyhouse for three to four weeks before planting in the field. Transplanting is initially more expensive than direct seeding but has some compensatory advantages. Use of transplants helps to mitigate adverse environmental factors during early seedling growth such as unseasonably cold temperatures which may induce bolting. Additionally, direct seeding requires more seed, extra labour for thinning, larger scale irrigation and more pest, disease and weed control.

Chinese cabbage requires large amounts of fertiliser, particularly the macronutrients nitrogen, phosphorus and potassium. Fertilisation often begins with an application of animal manure at least two weeks before planting. V.Q. Nguyen has recommended that a fertiliser with an N:P:K ratio of 5:5:5 should be broadcast at a rate of 1.5 t/ha before planting. After crop establishment, regular applications of N and K fertilisers are required with applications through the irrigation system (fertigation) being the most efficient. It should be noted though that excessive use of nitrogen has been linked to an increase in the incidence and severity of several disorders including tip burn, gomasho and soft rots. High applications of phosphorus have also been linked to an increase in the incidence of gomasho.

Chinese cabbage matures rapidly especially during warm periods with wong bok types tending to mature earlier than michihili types. For example, a range of cultivars grown in South Eastern Victoria took 65 to 80 days from planting to harvest in early autumn and 97 to 117 days when planted in mid-autumn. Heads should be harvested when they are well filled and firm but not very hard and before flower stalk initiation.

Pest and disease control

In general, Chinese cabbage is susceptible to a wide range of pests and diseases which affect other cruciferous crops. Some of the more important include the bacterium Xanthomonas campestris which causes black rot, club root caused by the slime mould fungus Plasmodiophora brassicae, turnip mosaic virus (TuMV), cauliflower mosaic virus (CaMV), diamondback moth (Plutella xylostella) and cabbage aphid (Brevicoryne brassicae). Only clubroot and diamondback moth will be discussed here.

Clubroot is a serious disease of cruciferous plants and Chinese cabbage is highly susceptible. The fungus is soil-borne and enters the plant through the root hairs on young plants or through wounds on the roots or stem, causing the roots to become thick and distorted. Severely affected roots cannot absorb water and minerals from the soil and produce stunted plants which usually fail to produce a marketable head. Clubroot spreads readily through infected seedlings, in water and in soil attached to equipment and the boots of workers. It is a very hardy organism and can survive and remain infectious for at least 20 years in the absence of a suitable host.

Diamondback moth is the most important world-wide pest of brassica crops. It is believed to have originated in the Mediterranean area and it can disperse over long distances. In the caterpillar phase it eats the leaves of cruciferous crops, often causing a skeleton effect where most of the green tissue is removed leaving the mid-ribs and veins. It attacks crops at all stages of maturity from the seedling stage on and can cause widespread loss.

Adult moths are about 9 mm long and greyish brown with three light brown to white triangular markings on the top edge of the forewing which form a diamond shape when the wings are closed and the moth is at rest. The smaller caterpillars feed on the green mesophyll cells from one side of the leaf often leaving the opposite leaf surface intact, creating a distinctive `window' effect. If disturbed the caterpillars drop from the leaf and hang suspended from fine silken threads. When mature, they spin a flimsy silken cocoon on the surface of the leaf and pupate within it. The adult moth emerges after a week or two.

For a comprehensive overview of the pests and diseases of Chinese cabbage and current control recommendations see Daly and Tomkins (1997).

Harvest, handling, and storage

Chinese cabbage heads should be harvested when they are well filled and firm but before the flower stalk starts to develop substantially. It is usually harvested by hand with the outer leaves trimmed off and the butt trimmed flush with the outer leaf bases. They should be harvested in the cool part of the day and handled carefully as they are very easily damaged. Heads should be rapidly cooled to as close to 0^oC as possible immediately after harvest and this temperature should be maintained during storage and distribution.

If Chinese cabbages are properly precooled, stored at 0^oC and protected from moisture loss they can be effectively stored for many months. Water loss can be prevented by providing a high humidity storage environment. A simple means of achieving this is to store heads in a plastic bag with the top folded over. Recent research has shown that storage life can vary substantially between cultivars and more research is required in this area. Some cultivars appear to suffer a form of chilling injury expressed as browning of leaf mid-ribs and some are more susceptible to storage rots than others.

Economics of production

Chinese cabbage production is best suited to existing brassica vegetable producers who wish to diversify. It does not require any specialised equipment apart from that used for the production, handling and storage of more traditional brassica crops such as cabbage, cauliflower and broccoli. Costs of production of Chinese cabbage are being prepared under the State Government of Victoria and RIRDC joint project `Access to Asia' and will become available to the public shortly.

Key contacts

Key references

Daly, Paul and Bruce Tomkins (1995). Production and Postharvest Handling of Chinese Cabbage (Brassica rapa var Pekinensis). Rural Industries Research and Development Corporation Research Paper No 97/1. 35pp

Daly, P. and R.B. Tomkins (1997). Developing a Sustainable Asian Vegetable Industry in East Gippsland. Final Report to the Rural Industries Research and Development Corporation. 160pp.

Endersby, N. and P. Ridland (1994). Diamondback moth now out of control! The Holey Leaf, Issue no. 1, Sept. 1994.

Nguyen, V.Q. (1992). Growing Asian vegetables. NSW Agriculture Agfact H8.1.37. 16pp.

Porter, I. (1986). Clubroot of cruciferous crops. Victorian Department of Agriculture Agnote 254/633. 3pp.

Waters, C.T., Morgan, W.C. and D.J. McGeary (1992). How to identify, grow and use oriental vegetables. Department of Food and Agriculture. 128pp.

*About the authors

Bruce Tomkins is the Leader of the Postharvest Technology Team at the Institute for Horticultural Development, Department of Natural Resources and Environment, Victoria (see Key contacts for address). He has over 20 years of research experience and has successfully led a number of projects on the postharvest handling, packaging, processing and storage of a range of Asian vegetables.

Paul Daly is a project scientist with over six years of experience in postharvest horticulture. He was responsible for a recently completed RIRDC project `Developing a sustainable Asian vegetable industry in East Gippsland' which centred on the production and storage of Chinese cabbage.