Daikon

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WARNING: The information on this page has been gathered from both published and unpublished material, and contains comments and opinions from people working in the field. CQUniversity cannot guarantee all the information, and we stress that it is necessary to CHECK WITH THE SOURCE of the information, before using it to make a business decision. Please read our disclaimer.Project experiments for 1998 / 1999

Daikon Links

• Thailand
• GPPIS (FAO)
• Purdue University, Indiana
• NSW Dept. of Agric.
• University of Florida
• Oregon State University
• botany.com

Species: Raphanus sativus L. Cv. group Chinese Radish

Family: Cruciferae

Crop status: Established

Varieties

There are numerous Japanese and Korean varieties to select from (Douglas 1997). Different cultivars exist for sale as fresh and processed product (Nguyen et al. 1997). Variety trials have been conducted at Gosford (Nguyen 1992) and the Department of Agriculture WA. Japanese breeders are combating the problem of bitterness in spring harvested varieties (Vinning 1995). See Seedquest for a list of seed companies.

Agronomic trials

Variety x season trials will be conducted at Gatton in 1999. Trials have been conducted by Agriculture Western Australia and Tasmania.

Production

Grown commercially in NSW, WA, NT, Vic and SA (Lee 1995).

Mixed cropping: Rotated with edible chrysanthemum to help reduce any pest and disease burdens (Tony Holder, Victoria, in Douglas 1997).

Season: Can be grown year round in NSW (Nguyen 1998a), Victoria (Tony Holder in Douglas 1997) and Western Australia but it is a cold season vegetable. The best time is spring and early autumn to produce a high quality radish (Nguyen 1998a), and different varieties should be used for each (Larkcom 1991).

Temperature: Ideal temperature is 20-25°C. Summer temperature and strong sunlight cause the roots to grow rapidly and become pithy soon after maturity (Nguyen 1998a), and can also cause internal browning in Japan (Kawai et al. 1992). Low temperatures at sowing (~12°C) increase the risk of bolting (Larkcom 1991) and shallow roots (Waters et al. 1992), as do low temperatures followed by a long day length (Piluek and Beltran 1994). Even storing the seed at a cold temperature (5°C) before sowing increase bolting (Yoo and Uemoto 1976). However, temperatures close to 0°C have little effect once plants are well established (Larkcom 1991).

Day length: Long daylengths of 15 hours cause early flowering and roots to become misshapen (Piluek and Beltran 1994).

Soil type: Rich, light, well drained (Chew and Morgan 1998) and deep soil is preferred. Heavy soils will cause misshapen roots (Piluek and Beltran 1994) but some varieties have become suited to heavy clay by producing much of the edible root above ground (Larkcom 1991). The crop requires clean soil, as returns are too marginal to include cleaning costs.

pH: Optimum is 6.0-6.5 (Piluek and Beltran 1994) but the crop tolerates slightly acid soils (Nguyen 1998a).

Soil preparation: A well prepared raised bed is best. Apply 15 t/ha manure or compost before sowing to improve water holding capacity and nutrient availability, then 1.5 t/ha of NPK fertiliser soon before planting to encourage water availability (Nguyen 1998a). Smaller clod size increases germination (Waters et al. 1992).

Germination: Daikon will germinate in temperatures as low as 5°C (Nguyen 1998a). Germination rate is increased by 30% in a magnetic field of 1 Hz (Namba et al. 1998).

Sowing: 10-15 kg/ha (Piluek and Beltran 1994) sown at 5-10 cm deep (Nguyen 1998a). Preferably sow into sunken drills 4 cm deep to support seedlings (Chew and Morgan 1998). It is usually sown directly though it is possible to transplant (Larkcom 1991).

Plant density: Recommendations for plant density vary considerably, reflecting the enormous variation in cultivar requirements. With a row spacing of 35 cm, optimum plant spacing can vary from 7.5-40 cm (Chew and Morgan 1998) but is generally about 15-20 cm (Piluek and Beltran 1994, Nguyen 1998a). Higher densities reduce the frequency and degree of pithiness (Fukuoka and Kano 1997) but excessive densities will result in small, irregular and misshapen roots (Nguyen 1998a). Late thinning (about 40 days after sowing) can be used to control product quality (Latimer et al. 1991).

Nutrition: Soil must be rich and fertile since the crop grows rapidly. Generally apply NPK before sowing and regular side dressings of an N fertiliser until the roots mature, but excessive N can cause excessive leaf growth (Waters et al. 1992). Preferably manured from the previous crop, rather than fresh (Larkcom 1991). Daikon can be difficult to grow, requiring attention to nutrition (Tony Holder, Victoria, in Douglas 1997).

Water: The plant must grow rapidly with plenty of moisture to produce a mild, tender and visually attractive product (Piluek and Beltran 1994). Water must be applied at the correct time and quantity (Tony Holder, Victoria, in Douglas 1997). The crop is sensitive to water logging and excessive watering can cause the root to split (Tony Holder, Victoria, in Douglas 1997). Too little water can lead to an under sized product (Tony Holder, Victoria, in Douglas 1997) and elongated roots (Piluek and Beltran 1994). Infrequent watering can also cause the root to split (Hugh Allan in Daley 1998). Overhead sprinklers provide a moist environment but also encourage fungal diseases, particularly in summer (Nguyen 1998a).

Time to emergence: About 4 days at 20-30°C (Piluek and Beltran 1994).

Bolting: Seedling bolting can be reduced by soaking seed in abscisic acid (Amagasa et al. 1993).

Time to harvest: The growing season varies from 50-90 days, depending on cultivar, desired product (Piluek and Beltran 1994) and season (Tony Holder, Victoria, in Douglas 1997). It normally takes 50-60 days in summer and 70-80 days in winter to produce a weight of 0.5 kg (Nguyen 1998a). Processing cultivars generally reach market size 5-10 days later (Nguyen et al. 1997).

Harvest: Roots for the fresh market are harvested when they are 5-10 cm diameter at the neck. In Japan they are left with foliage, either untrimmed or trimmed to 10 cm. Roots for processing are allowed to grow larger (Nguyen 1998a). Farm machinery for harvesting daikon is available commercially in Japan (Pan 1995).

Yield: 45-50 t/ha has been achieved in Hawaii (Orzolek and Ferretti 1995), but 15-20 t/ha is more common (Piluek and Beltran 1994). Japanese yields have climbed steadily to 41.0 t/ha in 1996 (Figure 3). Australian gross yields are around 40-50 t/ha (Pan 1995).

Figure 1: Japanese grade daikon according to type (long, short or stubby) and weight. Some prefectures also use a 2S or a 3L grade (Vinning 1995).

Postharvest

Temperature: Harvest in the cool and keep cool and moist until stored at near 0°C (Nguyen 1992). Thawing causes extensive damage, so they must not be frozen (Nguyen 1998a). Rapid cooling with forced draught air (Nguyen 1998a) or water is recommended (Piluek and Beltran 1994).

Humidity: 90-95% relative humidity (Nguyen 1998a).

Shelf life: With correct conditions they can be stored for 28 days, but at 7°C they will last less than one week (Nguyen 1998a). Many growers pick to order and deliver the same day (Douglas 1997). Shelf life is reduced if pithiness has developed in the root (Nguyen 1992), or if leaves are still attached (Piluek and Beltran 1994).

Cleaning: In Japan, roots are thoroughly washed mechanically or by hand (Nguyen 1998a).

Chemicals: Postharvest chemical treatments are generally unnecessary (Nguyen 1998a). Dipping in 2x10-3 M methyl jasmonate can reduce postharvest growth in radishes (not specifically daikon), hence improving quality (Wang 1998). Radish sprouts can be treated with 0.4% wt/vol calcinated calcium in the sprouting medium to inhibit E. coli growth (Bari et al. 1999).

Processing

The root should be crunchy, not pithy, and low in water content (Nguyen 1992). For takuan the roots should be dried to 50% fresh weight, by placing in a shaded, well ventilated area for 3-5 days. For dried sliced radish, the leaf is trimmed and the root sliced, and it is dried to approximately 10% of its original weight, either by the sun or drier. Dried radish is best kept in sealed plastic to retain the strong odour (Nguyen 1998a).

(A)

(B)

Figure 2: High and low prices (A) and throughput (B) of daikon at Flemington Markets during 1996 (green), 1997 (blue) and the first half of 1998 (red), recorded on a monthly basis (Flemington Market Reporting Service, NSW Agriculture).

Quality assessment

Smooth, white, unblemished skin is preferred. Internal flesh should show no sign of pithiness or hollowness (Nguyen 1998a) and should be free of fibrous tissue. If leaves are attached when sold, they should be turgid, green and free of pathogens (Waters et al. 1992). Japanese grade daikon according to shape and weight (Figure 1), and an acceptable size for export is approximately 1 kg (Nguyen et al. 1997).

Pithiness / hollowing: The major limiting factor for export of fresh daikon from Australia is the development of pithiness during growth and storage. Pithiness is highly genotype dependent (Harris et al. 1993) and is more common when temperatures are high during the early growing phase (Kano 1989). Incidence can be reduced by reducing peak tuber growth (eg; by increasing plant density, pruning leaves in immature plants or using suboptimal growth conditions). The physiology of pithiness formation is discussed in Kano and Fukuoka (1995).

Pungency: A rapid method for determining daikon pungency (4-methylthio-3-butenyl isothiocyanate) is described in Ohguchi and Asada (1990). Levels range from 2 (Chinese cultivars) to 17 m mol/ml and are negatively correlated to water content (Okano et al. 1990).

Roots harvested earlier in the season tend to have higher levels of vitamin C and b -amylase, while roots harvested later tend to have higher total sugar content (Ishii and Saijo 1987).

Daikon was linked to the Japanese outbreak of food poisoning in 1996, and was suspected in another 1998 outbreak (Anonymous 1998).

Pests and diseases

The crop suffers from the same pathogens as affect any Brassica crops (Nguyen 1992), as it comes from the same family. Rotate to avoid root nematode and eelworm populations building up (Larkcom 1991). Potential viruses are listed at Plant viruses online (Brunt et al. 1996). See Hawaiian pests & diseases.

Export market

(click here for exchange rates).

Daikon can be eaten raw in salads, cooked in stews, or grated as a garnish for dipping sauces. Leaves, roots, seedpods and seedlings are eaten. The root is processed as a pickle, salted or dried (Vinning 1995). Sold with the leaves attached or removed, depending on the market (Moody 1997). It was rated a priority Asian vegetable for developing export markets of fresh, diced and frozen, and dried strips products by workshop members reported in Lee (1996). Fresh export must be by boat to minimise cost, thus incurring a 4 week transit time (Harris et al. 1993). However since returns are marginal, exports are more likely to be as semi- or fully processed daikon.

Production is declining in Japan, Korea and Taiwan, but being replaced by cheap Chinese imports. Prices are generally low but there is some dissatisfaction with Chinese quality. Fresh exports are unlikely to be profitable but there may be opportunities in drying and pickling, at least to the first stage (Vinning 1995).

Figure 3: Japanese production of daikon (MAFF 1999).

Figure 4: Prices (¥/kg, red), and throughput (x100 t/month, blue) of fresh daikon at Tokyo Wholesale market (adapted from Anonymous 1996 via Nguyen 1998a).

 
Japan does not appear to be a viable fresh export market for Australia, but opportunities may exist for processed product (Lee 1998) such as dry and salted daikon, and cut daikon within frozen vegetable mixes (Pan 1995). Production of radish is steadily declining, down to 2.1 million t in 1996 (Figure 3). Total consumption is approximately 20 kg/person/year and is the highest of any vegetable (Otsubo 1996), but is also declining (JETRO 1995). Much has been semi-processed by salting, and imports are expected to increase. A demand for lightly pickled vegetables has resulted in a greater proportion of the crop being produced in the Spring (JETRO 1995). Tariff rates vary from 12 to 22.4 %, depending on sugar and processing level. Quarantine requires a declaration that it is free of Radopholus similis (Vinning 1995). Blanched seedlings with green cotyledons are sold in Japan as a pungent garnish (Kimura et al. 1995).

160 000 t of fresh daikon was traded through Tokyo markets in 1994 at an average wholesale price of ¥100/kg. Prices were rising but throughput was falling. Prices were highest from July to September (Figure 4) though there were considerable fluctuations (Vinning 1995). Daikon comprises 3.2% of all Japanese fresh cut vegetable products (Pan 1995).
2 900 t of dried daikon was traded through Tokyo markets in 1993 at an average wholesale price of ¥200/kg (Vinning 1995). Whole dried daikon was valued at around ¥115/kg and sliced dried daikon at ¥308/kg (Nguyen 1998a). Imports of dried daikon to Japan reached 3 983 t in 1996 at a CIF price of ¥171/kg (Nguyen 1998b). Import records commenced in 1995 (2 926 t at ¥137/kg) since the Ministry of Finance previously grouped this product with others. Most were from China (2898 t), followed by South Korea (27 t) and Indonesia (1 t). Daikon that is sliced and dried in sunshine and natural air seems to occupy a large share (JETRO 1996).
500 t of fresh preserved daikon (lightly salted) was traded through Tokyo markets in 1993 at an average wholesale price of ¥850/kg. Seasonal price did not show a clear trend but probably peaked December / January (Vinning 1995).

Organically grown daikon represented 13.1% of production in 1991, amounting to 2.32 million t (JETRO 1994).
Total pickled daikon consumed in Japan totals 250 000 t/year at an average price of ¥524/kg wholesale (Nguyen 1998b). 5 700 t of pickled daikon was traded through Tokyo markets in 1994 at an average wholesale price of ¥400/kg. Prices were rising but throughput was falling. Seasonal price varied with no clear trend (Vinning 1995). A range of pickling mediums are used (Table 4).
Daikon is the second largest vegetable crop in Korea due to its inclusion in Kim Ch'i (Vinning 1995). There may be a need for South Korea to import more materials for Kim Ch'i in both fresh and semi-processed forms (Nguyen 1998b). Korean production is approximately 1.7 million t/year and Australian exports were considered inviable (Lee 1996).

Chinese exports were increasing in both price and quantity, reaching 19 000 t of fresh and 5 500 t of dried product in 1992. Export prices were US$0.25 and US$0.44/kg respectively (Vinning 1995).

The Taiwan market has some potential for Australian exports (Lee 1996) but may be too small to be worth pursuing (Pan 1995). Production has steadily decreased to 120 000 t in 1993, but throughput at Taipei has remained steady at around 23 000 t in 1994, priced at NT$6.70/kg. Prices peak June to August. Exports must have a certificate declaring they are free of the white fringed beetle Graphognathus leucoloma, and fresh or chilled imports attract a 40% tariff (Vinning 1995).

The Hong Kong market has some potential for Australian exports (Lee 1996) but may be too small to be worth pursuing (Pan 1995).

The Singapore market has some potential for Australian exports (Lee 1996) but may be too small to be worth pursuing (Pan 1995).

Used in Indonesia, but not a major vegetable (Lee 1996). Production was around 37 000 t in 1989 (Vinning 1995).

The Philippines produced 6 500 t in 1992, but production is declining. Retail prices increased during the late 1980's (Vinning 1995).

Malaysia produced 5 500 t in 1990, but volumes are erratic (Vinning 1995).

South Korean production was about 1.4 million t in 1992, with wholesale prices of around 145 Won/kg in 1991. Prices were generally increasing, and peak in Spring and Autumn (Vinning 1995).

Related projects

SC Tan, developing new export vegetables with emphasis on burdock, daikon and globe artichoke. HRDC Project Number VG97042.

References

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Anonymous (1997). Fairbanks has a new oriental flavour. Good Fruit and Vegetables.

Anonymous (1998). News. Asia Fruit. May-June 1998: 6.

Bari, M. L., Kusunoki, H., Furukawa, H., Ikeda, H., Isshiki, K. and Uemura, T. (1999). Inhibition of growth of Escherichia coli O157 : H7 in fresh radish (Raphanus sativus L.) sprout production by calcinated calcium. Journal of Food Protection 62(2): 128-132.

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