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Cultivating Chinese waterchestnut without soil

Cultivating Chinese waterchestnut without soil
Kleinhenz, V.; Midmore, D. J., 1998
Access to Asian Foods, 5, 5-6


Cultivating Chinese waterchestnut without soil

Cultivating Chinese Waterchestnut Without Soil

(Project UCQ-8A)

 

Volker Kleinhenz and David J Midmore

A new crop to Australia with current plantings of one to four hectares per year, commercial production of Chinese waterchestnut [Eleocharis dulcis (Burm. F.) Hensch] only dates back 12 to 13 years. In a previous article (Access to Asian Foods, Issue 3, August 1998) we addressed physiological issues suggesting that environmental factors (eg soil properties, photoperiod, temperature) and/or cultivation management (eg. nutrition, irrigation, harvest timing) primarily determine quality of field grown waterchestnuts in Australia. Overseas information on cultural management of waterchestnut is limited and current and prospective producers seek guidelines. Some of the difficulties facing Australian producers are choice of growth media, plant nutrition and harvest procedures. Determining the optimal nutritional requirements of waterchestnuts was considered a priority issue for research (MIDMORE & CAHILL, 1998). Harvesting is still considered a major constraint to cultivation of waterchestnut in soil, particularly for `new' growers even though several functional mechanical devices are currently used in Australia.

 

In an effort to overcome these soil and management related obstacles to field cultivation, the Asian Vegetable Research Team at Central Queensland University studied the soilless culture of Chinese waterchestnut in a system which can easily be adopted.

 

Containers, growing medium and irrigation

For easy harvest of corms we used standard Australian polystyrene boxes used for packaging fruits, vegetables and seafood. To save on costs, second-hand boxes may be available through local foodstores. Polystyrene boxes are lightweight and provide some thermal insulation. Experience shows that these boxes are not perfectly waterproof and plant stolons can grow through the material so they need to be lined with plastic film. Since waterchestnut consistently produces new stems from mother corms and stolons, boxes cannot be enclosed from above as in other hydroponics systems (see for example MIDMORE & WU, 1999).

 

Many growth media are available for hydroponic production of vegetables. To protect the root system of waterchestnut in open boxes from light, a solid medium such as sand should be chosen. Open boxes cannot be kept clean of any organic contamination so used media should be discarded or sterilised before reuse.

 

Waterchestnut is an aquatic vegetable and the medium should be covered with water throughout the growth period. In addition to water loss through transpiration, water in open containers is also lost through evaporation which can be great during the summer season. Therefore, growth medium should not occupy more than two thirds the height of containers to leave space for sufficient water to reduce frequency of irrigation. Automatic irrigation has been successfully applied to this cultivation system and one grower is currently trialing oxygenation of irrigation water.

 

Boxes can be placed in protected areas such as green or polyhouse and also in the open. If placed outside, rainfall may supply a part of irrigation water but nutrient loss may occur when boxes run over during the course of heavy rainfall.

 

Nutrition

As there are few published recommendations for nutrition of Chinese waterchestnut (eg ANONYMOUS, 1996 and HIBBERT & FINLEY, 1989). Fertiliser trials were conducted to establish optimal nutritional requirements. A practical fertilisation guideline is to apply a total of 20-30 g per m2 each of N, P and K. Nitrogen should be applied in the form of ammonium (eg. Urea) rather than nitrate and potassium as muriate of potash (KCl) rather than sulfate of potash (K2SO4). KCl produced significantly higher total soluble solid contents than did K2SO4.

 

P and K can be applied entirely before planting. N should be split into two applications: 50 percent before (basal application) and 50 percent three months after (side dressing). If a greater percentage of N is applied before transplanting, the result is greater stem biomass at the expense of corms. However, if a greater part of N is applied as a side dressing, the result is a great number of corms of non-marketable size.

 

Although we have not researched effects of micronutrients on waterchestnut quality and yield, a volume of about 100-200 ml per m2 per month of a standard micronutrient solution seems to be sufficient. Such solutions can be obtained from suppliers of hydroponics equipment around Australia.

 

Harvest, quality and yield

A great advantage of soilless cultivation of waterchestnuts in containers is the ease of harvest. When most stems have died off in autumn, irrigation should be discontinued and/or water drained off to facilitate easier handling of boxes. After washing off the growth medium, corms are easily separated manually or mechanically from roots and rhizomes with no further washing being required.

 

We tested waterchestnuts grown in soilless culture and found their quality and yield comparable with those cultivated in soil at various locations in Australia (Figure 1).

 

Figure 1. Quality and yield of waterchestnuts cultivated with and without soil in Australia.


Scheduling

Scheduling of cultivation operations as described in Table 1 results from two years of experimentation in subtropical Rockhampton, Queensland and may vary according to climatic conditions at other locations. Since waterchestnuts do not tolerate temperatures below 0C, the growing season in southern parts of Australia is much shorter than in the subtropical and tropical parts and corms should be planted in a protected environment and/or as soon as possible after the last frosts in spring.

 

Table 1. Scheduling of cultivation operations for soilless culture of Chinese waterchestnuts in Rockhampton, Queensland.

Task

Date

Sowing corms in trays ('nursing')

Nov

Preparing boxes (eg lining and filling with sand)

Nov

Fertiliser basal application (N, P, K)

Nov

Transplanting of most vigorous plants

Nov/Dec

Irrigation (weekly if by hand)

Nov/Dec - Jun/Jul

Micronutrient application (monthly)

Nov/Dec - Jun/Jul

Fertiliser side dressing (N)

Feb/Mar

Harvest

Jun/Jul

 

References

Anonymous, 1996: Growing Chinese Water Chestnuts. Aqua-nut, Lauriston.

Hibbert, A, Finlay, G, 1989: Chinese water chestnuts - under trial at Redlands. Queensland Fruit and Vegetable News, November 16, 1989, 18, 23-24.

Midmore, DJ, Cahill, GT, 1998: The Chinese Waterchestnut Industry - A Situation Analysis and Industry Strategy, RIRDC Publication No 98/38, Rural Industries Research and Development Corporation, Barton (ISBN: 0-642-54057 8).

Midmore, DJ, Wu, DL, 1999: Work that water! Hydroponics made easy. Waterlines, 17(4), 28-30

 

Central Queensland University

Primary Industries Research Centre

Plant Sciences Group

Bruce Highway

North Rockhampton, Qld 4702

Tel: (07) 4930 9770/9445

Fax: (07) 4930 9255

Email: d.midmore@cqu.edu.au / v.kleinhenz@gmail.com

WWW: http://science.cqu.edu.au/psg/