Rural Industries Research & Development Corporation

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Introduction

Annual Australian production is now 600 t and is expected to increase. At present, the local market is limited to the large European population in major Australian cities, but export to Asia and Japan, in the northern hemisphere off-season, is considered to offer good potential for fresh nuts. In season 1995-96 Australia exported to Japan and Singapore a total of 19 t of chestnuts valued at $111,275.

Key strengths of the Australian industry are:

• export potential to the northern hemisphere in the off-season;

• access to a co-ordinated and cohesive approach to marketing and promotion by the industry body;

• the ability to replace inferior varieties with varieties of superior quality and so increase consumer confidence; and

• the opportunity and potential to replace imported processed products.

Markets and marketing issues

uture research is required for the development of the peeled, pre-packaged market and there are currently no large-scale processing or value-adding facilities in Australia.

The industry is actively examining the potential for export and processing through the industry body. It is essential for the industry that consumption of fresh chestnuts continues to increase and that substandard product that will discourage new consumers from repurchasing does not enter the market. The very nature of chestnuts, i.e. a seasonal product, considered as an epicurial delight, and requiring a degree of preparation for cooking, creates a challenge for the marketing of this nut.

The outlook for dedicated growers with nuts that have good eating, storing and peeling qualities can be viewed optimistically. In the immediate future there may be an oversupply of inferior nuts from older seedling trees, but with better quality nuts from improved varieties replacing inferior nuts, consumer confidence should increase.

The following graph shows the wholesale prices for chestnuts from the Melbourne Fresh Centre for the 1994 and 1995 seasons. The average wholesale price was between $3.00 and $3.75. The prices for 1996–97 ranged anywhere from $0.30/kg through to approximately $6.00. Higher prices can be achieved for sizes in the ‘special’ ( greater than 38 mm) range.

Production requirements

Irrigation should not continue too late into the growing season, as it can make nuts crack and over-develop.

Chestnuts require a well-drained, deep soil. The tree is deep-rooting, and the most suitable soils are deep, red basaltic types, with free-draining characteristics. Soil pH should be in the range 5. –6.0. Trees grown in shallow soils are short-lived, as are trees grown in heavy soils with impermeable subsoils. Good drainage is essential for tree health, as chestnuts are susceptible to root rots and other fungal diseases.

Varieties

‘Buffalo Queen’ peels in hot water and has good flavour when roasted. ‘Lucenti’ is as attractive, shiny, honey-coloured nut, free falling, of medium size, and slightly sweet.

‘Lucenti’ is a late maturing variety in Victoria.

‘Red Spanish’ is a medium to large nut, shiny and relatively sweet.

‘Purtons Pride’ (also known as ‘Emerald Gem’) is large, light-tan nut. This nut peels well when roasted and is tolerant to shell splitting.

Some named Chinese chestnuts (Castanea mollissima) imported into Australia include: ‘Nanking’, ‘Crane’, ‘Meiling’, ‘Skookum’ and ‘Kuling’. Most Chinese chestnuts have yet to bear commercial quantities in Australia or to be tested in the marketplace.

Trees of the European chestnut (Castanea sativa) are purchased as grafted trees, generally on seedling rootstocks, and are available from specialist nut nurseries.

Agronomy

Following ripping, soil pH should be adjusted if the soil is acid. Fine agricultural lime is normally spread and incorporated before the trees are in the ground. A suitable legume or cereal crop will increase organic matter and add nitrogen before planting. A soil test for nutritional status can also be conducted at this time.

Chestnut planting distances have become smaller in recent years, aiming for higher yields and better use of available land. New orchards are planted at spacings of between 7 ¥ 7 m and 12 ¥ 12 m, yielding the following numbers of trees per hectare.

7 m ¥ 7 m 204 trees/ha
8 m ¥ 8 m 156 trees/ha
12 m ¥ 12 m 69 trees/ha

Chestnuts are wind pollinated and should be considered to be self sterile for commercial purposes. More than one variety should be planted to ensure cross pollination.

Following planting of young trees, guards can be placed around the tree trunks if rabbits are a problem. The trunks of young trees can be whitewashed with a water-based paint to prevent sunburn if high temperatures are expected.

Most chestnut groves benefit from a balanced nutritional program that supplies mainly nitrogen, phosphorus and potash. Fertiliser application should commence in the second year to avoid fertiliser burn which can occur if the tree has insufficient roots. Further application of fertiliser will be determined by leaf tissue analysis, for which there are standards available.

Chestnuts do not require specialised pruning, but in the first year the tree may require pruning back to compensate for roots lost in the transfer from the nursery. During the first year of growth, train the terminal bud as a leader, and in later years do not allow the trunk to produce branches below 60 cm. Most chestnuts are trained to a central leader, and broken and crossed limbs should be removed early in the tree’s life.
 

Pest and disease control

Fungal root rots can cause major losses in nut groves, and trees of all ages can be affected. Deaths have been recorded in major growing areas, with healthy trees succumbing rapidly. Other trees may remain alive in a weakened state for a number of years.

Phytophthora cinnamomii is a common soil-borne fungus that can spread from the base of the tree at an infection point and then move downwards into roots and, later, upwards into the tree. Poorly drained soils aggravate the problem. Fungicides sprayed onto the ground or foliage can limit the spread but not eliminate the organism.

Armillaria root rot (Armillaria mellea) is another disease that can affect healthy trees. Like Phytophthora, the symptoms may not be evident until the tree is heavily infected. Armillaria can survive in root tissue from previous introduced trees.

Remove old and rotting roots or stumps before planting.

Fungal rots can also affect the nuts during postharvest handling and storage. Preharvest rots have also been observed on falling nuts, with Phomopsis castanea being the most likely causative organism. Losses in storage due to Phomopsis are often undetectable, as the nut will appear sound from the outside.
 

Harvest, handling and processing

During the harvest period nuts should not remain on the ground for long periods and should be collected at least every two days. Some selections dehisce completely, leaving the prickly burr attached to the tree. Most nuts fall within the burr and can be collected by hand. Purpose-built suction harvesters are available and usually require two people to operate.

After the nuts are removed from the burrs they are graded, usually using a slowly-revolving cylindrical drum that contains holes of different diameters through which the nuts fall and are sorted into different size classes. Chestnuts are currently graded into five industry recognised sizes:
 

• small (<25 mm)
• medium (29 mm)
• standard (32 mm)
• large (38 mm)
• special (>38 mm)

The nuts should be placed in a cool store at 0°C as soon as possible and then held at this temperature until marketed. Placing nuts in unsealed polythene bags will reduce excessive weight loss in a forced air cooled environment.

Unrefrigerated nuts should not be placed in plastic bags. Nuts are marketed usually in 5 or 10 kg cartons, or 25 kg hessian bags.
 

Economics of production

Suction harvesting equipment costs from approximately $10,000, dehuskers from $3800 and grading machines from $3,000. This equipment is purpose-built and readily available in Australia. A suitable tractor will be required for routine mowing, spraying and general nut grove operations.

Yields have often been difficult to predict because of seasonal variation, possible pollination problems, occasional poor tree health and varietal differences. This makes ‘typical’ gross margin data unreliable, but representative production figures are given in Table 1. (not available in this html version - ed)
 

Key contacts

Lester Snare
Orange Agriculture Institute
NSW Agriculture
Forest Road
Orange, NSW 2800
Phone: (02) 6391 3800
Fax: (02) 6391 3899
Email: sweetr@agric.gov.au

David Ogilvy
Brittle Jacks
Mullion Creek, NSW 2800
Phone: (02) 6365 8353
Fax: (02) 6365 8353
 

Key references

Jaynes, R.A. (ed) (1979). Nut Tree Culture in North America. Northern Nut Growers Association Inc., Connecticut.

Snare, L.N. (1996). Chestnut Production. NSW Agriculture, Agfact H3.1.50.

Woodruff, J.G. (1979). Tree Nuts. A.V.I. Publishing Co.
 

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