Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Guar

Introduction

Guar or cluster bean (Cyamopsis tetragonoloba) is believed to have originated in Africa but has been grown throughout southern Asia since ancient times as a vegetable and fodder crop. The plant is variable in form, ranging from 0.5 to 3 metres in height. The degree of branching is variable, and this variability influences its end-use.

This crop is a drought-tolerant, warm-weather, deep-rooted summer-growing annual legume. It grows well in soils of low fertility in the arid and semi-arid areas of the tropics and sub-tropics where the rainfall is summer-dominant. The green pods can be consumed as vegetables by humans and the crop grazed by cattle. Guar is also useful for green manure.

Guar has been trialled over some years in central and south-eastern Queensland. This interest has arisen because of the vegetable gum (galactomannan) in the guar seed. Guar gum has multiple uses in thickening, stabilising, sizing and strengthening all kinds of materials in the food, paper, textile, mining, petroleum and pharmaceutical industries. It has exceptionally high viscosity at low concentration and its cold-water swelling can function over a wide range of pH.

After removal of the gum, the seed material can be used for stockfeed as it has a high protein content (35%), but the material needs treatment before feeding to monogastric animals since it contains anti-nutritional factors (a trypsin inhibitor, polyphenols, haemagglutinin and saponins). The good ground-cover this crop provides can be useful for soil conservation.

Guar is currently grown commercially in north-western India. eastern Pakistan and the United States.

Markets and marketing issues

No crop of guar should be contemplated in Australia unless its end-use and price have been prearranged.

Seed yields of up to 4 t/ha have been achieved. Up to 35% gum yields have been produced, but this level is dependent on both variety and environment.

Production requirements

Guar can tolerate a wide range of climatic and soil conditions but maximum growth occurs at high temperatures (25-30°C). The crop is intolerant of shade and must be frost-free for 110-130 days. Guar prefers lighter soils within the pH range 7.5-8, is very intolerant of water-logging, has a moderate level of salt tolerance and good drought tolerance.

Varieties/breeds

Approximately 400 lines of guar have been introduced into Australia and more than 100 of these have been included in field trials. The strongly-branching varieties Brooks and ECR67 and the sparsely-branching CP177 have been commonly used for research in Queensland.

Agronomy

The type of branching of the variety will influence its suitability for the end-use envisaged: branching varieties are considered more suited to seed production, and the single-stem varieties better suited to vegetable pod production.

Optimum row spacings depend on the branching ability of the variety, with branching varieties more suited to lower planting densities. Row spacings of
45-60 cm are usually effective and sowing rates of 11-28 kg/ha used when the crop is grown for seed. Higher sowing rates are required if the crop is to be grazed or cut for forage.

The recommended sowing time ranges from November to early January in Queensland. Guar has been termed a quantitative short-day plant and most varieties are indeterminant.

CB756 has been found to be a suitable inoculum.

The most common nutrient deficiencies to be expected are zinc and phosphorus; this plant has a high phosphorus requirement.

Pest and disease control

Pod-sucking bug (Riptorus serripes) can cause some damage in guar, and diseases likely to be a problem are Sclerotium rolfsii and Alternaria cucumerina.

Harvest and processing

Most guar varieties reach maturity in 125-160 days. Normal harvesting machinery can be used but speeds need to be reduced to avoid damage to the seed. For storage, drying to at least 14% moisture is important.

Guar gum is located in a layer on the inner surface of the endosperm cell walls of the seed.

The gum is extracted by either a wet or dry processing method, neither of which is currently commercially available in Australia. The former method is more efficient and involves cleaning, boiling in NaHCO₃ and urea, washing, dehusking, drying, separation and grinding of the endosperm, suspension in isopropanol, heating, separation and drying, suspension in methanol, refluxing and drying.

Key contacts

Key References

Kay, D.E. 1979. Cluster bean. In `Food Legumes'. Tropical Products Institute, Ministry of Overseas Development, London. Crop and Product Digest 3, 72-85.

Murphy, H.E. 1997. The influence of leaf canopy on seed and gum yield of guar (Cyamopsis tetragonoloba [L.] Taub.). Ph.D. thesis, The University of Queensland Gatton College. 358pp.

Jackson, K.J. 1990. Guar evaluation in central Queensland 1978-1983. In: `Guar Research in Queensland 1978-1984'. (Eds M.A.Davey, K.J. Jackson and M.N.Hunter), pp. 1-13. (Queensland Department of Primary Industries Publication QC90006).

Jackson, K.J. and Doughton, J.A. 1982. Guar: a potential industrial crop for the dry tropics of Australia. Journal of the Australian Institute of Agricultural Science 42, 17-32.

Jackson, K.J., Doughton, J.A. and Berthelson, J. 1985. Guar: a versatile crop. Queensland Agricultural Journal 111(5),
273-283.

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