Sugar cane, Saccharum officinarum, had its origin in Asia, and was grown in India and China in ancient times. Sugar cane is grown along the eastern coast of Australia from Grafton in New South Wales to north of Cairns in Queensland, a distance of 2080 km.
The total area planted to sugar cane in Australia rose to 288 000 hectares in 1976-77. At the same time cane production rose to 23 million tonnes.
Over 70 per cent of raw sugar is exported, the main export markets being Japan, Canada, New Zealand and the USSR. Queensland grows 95 per cent of the Australian sugar cane crop.
Sugar cane is a tall perennial grass with 5 to 20 stems bunched into stools. The stalks are from two and a half to five cm in diameter, and may be four or more meters high. The internodes are short, varying from 5 to 15 cm in length.
Just above each node is a zone called the root band, from which roots will arise when the sections of stem are planted. Buds also occur above each node, and these give rise to tillers if the stem is planted.
The roots of sugar cane are of three kinds. Dense masses of fibrous roots near the surface absorb most of the water and nutrients needed by the plant. The buttress roots grow a metre or so downwards and outwards at an angle of about 60 degrees, and serve to anchor the plant. In some cases cane plants also form rope roots which grow down for great depths if the soil is well drained.
Sugar cane rarely makes an inflorescence or “arrow”. If formed, the inflorescence appears to be very fluffy, because the small spikelets are hidden by tufts of hairs.
Cane is a tropical plant, and will only grow in the warmer coastal regions which have at least eight months of hot weather. The plant is easily injured by frost.
There are two groups of cane varieties – one being harvested after one year of growth, and the other requiring two years in which to mature. Cane is planted by cutting the stems into short lengths called sets, and burying these under the soil. The crop is cut when mature, and this is called the plant crop.
If left in the soil, the plant will form fresh tillers, and a second, or ratoon crop may be harvested. Sometimes two ratoon crops are harvested, but the second one is rarely profitable, as the yield is low and diseases may be a problem.
Yields average is about 80 tonnes/ha in New South Wales. Low yields of 37 tonnes or less are common, but very high yields up to 270 tonnes/ha have been obtained by careful farmers.
The successful growing of cane depends on the following factors:
1. Providing suitable soil conditions, especially good structure, good drainage, and an adequate supply of soil nitrogen.
2. Control of pests and diseases.
3. Making use of improved varieties.
4. Good management.
Soil conditions have the greatest effect on the production of sugar cane. Although cane needs large amounts of soil water, it is extremely sensitive to waterlogging. Therefore drainage of cane fields is a matter of the highest importance.
Field drains thirty centimetres deep should lead surface water to farm drains sixty centimetres deep. These in turn should empty into main drains 1.5 or more metres deep. Neglected drains become blocked and can cause serious loss in production.
Ample supplies of soil nitrogen are needed for rapid growth of cane, and rapid growth is necessary if high rates of sugar storage are to follow. Nitrogen is supplied in two ways. Fertilisers, such as urea and ammonium sulphate, provide the bulk of this nitrogen, for almost half of the nitrogenous fertilisers used in Australia are applied to cane fields.
Green manure crops also supply soil nitrogen, and they have the added advantage of maintaining good soil structure. There has been a decline in the use of green manures, chiefly because Poona peas became subject to diseases. However, other legumes are now being used, like Honolulu cowpeas and Giant cowpeas.
If cane is planted after a green manure crop, 250 to 500 kg of ammonium sulphates are applied after the cane is up. If no green manure crop has been grown, 500 to 750 kg of the fertiliser must be added per hectare.
The chief cane diseases are red rot, Fiji disease, leaf scald, mosaic and ratoon stunt. The best way of controlling diseases is by growing resistant varieties, but no cane variety is resistant to all diseases.
Therefore attempts must be made to control the spread of diseases by selecting healthy cane for planting, by cutting out all diseased plants and by giving plants ideal soil conditions which will make them vigorous. Rats, black beetles and leaf hoppers are pests which may have to be controlled.
A new variety of sugar cane called NCO 130 is now being grown widely on the Clarence River cane fields and in other areas. This variety has higher sugar content than older varieties, is easier to harvest and is resistant to many diseases.