Saccharum officinarum (PROSEA)
- Protologue: Sp. pl.: 54 (1753).
- Family: Gramineae
- Chromosome number: 2n= 80
- Sugar cane (En). Canne à sucre (Fr)
- Indonesia: tebu (general), tiwu (Sundanese), tep (Halmahera)
- Malaysia: tebu
- Papua New Guinea: ale, kowu, tuma
- Philippines: tubo (Tagalog, Bikol), tubuh (Tausug)
- Cambodia: 'âmpëu
- Laos: 'o:yz
- Thailand: oi (general), oi-daeng (central), ka-thi (Karen, Mae Hong Son)
- Vietnam: mía.
Origin and geographic distribution
Sugar cane originated in New Guinea where it has been known since about 6000 BC. From about 1000 BC it spread gradually through the Malay archipelago. It is assumed that it then hybridized with the wild canes of India and China. It reached Hawaii between 500-1000 AD and the Mediterranean between 600-1400 AD. From there it was brought to the Caribbean and the Americas in the 16th and 17th Centuries. Currently, cane is being produced in almost 70 countries, mainly in the tropical zone but to some extent also in subtropical areas. In South-East Asia, the main cane sugar producing countries are Thailand, the Philippines, Indonesia, Malaysia and Papua New Guinea.
Sugar cane is cultivated for its stem (cane). The main product of sugar cane is sucrose, constituting about 10% of the crop. Sucrose is a highly valued food and sweetener but also serves as a preservative for other foods. Moreover, it provides the basis for various food products and beverages.
The fibrous residue of cane, bagasse, is mostly used as fuel for the generation of energy needed for sugar manufacture. However, it can also serve as raw material for fibre and particle board, plastics, paper and furfural. For these purposes, the fibre is separated from the pith which can, in turn, be used as a feed. Filter cake, consisting of juice impurities and lime (CaO), is mainly used as a soil amendment; sometimes waxes are extracted from the cake.
Molasses, left over after centrifuging the sugar crystals, is used as a feed; converted into a proteinic substance, it is used as a fertilizer or for the production of yeast, CO2and various acids such as essential amino acids for animal feeds, e.g. L(-)lysine. However, it is mostly processed into potable and industrial alcohols.
A more recent development is the direct production of industrial ethylene, not requiring refining and crystallization, in response to the energy crisis of the 1970s and the subsequent steep rise in oil prices. Brazil was particularly active in this development, but since the decline in oil prices no new investment has been deemed necessary.
Production and international trade
From 1986-1993, the annual world cane sugar production gradually increased from 62.8 million t to 79.2 million t raw value. In 1992, Indonesia produced 2.35 million t from 418 000 ha, Malaysia 105,000 t from 20,000 ha, the Philippines 1.92 million t from 350,000 ha, Thailand 5.08 million t from 915,000 ha and Papua New Guinea 30,000 t from 6000 ha. In 1992, consumption of cane sugar in Indonesia was 2.7 million t, in Malaysia 715,000 t, in the Philippines 1.6 million t, in Thailand 1.3 million t and in Papua New Guinea 27,000 t.
Exports in 1992 were 212 500 t from the Philippines, 3.7 million t from Thailand, and 7000 t from Papua New Guinea, whereas Indonesia imported 41,000 t and Malaysia 900,000 t. Sugar cane by-products provide a significant additional income, especially important in periods of low sugar prices on the world market.
The sugar sold on the world markets is valued according to colour, size of granules, polarization, and ash and moisture content. Most sugar is sold as coarse or fine granulated raw sugar with a purity of 97-99%. "Plantation white" sugar for direct consumption has a purity of 99-99.5%, while refined sugar's purity is virtually 100%.
Besides centrifugal sugar, various products obtained by traditional processing methods can be found in almost all cane-growing countries. The traditional cane sugar known as "gula jawa" and "gula mangkok" in Indonesia, "panocha" in the Philippines, and "jaggery" or "gur" in the Indian subcontinent, has an average composition of 3.5-9.5% water, 50-85% sucrose, 2.3-15.6% glucose and other sugars, 2.0-3.5% ash and some proteins and aromatic substances.
A large, perennial grass up to 6 m tall. Root system large, but concentrated in the upper 60 cm of the soil, adventitious. Stem robust, profusely tillering at base, 2-5 cm in diameter, and divided into 10-40 internodes; internodes long or short, swollen, spindle-shaped, conoidal, obconoidal, or cylindrical. Leaves borne at nodes, alternate in two rows on either side of the stem; sheath tubular, encircling the stem; ligule varying in cultivars, linear, deltoid, crescent-shaped or arcuate; blade linear, 70-200 cm × 3-7 cm, tapering, thick at the centre and paper-thin at the margins, rolling up under moisture stress conditions. Inflorescence a terminal panicle, 25-50 cm long; two spikelets borne at each node of ultimate branches, one sessile and one pediceled; spikelet consisting of two boat-shaped glumes, surrounded by long, silky hairs, and two flowers; lower flower sterile with a single glume, upper one bisexual with a small, thin palea, enfolded by the glume of the sterile flower, 2 lodicules, 3 long stamens and a pistil with 2 feathery, usually purplish stigmas. Fruit a small caryopsis, about 1 mm long.
Growth and development
Within 1-3 weeks the buds of planted cuttings start to germinate while set roots (primordial roots) start to grow from the cutting's root band. These set roots gradually die and are replaced by shoot roots growing from the basal part of the shoot. After germination, secondary and subsequently tertiary shoots develop. Each cane stool can consist of 1 primary, 3 secondary and 3 tertiary stalks, depending on the growing conditions. The tillering period starts at about 1.5 months after planting and continues for 1.5-3 months, depending on the cane cultivar. Late tillers (suckers) may develop before harvest (at 8-10 months). They are thick and succulent. They grow especially where light can freely enter, e.g. at field edges and in lodged cane. After the cane canopy has closed, fewer tillers will develop and most existing cane stalks elongate further. Their growth is influenced by the production of leaves and consequently of internodes. The time lapse between the formation of subsequent leaves is known as the "plastochrone". Under favourable growing conditions, the plastochrone is 5-7.2 days long and under unfavourable conditions it is 2 or more weeks. The growth period of cane in South-East Asia is 6-8 months and is related to water availability.
The final stage of sugar cane development is the ripening stage, and 11-14 months after planting, maximum sucrose content of the fully grown stalk will be reached. This stage can be recognized by reduced growth of the stalks and by yellowing of the leaves. With increasing maturity, the sucrose content rises, especially in the top part of the stalk. Whereas in earlier stages, sugar is accumulated mainly in the bottom part, there is hardly any difference in sucrose content between the top and bottom parts at full maturity.
Other botanical information
Besides S. officinarum , four other Saccharum species have been used for sugar production or as hybridization material for commercial cane breeding. S. officinarum is known as "noble cane" and has a high sucrose content, low fibre content, long and thick stems, and long and broad leaves.
- S. barberi Jeswiet (2 n = 82, 90, 124), known as "Indian cane". The sucrose content is medium, the fibre content high. The plant is semi-early maturing, has slender and medium long stems, with short and narrow leaves. It originated in India but was distributed early and was the major cultivated species in America until the 19th Century.
- S. robustum Brandes & Jeswiet ex Grassl (2 n = 70, 80, 84). The sucrose content is low, the fibre content very high. The plant matures early or late, and has very long and thick stems, with broad leaves of medium length. It is indigenous in New Guinea and adjacent islands in Melanesia. It probably gave rise to S. officinarum .
- S. sinense Roxb. (2 n = 116, 118), known as "Chinese cane". The sucrose content is medium, the fibre content high. The plant is semi-early maturing, has long and slender stems, with long and narrow leaves. It is thought to be a hybrid between S. officinarum and S. spontaneum and is found in India, Indo-China, southern China and Taiwan.
- S. spontaneum L. (2 n = 54, 112, 118), known as "wild cane", is used for hybridization purposes. The sucrose content is very low, the fibre content very high. The plant is early maturing, has slender but short and hard stems, narrow leaves, and is resistant to most cane diseases. It occurs wild from eastern and northern Africa through the Middle East to India, China, Taiwan and throughout South-East Asia.
Cane breeding for commercial cane is carried out in Indonesia, the
Philippines and to some extent in Papua New Guinea. Commercial cane
cultivars produced are POJ and PS (Pasuruan, Indonesia), CAC and Phil (Philippines) and NG (Papua New Guinea). At present the major cultivars in Indonesia are PS 56 and PS 58, and two imported ones, i.e. M (Mauritius) 44251 and F (Formosa) 154. The major cultivars in the Philippines are Phil 56226 and Phil 66-07, and in Thailand Q 83 (Australia), F 140 and local cane cultivars Chainant 1 and Uthong 1.
Sugar cane, being one of the most efficient natural converters of solar energy and carbon dioxide (C4-cycle photosynthetic pathway), makes optimum use of arable land. Its photosynthetic efficiency is 20 times higher than the average world's biomass production. However, it needs high temperatures. The optimum temperatures are 26-33°C for germination and 30-33°C for vegetative growth. During maturation, a period with relatively low night temperatures (below 18°C) is conducive to the formation of a high sucrose content.
Sugar cane thrives under full sunlight where its leaves saturate at about 10 750 lux and the compensation point is approximately at 430 lux. It is a quantitative short-day plant; a daytime period of 12-14 hours is optimum for growth and flowering.
An average rainfall of 1800-2500 mm/year is desirable. If rainfall is insufficient, water should be supplemented by irrigation. Vegetative growth is promoted by a uniform and high precipitation; during maturation the cane requires a marked dry spell in order to reduce growth and induce sugar accumulation. Air humidity is of little importance for cane development.
At high altitudes, the potential to grow cane is limited because lower temperatures, particularly during the night, retard growth and development, although they increase the sugar content. Within the South-East Asian region, the maximum altitudinal limit for normal cane growth is 600-700 m above sea-level. At higher altitudes longer growth cycles of 14-18 months must be adopted.
Sugar cane thrives on a wide variety of soil types, but deep, friable and well-drained soils with a pH of 5-8, ample nutrient and organic matter contents and a good water-holding capacity are most suitable. Some cane cultivars can stand relatively high soil salinity and an extended period of deep inundation, especially in flowing water. Being a vegetative crop, sugar cane requires large quantities of nitrogen, although potassium, phosphorus, calcium and silica are also in relatively large amounts. Trace elements play an important role in the development of cane. Insufficient availability of each of these elements may cause growth disorders. The related symptoms, however, may be mistaken for those of diseases and mechanical damage.
Propagation and planting
Generally sugar cane is vegetatively propagated by cuttings of mature stalks. Each cutting or "seed set" usually has 2-3 buds. The cuttings are put down horizontally and covered with a thin layer of soil. There are three kinds of plant materials, i.e. top cuttings, stem cuttings and "rayungans". Top cuttings are "seed sets" taken from plants in the upper part of the stalks of recently harvested cane. Stem cuttings are "seed sets" taken from plants in special nurseries at about 6-8 months of age. Whole cane stalks can also be planted; because of top dominance these are cut up into "sets" in situ, using an ordinary cane knife. "Rayungans" are obtained by removing leaves and top ends of seed cane in the field, the buds of which are then allowed to germinate on the standing cane stalk. When the new shoots have attained a certain length, the cane is cut into sets and planted. These pregerminated sets are excellent planting material but vulnerable during handling and transport and very labour-intensive to produce.
True seed of sugar cane is only used for the purpose of breeding new cultivars.
"Seed sets" are planted in a narrow planting furrow which should have good tillage. They are covered with a thin layer of soil from the interrow. These planting furrows can be made on flat land or on the bottom of an irrigation/drainage furrow. In wet sites, planting may be on the top of the ridge between the furrows. Alternatively, planting is mechanical: the stalks are cut into pieces, disinfected, fertilized, planted and covered with soil in one go. Irrigation water is usually applied before or immediately after planting. The multiplication rate of cane is about 8-10, i.e. a nursery of 1 ha is needed to plant 8-10 ha of cane.
Cane is usually planted as sole crop. However, in areas with light soils and sufficient irrigation water, cane is intercropped, e.g. with maize, groundnut or soya bean. In such cases the intercrops are planted on the ridges and the cane is planted 3-4 weeks later in the furrows.
After levelling the land and determining the direction of the cane rows, the land is disk-ploughed to a depth of 30-40 cm and harrowed into a fine tilth. If required, irrigation furrows with a depth of 25-30 cm and a spacing of 1.10-1.30 m are made for hand-cultivated cane. For mechanical cultivations, a minimum furrow distance of 145 cm is required (minimum wheel base of tractors).
In irrigated rice fields in Java, the "Reynoso" method is followed for preparing the land for sugar cane. This highly labour-intensive method, necessary for a good aeration of the heavy soil, consists of digging 30-45 cm deep and 35-45 cm wide trenches. In between these trenches high ridges of dug-up soil are created.
The planting time is early in the dry season for irrigated fields; unirrigated fields are planted at the onset of the rainy season.
Weed control is carried out manually, chemically and mechanically. Where sufficient labour is available, weeding is carried out at 3-4 week intervals with 3-4 weedings per season. In areas with less labour, herbicides are applied, sprayed twice, at 1-2 weeks after planting and 4-6 weeks later. The chemicals commonly used are one or two of the following: diuron, ametryne, atrazine, paraquat + diuron, or asulam + atrazine, mixed with 2,4-D amine salt. Other herbicides, e.g. pre-emergence ones, may also be used. Mechanical weed control, if economically more justified, is done with tractor- or bullock-drawn cultivators.
Irrigation water, if necessary, is supplied every 2-4 weeks to the cane rows in the case of furrow irrigation, and to the cane on flat land or in small furrows in the case of sprinkler irrigation. When the cane grows taller, more water has to be applied, but intervals between the applications need not always be shortened.
Fertilizers are given twice, the first application during planting or one week later, the second application 4-6 weeks later. The fertilizers commonly used are urea or ammonium sulphate as N source at rates of 120-180 kg/ha, triple superphosphate as P source at 45-180 kg/ha and muriate of potash as K source at up to 180 kg/ha. In newly established sugar cane fields, additional applications of dolomite at 1 t/ha and limestone at 1-4 t/ha are given every three years. Actual application rates for each fertilizer depend on physical soil conditions and fertility.
In most cane fields the cane rows are earthed up 1-2 times by hand or mechanically. On the heavy clay soils of Java this is even done several times. Eventually the cane stands on ridges separated by furrows. This practice stimulates root growth, consolidates the cane stools and improves drainage on the heavy clay soils. On the lighter textured soils it helps against early lodging of cane and can prevent erosion (if the direction of the furrows is chosen well).
The official rotation of crops, particularly in farmers' cane on irrigated fields in Java, is conducted in such a way that 2 consecutive cane crops (planted cane and first ratoon) are followed by maize, soya bean or groundnut, and later by rice. In other areas 4-6 ratoons are maintained, after which the old stubble is ploughed-up and the field replanted to cane again. Ratoon management after harvesting the previous crop consists of stubble shaving, burning the cane residues and trash, trash raking, filling the gaps with top cuttings, fertilizer application at 0.5-1.5 month after stubble shaving, and, if necessary, subsoiling the interrows. Weed control usually follows immediately after fertilizer application.
Diseases and pests
Four major sugar cane diseases are encountered in the South-East Asian region: mosaic virus disease, ratoon stunting disease (caused by the bacterium Clavibacter xyli var. xyli ), yellow spot ( Cercospora koepkei ) and rust ( Puccinia melanocephala ). Growing cane cultivars resistant or tolerant to these diseases is considered an economic and effective control measure. Hot water treatment (at 50°C for two hours or at 52°C for 20 minutes) of seed canes is a satisfactory control measure for ratoon stunting disease. If not controlled properly, both mosaic virus and ratoon stunting disease may depress sugar yield by 10%, especially in ratoons. In Papua New Guinea, a previously unknown etiology disease ("Ramu stunt disease") was first recorded in 1985; it severely reduced growth and yield.
Major pests attacking sugar cane are the stem borer Chilo sacchariphagus , the top borer Scirpophaga nivella var. intacta , the woolly aphid Ceratovacuna lanigera , and the rat Ratus-ratus argentiventer . Satisfactory control of the stem borer can be achieved by releasing the larvae parasite Diatraeophaga striatalis and the egg parasites Trichogramma spp. Partial control of the top borer is achieved by treating the soil and injecting the cane plant whorl with carbufuran granules. The woolly aphid is controlled with insecticide (dimethoate and monocrotophos) fogging, or at the initial infestation by releasing Encarsia flavoscutellum parasites. Every 5-6 years rat explosions occur, mainly attacking food crops and sugar cane. Distribution of anti-coagulant poisoned baits can control the plague in sugar cane crops.
The harvest time of sugar cane for most Indonesian sugar factories is between May and October. In the Philippines and Thailand, the harvesting season is from November to March/April. The cane is cut and loaded manually, hand-cut and grab-loaded or loaded in bundles by chains pulled by a tractor. Mechanical harvesting by chopper harvesters or whole-stalk harvesters has not yet been adopted on a large scale. Burning before cutting is not practised, except in several areas in the Philippines.
Average sugar yields in 1992 were 7.86 t/ha in Indonesia, 5.62 t/ha in Malaysia, 6.62 t/ha in Papua New Guinea, 8.27 t/ha in the Philippines, 6.11 t/ha in Thailand, 4.13 t/ha in Vietnam, and 4.53 t/ha in Burma (Myanmar). The average world sugar yield is 5.16 t/ha.
Handling after harvest
Production processes in sugar mills are as
- Extraction of juice from the cane by passing the cane through crushers or shredders and subsequently through a 3-5 roller tandem. At each roller unit the crushed cane is subjected to an imbibition process by addition of water or cane juice. Alternatively, shredded cane is passed through a diffuser in which sugar is extracted from the cane by osmosis and lixiviation at increased temperatures. The juice eventually obtained, which is turbid and slimy, is then sieved through fine-mesh copper or stainless steel gauze in order to remove mechanical impurities.
- Purification of juice by precipitating non-sugar constituents by treatment with sulphurous acids and phosphoric acids or surface active substances such as silicious earth (sulphitation process). Another method is treatment with a large excess of lime followed by heating (carbonation process). The flocculated impurities are then separated from the juice during the filter process.
- Crystallization of thickening juice is carried out under vacuum in the evaporation and boiling station. With a vacuum of 710 mm Hg and a temperature of 60°C, the extraction of water proceeds rapidly and sugar crystals soon begin to form.
- Centrifuging is conducted in cylindrical or conical drums whose walls are lined with perforated copper or stainless steel gauze. The sugar crystals are separated from the mother liquid at rapid rotation (800-1400 rpm).
- The sugar is packed by bagging either directly from the grasshopper conveyors or after passing rotating driers and cooling towers.
Global germplasm collections exist in Cannanore
(Coimbatore, India) and in Canal Point (Florida, United States). A minor collection from the Indonesian archipelago is present in Pasuruan (Java, Indonesia); it consists of wild canes, such as Erianthus spp., Miscanthus spp., Saccharum barberi , S. robustum , S. sinense , S. spontaneum , and cultivated cane S. officinarum and their hybrids; the collection has been used worldwide by sugar research institutes for breeding purposes.
The main breeding objectives are to develop cane cultivars with the following characteristics: high and stable cane yield, high sucrose content, good ratooning ability, resistance to major diseases and pests, and tolerance of adverse environmental conditions, especially water stress. Furthermore, cultivars should not require exact harvest scheduling and should have desirable characteristics for local farmers, e.g. self-trashing and erect stalks.
Cane sugar underwent severe competition from other sweeteners in the early 1980s. Recently, however, the demand for sugar as compared with high fructose syrup sources is expanding. It seems to be regaining its former public acceptance as a natural sweetener with a stable form and chemical composition and without health hazards. Consumption may rise with higher incomes, especially in developing countries with relatively high population increases and low sugar consumption levels.
The development of sugar cane by-products offers new and very promising prospects. Recently, demand for animal feeds originating from cane and
sugar by-products has increased. Japan is interested in silage from dry cane leaf tops while the EU countries have a significant demand for fodder yeast. Sugar as a primary chemical raw material can be used for the production of a wide range of derivatives such as esters, ethers and urethanes. These again can be used as components of synthetic resins and for the production of solvents, various acids, polysaccharides, amino acids, antibiotics and gases. One of the most promising developments is ethanol production, a renewable energy fuel as a substitute for dwindling fossil fuel. A recent development is the use of by-products of monosodium glutamate, itself a by-product of sugar cane processing, as liquid organic N fertilizer.
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T. Kuntohartono & J.P. Thijsse