sugarcane cultivation Introduction Sugarcane, Saccharum officinarum L., an old energy source for human beings and, more recently, a replacement of fossil fuel for motor vehicles, was first grown in South East Asia and Western India. Around 327 B.C. it was an important crop in the Indian sub-continent. It was introduced to Egypt around 647 A.D. and, about one century later, to Spain (755 A.D.). Global Distribution of Sugarcane (Click to Enlarge) Since then, the cultivation of sugarcane was extended to nearly all tropical and sub-tropical regions. Portuguese and Spaniards took it to the New World early in the XVI century. It was introduced to the United States of America (Louisiana) around 1741. Botanically, sugarcane belongs to the Andropogonae tribe of the family Gramineae, order Glumiflorae, class Monocotyledoneae, subdivision Angiospermae, division Embryophita siphonogama. The subtribe is Sacharae and the genus, of course, Saccharum, derived from the Sanskrit "sarkara = white sugar", a reminder that the plant reached the Mediterranean region from India. Sugarcane growing countries of the world lay between the latitude 36.7° north and 31.0° south of the equator extending from tropical to subtropical zones. This map depicts the distribution of sugarcane in the world.    Worldwide sugarcane occupies an area of 20.42 million ha with a total production of 1333 million metric tons (FAO, 2003). Sugarcane area and productivity differ widely from country to country (Table 1). Brazil has the highest area (5.343 million ha), while Australia has the highest productivity (85.1 tons/ha). Out of 121 sugarcane producing countries, fifteen countries (Brazil, India, China, Thailand, Pakistan, Mexico, Cuba, Columbia, Australia, USA, Philippines, South Africa, Argentina, Myanmar, Bangladesh) present 86% of the area and 87% of production (Table 1). Out of the total white crystal sugar production, approximately 70% comes from sugarcane and 30% from sugar beet. Table 1. Sugarcane In The world: Area, Production And Productivity Country Area (million ha) Production (million tons) Productivity (Tons/ha) Brazil 5.343 386.2 72.3 India 4.608 289.6 62.8 China 1.328 92.3 65.5 Thailand 0.970 64.4 66.4 Pakistan 1.086 52.0 47.9 Mexico 0.639 45.1 70.6 Colombia 0.435 36.6 84.1 Australia 0.423 36.0 85.1 USA 0.404 31.3 77.5 Philippines 0.385 25.8 67.1 Indonesia 0.350 25.6 73.1 Cuba 0.654 22.9 35.0 South Africa 0.325 20.6 63.4 Argentina 0.295 19.2 65.2 Myanmar 0.165 7.5 45.4 Bangladesh 0.166 6.8 41.2 WORLD 20.42 1333.2 65.2 Sugarcane is a renewable, natural agricultural resource because it provides sugar, besides biofuel, fibre, fertilizer and myriad of by products/co-products with ecological sustainability. Sugarcane juice is used for making white sugar, brown sugar (Khandsari), Jaggery (Gur) and ethanol. The main byproducts of sugar industry are bagasse and molasses. Molasses, the chief by-product, is the main raw material for alcohol and thus for alcohol-based industries. Excess bagasse is now being used as raw material in the paper industry. Besides, co-generation of power using bagasse as fuel is considered feasible in most sugar mills.   For higher sugarcane yields, providing optimum soil environment is an essential pre-requisite since the crop remains in the field for about 5 to 6 years due to the practice of raising several ratoon crops.  Good Land Preparation  Improper Land Preparation Further intense mechanization involving traffic of heavy machinery from planting to harvesting and transporting to the sugar mill or distillery, can cause the deterioration of soil physical conditions. This translates into soil compaction with a cohort of harmful side effects viz., reduction in storage & movement of air and water, mechanical difficulty for root growth and difficulty in absorption of nutrients from the soil itself and from the fertilizer. Therefore a through land preparation every time a new crop is planted is absolutely essential to bring the soil to fine tilth for proper germination of the sets and field emergence and root growth. Tillage is the physical manipulation of the soil with appropriate implements to loosen the surface soil layer. Objectives of Land Preparation To prepare a seed bed which permits optimal soil water air relations Good physical conditions for early root penetration and proliferation To incorporate preceding crop residues and organic manures To destroy weeds and hibernating pest & disease organisms To facilitate proper soil chemical and microbial activity Tillage operations through tractor drawn implements are most ideal and quick. For initial ploughing use either mould board plough or disc plough. Whenever, soil turning is desired, a mould board plough should be used. On the other hand when the soil is hard, uneven and composed of crop stubbles, a disc plough is preferable. Ploughing at optimum soil moisture content is very essential to achieve tilth. Too wet soil interrupts movement of machinery and causes destruction of soil structure. On the other hand too dry soil will not allow tynes to penetrate deep and results in frequent mechanical breakdowns, increased power requirement and cloddy soil surface affecting soil water air relations. Without Subsoiling  With Subsoiling The secondary tillage operations are carried out using disc harrows, tyned harrows or rotavator. The rotavator is a very useful multi purpose implement, which cuts the crop residues, shred them and incorporates in the soil in one pass. Use mechanical methods (subsoiling or chiseling or deep ploughing) or biological means (green manuring between last ratoon harvest and start of a new crop) to destroy the compacted layer and to allow roots to develop normally. Subsoiling was also shown to reduce fuel consumption, working time and facilitate optimum plant population. Steps in Land Preparation Involve the Following: Subsoiling or chiseling to a depth of 50 to 75 cm to break hard compact sub-pan layer Ploughing to incorporate previous crop's crop residues and organic manures Discing to break clods Land shaping to provide the required gradient for draining excess water during rainy season Field layout - Construct ridges & furrows and shape them. Depth of furrows should be 25 cm. The furrow bottom should be loosened to about 10 cm. Provide drainage channels, which are deeper than the furrows along the field borders as well as within the field at regular intervals. Drainage channels are particularly important in the high rainfall areas to drain the excess water during rainy season. Table 7 summarizes the power requirement and output during land preparation. Table 7. Sugarcane: Power Requirement and Work Ouput for Land Preparation Operation Power requirement/ha Output (ha/hr) kWatts Diesel (Litres/ha) Pre-discing 125 18 2.5 Ripping 165 48 0.5 Ploughing 165 24 1.7 Post-discing 125 18 2.5 Land leveling 125 7 3.5 Ridging 70 16 0.5 Planting Material Sugarcane is vegetatively propagated for commercial cultivation. Different kinds of planting materials viz., cane setts; settlings and bud chips are used for raising sugarcane crop. Cane Setts Stem cuttings or sections of the stalks are called "setts" or seed pieces. Each sett contains one or more buds. Always use fresh, genetically pure, pest and disease free setts as seed material. Generally, three bud setts are used for planting throughout the world, while in some areas two-bud setts are also used. Three Bud Sett (Source: Verma, 2004) Experimental evidence shows that germination percentage of 3-bud setts is higher than the setts having more or less than 3-buds. The middle bud of a 3-bud sett has the highest germinating capacity followed by top end bud and the bottom end bud, respectively (Verma, 2004). The middle bud has an advantage in germination because, as a non-terminal bud having nodes on either side, its moisture resources are better protected than those of the terminal buds. Middle bud showing the highest germinating capacity in 3-Bud Sett (Source: Verma, 2004) Germination capacity of single-bud sett is very poor due to loss of moisture from cut ends on either side. Further the plants arising from single-bud setts also lack vigour and yield low as compared to those from three-budded setts. Thus the preference given to three-budded setts over single-bud setts is partly based on germination capacity and partly on initial vigour of the germinated plants and cane yield. If whole cane stalk is planted without being cut into setts, usually few buds at its top end germinate and the lower end buds remain inactive due to top dominance. The effect of top dominance is eliminated when stalk is cut into pieces. Settlings Cane setts with roots and shoots are known as settlings. Settlings can be raised either in nursery beds or in polythene bags. Single node settlings are used as a planting material in spaced transplanting technique of raising sugarcane crop. Single bud settling (Source: Verma, 2004) Bud Chips Little portion of stem with one bud is known as bud chip. Bud chips are used to raise settlings in nursery. They were found to produce a good crop when transplanted in main field. The principal advantage of bud chips is substantial saving in seed material. Seed requirement is reduced to less than one ton per ha. Adopting the following procedure raises settlings from bud chips: Prepare the bud chips from whole cane using a sharp edged knife in such a way that each bud has a little portion of stem Plant the bud chips on raised nursery beds adopting a inter-row spacing of 7.5 cm at the rate of 300 buds/m2 Alternatively nursery can be raised in polybags of 15 cm x 10 cm size Fill the polybags with homogeneous mixture of equal quantity of soil, sand and well rotten compost Plant the bud chips in polybags with the bud facing upwards and cover with soil mixture to avoid drying of the bud Bottom of the bags should have holes to facilitate drainage Ensure regular watering of bags or nursery area Settlings are ready in 5 - 8 weeks for transplanting in the main field Under good management conditions establishment of transplanted seedlings in the main field is high (90-100%) Raising of Seed Cane Crop The normal practice in many parts of the world is to use commercial crop of sugarcane for seed purposes. Characteristics for good seed are seldom taken into consideration. Many growers do not care for seed quality and many of those who do, select the seed only at the sett cutting and planting stage. This is not enough. If a grower wants to be sure of getting good and disease free seed cane he should raise the seed crop separately. This crop should be kept completely free from pests and diseases by constant field scouting from the very beginning. Moreover, seed quality is not merely a matter of pest and disease freedom. Seed has to be in high water content and of good nutritional status. Neglect in raising good seed crop is one of the major defects in sugarcane cultivation all over the world. (In the picture above: Bud Chip)       Use of sugarcane seed from the commercial crop has been responsible for rapid multiplication of a large number of diseases like red rot, wilt, smut, ratoon stunting and grassy shoot which adversely affect the cane yield and quality. It is, therefore, raising of healthy and vigorous sugarcane crops for seed purpose is essential and recommended. Select an upland field for raising seed crop with no soil problems (soil salinity, acidity, waterlogging etc) and adequate irrigation facility Prepare the soil thoroughly and incorporate 20-25 tons/ha of FYM 15 days before planting Provide field channels and field drains to prevent rain water traversing from adjoining field to check spread of red rot disease Select seed material from previously raised seed nursery crop and prepare the setts. Use only sterilized setts to avoid transmission of certain diseases like RSD and GSD Give heat treatment (heat therapy) to eliminate seed borne diseases and organomercurial treatment to protect the setts from soil borne diseases to ensure better germination Adopt narrow spacing of 75 cm to obtain higher yield of setts per unit area Use 25% higher seed rate than normal cane crop Apply higher nutrient dose of 250 kg N + 75 kg P2O5 + 125 kg K2O/ha Irrigate the crop at optimum levels to avoid any water stress during crop life taking in to account evaporative demand of the atmosphere (ETo) and Crop characteristics (Kc) at different crop growth stages Provide weed free environment for better growth of the crop and also to avoid infestation of pests and diseases Adopt field scouting for timely control of pests and diseases Rouge out the affected clumps and plants of other varieties Protect the crop from lodging, binding and propping Crop is ready in 7 - 8 months. Setts obtained from such crop contain healthy and sound buds, higher moisture content, adequate nutrients, higher amounts of reducing sugars, therefore, establish quickly and grow vigorously thus ensuring a good commercial main field crop. Preparation of Setts for Main Field Planting Harvest the seed crop one day before planting to obtain higher percentage and uniform germination. Prepare the setts always one day before planting by giving sett treatment. Planting material or seed cane should be free from aerial roots and splits. Avoid damage to buds while cutting setts. Change the seed material after every two to three seasons. In case if it is inevitable to use mature cane as seed, the top one-third portion can be used satisfactorily. Ideal Seed Cane Always use seed cane obtained from a seed crop of 7-8 months Free from disease and pest infestation like red rot, wilt, smut, ratoon stunting disease etc Possesses healthy buds without any damage in handling and transport. Buds with higher moisture content, adequate nutrients, higher amount of reducing sugars and viability. Free from aerial roots and splits. Pure in quality. Seed Cane Treatment Objective: To protect the crop from soil borne diseases causing pathogens, which usually gain entry into the setts through the cut ends following planting and cause sett rotting and damage to buds, thus affecting germination. Most farmers don't treat the setts before planting which results low plant population per unit area consequently reducing the yield Treat the setts soon after cutting in 0.1% (at 1g/liter) Carbendazim solution for 15 minutes. Three important diseases viz., grassy shoot disease, smut and ratoon stunting disease are carried forward through seed cane material. These diseases lead to progressive decline in yields and degenerate sugarcane varieties. For control of these diseases treat the seed material (setts) with moist hot air at 52°c for 30 minutes. To control termites early shoot borer and scale insects treat the setts in a systematic insecticide viz. Malathion 50EC (at 2 ml/liter) or Dimethoate 30EC (at 3 ml/liter) for 15 minutes. In the Pictures above: Sett treatment with fungicide against soil borne pathogens + moist hot air treatment of setts against seed borne diseases In the picture below: Termite damaged setts (Source: Verma, 2004) Seed Rate Under drip irrigated paired-row system of planting [(0.6m + 1.20m) x 0.12m], about 60,000 two-bud or 40,000 three-bud treated setts would be required to plant one ha of land. With proper germination of buds, this seed rate is adequate to give a gapless stand and raise a successful crop. Nearly 10-12 tons of seed cane is required to plant one ha of field. However, it is better always to go by number of setts per ha rather than weight basis as sett weight in sugarcane varies largely with varieties. Measures to obtain higher germination Some important yet simple measures to obtain higher uniform plant population are as follows: Using quality setts as seed material obtained from a short seed crop devoid of any primary infection Using preferably two eye bud setts instead of three bud setts as seed material Careful preparation of setts without damaging the buds or setts Using sterilized knives for preparing setts to avoid transmission of root stunting and grassy shoot diseases Planting freshly prepared and treated setts Giving adequate and frequent irrigation's during germination phase Control of weeds through pre-emergence herbicides Seed treatment with fungicide and pesticides Transplanting Technique Seedlings are raised in a nursery bed using single bud setts. When the seedlings are of about 6 week old, they are transplanted in the prepared main field. In the pictures on the right and below (Source: Verma, 2004): Single bud sett nursery Single bud sett settlings from nursery for transplanting in main field Transplanting In main field Advantages Saving in the seed cost as the seed requirement is only about 2-3 tons/ha against the normal seed requirement of 10-12 tons/ha. Synchronous tillering leading to uniform growth and maturity of stalk population, which usually gives better yield and sugar recovery. Sufficient time for main field preparation Saving in water and fertilizer Better weed management Harvesting Management Harvesting of sugarcane at a proper time i.e., peak maturity, by adopting right technique is necessary to realize maximum weight of the millable canes (thus sugar) produced with least possible field losses under the given growing environment. On the other hand harvesting either under-aged or over-aged cane with improper method of harvesting leads to loss in cane yield, sugar recovery, poor juice quality and problems in milling due to extraneous matter. Therefore, proper harvesting should ensure: To harvest the cane at peak maturity (i.e., avoiding cutting of either over-matured or under-matured cane) Cutting cane to ground level so that the bottom sugar rich internodes are harvested which add to yield and sugar De-topping at appropriate height so that the top immature internodes are eliminated Proper cleaning of the cane i.e., removing the extraneous matter such as leaves, trash, roots etc. Quick disposal of the harvested cane to factory Several standard analytical methods are available to determine the peak maturity or quality so that the cane is harvested at right time. Without such analysis also several farmers take-up cane harvesting based on crop age and appearance. Sometimes farmers harvest the crop even before the crop fully matures due to necessity to supply cane to the mills early. Likewise delays in harvesting are also quite common, particularly when there is excess cane area. To avoid such extremes harvesting should be done at right time employing right method. The following criteria enable harvesting of cane at right time adopting proper procedures: Crop Age Harvesting is done based on maturity (age) group. Farmers who grow a particular variety are usually conversant with the harvesting time. Even most sugar factories give cutting orders to farmers based on crop age. This is not a scientific method since, planting time, crop management practices, weather conditions etc influences maturity. Visual Symptoms Yellowing and drying of leaves, metallic sound of mature canes when tapped, appearance of sugar crystal glistening when a mature cane is cut in a slanting way and held against the sun are some of the visual indices of assessing maturity of cane. Quality Parameters Important sugarcane quality parameters for assessing cane maturity are the juice Brix, pol or sucrose percentage and purity. Juice Brix: Juice Brix refers to the total solids content present in the juice expressed in percentage. Brix includes sugars as well as non-sugars. Brix can be measured in the field itself in the standing cane crop using a Hand Refractometer. This is usually referred as a Hand Refractometer Brix or HR Brix. In the field using a pierce collect composite juice samples from several canes. Then place a drop of the composite juice sample in the Hand Refractometer and measure the Brix reading. The circular field gets darkened relative to the Brix level, which could be easily read. The HR Brix meter has graduations from 0 to 32 per cent. The HR Brix readings can be separately taken from both top and bottom. A narrow range indicates ripeness of the cane, while a wide difference indicates that the cane is yet too ripe. On the other-hand if the bottom portion of the cane has lower Brix value than the top, it means that the cane is over-ripened and reversion of sugar is taking place. Juice Sucrose Or Pol Per Cent: The juice sucrose per cent is the actual cane sugar present in the juice. It is determined by using a polarimeter, hence sucrose per cent is also referred to as pol per cent. For all practical purposes pol % and sucrose % are synonyms. Now a days an instrument called sucrolyser is also available for determining sucrose % in juice. Purity Coefficient: It refers to the percentage of sucrose present in the total solids content in the juice. A higher purity indicates the presence of higher sucrose content out of the total solids present in juice. The purity percentage along with sucrose percent aids in determining maturity time. Purity Percentage = (Sucrose %/HR Brix)100           A cane crop is considered fit for harvesting if it has attained a minimum of 16% sucrose and 85% purity. Reducing Sugars: The reducing sugars refer to the percentage of other sugars    (fructose and glucose) in the juice. A lower reducing sugars value indicates that much of the sugars have been converted into sucrose. Commercial Cane Sugar: The commercial cane sugar (CCS) refers to the total recoverable sugar percent in the cane. This could be calculated by the following formula: CCS (tons/ha) = [Yield (tons/ha) x Sugar Recovery (%)] /100 Sugar Recovery (%) = [S - 0.4 (B - S)] x 0.73           Where, S= Sucrose % in juice and B= Corrected Brix (%) Manual Harvesting In many countries even today harvesting is done manually using various types of hand knives or hand axes.Among the several tools the cutting blade is usually heavier and facilitates easier and efficient cutting of cane. Manual harvesting requires skilled labourers as improper harvest of cane leads to loss of cane & sugar yield, poor juice quality and problems in milling due to extraneous matter. (In the picture: Manual harvesting of sugarcane) Mechanical Harvesting Harvesting labour is becoming scarce and costly in view of diversion of labour to other remunerative work in industry, construction, business etc. Mill stoppages because of non-availability of canes are not uncommon owing to shortage of harvesting labour. And, most of the new mills are of higher crushing capacity and many are expanding their crushing capacities. Therefore daily requirement of cane is increasing and hence greater demand for harvesting labour. Added to this most of the present day agricultural labourers are not interested in field operations involving much drudgery. Thus in years to come, the labour position is likely to deteriorate further. Therefore mechanization is inevitable and hence, adoption of mechanical harvesting of cane in future is inevitable.(In the picture: Mechanical harvesting of sugarcane) In countries like Australia, Brazil, USA, South Africa, Taiwan, Thailand etc where sugarcane cultivation is highly mechanized huge harvesters are employed for cane harvesting. In these countries, sugarcane is grown on large plantation scale in large farms owned by either mills or big farmers. The field capacity of mechanical cane harvesters varies with the size (2.5 to 4 ha per day of 8 hours. The limitation of mechanical harvesters is use of such machines in small, irregular and fragmented holdings, diversified cropping patterns, limited resource capacity of small & marginal farmers in several countries.