Ripen Canes For Profit (2003, Vol. 23 No. 1) - SIA

Serving Jamaican Cane Farmers with Research and Technical Expertise
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In Jamaica the cane harvesting season begins late November or early December at the onset of the dry season. However as soil is only just beginning to dry out following the September-October rainy season, cane tends to be still actively growing and not as sweet as it will become later in March-April. This early part of the crop is when factories use as much as 13 and 14 tonnes of cane to make each tonne of sugar. A similar unprofitable time of operating occurs also towards the end of crop for factories operating during and after the May rains.
Fortunately, there are a number of ways that cane can be assisted to become sweeter - a process known as cane ripening.

What is cane ripening?
Ripening of sugar cane is the storage of sugar (sucrose) in the cane stalk. It involves a slowing-down in the growth of leaves, and stems, while allowing sugar formation to continue. A fully ripened cane stalk typically is made up of 15 to 20% sugar. The process of ripening occurs naturally as cane matures. In young cane, sugar content is highest in the joints which are near ground level and decreases towards the top. As the cane matures, distribution of sugar from top to bottom becomes more uniform leaving only the few joints at the top noticeably less sweet. Ripe canes, therefore, have stalks with joints nearly as sweet at the top as they are at the bottom.

How to tell if cane is ripe?
The appearance of ripe canes is variable and quite often depends on location and variety. It is not like fruits where a distinct and noticeable change in texture, odour, or colour is seen. In general, the following can be used as indicators:
1. Shortened leaf blades
2. General yellowing of leaves
3. Dieback of leaf tips and lower leaves
4. Very short joints towards top
5. Death of roots in the band around joints
6. Waxy covering on young stems tending to darken
7. Buds becoming dry, hard, and scaly
When cane is grown in wet swampy areas or in soils which still have unused fertiliser (especially nitrogen), stalks will not be very sweet. This is so because the continuous supply of nutrients and water will cause canes to keep growing and use up sugar which would otherwise be stored in the stalks.

Cane Ripening
Mature cane ripens naturally when soil moisture and nutrients are reduced, and night temperatures become lower. Lower night temperatures cause a slowing down of the process by which sugar is broken down to release energy needed by the plant. Canes can also be ripened artificially by using chemicals.
Natural ripening is a slow process and, with variations in the weather, full ripening may not occur in many seasons. Farmers, however, can assist cane ripening by:
1. Applying fertiliser early in the growing season so that all is used up by 8-10 months of growth. Sugarcane will ripen better when nitrogen is completely used up by 6-8 weeks before harvest.
2. Removing shade from around, or within fields. Sugarcane needs sunlight to make sugar.
3. Reducing water 30-45 days before harvest, either by improving field drainage or withholding irrigation water
4. Reaping canes that are mature in age. Jamaican varieties are selected to mature in roughly 12 months. If such canes are reaped much earlier, at say 9 months, they would be considered young and this would be reflected in low sugar content and low cane price. Also, if fields get older than 12 months and are reaped at say 15 months instead, there is likely to be a reduction in sugar content as growth rate starts to increase again.

Ripeness test
A grower can do his own test to determine whether his cane is ripe and ready for harvest. This maturity testing, as it is called, is conveniently done with an instrument called a hand refractometer. Juice may be collected from a number of canes by a metal tube called a “Jukker.” A drop of this juice, viewed through the refractometer, gives a measure of the brix (which is a close estimate of sugar in cane). Usually brix readings from the top of canes are compared with readings from the bottom. The closer the average top brix is to the average bottom brix, the more mature the cane.
In the early portion of the harvest season, when cane tends not to ripen well because of high soil moisture, relatively high soil nitrogen and warm night temperatures, growers may resort to ripening cane artificially to ensure profitability.

Chemical ripening
Certain chemicals may be applied to the foliage, usually by aircraft when the field is about 10 months old. This “ripener,” speeds up sugar storage in stalks and lengthens the time when storage is at its peak. Depending on the type of chemical used, such fields should then be harvested between three and six weeks after treatment. The ripener is therefore a tool the grower uses to ensure that cane is nearing its sweetest for harvesting. Ripeners tend to reduce growth and it is believed that this allows energy which would otherwise be used in producing leaves and stalk, to be used to make and store sugar instead.
All varieties treated in Jamaica increase sugar output to varying degrees. Some may give a better response and factors such as timing, location, weather, the chemical used and how well the chemical is applied may affect results. The higher the cane yield the greater the increase in sugar per hectare and the more profitable the operation. Fields estimated to yield below 60 tc/ha should not be treated as returns may not be economic. For this reason, over the years most chemical treatment has been carried out in high yielding rain-fed areas of St Thomas Sugar Co, Appleton and Frome. However ripeners may be profitably used even in irrigated areas where high cane yield is achieved.

Results of ripening
Ripening is therefore the growers best defence against the tendency towards poor cane quality, and a most effective means of boosting cane payments. When done correctly, the results are positive and profitable. An increase in JRCS by 0.5 points from artificially ripened canes is usually adequate to offset the cost of treatment. One may think that at Worthy Park, for instance, where conditions for natural ripening are usually good, chemical ripening may not be profitable. However, during the 2000/2001 Crop Year, artificial ripening improved JRCS by 1.03 points or 8.68% (11.87 vs 12.9 JRCS). This would have been worth an extra J$116/tc. In St. Thomas area where the conditions for natural ripening were relatively poor, ripeners improved JRCS by 2.65 points or 29.8% (8.89 vs 11.54) or some $277/tc.

Parting Thought
Sugarcane ripening, be it natural or artificial, is essential to high sugar recovery in factories. All producers - small, medium, large - should see ripening as a means of increasing earnings from cane farming. Growers should make every effort to ensure that conditions in each field are suitable for cane ripening. Ripening is profitable, get involved!
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