Increasing yield of ratoon sugarcane

Source: http://dawn.com/2008/04/07/ebr7.htm


By Atique-ur-Rehman and Dr Ehsan Ullah

SUGARCANE, an important cash crop, is grown on 4.5 per cent of the total cropped area of the country. Ranking fifth in the world in growing sugarcane on area basis, the country has 12th position as regards recovery of sugar from the cane.

One of the major reasons of low yield is the poor management of the ratoon crop. Sugarcane ratoon occupies more than 50 per cent of the total sugarcane area in the country. However, its contribution to the total cane production is about 25-30 per cent. Productivity of ratoon crop is 10 to 30 per cent less than the plant crop of sugarcane.

Ratoon sugarcane is not given due attention as a result its productivity is less than the plant crop. However, it has been established through research that if the crop is grown adopting proper ratoon management technology, the yield could be much higher than obtained from the plant crop.

Growing ratoon crop costs less than plant cane and therefore, achieving high yielding ratoon cane is a valuable objective. This crop is most economical by 25-30 per cent saving in operational cost along with seed material. There is no need for preparatory tillage to grow this crop. Ratoon cane matures earlier than plant cane and thus early supply of cane is assured. As the crop matures earlier, harvesting is easier and field is available for the timely sowing of the next crop.

The ratoon crop often gives better quality than plant cane and also better sugar recovery. Low yield of this crop is mainly due the low and differential ratooning potential of cultivars and suboptimal crop management. Other reasons for low yield of this crop include formation of toxic substances in the rhizosphere, low nutrient uptake ability of ratoon, depletion of soil nutrients, shallow ratooning, soil compaction and increased incidence of pests and diseases.

For growing ratoon cane crop, late maturing varieties with good yield are suitable. Early maturing varieties should be avoided because these are poor ratooners. Proper time for this crop is very important for good yield. Spring harvested crop give better ratoon than autumn harvested due to moderate temperature which is most conducive for stubble sprouting. Plant crop should be harvested close to the ground level for optimum tillering.

Yield of ratoon cane mainly depends on the number tillers from the stubbles of the previous crop. Timely stubble shaving or inter row cultivation is usually carried out to straighten the rows. This is done to expose the subterranean area and to facilitate the germination of deeply located healthy buds. This will loose the soil and help to develop a deep root system which is important for nutrient uptake and water absorption from deeper soil profile.

By harvesting of plant crop, there may be some gaps due to the death of stubbles. A good ratoon crop should have not more than 15 per cent gaps of the total population. Gap filling should be done with healthy and disease free plants..

Sugarcane ratoon crop has high demand for fertiliser because of shallow root system, decaying of old roots, sprouting of stubble buds and immobilisation of nitrogen. It is, therefore, recommended 25-30 per cent more fertiliser for ratoon crop than the plant crop. Experiments show that a nitrogen rate of about 210 kg ha-1 along some nitrogen fixers such as Azotobacter and Azospirillum has a significant effect on ratoon cane yield. Phosphorous and potassium both at the rate of 85 kg ha-1 are recommended for ratoon crop. In case of micronutrient deficient soils, foliar application of micronutrients play a vital role to optimise the yield.

Ratoon crop has shallow root system and hence require more number of irrigations. Moisture conservation practices such as mulching should be used to decrease number of irrigation. Mulching of previous crop residue helped not only to conserve soil moisture but also to increase the organic matter in to the soil. This also suppresses the weed growth and improves fertilizer use efficiency of the crop. In spite of crop residue, addition of cow dung, slurry or press mud may be used for this purpose. A number of irrigations of 15-20 with an interval of 20-25 days interval is sufficient for ratoon crop.

Excessive tillering of ratoon crop is a desired character for optimum yield. For this purpose earthing up and moulding up is done to facilitate the germinated buds to develop into a useful tiller. This also helps prevent the crop against lodging and weeding out the pest plants.

Lodging of the crop has an adverse effect on the yield by increasing the disease and other pest infestation. Proper practices to avoid lodging are necessary for good yield. To prevent the crop against lodging, propping is done by tying the canes together with dry leaves and bottom green leaves.

Protection of crop against diseases and insect pests is necessary for good yield. Insect pests specific to ratoon crop are termites, mealy bugs, top borer, stem borer, root borer, white fly, army worm, sugarcane leafhopper and field cricket. Diseases associated ratoons are smut, grassy shoot disease and ratoon stunting disease. These can be controlled by the removal of poor stubbles, growing disease resistant varieties and proper management practices.

Intercropping in ratoon cane crop is an important practice which can increases the income for the farmer from the same field. Intercropping of berseem and wheat shows a significant increase in the income per hectare. Besides the berseem and wheat, intercropping of pumpkin and water melon is also useful. Sugarcane crop planted in strips is most suitable for the intercropping of other crops.