Ratooning and ratoon management in overseas cane-sugar industries
Travel was undertaken to Florida, Louisiana, Brazil and Argentina in March-April 1994 and to southern Africa in October 1994. I assessed the environments and management of production systems in relation to productivity and length of the crop cycle. This followed the perception that crop cycles in Australia were much shorter than in some foreign sugar industries.Many of the areas visited have been growing cane for as long as, or longer than, some districts in the Australian industry. In most cases, cane was grown as a monoculture, where succession rather than rotation or fallow-planting systems were the norm. Large areas of the Brazilian industry in S?o Paulo state were an exception in that soybeans or other legumes were used in a rotation; a rotation with rice and vegetables was also applied to large sections of the industry in Florida. However, I gained the impression that the monoculture system was not seen as a major impediment (in 1994) to continued productivity and length of the crop cycle, particularly in Africa.Longest ratoon cycles (> 12 years) were achieved in southern African production systems still employing manual harvest systems on clay to clay-loam textured soils and in some cases still relying heavily on the cultivar NCo376. Similarly, long crop cycles have also been achieved in Florida in the warmer areas of very high fertility soil close to Lake Okeechobee. This result has also been achieved with manual harvests.In most industries, the crop cycle varies from 4 to 8 years, with increasing tendency to shorter cycles with increased mechanisation of harvest and increased weight of in-field transport vehicles that cause damage to stools and compact soil.I conclude that the Australian industry has maximum exposure to the adverse effects of mechanised harvest (stool damage from the harvester) and damage to stool and soil from transport traffic. Our soils tend to be of lower clay content than most other sugar industries. This influences cation exchange capacity and, therefore, nutrient requirement. This factor also influences available water capacity of soils. Fertility and moisture characteristics combine to place greater pressure on farm managers for timeliness and effectiveness of operations. Our industry also has the greatest exposure to impact from yield-reducing soil-insect populations.I recommend that the Australian sugar industry moves towards a harvest/transport system that minimises physical damage to the cane stool, while minimising soil compaction. These goals might be achieved by adopting a production system that keeps wheels in the centre of the interspace and as far as possible from the cane stool. Such a system would require expanding row spacing from about 1.5 m to at least 1.8 m in combination with a strategy to avoid the inevitable loss of cane yield that occurs if single rows of cane are wider than 1.65 m. The harvest strategy should also include optimisation of base-cutter height and speed for forward speed of the machine to minimise shattering and removal of stool.Our production strategies should also continue to focus on improvements to weed control, removal of constraints from nutrition, water management, and pest and disease management.