Lynne Wong's PhD thesis

Lionnet (1996) explained that for pol % cane, there was a slow decrease over the years
until about 1987 when a strong recovery took place. This was unfortunately stopped by the
droughts which lasted from 1992 to 1995. Fibre % cane shows a clear decrease from 1983
onwards due to harvesting of younger cane with the incidence of the Eldana borer, which
tends to affect older or carry-over cane. Lionnet (1996) also noted that an improvement in
mixed juice purity (see Fig 1.9) started in 1985, except for the drought years of 1992-1995.
Compared to the trends of fibre % cane and sucrose % cane in Mauritius (see Fig 1.6),
those in South Africa (refer to Fig 1.8) do not show great changes over the years, although
a downward trend in fibre % cane and an upward trend in sucrose % cane are evident as
from 1985 onwards (except for the drought years). It is worth pointing out that while the
values of sucrose % cane and sucrose/fibre ratio in cane are comparable in the two
countries, this is not the case with the fibre % cane data. In Mauritius, fibre % cane was
stable at 13.2 up to 1975, and gradually increased to about 15.0, whereas in South Africa, it
averages 15.3% over the years. Purity of mixed juice is higher in Mauritius; it averages
86.7%, whereas in South Africa it is 85.6%.
Numerous literature exists on trends in cane quality. Clayton and Roberts (1971) stated
that in Florida, the trash content of cane just before harvest is about 30%. Kampen (1974)
had shown that extraneous matter in Louisiana cane was very much dependent on cane
variety and the harvest method used, and it had gradually increased from less than 1% in
1945 to more than 13% in the early 1970s, with total mechanization of field operations
since 1950. Legendre and Irvine (1974) reported that when hand cutting, stripping and
loading were practised in Louisiana prior to 1942, the amounts of extraneous matter rarely
exceeded 4%; by 1947, when mechanical harvesting had become predominant, the total
extraneous matter level had nearly doubled. In Puerto Rico, Cabrer et al. (1965) estimated
that as high as 25% of cane crushed consists of tops, trash, sand and other extraneous
matter while in South Africa, according to Smits and Blunt (1976), the amount may be
about 12% or more during rainy periods. Lamusse and Munsamy (1979) reported that
after measuring tops and trash at five factories in South Africa during the whole season, the
cane was found to contain on average 2.1% tops and 5.3% trash; de Beer et al. (1989)
carried out an experiment with 800 tonnes of cane, and found that unburnt, untopped cane
contained 22.2% extraneous matter whereas burnt, topped cane, contained only 3.2%.
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