Lynne Wong's PhD thesis

Snow (1974) investigated the seasonal variations in the ratio of hard fibre to pith within a
cane variety at regular monthly intervals for 7 through 12-month old cane. Young or
immature cane had more pith than hard fibre with a fibre/pith ratio of about 0.58 at 7
months. As the cane reached maturity (9 months) more hard fibre was present in the stalks
giving approximately equal amounts of hard fibre and pith. This fibre/pith ratio of 1
remained constant for the duration of the season.
From Tables 3.14 – 3.16 for the four cane varieties, the pith % cane increases in all cases
(except R 570) as the cane matures from 36 to 44 weeks, but decreases (except M 1400/86)
from 36 to 52 weeks. However, there is no indication of an increase of hard fibre % cane
with age in any of the four cane varieties. In fact, the value found for the total fibre % cane
was on the low side. This can be attributed to the fact that the samples examined had the
nodes eliminated, some probably had more stalk and rind removed in the process as in the
case of cane aged 52 weeks. However, R 570, M 1557/70 and M 1400/86 did show an
increase in hard fibre % cane from 36 weeks to 44 weeks. In spite of this shortcoming, the
fibre/pith value in cane calculated can still be considered as reliable since both Moodley
(1991) and Snow (1974) had found that fibre/pith ratio remained more or less constant.
3.5.3.2 Effect of cane variety on fibre/pith ratio in cane
From Table 3.14, for the mature cane aged 52 weeks, the fibre/pith ratios of R 570 and
M 1400/86 were close to the expected value of one with values of 1.08 and 1.06
respectively, whereas those of R 579 and M 1557/70 were high, at about 1.20. According
to Snow (1974), cane with high ratio of hard fibre to pith e.g. 1.52, causes problems in
milling due to the toughness of the stalks entailing excessive maintenance of the equipment
due to stress and, mill chokes induced by bagasse jamming in the radial and juice grooves,
whereas cane varieties with more pith than hard fibre, with a fibre/pith ratio of about 0.6,
cause an overall slowdown in mill operations manifested through occasional reduced
grinding rates due to the soft “mushy” consistency of the macerated material leading to
mill roll slippage or chokes, and high residual moisture content of the bagasse. Varieties
with approximately equal amounts of hard fibre and pith proved to be the best milling
varieties. Hence the varieties investigated here should be considered good milling varieties
if judged on their fibre/pith ratios.
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