Contents - Greenmount Press

Ginning & fibre quality
Series supported by ECOM Commodities
Predicting the influence of
harvest aids on fibre quality
■■By Michael Bange 1 and Robert Long 1
Immature bolls will usually contain immature cotton fibres
which are prone to the formation of neps. Neps are small
entanglements of cotton fibres that are created during
mechanical processes like machine harvesting and ginning.
Immature fibre and neps even in small amounts are undesirable
as they decrease mill processing efficiency and ruin the
appearance of finished yarns and fabrics.
Immature fibres and neps absorb less dye and reflect light
differently, and consequently appear as under-dyed patterns and/
or ‘flecks’ on finished fabrics. Their presence in large quantities
can negatively affect an industry’s reputation when cotton arrives
at spinning mills.
The impact of defoliation timing on the maturity of cotton
fibre (Adapted from Long and Bange, 2011). Note that the
fibre walls are thicker with the later harvest aid treatment.
Precise identification of cotton crop maturity is important for
maintaining yields and fibre quality when preparing for harvest.
Delayed harvest increases the chance of fibre weathering and
harvesting more leaf trash; while prematurely harvesting cotton
with significant amounts of immature bolls may lower lint yield
and micronaire, and increase neps. Methods employed by crop
managers to identify when cotton crops are mature include:
■■
When the crop has 60 per cent or more open bolls;
In Brief…
To optimise both yield and fibre quality, boll cutting can
be used by cotton managers to determine when crops are
mature and ready for defoliation. A study conducted in three
seasons varied the timing of defoliation to vary the amount of
immature, mature, and open bolls to assess:
■■
The fibre quality of open, mature, and immature bolls;
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The variation that exists within and across seasons; and,
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If quality of immature, mature, and open bolls taken at the
time of defoliation is related to final micronaire.
As expected there were differences between the classes
of bolls with the immature bolls generally having lower
micronaire. The greatest variation in micronaire within a boll
class with different defoliation times was also associated with
the immature bolls. When data were combined across seasons,
relationships were successfully developed that predicted
micronaire at harvest using the micronaire of the immature
bolls measured at defoliation (r2 = 0.73). Relationships were
significantly improved when per cent open bolls was also
included as a factor (r2 = 0.86).
The ability to estimate defoliation timing influences on
micronaire may help avoid discounts. But this concept requires
more testing and would be enhanced with access to reliable
and simple methods to measure quality of small field samples
taken prior to harvest.
Ginning & Fibre Quality
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42 — The Australian Cottongrower October–November 2012