67
Objective basis for evaluation of differences in
fibre
quality between male, female and monoecious hemp
E. Horkay and I. Bócsa
Rudolf Fleischmann Agricultural Research Institute of
Gödöllö,
University of Agricultural Sciences,
Kompolt, Hungary.
Horkay, E. and
I.Bócsa 1996. Objective basis for the evolution of differences in fibre quality between
male, female and monoecious hemp plants. Journal of the International Hemp
Association 3(2): 67-68.
Modern fibre quality testing instruments were used to make
separate examinations on the fibre quality (fineness) traits of male and female
hemp. During the processing and fibre analysis of the monoecious hemp variety
Fibrimon 21-63 and of male and female hemp plants pulled separately from a dense stand of
the variety Kompolti, it was found that with respect to inclination and torsional
resistance, which are indicative of fineness, the fibres of male hemp considerably
surpassed those of female hemp. As regards to fibre fineness (strength), however,
the female hemp exhibited a slight advantage. The fineness value of fibre obtained
from a mixed stand of the same variety, containing both male and female plants, represents
a figure approximately halfway between those of the two sexes. The values obtained
provide a good explanation of the previous experience of small-scale producers and the
cottage industry regarding the qualitative superiority of male hemp. At the same
time, all the quality parameters of monoecious hemp are lower than those of any fraction
of the dioecious variety Kompolti, at best approaching the level of the female plants, as
could be expected from their growth habit.
Introduction
Hemp is well known as a dioecious
plant. This specific property has been known since ancient times and was taken into
account even during primitive home-processing. The dioecious nature of hemp played
an important role in peasant self-sufficiency, since it was observed during weaving that
the fibre quality of the male plants was considerably finer than that of female
plants. Consequently, the male and female plants were pulled up separately from part
of the hemp plot, involving what would now be considered as incredibly hard work.
These were then separately retted, scutched, swingled, spun and woven. The fibres of
male plants were used for finer household purposes, such as towels, tablecloths,
teacloths, and perhaps for hard-wearing bed-linen, while the female plants were used
chiefly for making canvas and sacking. Naturally, the mixed stands, containing the
usual ratio of male to female plants, were also processed. Of course, even on a
small scale, it was impossible to completely separate the plants according to sex, due to
the enormous manual labour demands, but this was not in fact necessary, as male plants
were only chosen in the quantities required for finer weaving tasks. Three
fractions were thus processed from dioecious hemp (male, female, and male + female).
Experience in the cottage industry had thus
long shown that the male hemp is finer, and that thinner, more easily divisible yarn can
be spun from it, though due to the lack of special instruments, the various fibre quality
parameters could not be determined. By the time such instruments became available,
the cultivation and home-processing of hemp had become a thing of the past. The
debate on the production of monoecious or dioecious hemp has, however, given new urgency
to this problem, since dioecious hemp varieties not only have greater stem yield potential
(Bócsa, 1969), but also posses better fibre quality, thanks exclusively, or to a great
extent, to their male hemp content. It thus appeared opportune to use the fibre
quality testing instruments now available in Hungary to determine the major fibre quality
parameters of male and female hemp separately, especially since no data of this kind seems
to have been published to date.
Materials and methods
The hemp variety Kompolti, which
is well known in hemp-growing countries and is cultivated on a large proportion of the
growing area in Hungary, was used in these experiments. One standard sheaf each of
male and female hemp were selected at technical maturity from an experiment sown for other
purposes. These were sun-dried in the field in the usual manner (to a water content
of 12 %), retted in water storage under temperature of 19°C for 3 weeks, air-dried and
then mechanically processed. The scutched fibres were afterwards stored for
approximately 5 months. The total fibre content of the two fractions was previously
determined in terms of both green and dry stems. For the sake of comparison, a mixed
dioecious, i.e. not separated, sample of Kompolti hemp from the same plot was
also included in the studies, as was the Kompolt-bred monoecious variety Fibrimon 21-63,
in order to study the monoecious-dioecious problem from the quality point of view.
To begin, the male-female
ratio of the Kompolti hemp was determined. This was followed by a determination of
the flexibility of the fibres, using a fibre inclination tester (developed at the Textile
Research Institute), of their torsional resistance (using another Hungarian patented
instrument), and of their yarn strength (using a Schopper yarn tester). The first
two values were used to calculate the Nm (metric fineness) value (required for a complex
evaluation), which indicates the fineness of the fibre bundles. (Flexibility and
inclination data are multiplied with a constant number and the multiplied values are
summed. This calculation is used by all the textile industry laboratories of
Hungary).
Result and discussion
The fibre content percentage is
almost identical in all three fractions (Table1), though the absolute value is lowest for
female hemp. The fibre content of the monoecious variety Fibrimon 21-63 is lower
than that of any Kompolti fractions, despite the fact that it has been selected for fibre
content for more than 30 years. Since male line selection is impossible in
monoecious cultivars, selection progress is much slower. In addition, the habit and
fibre structure of the monoecious variety are identical to those of the dioecious female
hemp. It can also be seen that the male-female ratio of Kompolti hemp is slightly
below 1:1, while the dry weight proportion of males is somewhat less than 50 %.
Table 1. Different qualitative properties of male, female and monoecious hemp plants.
Cultivar | Fractions | Sex ratio % |
Weight % |
Fibre % |
Flexibility HMM |
Torsionnal Resistance 103/T |
Strength Pkp |
Metric fineness Nm |
||
Kompolti Kompolti Kompolti Fibrimon 21 |
male female male + female monoecious |
48.5 51.5 - - |
49 51 100 - |
31.5 29.6 30.4 26.7 |
26.8 18.3 24.3 16.0 |
19.31 13.23 16.78 11.80 |
6.16 7.26 6.04 6.25 |
141.72 109.63 131.23 101.25 |
It is clear from Table 1 that
flexibility and torsional resistance, which reflect fibre fineness and spinning value,
exhibit enormous differences between the fibres of male and female hemp, in favour of male
hemp. With respect to fibre strength, the female hemp is slightly superior.
This is not exactly a fibre fineness trait, though it undoubtedly has an influence on
fibre quality and spinning value because there is negative correlation between strength
and fineness (Kerékgyártó-Nagy 1967). The great differences recorded for the two
traits most characteristic of fibre fineness explain the trend observed for the complex
index Nm, demonstrating the high superiority of male hemp. In light of these
measurements, it is easy to explain the great differences observed between the two sexes
as regards to yarn fineness, and the quality of the fabric and end-products which can be
produced from them.
If the quality and fineness parameters of
fibres produced from separate male and female hemp are compared with those of fibres from
a mixed stand having the usual sex ratio of individuals from the same variety, it can be
seen that the fibre fineness of the latter would lie between the values recorded for each
of the two sexes, but is closer to that of male hemp. In the case of the monoecious
variety Fibrimon 21-63, all the major fibre fineness parameters have lower values than
those recorded for the various fractions of Kompolti. Only in yarn strength does it
equal the mixed fraction of the dioecious hemp.
These data suggest that in dioecious hemp, the
male plants are the repositories of better fibre quality. The data also explain why
both the literature and experience gained in the finishing industry and spinning mills
indicate that the fibres of monecious hemp are coarser than those of the dioecious form
(Kerékgyártó et al. 1966), since the habit of monoecious hemp is completely
identical to that of the female plants of the dioecious form. This fact, and the
lower stem yield potential of monoecious hemp make it very doubtful whether these
varieties can be grown in the southern hemp-growing region, because they are not
competitive with the finer fibre and higher yields of the southern varieties.
References