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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.

        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

• Bócsa I., 1969.  Möglichkeit der Umänderung des ausländischen einhäusigen Hanfbaues mit Hilfe von neuen Formen des unisexuellen Hanfes. (Hungarian with summary in German).  Rostnövények, 27-32.
• Kerékgyártó P., Nagy K., Gehring J., 1966.  Mezögazdasági minösités alatt álló kenderfajták rostipari értékelése.  Textilipari Kutató Intézet kiadványa, 112 p. [Evaluation of industrial properties of officially tested varieties] (in Hungarian).  Proceedings of the Research Institute of the Textile Industry, Budapest, 112 p.
• Kerékgyártó P., Nagy K., 1967.  Der Einfluss der Mineraldüngung auf die Faserqualität des Hanfes (Hungarian with summary in German).  Rostnövények, 23-31.