Influence of the growth stage of industrial hemp on the yield formation inrelation to certain fibre quality traits

To study the influence of the stage of growth of industrial hemp (Cannabis sativa L.) on yield formation and fibre morphology, a field trial was carri ed out in Switzerland in 1997. Different harvests took place at 7-14 day in tervals, from the vegetative stage of growth to the senescence of the crop. Total yield and its components, fibre content and the frequency of primary and secondary fibres as well as the exact stage of growth were determined in male and female plants. Stem. bark and fibre yield reached their maximum at the time of flowering of the male plants ('technical maturity'). Maximu m stem yield amounted to 14.8 tons of dry matter (DM) per hectare. Bark yie ld showed a development similar to that of the stem yield and reached 5.8 t ons DM:ha. Fibre yield was highly correlated with stem and bark development and also reached its maximum at the time of flowering of the male plants ( yield: 4.1 tons DM:ha). During the vegetative phase, primary fibres were fi rst created and then filled. The peak of the stem and fibre yield at the ma le plant flowering stage was probably caused by an increase in production a nd lead to a filling of secondary fibres. After that, and because of their characteristics, secondary fibres may cause a decrease in bark quality. Wit h regard to fibre production, the upper third of the stem did not account f or much fibre yield. (C) 2001 Elsevier Science B.V. All rights reserved.