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

To study the influence of the stage of growth of industrial hemp (Cannabis sati6a L.) on yield formation and fibre morphology, a field trial was carried out in Switzerland in 1997. Different harvests took place at 7‐14 day intervals, 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’). Maximum stem yield amounted to 14.8 tons of dry matter (DM) per hectare. Bark yield showed a development similar to that of the stem yield and reached 5.8 tons 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 first created and then filled. The peak of the stem and fibre yield at the male plant flowering stage was probably caused by an increase in production and lead to a filling of secondary fibres. After that, and because of their characteristics, secondary fibres may cause a decrease in bark quality. With regard to fibre production, the upper third of the stem did not account for much fibre yield. © 2001 Elsevier Science B.V. All rights reserved.