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Effect of variety, seed rate and time of cutting on fibre yield of dew-retted hemp

Bennett, S.J., Snell, R., Wright, D.
Industrial crops and products 2006 v.24 no.1 pp. 79-86
Cannabis sativa, hemp, fiber crops, plant density, cultivars, crop yield, harvest date, field experimentation, fiber quality, phenology, flowering, stems, lignification, latitude, weed control, crop-weed competition, climatic factors, retting, Wales
A field trial was conducted at the University of Wales Bangor Research Centre, Gwynedd using five varieties of hemp, sown at two seed rates: 150 and 300 seeds m-2 to determine the optimum time to cut hemp to maximise fibre yield and quality. Three cutting times were imposed from mid-August to mid-September, corresponding to start of flowering, mid-point of flowering and end of flowering, and following dew-retting in the field fibre from the stems was extracted to determine fibre yield and quality. A wide variation was found in fibre yields between the five varieties, although the first cut in mid-August resulted in the highest yields in all varieties except for Beniko. A decline in fibre yield was recorded from the first to the third cut and it is suggested that this is a result of lignification of the fibres occurring after mid-August. The importance of cutting hemp early in autumn to avoid lignification of the fibres is discussed, and it is suggested that varieties with reduced or delayed onset of lignification are important in the prevailing colder, wetter climates of the more northerly latitudes. The higher seed rate led to better weed suppression and higher fibre yields in all varieties. The monoecious varieties performed better than the dioecious and hybrid varieties in the northern climate where the trial was conducted. It is suggested that further research is required to develop a more accurate method of monitoring retting in the field.