Higher yields from late hemp

        By growing very late-flowering cultivars at a relatively low plant density, fibre hemp yields can be much higher than when using conventional cultivation techniques.  This is the main practical conclusion from the research on fibre hemp conducted by Dr. H.M.G. van der Werf at the Research Institute for Agrobiology and Soil Fertility and the Agricultural University in Wageningen, The Netherlands.
        In his PhD thesis, "Crop physiology of fibre hemp" (available through the IHA), which van der Werf defended on June 30, he concludes fibre hemp may be an interesting new crop.   Traditionally fibre hemp is sown very densely (300-400 plants/m
2), and harvested in August.  By using late-flowering hemp cultivars and harvesting these at the end of September the growing season is longer and yields can be increased by about 30 %.
        Such late high-yielding hemp crops are not compatible with the traditional high plant density.  As a result of severe inter-plant competition, many plants die during August and September in these late crops ("self-thinning").  As a consequence of the occurrence of self-thinning, in fibre hemp optimum plant density is lower when the yield is higher.