Evaluation of a phenological model for strategic decisions for hemp (Cannabis Sativa L.) biomass production across European sites

The optimal combination of yield and quality of hemp fibres from field grown crops is around flowering. Therefore prediction of flowering time would support in planning production and optimization of the cultivar choice for different agro-ecological zones. In the current paper the validation of a recently published model (Amaducci et al., 2008a) is carried out for four varieties across a wide range of sites and thus of air temperature–photoperiod combinations. The model was evaluated by comparing its output to field observations of the duration between emergence and 50% flowering. The model output and observed times from emergence to 50% of flowering generally corresponded well, but some discrepancies were apparent. The biggest discrepancies between estimates and actual data were observed at extreme latitudes. The level of accuracy of the model predictions is satisfactory for strategic decision regarding sowing and harvesting time and cultivar choice, but tactical decisions (e.g. time of harvest based on flowering time) cannot be accurately supported.

► The accuracy of model predictions is satisfactory for strategic decisions regarding sowing, harvesting time and cultivar choice.
► Model output and observed times from emergence to 50% of flowering compare well, with higher discrepancies at extreme latitudes.
► At high latitudes (Finland), late-flowering cultivars should be discouraged given the uncertainty whether flowering is induced.
► Appropriate sowing dates and cultivars are critical to maximise yield at Southern conditions.
► At low latitudes (Sicily), crop yield is limited by very inductive flowering conditions and even late cultivars exhibit short cycles.